Been fighting with this issue for a year now. Hoping someone here might have some experience to share since I've been striking out. Local race shop couldn't find anything wrong either.
Some background first:
- 1990 car, straight tub, no accidents
- brake calipers and master cylinder were bought new from Mazda Comp in 2010 when the car was built to SM
- all tie rods, ball joints and wear parts in the suspension were replaced in 2010. The pax side front ball joint, outer tie rod and spindle and LCA were replaced again in 2011 when I had a bad spin.
- front upper control arms were new in 2010
- rear upper control arms came from a 96 with 20k miles on it
- all other control arms are used with unknown mileage.
- passenger side rear caliper was replaced with one from the local O'Rielly's in 2012 http://mazdaracers.c...aliper-pistons/
- the caliper brackets were either original to the car or replaced with the brackets from Mazda Comp if they are included
- both subframes look straight and the car aligns to spec. I measured and compared distance between attachment points of the control arms on the rear subframe with a known good spare I have and it looks good.
Under hard braking in a straight line setting up for a turn, the car will pull pretty hard to the right requiring me to add a decent amount of steering to the left.
Most noticeable setting up for fast right hand turns like Turn 10 at Laguna where it literally feels like the rear wants to step out on me under braking.
Not as noticeable on slower turns like T3 at Thunderhill which don't require much braking.
I don't really notice is on left hand turns like T1, T2, T6, T8 at Thunderhill. Car turns in and sticks nicely there. Heck, braking and turn-in is probably helped by the pull on those turns...
What I have done so far:
Local race shop checked, "mic'ed" and lubed the calipers and caliper brackets. I had already checked all the sliders and bled brakes various times w/ no change in behavior.
Already re-torqued all the bolts on the suspension, brakes, subframes to unibody, diff and PPF.
Car's been aligned a couple of times but I'm starting to doubt the accuracy of the alignment after checking Toe settings with a set of Longacre toe plates I bought recently. I'm seeing 1/4" toe out in the front and about 2 mm toe in rear. Not sure if the toe is square though since toe plates won't tell me that.
I recently replaced front pads and noticed that they had a huge taper from "front" to "back". I'm thinking this wear pattern is consistent with braking while the steering wheel is turned left. Pic for reference of "front and back":
What should I check?
I've wondered about dynamic toe changes from the weight transfer that happens under braking caused by something like a bad bushing but not sure if that sort of thing happens with the Miata and, if it does, which bushing? I don't notice any play in any of the bushings when prying on them with the car on jackstands. Is there anything else that would cause dynamic toe changes?
Could the pax rear caliper that I linked to above cause something like this since it is different from the others? Maybe the piston doesn't move as freely b/c it's not a smooth, polished surface?
Input is greatly appreciated!