Tire Contact Patch and Vehicle Stability - Alignment

[churchx]

Yes, imho bad one. With toe misset there might appear all sorts of handling issues, and toe should be dialed much more precise then camber, so without some means to properly measure it .. better not. (it's possible to DIY alignment using strings method, but imho it's major PITA and takes lot of time. Much better is to do alignment in shop on alignment rig while having coffee ).
Then again, i'm sure that you'll take first trackday, in car you are not very familiar with if driven on limits, rather lightly, so there won't be THAT bad of issues. But i'd do more optimal alignment prior next one.

[ZDan]

Originally Posted by gcmak

This will be my first ever track-day with the BRZ and RWD car. I'll have photos after this weekend.

Hopefully I won't get roasted for asking but...since there's a strong consensus that 0 camber is not good for track, absent the shop willing to redo my alignment for free (I haven't asked), I could add negative camber by adjusting the bolts myself. I know that'll impact toe too. Bad idea?

I think it might be a fine idea, I bet a 6-pack that the reason your toe is out is that they just took away all your front negative camber, then saw that the toe change was still "within spec" and called it done...

[femaledog]

Originally Posted by ZDan

I have no instability whatsoever under hard braking at the track

I have mental instability under braking

[strat61caster]

Originally Posted by ZDan

I think it might be a fine idea, I bet a 6-pack that the reason your toe is out is that they just took away all your front negative camber, then saw that the toe change was still "within spec" and called it done...

+1 I bet you end up right back at your before numbers


imho your (OP's) instability has to do with your almost zero rear toe, tweak that in a bit to ~1/16" total (0.05° to 0.1° per wheel) and it should be a lot better. Seems like they're used to setting up awd subarus where they understeer so hard that some people like to toe out the rear to help it turn. This ain't a wrx.

[gcmak]

Originally Posted by churchx

Yes, imho bad one. With toe misset there might appear all sorts of handling issues, and toe should be dialed much more precise then camber, so without some means to properly measure it .. better not. (it's possible to DIY alignment using strings method, but imho it's major PITA and takes lot of time. Much better is to do alignment in shop on alignment rig while having coffee ).
Then again, i'm sure that you'll take first trackday, in car you are not very familiar with if driven on limits, rather lightly, so there won't be THAT bad of issues. But i'd do more optimal alignment prior next one.

Yeah no DIY alignment for me - I've seen the tutorial Donut Media and other channels have made for it and I draw the line of my DIY abilities before alignment lol.

Yeah I don't plan to drive balls out at all, especially not on these sporty Eco tires and would love to drive home with a car that is in good shape minus some of the consumables.

Originally Posted by ZDan

I think it might be a fine idea, I bet a 6-pack that the reason your toe is out is that they just took away all your front negative camber, then saw that the toe change was still "within spec" and called it done...

I feel the same way or else they should have been able to get the toe to be equal on both sides. I'll ponder this some more because I do think I'll be very miserable in the turns and the computer will have to use the brakes a ton to intervene or I'll just have to drive REALLY slow. I expect to work my point-by arm but I don't want to be THAT slow on track.

[churchx]

gcmak: rear toe-in should help maximizing exit speed/accelerating out from corners. Which in addition to outbraking heavier cars should help laptimes in car like twins, low power but also lightweight. Also even rear toe-in during reduced grip (winter/rain/gravel) helps track straight with slipping traction without excessive steering corrections.
For next alignment remember hint of reusing lower 14mm OE bolt in top 16mm mount hole. It should help up front camber -1.5>~-2 with no extra part purchase.
Or if going all out for track alignment (depends on planned trackday amount), consider prior it getting also Pedders PED-580096 eccentric top mounts & front lca rear eccentric bushing PFF69-801G by Powerflex, to up total with camberbolts camber to -3deg. Or just those top mounts+current camberbolts+second camberbolt set (for top hole, Whiteline KCA416). And some adjustable rear LCA (eg. cheaper stamped steel ones like spc/whiteline/eibach) for ~ -2.5 rear camber.

[ZDan]

Originally Posted by RToyo86

A few on here suggest 0 front toe and either 0 rear toe, or 1/15 total toe in.
I went with 1/15 toe in on the rear and that setup was pretty fantastic.

One fifteenth of an inch?

Originally Posted by strat61caster

imho your (OP's) instability has to do with your almost zero rear toe, tweak that in a bit to ~1/16" total (0.05° to 0.1° per wheel) and it should be a lot better..

Originally Posted by churchx

gcmak: rear toe-in should help maximizing exit speed/accelerating out from corners. Which in addition to outbraking heavier cars should help laptimes in car like twins, low power but also lightweight. Also even rear toe-in during reduced grip (winter/rain/gravel) helps track straight with slipping traction without excessive steering corrections.

I've never found more toe to feel more stable, sometimes the opposite. I've never had issues running minimal rear toe-in. IMO anywhere from zero up to 1/16" (about 0.15 degrees) TOTAL rear toe-in is going to be fine. Looking at my alignment sheet I'm at 0.07 degrees total rear toe. Seems to work

[Icecreamtruk]

Originally Posted by gcmak

This will be my first ever track-day with the BRZ and RWD car. I'll have photos after this weekend.

Hopefully I won't get roasted for asking but...since there's a strong consensus that 0 camber is not good for track, absent the shop willing to redo my alignment for free (I haven't asked), I could add negative camber by adjusting the bolts myself. I know that'll impact toe too. Bad idea?

I would do it, but it will affect toe a little bit as well. Since the steering is behind the middle of the front wheel, if should toe-in even more, not good, but oh well.

By the way, the whole "unstable while braking" seems like such a moot point every time its brought up. Yes the car might move one or the other direction when braking, but unless you are braking over perfectly flat asphalt, this will be the case anyways. Its not like you are just letting go of the wheel, your hands are on it, you steer the car, not the other way around.

[RToyo86]

Originally Posted by ZDan

One fifteenth of an inch?

LOL
A dyslexic moment.
0.15 degrees...

[ZDan]

Originally Posted by RToyo86

LOL
A dyslexic moment.
0.15 degrees...

Which, funnily enough, is 1/15 of an inch!

[churchx]

ZDan: my experience was on stock shocks though. And before proper alignment i had even less toe then yours and uneven at that. Result was too tail happy on accelerating out and in some tight turns i often got rear out and lost exit speed due correcting .. or lost exit speed if erring on safe side and opening way later and less/during longer distance. In winter on iced road i also disliked car behavior. Extra (vs what was there, after all, isn't +0.1dg/wheel toe-in still within stock alignment range?) rear toe-in fixed all that for me allowing opening sooner/more and way less nervous. On stock shocks/springs and both primacies at very first & PSS level tires later on. Maybe on aftermarket shocks and other spring & damping rates there is less need for toe?

[strat61caster]

Originally Posted by ZDan

One fifteenth of an inch?

I've never found more toe to feel more stable, sometimes the opposite. I've never had issues running minimal rear toe-in. IMO anywhere from zero up to 1/16" (about 0.15 degrees) TOTAL rear toe-in is going to be fine. Looking at my alignment sheet I'm at 0.07 degrees total rear toe. Seems to work

I've had <0.05 degrees total and noticed a big improvement in stability going up to 0.1-0.15 degrees. I wouldn't go that low again unless I was trying to compensate for a compromise somewhere else in the setup. To each their own.

[ZDan]

Originally Posted by strat61caster

I've had <0.05 degrees total and noticed a big improvement in stability going up to 0.1-0.15 degrees. I wouldn't go that low again unless I was trying to compensate for a compromise somewhere else in the setup. To each their own.

IMO dialing in more scrub, i.e. more toe, would be more considered compensation for a compromise elsewehere!

Ive never had any problems running near-zero toe on any of the rear-drive cars I've tracked, including the 550hp FD. I *have* run into godawful handling issues running excessive rear toe-in, both intentionally and unintentionally in unintended "blind" tests where the toe-in was either set incorrectly or drifted off where it had been set.

I wouldn't argue against 0.15 degrees though, I've run that and it's fine. I've never had a car where the difference between 0.15 degrees and zero degrees total rear toe was that big a deal. If the car is well setup, and toe is near-optimal, the setup should be relatively insensitive to small changes in either direction.

[gcmak]

Just an update. I decided to just go full negative on the camber bolts - didn't care about the rest of the alignment - and had a fantastic time with very even tire wear (managing pressures). What a fantastic little car. I found the tires to be super consistent for each 20 minute session beginning to end and really the same experience from start to finish.

I could run consistent 1:58/laps and did a few 1:57/laps - about 3 seconds faster than I can do on Assetto Corsa (with the car setup in a similar way). I will say the game is shockingly similar in terms of how the car reacts and how the steering feels in almost all situations.

Here's some images of the tire wear - really all 4 corners look the same.
There's almost a line at the outer shoulder block that reminds me of fender rub but that shouldn't be the case. I'm assuming it's mostly how the tire is flexing under load/heat and it just wears a bit unevely. I'm not concerned about it at all just curious as to what might cause an almost 'v'-shaped wear pattern vs. a rounded off wear pattern that I'm more used to seeing with cars that lack camber.

(after the first 2 sessions)



(after I got home and cleaned the car)