Surprise, suprise, the FD exhibits a ton of factory bump steer. Minds were blow when Ronin proved this in testing: https://youtu.be/tN4JNP2yN6c in case you missed it. It certainly proves that certain claims about the "magic" of the FD steering rack placement are pretty much crap. However, it also left us scratching our heads a bit about where exactly folks might want to dial in their kits to. Would folks want it closer to racecar theoretically perfect, or do folks actually like some lively but less stable handling like that which Mazda used?
It's such a call on preference that at least to launch with we decided to give folks full adjust-ability. We're giving you both the ability to shim the steering rack since you'll want this close to your oil pan--1/8 to 3/16" clear is a good target--and including adjustable Speedway Motors spindles.
One twist though... One of the few complaints about adjusting bump steer by shifting the ball joint lower (rod end sphericals in this case) is that it puts more load into the spindles. The Speedway spindles are quite long. For rx7 applications most folks will cut these down but still… A few folks have managed to bend spindles--both Samberg and Speedway--in off track adventures. As such, in addition to the pieces of a bump steer kit folks are used to we're also including a Ronin exclusive support piece. This effectively slides over the spindle hex and is tightened ONLY snug tight.
WARNING, this spindle support part should be snug tight only!!! We don't want to unload the taper but it gives a nice wide base supporting the bending load as it enters in the steering knuckle. Do not direclty pinch the rod end against the spindle support nut!
If your rod end is choked up high enough on the spindle that the support doesn’t fit vs where the tie rod wants to be, then the added bending is small enough that you don’t need the support. Make sense?
The full bump steer kit includes:
-2x steering rack interface pieces
-8x steering rack spacers (1/8” each, so up to ½” rack motion possible)
-2x Mazda tie rods to rod end adapterr pieces (custom machined from high strength stainless steel)
-2x Aurora rod ends (only brand name, quality bearings for us)
-2x Speedway Motors “pinto” steering rack spindles (w/ nut and lock nut to locate the rod end)
-2x Ronin spindle supports w/ 2x locking jam nuts.
So how do you adjust bump steer? You can track down a gauge and measure via a dial indicator. You can also do a simple DIY version with a laser pointer.