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 !)