BC Racing BR Type Coilovers - Mazda 5 (Review and Install)


Admin with a big stick
[size=+2]BC Racing BR Type Coilovers - Mazda 5 (Review and Install)[/size]

Import Auto Performance: BC Racing Coilover Kit 05+ Mazda 5

A big thanks goes out to Import Auto Performance for making the deal with me on these coilovers. The price is fixed by BC Racing at $1000 shipped a set, but the friendly customer service and quick response times from IAP on my many questions made all the difference between them and another vendor.


Information copied straight from BC Racing NA's web site:

- Mono-tube shock design
- 30 levels of damping force adjustment, adjust compression/rebound
- Pillowball mounts and adjustable camber plates included (where applicable)
- Separate full length height adjustable
- One year warranty
- Rebuildable

- Coilovers use 46mm pistons and 53mm shock housings, the enlarged shock cartridges with specially designed pistons and rods provide a wide range of damping force.
- Valves are constructed of special spring steel, which outperforms stainless steels and produces longer valve life. Valve stacks use a patented deflective system to provide more precise control.
- Patented concave lower locking ring, to prevent unseating.
- Springs are made of SAE9254 high strength, durable steel. Compression tested at over 500,000 tires with less than 5% deformation.
- T6061 Aluminum utilized in spring locks and seats for high strength and lightweight.
- Iron lower brackets on MacPherson struts to ensure rigidity.
- Piston rods are constructed of highly polished steel to lengthen oil seal life and prevent leaking.
- High pressure inner rod guide seals ensure a perfect fit for consistent fade resistant damping and long shock life.
- 2 step coating process utilizing nickel and chromium plating to prevent corrosion.
- Newly developed lubricant oil in shock cartridges minimizes aeration and cavitation.
- An additional bearing beneath each pillowball mount provides the smoothest action and prolongs the lifetime of the pillowball itself.

Application Guide Link


Related threads:
BC Coilovers Unboxing Mazdas247 HondaSwap
Brake Fluid Reservoir Relocation


Ride impressions:

At the stock settings out of the box (8/30 all around, 1 is stiffest), the ride is actually very smooth. The damping and rebound is firm but not harsh. All the float at highway speeds is gone- on a large rise/dip the car just has one nice smooth oscillation and then it's settled again. No bounce like the stock suspension. The balance feels very neutral. The delay that you feel with the stock suspension after cranking the wheel really fast (like doing an emergency lane change) is pretty much gone- you crank the wheel and the rear of the car follows the front almost without delay. I do have the Mazdaspeed3 rear sway bar though, so keep that in mind- it's a good bit stiffer than the stock bar and increases turning response.

I do get a little inside wheel spin when going around really tight corners and mashing the gas, but this really only happens if I add up the rare combo of turning 90 degrees (right turn from stoplight) with my foot on the floor. I can't say that this didn't happen with the stock suspension since I didn't trust it to run corners at high speed- but I do know that most front wheel drive cars will lose traction on an inner front wheel on a quick 90 under power. No LSD kinda sucks. This is the only situation where this happens, so it's not really a big deal.

On all other types of driving- rolling through the twisties, zipping through traffic, and even just long distance highway trips- the car is much more planted than it ever was with the stock suspension. I do feel the contours of the road a LOT more than stock, but it's never harsh (with 235/45-17 tires). U-turns going under freeway overpasses are a piece of cake at 60mph, and bombing down canyon roads in the Texas hill country is actually quite fun. The limits are high enough now that you're solidly in "oh crap I'm going to get a HUGE ticket" before you get anywhere near losing control of the car. Now I need more power and more brakes...

With the setup now (coilovers, rear sway bar upgrade, 235 tires) it's possible to get the rear end of the car to step out in a tight corner, but it's very easy to control and catch. Even with a fairly aggressive alignment (for this car), it's not twitchy. If I let go of the steering wheel on the highway the car will drift slightly to one side or another, but it's not what I would consider a handful. Keep in mind that the alignment has a HUGE role in how a car feels going off center, and that I typically run settings on my cars that are right at the edge or outside of manufacturer recommendations, so you can dial out whatever twitchiness you want when you get your car lined up. My wife and I prefer cars that respond like go-karts, so I set all my cars to my own specifications.

Empty vs loaded: Driving solo, the car encourages you to do bad things. You really can whip it around like any other compact car that has a decent suspension setup on it. Driving loaded (4 adults, 2 kids + roof box loaded with 100+ pounds of stuff), the suspension still handles fine. You're not going to attempt sliding around a corner or anything for the sake of your passengers, but the response is still plenty good to feel what the car is doing. It doesn't bottom out as far as I can tell, and there's enough damping and rebound on the same settings to keep the car from oscillating over large bumps.

BC vs Tein Flex (on my 95 Civic): Honestly, the BCs feel pretty similar to the Tein Flex setup I had on my Civic. They're not nearly as stiff because I had a custom spring setup and the suspension geometry is different (and the Civic was 1100 pounds lighter), but the level of control and confidence gained is right up there with it.

BC vs AST 4100 (on my S2000): Sorry, no comparison... but then you're comparing $1000 universal cartridge coilovers vs $3000 custom valved coilovers that were designed specifically for one car. I don't hesitate to take a high speed sweeping turn with bumps at 1G in the S2k, but I might have to think about it with the BCs- not that I would ever be in a position to try that out with the 5 being the family vehicle. Who knows? I might decide to take it to the track one day to screw with newbies who think they're hot in their Corvettes. Either way, the BCs are a hell of a deal for what you pay.

Three months and 5k miles later, the BCs are still performing like day 1. They still feel great, and I really like driving the car with the stiffer suspension. It adds a lot to the driving experience, and the value for what you get is excellent. If you have to replace the mounting hardware on your 5 (commonly breaks) and you buy the cheapest shocks you can find new plus lowering springs, you're going to end up right on the price of the BC setup.

Pictures after the install:


Build Quality / Design:

If you look at my unboxing thread (linked above), the build quality of the coilovers looks very good. The paint did scratch a bit during the installation, but I'm a klutz, and the paint will get worn off at metal to metal interfaces no matter what. The one issue I had with the build was with the studs in the top mount on the front struts. The studs start to spin as you get close to the torque value called out in the factory service manual, so it can be difficult to torque to the right level. The studs don't back out though, and I've had no issues with them after 5k miles, so it doesn't seem to be a real issue- just a minor annoyance on assembly.

One issue I have with the design is the double locking ring setup on the front struts. It's nice to say that you have some kind of "Patented concave lower locking ring, to prevent unseating" according to the web site literature, but the locking rings come loose. It only loosened up on the driver's side, but it happened 2-3 times (and extended the length of the strut, raising that corner of the car) before I dumped a ton of blue Loctite down all the threads. Issue solved. The passenger side didn't have the same problem of the shock extended over time (from vibration? turning?), but the adjuster rings were still loose, so I applied Loctite there too. Maybe I just have a one-off because only one side had a real issue, but it's worth mentioning because it can be a pretty big problem if the threaded housing decides to back all the way out while you're driving. If BC just used a non-fancy adjuster ring with a gap and bolt through it that physically cinched down on the threads to keep it from moving (like my ASTs), this would never happen. It's also worth mentioning that this was never an issue on my Tein Flexes, even after 20k miles of driving in MUCH more abusive situations than the 5 will ever see- but those cost over 50% more too. I'm ok with a $5 tube of Loctite- I can still break the threads loose later if I want to change the ride height and then dump another $5 tube in to lock it down. Look for the adjustment section after the installation for more info.


Factory hardware vs BC coilover:

Front side by side:

Front OEM weight, 16.6 pounds including ABS sensor wire bracket which I did not reinstall:

Front BC coilover weight, 11.8 pounds (4.8 pound savings per front corner):

Rear side by side:

Rear OEM weight, 10.8 pounds:

Rear BC coilover weight, 9.4 pounds (1.4 pound savings per rear corner):

Overall, 12.4 pounds is lost from the car after this coilover installation. It's not much, but it was something I could measure- so why not document it? If you're wondering about the scale, its measurements are repeatable with the same items every time, no matter what order you weigh in, what times, how many times etc. It's dead nuts accurate down to 0.2 pounds, verified against industrial/calibrated scales that I have access to.
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Admin with a big stick
Installation: All install pictures were taken from the right (passenger) side of the car unless otherwise noted.


Initial measurement:

Using a high precision preschool project yardstick while parked on a flat slab (garage), the front fenders measured 27 inches from the top of the arch to the floor and 27.5 inches in the rear. These measurements were taken on the stock suspension for a 5 Sport, on the stock wheels and Bridgestone G019 Grid tires (205/50-17) that were on the car when I bought them. The tires were at 8/32 tread depth when I took the measurements, so their overall diameter should only be 1/8 of an inch smaller than Bridgestone's 25.1 inch specification. That gives a 2 inch gap in the front and a 2.5 inch gap in the rear in stock form.




Tools you're going to need:

Wrenches: 12mm, 14mm, 17mm
Metric sockets, 12mm, 14mm, 17mm, 19mm, 21mm
Allex / Hex wrench, 5mm
Pry Bar
Pliers (I like 90 degree angle pliers for clip removal)
Flathead screwdriver
Breaker Bar
Torque Wrench, 20-100 lbft
3 1/8 inch hole saw (for metal) and mandrel
Jack stands


Raise the car:

The next step was to put the whole thing (level) up on jack stands. I used my trusty floor jack and the lift points up front behind the wheel wells, plus the center jack point in the rear between the lower control arms. Before the wheels leave the ground, make sure you break the lug nuts loose (21mm socket)! It's a lot harder to do once there's nothing to keep the wheels from spinning on you. One thing to note here is the large amount of droop available in the stock suspension (good thing). This is important later, so remember it.

Up on jack stands:

4.5 inches of front droop travel! (subtract the 2 from earlier)


Front strut removal:

Remove the wheel so you can get to the fun part. You should see this if everything in your car is healthy:

There are really only 5 fasteners that you have to mess with on the front if you're just installing new struts- the nut holding the ABS sensor cable bracket and sway bar link, the lower strut bolt, and the three at the top of the strut itself.

Sway bar link / ABS sensor cable nut:

Lower shock bolt:

Upper strut mount:

Remove the nut holding the sway bar link and the ABS sensor cable bracket to the strut housing. You'll need a 14mm wrench here. If the bolt spins with the nut, use a 5mm hex wrench to hold it in place.

I bolted the ABS sensor cable to the sway bar link to keep it suspended and not loaded with the weight of that heavy rubber block.

Unplug the cable from the ABS sensor in the steering knuckle. You will probably be ok away without disconnecting the cable, but you don't want to risk breaking it later when you're smacking things with a mallet. Remove the brake line clip while you're here too. A flathead screwdriver and a pair of pliers makes short work of this.

Now you have to loosen the bolt on the steering knuckle that holds the lower part of the strut in place. Use a 17mm socket or wrench. Remove the bolt. Stuff a pry bar in the gap on the back side of the strut and spread it open as much as you can.

Fun time! You've probably discovered that you can't just slide the steering knuckle off the strut housing. Take your favorite mallet, hammer, sledge, beer stein, or whatever and beat the crap out of the knuckle. The arrow shows where you want to aim. Try not to hit the sensor, wires, or your brake hardware. I used a piece of 2x4 with a heavy deadblow to break it loose. This took me about half an hour per side, even with the whole joint soaked with penetrating oil. Based on the how-to videos I've seen online, this is pretty common, so just be ready to cuss your head off for a while and keep going. After you're done with this step, everything else is EASY.

WIN! No prize. Sad Mike.

You have the bottom of the strut loose now, so it's time to stand up and loosen the top and try not to drop the strut on your foot. You need a 14mm socket to take these bolts out. The one in the very rear has almost no clearance to get to the head underneath the cowl/firewall, so you might have to use a combo/box wrench to get it out. These bolts are the only thing holding the strut in place at this point, so you'll want to make sure you have your hand on the strut body (or a helper) when you remove the last bolt. The strut is heavy, and it hurts if it falls on your foot (didn't happen to me this time)!

That's it for front strut removal!


Cutting steel (strut tower) for camber plate clearance:

For those of you questioning the wisdom of cutting through the structure of your vehicle, this is the accepted method (I called a few race shops to be absolutely sure) for adding clearance to use camber plates on a strut vehicle. On the Mazda 3 and Mazda 5, you have a stiffener plate that sandwiches the steel of the strut tower between it and the upper strut mount, so any structural integrity concerns really aren't an issue- all your load is transmitted through the bolts to the rest of the strut tower and then your car's unibody. Since you have a pretty beefy stack of hardware surrounding the thin stamped steel of the strut tower, the size of the hole inside the stiffener really doesn't matter as long as you have enough material to bolt through. As an engineer, I had no hesitation with cutting through this section of the car- plus you lose a few ounces of weight out of the front end!

This is the stiffener plate. If you don't have a camber plate to make room for, don't worry about it. I had (wanted) to cut steel, so I removed it to use as a drill template. If you're going to use this as a template like I did, it gets really scratched up- so you could buy another one from Mazda (passenger side! driver's side has extra tabs hanging off of it that you don't want in the way). You'll want to use the passenger side stiffener plate to drill BOTH sides of your car, so make sure you finish all cutting operations before making it look pretty again.

Note: if you want to be able to adjust your passenger side coilover stiffness and camber later, you might want to take a look at my brake reservoir relocation thread (also linked above).

This shows you why you need to enlarge the hole. You can see the stiffness adjuster for the damper just fine, but there's no way that you're going to be able to get to the top plate to play with the camber settings.

Remember the clearance issue you had removing the rear bolt from the upper strut mount? There's no good way to cut your hole from the top of the strut tower, so you need to go in from below. If you're thinking about getting an angle drive to cut from the top, everything I found on the market that would fit wouldn't be able to handle the torque required to drive a hole saw for extended periods of time. This is where you're going to cut:

To help guide your 3 1/8" hole saw, you're going to use all the hardware you just removed from the upper strut mount (stiffener plate, bolts) plus the nuts and washers from one of your BC coilovers. The nuts and washers from my coilovers got a little dinged up as I got tired and the hole saw bounced a bit, so you might want to run to the hardware store and pick up some extras to use for drilling if you're worried about appearances. I just put my scratched up nuts into parts of the install that weren't as visible (closest to the firewall). Take one of the OEM bolts with you to the store if you're going to get extra hardware- it makes matching up parts much easier.

Bolt the stiffener into place on the bottom surface of the strut tower (inside the wheel well). I chose to bolt it in with the upper face pointing up- that way it wouldn't get scratched up as much. Try to center the stiffener on the hole.

Top view with the stiffener underneath.

This is the 3 1/8" hole saw I used- it was about $15 at Home Depot, and another $10 for the arbor (couldn't find mine). Make sure you get one that's meant to cut steel. The Milwaukee brand arbor I bought screws into place and then has a collar that you snap into the alignment holes on the saw. You can see that the saw is almost a perfect fit!

Cover up the ABS sensor with some tape before you start cutting. You don't want steel chips falling into your sensor and damaging it or shorting it out later.

Hole saw ready to go. This is the wrong drill for this type of application (too fast), so I pulsed the drill on and off to keep the speeds in check and to prevent temper hardening the steel and making it difficult to cut. You ideally want a low speed high torque drill. I couldn't find mine. Use lots of cutting oil and wear gloves and your safety glasses! Those steel chips burn...

Business end.

Aim this way, apply steady but light pressure. Let the tool do the work.

Now hold this pose for half an hour or so until you break through. You can see that I ignored my own advice and did not wear gloves. I guess I had a hot steel chip assisted exfoliation done on my arms that night. Yay!

Leftovers after the cutting (and cussing) is done:

You can see how nasty the stiffener plate looks after its had a hole saw spinning inside it for a while. This is easily taken care of later- but look! Big hole!

Take a file (I used a wire brush wheel on my drill too) and deburr the area. You don't want your alignment tech cutting his/her fingers on this area later. Clean with vacuum, degreaser, and isopropyl (rubbing) alcohol. Mask off the area with painter's tape (top and bottom) and spray with matching paint. I shot two coats on each side, waiting for the paint to dry each time, and re-masking to shoot from underneath so I didn't spray against the underside of the hood. I used Charcoal Grey Rustoleum to almost match my Galaxy Grey paint (it doesn't quite match). The mismatch doesn't matter though since you'll be covering up the paint "seam" with the stiffener plate. As for the scratches on the stiffener, I ground/sanded out the burrs from the hole saw hitting it and shot it with two coats of gloss black Rustoleum- and it looks like new again.

That's it for the camber plate clearance hole! My alignment tech remarked that it looked like the hole was there from the factory. Just don't do something stupid like this and knock a jug of oil over in your garage when you're getting tired of holding a heavy bucking drill upside down- this will drain all your will to continue and send you to bed greasy with your car still torn apart in your garage.



Admin with a big stick
Front strut installation:

Set up your camber plates before the install. The struts come out of the box with the camber plate bolts in the outermost positions. There are 6 screw holes total. If you leave the struts as they are, you won't have any room to move the strut in/out to adjust your camber. I didn't want the alignment tech to have to deal with removing and reinstalling the screws with minimal clearance under the hood (and possibly dropping/losing them), so I moved the outer screws to the middle holes. My assumption was that after lowering 1.25 inches in the front, I'd need to pull some negative camber out, so making room to lean the strut to the outside is what I required. In the pictures, this is the passenger side strut, with the strut oriented so the front of the car is towards my feet. Stock position, then screws moved over. I didn't measure a torque for these- just got them as snug as I could.

Push the strut up through the strut tower and loosely fasten nuts on top of the studs. The BCs have studs in the camber plate instead of holes that bolts go into from the top, so the installation is a little different. Make sure you have the washers under the nuts. Use a 12mm tools to tighten, then torque to 26 lbft (spec is 22.2-29.4).

Top view of the strut bolted into place- you can see how the size of the hole matches up with the recess in the camber plate, and how there's still plenty of material left to support the bolts going through the shock tower.

Now that you have the top of the strut bolted into place, move into your wheel well. Slide the bottom of the strut housing into the collar on the steering knuckle. There's a tab that you want to make sure is lined up with the gap on the back side (where you removed the bolt). If you misalign the tab and start to raise the suspension to bottom the strut out in the collar, you'll crush the tab. This is what helps to rotate the strut when you turn, so you need to keep that tab intact. Slide the brake hose into place on the bracket, and hook up your sway bar link. This general picture shows you how everything should loosely go together.

Closer on the lower hardware:

To lift the suspension into place so you can tighten the lower strut mount against the strut housing, you must lift the lower control arm. I used my floor jack against the lower ball joint to move everything together. This is where you need to pay attention and make sure that the steering tab goes into the gap in the mount collar! Do not crush it! Take your time.

Once you have the lower mount bottomed (topped) out against the strut housing, reinsert your bolt and tighten with a 17mm socket. Torque to 47 lbft (spec 39.8-54.2).

Use a 14mm on the sway bar linkage nut. You might need a 5mm hex wrench behind it to keep the bolt from spinning. Torque to 38 lbft (spec 31.2-44.3). You'll notice that I didn't reattach the heavy rubber piece that acts as a mount for the ABS sensor wire. I couldn't find a place to mount it on the BC coilovers. It's not a big deal; I zip tied the line onto the strut housing later. If you're reusing OEM style struts, you'll want to try and put the mount back on.

Mount the brake line- slide the line into the slot on the bracket, then put the spring clip back into place. Pliers help here.

Reconnect the ABS sensor line. You did blow/vacuum out all the metal shavings before removing your tape in the earlier step right? You don't want any steel chips in your sensor connection.

Since you now have the end of the ABS sensor wire anchored, you can work out how much slack you need in your wire to account for suspension movement and zip tie it into place. The distance between the sway bar link mount tab and sensor won't change much, so you only need to leave a enough slack in the lower section of the line to allow the strut to rotate. The part you're going to have going back into the car needs to move up and down with the suspension though, so you want to give it a little more wiggle room. This is how I tied mine up. I just used the original grommet as a cushion and tied the wire to the tab for the sway bar link. The U-shaped loop gives plenty of room for the wire to move with the suspension, and using the grommet as a mount puts the wire in a location very close to the factory setup.

You're done with the front! Repeat on to the other side.


Rear shock/spring removal:

This is very similar to the front. Picture of what a healthy rear suspension looks like from the factory:

Start with the sway bar. You'll have to disconnect it from both sides to make moving the suspension independently up and down easier. This is the view inboard of the spring on the lower control arm.

Use a 5mm hex wrench to keep the bolt from spinning, then use a 14mm wrench to remove the nut. Sockets won't fit in here unless you use a GearRatchet- I couldn't find mine, so I used a GearWrench. Better.

Remove the bolt holding the lower control arm to the trailing arm using a 17mm socket. You'll want to put your floor jack under the control arm- this bolt is what holds the spring in place.

Use your 17mm again to remove the bolt holding the bottom of the shock to the trialing arm. This is the view from underneath. You'll find the shock on the inner side of the trailing arm.

Use a 12mm deep socket to remove the two nuts holding the top of the shock in place. Once you have these off, you might be able to maneuver the shock out- if not, don't worry.

Lower your jack slowly- it'll have the spring pushing against it. If your suspension behaves like mine did, the spring will be slightly stuck and won't release completely out of the lower control arm. Once you have the jack all the way down, there is no more compression on the spring, so you can safely remove it without fear of losing any body parts. Bring the control arm down and remove the spring and shock if you didn't do so earlier. Remove the rubber spring mounts/isolators if they didn't pop out with the spring.

Easy. Repeat on the other side.


Rear shock/spring installation:

This is a piece of cake. You're only going to put 5 bolts back in (1 more than on removal). Take your trusty 12mm deep socket and bolt the top of the new shock into place. Torque to 20 lbft (spec 15.7-21.2).

Bolt the lower mount on the shock back into the trailing arm with a 17mm socket. Torque to 66 lbft (spec 56.35-74.49).

This is the adjustable perch for the rear spring. The threaded section (black part) with the flange fits into the top of the hole on the top side of the lower control arm. The flange lip should match right up to the hole and pretty much snap into place. The bolt and giant washer go on the underside of the control arm to hold the perch in place.

Use a 19mm socket/wrench to bolt the perch into place. There's no factory torque spec for this bolt since it doesn't exist on the factory suspension, so I flipped through a few other service manuals to decide what torque value to use and settled on 90 lbft. This is based solely on the head of the bolt and the approximate size of the threads on the fastener itself, so it's really not needed since it's really under that much stress, but the fastener took it with no issue, and it's definitely not going to come out!

The spring perch looks like this from the top when installed.

The upper spring perch is part of the suspension crossmember. This is a closeup.

The large hunk of rubber that comes as part of the rear spring stack gets shoved up inside the upper perch area. You need this because the BC spring is a smaller diameter than the OEM spring. Just ram it into the recess until it stops. Friction should be enough to keep it in place until you mount the spring.

Put the spring onto the lower perch and slowly lift the lower control arm into position until the spring touches the top rubber mount. You won't be able to make both the top and bottom of the spring have a complete coil sitting on their respective perches because of the angle of the control arm. I just went with the top coil on the spring making full contact with the rubber mount and the bottom coil on the spring making contact with the adjustable perch at an angle. There is a lot more threaded perch coming up through the lower mount than there is rubber flange on the upper mount, so I thought this was the safer way to push the spring into place. Your floor jack should make this easy- just use it to push the LCA into place until you're able to put the bolt through to connect the trailing arm and lower control arm.

Use a 17mm socket to run the bolt down, then torque to 66 lbft (spec 55.69-75.15).

Go ahead and remove the jack. Repeat on the other side of the car. Reconnect the sway bar when you're finished. Use your 14mm wrench and 5mm hex to reconnect the link to the lower control arm. Torque to 35 lbft (spec 29.8-40.3).

That's it! You've now installed your new set of coilovers.


Admin with a big stick
Reference section for torque values, exploded diagrams:


Adjusting the coilovers before you drive off:

The compression/rebound damping is ganged together on the adjustment knob. This means that as you increase compression damping force, you also increase rebound damping force. In higher level coilovers, these adjustments are independent along with high speed (bump) and low speed (cornering) damping rates. These coilovers don't have that option, but you're also not paying for it either. To be fair, most aftermarket shocks that have damping adjustments in the price range will be set up exactly the same way. Not a big deal.

You've seen this picture before for the front strut. You twist the knob clockwise to increase stiffness and go counterclockwise to decrease. Both the front and rear come set to 8/30 from the factory, with 1 being the hardest setting. After driving around for a hundred miles or so, I settled on 6/30 for the front and 8/30 for the rear. I haven't changed that in 5k miles. The front camber adjustment is obvious- slide the top of the strut in and out to increase or decrease negative camber.

If you're worried about how you access the rear damping adjustments, you're in luck. The adjustment knobs come up through the unibody right under the rear cup holders. There's no need to remove any of the rear plastic aside from the cup holders, and they pop right out with a firm tug.

The front height adjustment is pretty simple. The two locking rings just under the spring shouldn't be moved if you're just adjusting the height of the car- they control the spring preload. This is set from the factory and BC recommends that you don't touch it. If you want to corner weight your car and still keep ride height the same at every corner, you'll have to mess with the spring preload- but if you're going to corner weight, I hope you already know enough about suspension to not have to read how to adjust a set of coilovers. The lower ring locks against the lower strut housing. When you loosen it, the upper threaded strut housing is free to spin. You can twist it up or down with your hands to change your ride height, then lock the lower ring back into place against the lower strut housing.

This is where I ran into trouble later. The lower ring on the driver's side strut kept coming loose. You can see from this picture that it backed out a LOT. I don't know how long the threads are on the strut housing, but it could theoretically back out enough to cause a major catastrophic failure (backing all the way out, collapsing) while driving. I spun the strut back into place 2 times before I gave up and dumped Loctite Blue down the threads to keep it in place, and haven't had any problems since. Blue seems to be strong enough to hold the strut height, but it's not so strong that you couldn't break it loose later if another adjustment had to be made.

Passenger side, no unthreading strut:

Wheel gap on driver's side after strut loosened, over 3 inches! That's about 2.5 inches higher than where I had set it after my install. Scary.

The rear height adjustment is also fairly simple, but there's one thing that sucks about it- the spring perch adjuster is practically impossible to get to with the spring on the perch. The easiest way for me to get to the rear perch was to unbolt the lower control arm, remove the spring, remove the perch, make my adjustment, then put it all back together again. If you're doing this, make sure to follow the torque values for reassembly! The shock also has to be adjusted up/down the same number of turns as the spring perch. The shock only has one locking ring, but the threaded body can be spun up/down without unbolting either end- just adjust, then tighten the locking ring back down against the lower shock housing. The spring perch has two locking rings that must be jammed against each other to stay in place.

To get my ride height just right compared to the out of box settings, I only had to lower the rear by 5 turns in the passenger side and 3 on the driver side. My total drop amount was 1.25 inches in the front and 1.75 inches in the rear. Given that I ended up with about a 1 inch gap up front and a half inch gap in the rear after everything settled, I'd say that the ideal drop on the Mazda 5 to maintain even wheel gap all around is right about the H&R Sport drop amount (1.3F, 1.4R).

Technique for adjusting: Use an area you KNOW to be flat (garage slab works). Lift corner to be adjusted, remove wheel, make spring/shock height adjustment, install wheel, lower car, drive away a few car lengths, then come back (allows the wheels to settle after being in the air) and make your measurements to decide what you need to change next. It can be a drag, but that's the advantage (or disadvantage) that you have with adjustable height coilovers- you have to spend some time to get things looking just right! It took me probably about an hour to get my ride height dialed in.

When I started driving around after the coilover install, I found that the rear springs made quite a bit of noise. They took about 100 miles to settle in and quiet down. I think the cause was either the fact that the perches aren't parallel to each other so the spring is bouncing between them until it has time to loosen up and take a curve to sit flat on both ends, or the fact that the plastic lower isolator on the adjustable perch is brittle and cracks/breaks out within a few suspension cycles. Either way, it hasn't been an issue after a few hundred miles, even after I've had the rear wheels in the air again.

After your height adjustments are where you want them, take your car to get aligned!



This is just where I decided to set the car. This is NOT the factory recommended alignment. I set the toe to zero all around to maximize tire life. My camber target was -1.0 degrees in the front and -1.5 degrees in the rear. The initial hunch was that the zero toe would cause the car to be a bit twitchy, and the higher camber in the rear would help to promote a bit of initial turn-in stability. My "twitchiness" fears were unfounded- the car drove extremely well with these alignment settings, and there were no complaints from my wife about the car being hard to handle. The front camber didn't quite match, but both were floating on/off of -0.9 degrees because of some dirty sensors in the alignment bay. This wasn't a big deal since I have the 5 year unlimited alignment policy with NTB, and intended to bring the car back after the springs settled in. So far I haven't had any ride height changes (other than the loose adjuster) since installation, so ride height has stayed the same.

Shot of the front tire (205/50-17, OEM wheel) vs fender with these alignment settings:

Shot of the rear tire (205/50-17, OEM wheel) vs fender with these alignment settings:

These are the only real good closeups I had of the 205/50 tire inside the wheel wells too before I went larger, so here they are so you can get a better idea of what the wheel gap looked like:


Droop travel issue:

In the very beginning of the article, I mentioned droop travel. If you don't know, droop is the measurement of suspension travel extension beyond rest. The stock front suspension had 4-4.5 inches of droop, which means that the car could go over a rise at high speed and lift the front end 4 inches higher than normal and still have the tires touching the ground. You can't accelerate or brake without your tires touching something, so droop is a good thing! Now remember what the picture at the beginning looked like:

Now this is what the car looks like with the wheels in the air after the BC coilover install:

Rear view:

Big difference, even taking into consideration the slightly taller tires in the second picture. In a closeup comparison, this is what comes up:

You now have about 1.75 inches of droop in the front and 1.375 inches in the rear. That's quite a bit less than 4 inches! Loss of droop means that there are now situations where your tires would normally be in contact with the ground, but they are now in the air. On large dips/rises this could mean that your car doesn't come down as smoothly because the shock can't dampen the full range of the drop on the way down; it could mean that you lift an inside wheel in an aggressive turn, and it could mean that you lose braking ability when trying to stop on a rough road. This is the only case where the reduced droop travel has affected me so far- trying to stop when one of the tires skates over a pothole. The reduced droop may not be an issue for you, but it's good to know about. Do be aware that many aftermarket suspension setups designed to lower a car will lose a bit of droop travel because of shorter shocks. You preserve some of your suspension compression travel with shorter housings (and prevent bottoming out), but lose on the maximum extension, hurting droop. Gain one, lose another. All you have to look at is the OEM vs BC comparison to see that the BCs are quite a bit shorter than the OEM pieces.


wow dude... i gotta hand it to you... garage installs are lengthy by themselves... but documenting and taking pictures of everything makes it like a bazillion times worse...you either have a TON of time or patience... my hats of to you sir!


Admin with a big stick
Thanks! I actually did this whole thing over 2 weeks' time... all at night after work, no weekends!


New Member
Calesta, this write-up is incredibly useful for me. I just purchased a Mazda5 and will be putting coilovers on it in the next couple weeks. (I'm in TX, too)

My big question has been what coilovers to get. I've previously been a BMW guy, loyal to GroundControl and AST, they don't make any applications for Mazdas.

I don't know the typical players in the Mazda aftermarket, so I'm on a steep learning curve right now. I'm trying to figure out who builds the "cheap", the "decent", and the "high-end" coilovers.

I've seen BC Racing mentioned several times as an "inexpensive, but decent" coilover option. It seems that - at least during your initial ownership - you seemed to have the same opinion.

My question: Can you give me an update on the BC coilovers, now that you've had them for over a year? Have you had any further issues other than the loose adjuster? Are they still driving and performing well, or are they due for a rebuild after 1.5 years?

If you had to purchase a new set of coilovers for a Mazda5 now, would you purchase BC again? Or are there other options that you would consider?

Thank you very much!


Admin with a big stick
Hi! Where in Texas?

So BC to me is probably at the cheapest end of the "decent" cheapo coilovers. I wouldn't put them in the same "decent" category as a set of KWs- probably more on the "decent" end of cheap. It seems like they dyno halfway decently for the price even though they're universal cartridge coilovers, but I haven't had mine apart and on a shock dyno myself.

So 1.5 years later they still feel great. I softened the front a good bit and went 2 clicks softer in the rear after a lot of playtime, but the shocks are still good. The fronts are a little noisy on turns because they don't have Torrington bearings like the stock Mac struts have (Yellowspeed's coilovers do for a similar price), but I can live with a little spring rotation noise every now and then.

As far as your experience, I think AST does have Mazda 3 applications now- I remember talking to them at their headquarters up in Plano a while back about stuff that would fit the 5. I have a set of ASTs on my S2000. Love them.

Would I purchase again- probably. If I thought I would be happier with a lower spring rate I would go with H&R springs and Koni Yellows- the drop level is identical to what I finally set my coilovers at. Given that, the spring rate on the BCs is almost double what the H&R springs come at, and I like the higher rates in the back that prevent excessive squat when the car is loaded up.

And not to chase you onto another board, but mazdas247.com is probably the best place with the most active Mazda 5 people on it, at least in the US. I'm there under "phunky.buddha" .


New Member
I'm in San Antonio. My wife is from (and still has family in) Carrollton; we are actually travelling up there this weekend in fact.

I did post at mazdas247, but didn't get much feedback so far. (just a link to this thread, but the mz247 version) I will continue to monitor and post on that board, thanks for the pointer. Who makes good quality coilovers for the Mazda5?

So you would say KW is considered higher quality than BC? I haven't ever seen or driven a set in person. I just emailed them to ask about custom spring rates, since their website lists an application for mz3, but not mz5.

When you mention the AST headquarters in Plano, are you referring to Vorshlag? They are who I dealt with previously for my ASTs, and they are in Plano. I just assumed they were a vendor, didn't realize they may be the US headquarters/importer for AST. I also just emailed them about the possibility of custom rear rates, so we'll see what they say.

You mention the spring rates for the BC kit (8k/7k) are about double the H&Rs - do you have any clue what the stock spring rates are? I'm not necessarily chasing the perfect drop height, my priority is the best balance of ride quality and handling I can find (though like you, my idea of good ride quality is probably a little firmer than most). Do you feel the BC's are "too firm" unless I'm regularly loading the vehicle like you mentioned? I'm an engineer in the auto industry, with a decade or two of auto-x, track days, and recently LeMons under my belt, and I love to obsess about this stuff...

Your thread on mazdas247 says that you suspect the plastic spacer is the cause for the noise you experience - do you think a pretty basic needle roller thrust bearing from McMaster would solve that issue? McMaster-Carr They are pretty thin (bearing+2 washers=3.6mm) so wouldn't add much to the stack height. (No clue how thick the current plastic part is).

Sorry for the long post, but thanks a lot for all the info already.


I wear stretchy pants
good write up Mike!! My Sti came with the same coilovers and I used BC on my last WRX too.

love them and have no complaints. :)


Admin with a big stick
I'm in San Antonio. My wife is from (and still has family in) Carrollton; we are actually travelling up there this weekend in fact.
Cool. Maybe I can work out a way for you to experience the car? When are you traveling? PM me here. :)
I did post at mazdas247, but didn't get much feedback so far. (just a link to this thread, but the mz247 version) I will continue to monitor and post on that board, thanks for the pointer. Who makes good quality coilovers for the Mazda5?
I've been offline the last few days- when I log in there I'll check your post too. :) There is quite a good bit of Mazda 5 info on that site.
So you would say KW is considered higher quality than BC? I haven't ever seen or driven a set in person. I just emailed them to ask about custom spring rates, since their website lists an application for mz3, but not mz5.
Much higher quality than BC. They engineer their coilovers specifically per car- damping, spring rates, mounts etc- their adjusters actually work, and the shocks dyno consistently within a set.
When you mention the AST headquarters in Plano, are you referring to Vorshlag? They are who I dealt with previously for my ASTs, and they are in Plano. I just assumed they were a vendor, didn't realize they may be the US headquarters/importer for AST. I also just emailed them about the possibility of custom rear rates, so we'll see what they say.
Yup, Vorshlag. Terry's a pretty cool and straight up guy. They're the US headquarters for AST/Moton. Or maybe I'm mixing things up and it's actually another office... but AST and Vorshlag are in the same business park up in Plano. AST and KW will both supply you with whatever springs you want to match up to your desired application. My ASTs are valved to my car and my spring rates- the KWs that I had bought before came with stock springs, and I bought KW branded springs of another rate to fit on the rear in the rates that I wanted.
You mention the spring rates for the BC kit (8k/7k) are about double the H&Rs - do you have any clue what the stock spring rates are? I'm not necessarily chasing the perfect drop height, my priority is the best balance of ride quality and handling I can find (though like you, my idea of good ride quality is probably a little firmer than most). Do you feel the BC's are "too firm" unless I'm regularly loading the vehicle like you mentioned? I'm an engineer in the auto industry, with a decade or two of auto-x, track days, and recently LeMons under my belt, and I love to obsess about this stuff...
I do, but I don't have them handy right now. I think ballpark from memory, the 8k/7k is about triple the stock rates for the front- the rear is quite a bit more of a ramp up from stock.

As far as "too firm," nope. The BC shocks seem to have a part of their range that works well with the spring rates that are included for the 5. It's not overly bouncy, but it is a linear damper for a very high spring rate- so you won't have any of that nice digressive damping curve that the higher end shocks have for large impacts vs the slow speed damping for the high velocity corners. Don't go into a high-G turn at 90mph and expect to weather the bumps like the ASTs on my S2k.

The adjusters are also linked, so you'll change the damping and rebound at the same time... which isn't really a big deal at this price point and this car- you're not going to go race time attack around a mountain in a 5.


So Toyota?
Your thread on mazdas247 says that you suspect the plastic spacer is the cause for the noise you experience - do you think a pretty basic needle roller thrust bearing from McMaster would solve that issue? McMaster-Carr They are pretty thin (bearing+2 washers=3.6mm) so wouldn't add much to the stack height. (No clue how thick the current plastic part is).

Sorry for the long post, but thanks a lot for all the info already.
No problem- those look like they'd work find, but you'd have to disassemble the struts and springs to get them in there. I might pick up a pair for mine- we'll see. Just make sure you get your ID/OD right!


New Member
If it's possible to meet up with you and maybe ride a lap around the block in your 5, that would be ideal. There would be no better way for me to understand how the BC setup rides and handles than to actually experience it. We will Berryville in DFW approx 5pm Fri, and leaving "whenever" Sunday.

Hmm, I don't see an option to PM you - maybe because I'm a new member? Is there a minimum post count required to send PMs? Since you're an admin, can you see my email address? I could correspond via email easily.

Yes, Toyota - I guess when I say automotive and San Antonio, it isn't much of a mystery...

KW kind of brushed off my email with a nearly form letter response saying they don't do custom spring rates, and don't recommend installing their product on a vehicle it's not intended for (since they have no listed mazda5 application.) I plan to call tomorrow and see if they might be a bit more helpful in person over the phone.