Grabbed_Crow_Mobe

My question: Can low tire pressure cause premature outer edge wear similar to not having enough camber?

I recently just did two HPDE events on a set of Toyo R888 tires and was my first time on these tires. When I bought them I had a more aggressive alignment done (compared to stock). After two events, the tire wear is uneven towards the outside of the tire. Normally I would just assume that the camber setting isn’t aggressive enough. However, I did a few sessions with the tire pressures way too low. I’m curious to know if this could be the problem or the camber settings. Or both. I am going to rotate the tires (remount the fronts and rears on the opposite side) to give me some more life out of the tires. I’m also curious to know if I need to get another alignment. Any input would be greatly appreciated.

Specs:

2005 C6 Z51
Front Tires: 295/30/18 on CCW 10”
Rear Tires: 305/35/18 on CCW 11”

I had the alignment done based on pfadt recommendations for a “performance street” car. “Track use with race tires”. This is what I ended up with:
Front:
Camber = -1.7
Caster = 8.5
Toe = -.05

Rear:
Camber = -1
Toe = -.11

Bill Dearborn

You probably don't have enough camber. After playing around with pressures for a day and having somebody else drive my car I settled on 30 front and 28 rear for cold pressures. I have -3 degrees of camber in the front which is in the low range suggested for the R888s.

Here are the R888 setup recommendations from the Toyo web site:

• Operating Temperature: 160°F to 220°F
• Hot Inflation Pressures: 32 to 38 (psi)
• Camber: -2.5° to -5.0°
• Caster: As much positive as possible

Are you referencing toe in as negative or as positive? There seems to be some confusion between the Pfadt numbers and how GM and others reference toe. Pfadt shows toe in as negative and GM shows toe in as positive.


Bill

trapp

Try more aggresive neg camber:

- 2.5 front
-1.5 rear

rfn026

Here's a good rule of thumb about pressures.

If the center temperature is higher than the average of the outside and inside temperatures then the tire is overinflated.

The magic number is when the center is very close to the average of the inside and outside temperatures.

btw - you never said what your hot tires pressure are.

Richard Newton
Tire Tools

Grabbed_Crow_Mobe

Good point. I was trying to keep them hovering around 35 as recommended by Toyo. I started at 32 cold (which is what I used to start at with my run flats) and they got hot quick and were jumping way over 40. I kept taking PSI out and ended up at 35. After the first day I didn’t notice any heavy wear on the outside of the tires.

The second track day I started out at 28 cold in both front and rear. After the first two sessions I noticed the tire wear was way outside the arrows indicated on the tire and the tire wear was heavy on the outside of the tires. I started adding PSI and eventually got to a good wear pattern at 38 or so (depending on the tire). But before that point, there was some heavy wear.

Based on the advice already given on the thread (thanks guys!), I’ll get another alignment. But to reword my original question: Does a low tire pressure with a correct camber wear the tires evenly or would it focus the tire wear to the outside of the tires?

Based on the input provided, I’m going to go with the following numbers:

Front:
Camber = -2.5
Caster = 8.5
Toe = -1/16”

Rear:
Camber = -1.5
Toe = -1/8”

383

So how did that alignment change do?

Grabbed_Crow_Mobe

I wasn’t able to get my car realigned before my last event. I was unaware that you needed to remove the upper A-arm washers in order to get more than -1.8 of camber. However, I was able to remount the tires. I switched the fronts with each other and the rears with each other. This put the more worn outside edges on the inside edge on the opposite side (does that make sense?).

In doing so, I was able to answer my original question. Having the too low tire pressures wore the outside edges way faster. In the last event, I kept the tires pressures much higher (38 +/- range) and the outside edges didn’t wear nearly as badly.

A really cool Z06 owner (C5lion) taught me how to adjust the camber/toe myself by adding/removing shims on the upper arms and adjusting the tie rods. I’m going to an alignment shop this week and setting the car up for street and for the track and take notes about the different shim settings and turns of the tie rods to get from one to the other for the front (going to leave the rear alone).
I’ve decided on the following settings. I also purchased a pyrometer and will post my results after my next session.
Street:
Front:
Camber=-1.5
Caster=8.5
Toe=0

Rear:
Camber=-1.5
Toe= 1/16th IN

Track:
Front:
Camber=-2.7
Caster=8.5
Toe=1/16th OUT

Rear (same):
Camber=-1.5
Toe= 1/16th IN