Instability under hard braking on track, rear cross camber, road undulation, or toe?
 

Hi all,

I took my Performance Pack BRZ to the track for the second time this past week (I am addicted!) I noticed one time that while under hard braking (perhaps not quite threshold braking, I am still working up to being to hit 100% braking later in the braking zone confidentally), the steering wheel danced around on me. The track I was had a lot of undulation and quick elevation change. How do I know if it’s normal or if it’s because my alignment needs work? It didn’t quite feel like the tail coming out (I autocross a lot and am comfortably correcting some entry oversteer).

I got my car aligned at a local FireStone a few months ago. At the time, I was (still am?) at:
0.1 deg toe out in the front
-0.4 front camber
0 degree toe in the rear
-0.7 rear left camber, -2.3 rear right camber (I bought the car new so this big cross camber was surprising).


This was on stock PP suspension. I have SPC 14mm front camber bolts coming in. Wondering if I should get SPC/SPL LCAs and get the car aligned along with the camber bolt install.

While the cross camber is pretty awful, I'd add rear toe in. Absolutely pick up the rear camber arms if it's not too much trouble though, hopefully your Firestone is a good one and gives you what you want.

Based on my measurements as the rear suspension compresses it toes in, conversely as it extends it toes out. So under hard braking you are likely seeing toe out at the rear which makes sense that you feel the car dance around. It may be course or technique related, but the whole point of adjustable suspension is dialing in what works for you.

idk why so many people shoot for zero toe rear, a small amount does wonders for stability basically everywhere and I doubt there's a measurable advantage that isn't given up as soon as the car surprises you.

Agree with the above statement regarding rear toe. I would definitely dial in some toe in. Doesn't need to be a bunch, but I'd recommend some.

The rear camber is pretty bad too. There isn't much adjustment back there, so I'm struggling to understand why it would be off so much from one side to the other. Did you buy the car new? Has it ever been in an accident?

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Just re-read your post.

Given that you bought the car new, my guess is that the tech who set the car up on the alignment reach did something wrong with the right rear wheel/tire given the massive camber discrepancy.

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As in, the tech from the factory? The rear right camber was already super off before my first alignment. I did hit a big pot hole but that the left front wheel so should have had little to do with the right rear.

I know that feeling under braking on the track. A little rear toe in fixed it for me.

You want 0 toe in front or a little bit of toe in.

No, the tech that put it on the alignment rack and provided you with those figures.

The car has to be "set up" on an alignment rack property and calibrated before getting a read out with measurements......it's not as simple as just driving the car onto the rack and attaching the heads......it requires more than that.

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I run 0 toe all the way around and never experienced instability under braking . It sounds like you are locking up a bit up front and triggering ABS.

Are you running stock tires?

I'm running 0 toe and have felt the rear dance a bit under hard braking in certain corners. Always chalked it up to undulations in the pavement, but I'm sure the 0 toe isn't helping. That said, it's never felt like it was going to come around and I prefer getting some rotation under trail-braking.

Thanks everyone!

I am running PS4Ses @norcalpb