help me diagnose tire wear please.

#1

Hi all…

I was hoping for some good e 30 tire insight here…

90 325i…spec style set up w/ Koni SAs rather than billies…and RA 1 ( shaved to 4/32) 225/50s on 15 x 7…et 25’s.

car runs at Lime Rock 8-10x per year…mainly rt handers…actually only 1 lt hander

She gets “scalloping” on outside of lt frt tire…

its set up w/ neg 3.2 frt camber…no toe out. Around 32 cold…37 hot( after a cool down lap). She understeers a bit…mostly mid /late corner…stock bars.

all 3 other tire are wearing rather evenly

Im thinking:
excessive push/understeer?
temp or press issue?( Ill take temps in future)
suspension component issue?..altho she seems just fine while on track.
needs more neg camber?

or is it:

all these cars w/ such a conservative set up do that?

tia

Joel!

#2

How often are you rotating your tires? Lime rock will be pretty brutal on the left front. Rotate at a mimimum daily at a track like Lime rock. Also I would run a lower starting air pressure on that left front as well, try 28-30. You should have a pretty significant starting tire pressure difference between left and right tires with the left front having the lowest starting pressure.

#3

I don’t know how similar your whole system is to the Spec setup. What kind of tires?

I don’t believe scalloping is the result of any of the causes you list. Most of the guys here run all new/newish bushings, Spec bars, strut tower brace, and RA1s or R888s. I think you may have worn out suspension components.

With stock bars and no strut brace, I doubt you are keeping much of that static 3.2 deg of camber in the turns.

With unadjustable bars, you can play with toe, pressures and trail braking to eliminate the mid- and late-corner push. Are you getting on the throttle too abruptly and transferring too much weight back? (Not that you can really tell when you are on the throttle in an E30…:laugh: ).

Rotate the tires and save up for sway bars.

#4

Simon…

I know you know that track…I only rotate like every 3 days( 9-12 x 20 min sessions)…Ill get it done more.

Steve…

perhaps its not as “spec like” as I implied…my bad

RA1’s…HR race…koni’s…stock bars…poly bushes…

no obvious components that are “worn” out…but Ill re check everything.

#5

I would say try one of the following:
increase tire pressure
decrease tire profile. ie run 225/40
increase negative camber
increase caster
get a stiffer front anti-sway bar

If you have excessive understeer I would suggest straight toe in front and increase toe out in back. But then again I’m more of expert when it come to autoxing E30s. You can’t go wrong with a stiffer sidewall and lower profile tire if your class allows it though.