Suspension Geometry Kit

Suspension Geometry KitBased on extensive study of the geometry of the 90-99 SW20 MR2 suspension, the Wilhelm Raceworks Suspension Geometry Kit is designed to correct the negative effects of lowering, and to improve on the stock geometry by reducing dynamic toe and adjusting the roll axis of the chassis.  The result is significant improvements to turn-in and front end grip, while also reducing the oversteer tendency that the SW20 is so known for.  The kit also makes it much easier to catch or control oversteer once it starts.

Made in the USA!

Premium Rod End Upgrade?
Rear Suspension Style
 

Installation Instructions

Ride Height Calculator

Warning regarding Moog ball joints:  Moog seems to have recently changed the design of their ball joints for the MR2.  These new ball joints will fit my currently produced RCAs, but will NOT fit RCAs produced prior to December 2016.  Also, the new ones may have a longer stud, leading to reduced wheel clearance (possibly even preventing 17" rear wheels from fitting without ball joint modification).


Replacement Rod Ends

Eventually, it is possible that the original rod ends supplied with the kit will need replacement.  These can be purchased below as a full set of six rod ends.  If you are switching from standard to premium rod ends, or replacing the original QA1 rod ends supplied in my kits from 2010-2015 please let me know in the comments section so I can supply the proper bump steer spacers to match the new rod ends.

Rod End Type
Bump steer spacers required?
 

Technical

This kit improves the MR2's suspension geometry in several ways. First, it corrects the negative effects of lowering. As discussed in my suspension geometry analysis, lowering the MR2 (or any McPherson Strut based vehicle) has negative effects on the suspension geometry.  In particular, lowering degrades the camber curves and lowers the roll center, effectively softening the suspension.  The kit is designed to fully compensate for 1.25" of lowering. However, lowering further than that will not negate the effects of the kit. If anything, the lower your car is the more you can benefit from geometry correction.

Second, the front RCAs are thicker than the rears, further raising the front roll center resulting in improved grip and reduced body roll.

Third, the kit enables rear toe change (bump steer) to be nearly eliminated on a 91/92 MR2. I have found this to have a significant positive affect on stability at the limit, making the car much easier to drive fast, and consistently.  With this adjustment I run my 91 at 1/16" total toe in with no loss of stability, leading to greatly improved rear tire wear.  More information on that can be found here.

This kit is designed to be completely bolt-on, and completely reversible. A little work with a press is required on the rear knuckle.

The "standard" rod ends are a good, budget friendly rod end sold by Midwest Control. For those looking for the very best, I now offer the option of upgrading to 3-piece, USA made FK rod ends for improved durability.


Original prototypes installed on my car:

Front Geometry Kit

Rear Geometry Kit


Front tie rods use a tapered stud (no drilling the knuckle), aluminum spacer matched to the roll center adjuster (RCA), aluminum tie rod adapter, and your choice of Midwest Control or FK high misalignment rod end.

For the rear tie rod the spherical bearing is removed from the knuckle and a steel slug is pressed in its place. The tie rod drop bracket is a welded steel assembly that simply clamps onto the knuckle. In addition to shifting the pivot point down to match the RCA, this also shifts the pivot point rearward, which reduces the natural toe changes of the rear suspension, aka bump steer. The stock rear tie rod is completely replaced by an aluminum hex tube with rod ends at both ends, and custom bushings to adapt the rod end to the chassis at the inner end.

One design improvement from early versions is the addition of a pair of locating bumps on the rear tie rod brackets. One for the standard "vertical" position, and one for rotating the bracket as shown here. This rotation significantly reduces rear bump steer on the 91 suspension, greatly enhancing stability. The locating bumps also make installation easier in either configuration.

Roll center adjusters are machined from 6061-T6 aluminum, and designed to fix and improve the suspension geometry.  All aluminum parts are anodized black, the steel front tie rod studs are yellow zinc coated, and the rear tie rod brackets are powder coated in black.  All hardware is grade 8 standard / grade 10.9 metric.

This kit requires at least 16" wheels. I know the fronts will fit with 16's, the rears will probably fit, depending on the wheel. 17's will fit for sure.  The stock brake dust shields will need to be modified (bent) or removed to clear the front ball joint / RCA.

So, what does this all do for you? Better camber curves, reduced bump steer, improved roll center location (reduces body roll), and reduced roll center migration for more stable cornering.