Mazdaspeed3 Mazdaspeed Coilover Impression

After driving my Mazdaspeed/K&W Variant 3 coilover in variety of conditions from LA freeways, downtown pot holes, mountain roads, and competing in NASA time trial.  Here’s my impression of the setup and some tips on optimizing the setup.

Installation:

Installation is pretty straight forward, just follow the supplied installation manual and Mazda shop manual.  One of the biggest handling improvement to Mazdaspeed3 is increasing the front negative camber.  However the coilovers do not come with camber plate, it was designed to fit the stock top hat.  I ordered the K-Mac adjustable top camber/caster plate from StreeUnit.com, and had Tri-Point make a custom adapter to fit the top hat onto coilover.

Jeff Wong at Tri-Point looked over the coilover, and proposed a cost effective solution.  It consist of a off the shelf Koni Upper Spring Perch (Part# 80.0000.0008), boring out the koni  perch center hole to clear the coilover shaft, then custom machine a spacer to fit the 60mm spring properly onto the 2.5” spring perch.  I also had them put in a Torrington bearing under each spring, this bearing allows the spring to rotate freely under compression, helping the suspension to work smoother.  This is a little trick that race car builders use on their McPherson strut suspensions.

Finished Coilover Assembly with KMac Camber/Caster Plate and torrington bearing

Once installed, I realized that the front lower control arm had very little clearance to the sway bar end.  I got a pair of adjustable end links from AWR Racing, and the problem was easily solved.

The last problem I encountered was that the KMac plates had tabs underneath to clear the shock tower on regular Mazda3, however since Mazdaspeed3 has a shock tower plate, the tab raises the camber plate too high.  Luckily the tabs were simply glued onto the plate, all I had to do was tap it with a flat screwdriver and it came right off.

Compare to other coilovers currently on the market for MS3, this setup gives you the best camber adjustment, since the top nut clears the shock tower, you can move it further underneath the shock tower for more negative camber.  In fact, if you were to go to the extreme, you can even cut off part of the bottom KMac clamping plate to get even more negative camber.

You can still install the stock strut tower plate by knocking off the 3 tabs underneath

Note that the orientation shown on the KMac manual is not the optimal position for negative camber.  Play around with the camber plate by rotating the bottom clamping plates, and you’ll be able to get the maximum negative camber plus a little bit more of caster as well.  This is a win-win situation.

Impression – Street:  Being a twintube shock made by K&W, it’s got the signature smoothness known for the products made by the German manufacture.  Despite the stiffer spring rate, the car was actually more pleasant to drive around town.  Even through rough patches of the road here in the city, the car was silky smooth.  Imo, this is an excellent shock for daily driving.

Impression – Track:  The spring rates are said to be 400lb/in front, and progressive in the rear up to 290lb/in.  Overall the on-track performance was average.  While a twintube shock has excellent characteristic over bumpy street roads, it also contribute to its downfall on track.  The shock was slower acting compare to a monotube shock, this gives the driver a vague feeling and more disconnected from the track.  The front grip felt good, the front spring rate is about right for a medium grip tire (Toyo RA1), however I didn’t like the rear, I felt it was too soft and could use a much higher spring rate.  Due to the ControlBlade rear suspension design, the rear spring is placed much further inboard, which reduces the motion ratio.  While the front wheel rate would be very close to the actual spring rate.  The rear motion ratio would’ve resulted in a wheel rate about 60% of the actual spring rate.  As you can see, the rear spring rate is very soft for a track setup.  Unfortunately the rear spring is not a standard diameter, finding a replacement spring will be difficult.  I used standard compression/rebound setting supplied by Mazdaspeed, and it was fine.  I didn’t feel an adjustment to damping could’ve improved the performance further.

Problems to watch out for:

Shock travel - our beloved MS3 weights nearly 1,000lb on each front corner.  This means we have to allow plenty of shock travel to prevent the shock from bottoming out (hitting the bump rubber).  Unfortunately due to the added height of the KMac clamping plate, and custom adapter, it took out abit of shock travel.  If I were to improve the setup further, the next step is to order a short and progressive bump rubber to allow for more shock travel.

Rideheight setting - I feel the Mazdaspeed manual reference rideheight setting was abit too low.  It placed the front control arm in a position where it lowers the roll center too much, thus causing a vauge steering feel in the corners.  I tested different front ride height settings in a local canyon road, and the best result was using a setting where the front lower control arm was about parallel to the ground, with the chassis side just abit higher than the hub side.  When the front was too high, the turn in was very positive, but the front end washes out afterwards.  When the front was too low, turn in was vague, and the steering feel changes through out the corner.

As you lower the chassis the roll center begin moving closer to the ground, and the distance between the roll center and center of gravity increases. This causes many bad handling effects, such as increased body roll, and migrating instaneous roll center.

Overall, I feel this coilover is an excellent for street/occasional track purpose.  It is the best setup on the market thus far for Mazdaspeed3.  The fact that it clears the shock tower and allows maximum negative camber adjustment for Mazdaspeed3 is a crucial advantage.  However, if you are building a serious track car, you’ll be better off with a true custom built racing shock.  (No surprise here !)

Mazdaspeed3 Racing Seat/Harness Install Write Up

The stock seats are great for driving your girlfriend around town, but to maximize the performance on the track, a racing seat/harness is a must. I went through 3 seat rails before I finally found the right setup that allows me to sit in a low position. Hopefully this write-up will help other Mazdaspeed3 owners to do it right the first time.

Parts to buy:

1. Racing Seat: I chose the Sparco Corsa seat for it’s superior lateral holding capability. It’s very comfortable and supportive, I would highly recommended to anyone.
2. Side Mount: Order Sparco Aluminum Side Mount (Part# 00490W)
3. Sparco Hardware Kit: Needed to mount the side mount onto the seat (Part# 50001)
4. Seat Slider: Sparco Flat Slider (Part# 00493), this slider gives you the lowest mounting position.
5. Seat Rail: Call Wendell at Wedge Engineering and order a driver side seat rail for Mazda3, specify you’ll be using it with Sparco Flat Slider, and also tell him your seat width measurement (install side mount on the seat and measure across from the middle of the bottom mounting holes). Since their rails use threaded mounting holes, ask him to include the 4 mounting bolts, they are the perfect size and are very strong.
   

   The Wedge Engineering rail turned out to be a very study piece.

6. Racing Harness: I chose Schroth Profi-II ASM. You can leave it in 4 point configuration for ease of use driving around town, and the ASM technology will prevent you from sub-marining (common with traditional 4pt belts) in an event of crash. For more information see HMS Motorsport. I also highly recommend reading the Schroth Competition Manual to understand proper mounting of racing harnesses.
7. Schroth B24 Bracket and SG11 Bolt: The Profi-II harness came with snap-in ends for use with eye bolts. Unfortunately the right side lap belt mounting point on this rail will not work with an eye-bolt in this configuration. If the eye bolt is installed with the eye on the right side, it will hit the tranmission tunnel. If the eye is on the left side, it blocks the side mount. So it’s necessary to convert the right side lap belt end into a bolt on bracket. It’s important to get the SG11 bolt, so that in a bolt on configuration, the harness end can still rotately freely.
   

   Schroth B24 Bracket. Watch HMS Motorsport's youtube video on how to dissamble the flexi-belt end.

   
   

   SG11 Bolt has a machined shoulder that will allow the B24 bracket to rotate freely.

8. Spacer or washers with ID just big enough to slide over the SG11 bolt but not go over the machined shoulder. This is needed in step 8 to clear the harness of the sharp edge.
9. Sparco Harness Bar for 02+ Subaru WRX (Part# 300175): Thanks for the Cobb Tuning guys who measured the B Pillar distance, it turned out the WRX harness bar from Sparco is a direct fit to Mazdaspeed3 as well ! You’ll also need a longer bolt than the supplied one, take out the stock mounting bolt from B Pillar, go to the hardware store and get 2 Grade 8 or higher bolts that are 1″ longer.
10. Schroth Profi Single Sub Strap: This is optional, I have to use it because NASA requires atleast a 5 point harness. I tried to use a 6 point sub-belt as well, but with the shape of the floorboard, it’s difficult to mount a 2 point sub-strap correctly. Installing this will require driling a hole on the floor board, and cut away the plastic AC vent under the seat.

Install: Now that we have the proper that are tested to work, installation is a breeze.

1. Begin by removing the 4 bolts that hold the factory seat rail down.
2. Reach down and disconnect the air bag sensor. (Push the ribbed tab in a downward direction to disengage the sensor)
3. Carefully remove the seat from the car
   

   Seat Removed

4. Mount side mount on to the seat first (this way the side mount won’t stress the fiberglass after bolted down)
5. Install Sparco flat slider on to the wedge rail
   

   Slider Installed

6. Install Sparco adjuster handle onto the 2 slider adjuster prong (you’ll have to bend the handle alittle bit to the right shape, and then use a rubber mallet to hammer it down, make sure it’s secure)
7. Install the seat onto the Sparco seat rail
   

   Seat Installed

8. At this time you should install the right side lap belt harness onto the rail. Convert the Schroth right side lap belt end into B24 bracket (follow instruction on here). Install the B24 bracket into the seat rail by using the SG11 bolt (the bolt will thread right into seat rail hole). Install the bracket on the outside, and point it away from the sharp edge to prevent damage to the belt when being used. I had to use a spacer to get enough clearance, I found the spacer in my partsbox, you can use washers or find a spacer in the hardware store, just make sure it slips over the the bolt thread, but doesn’t go over the machined shoulder, the shoulder allows the seat belt end to rotate freely.
   

   It should look like this after installed.

9. Go back to the car and install the Sparco Harness Bar, it’s pretty stright forward, follow the instruction here. I did not reinstall the driver side stock seat belt, because it no longer rotates freely. On the passenger side, I angled the upper seatbelt guide forward so that it doesn’t bind when being pulled, a better way to do it is to use the right spacer that’ll allow the seatbelt guide to rotate freely. **Take care to insure the harness bar is nearly horizontal with your shoulder, the harness should be installed at no more than a 20deg downward angle, for more information on this consult Schroth Competition Manual. Torque the top bolt to 57 ft. lbs.
10. Install an eye bolt in the left OEM lap belt bolt hole. This is also were you’ll be mounting the harness bar support. On the passenger side, the hole is there, you just have to cut the carpet to expose it. Torque the passenger side bottom bolt to 57 ft. lbs.
    

    Driver side installed

11. Install sub strap (optional): I had to install a 5th point sub-strap to fulfill NASA requirement. I had to cut enough carpet to expose the floor board, and cut off the plastic a/c vent piece. I then put the seat in position and marked approximately where the sub-strap should be mounted. On a 5 point harness, it’s recommend that the mounting point is inline with the upper body angle, or further forward. This is to prevent your family jewel from getting squashed in an event of crash. Consult Schroth Competition Manual for more information. I then removed the seat, took out the underbody plastic panel, and drilled a hole using 7/16 drill bit. Schroth sub-belt comes with an eye bolt and a reinforcement plate. Place the reinforcement plate under the car, and thread the eye bolt in from top. Use a screw driver to torque it down. Reinstall underbody plastic panel.
    

    Cut Off the A/C Vent

12. Now we can finally mount the seat into the car. Torque the 4 seat rail mounting bolts to 39 ft. lbs. Clip the left lap belt/sub-belt in place. Wrap the shoulder harness around the rear harness bar. Again refer to Schroth Competition Manual for proper wrapping instruction.
    

    Finished Install ! I'm not trying to make a fashion statement with the seat padding ! It's temporary until I shave off some height off the Sparco padding for a lower seating position.

    

    Note the shoulder harness adjuster are placed as rearward as possible to prevent getting caught in the event of a crash.

    Congratulations ! You’ve got your racing seat and harness installed in a safe maner. You are now ready to rock out on the track !