Reading your tire wear - info thread

[Synner]

While everyone seems focused on what tire to run, I haven't read anything about reading and understanding what your tires are doing so I thought I would share some info and experience from my most recent track day.

Knowing what is going on with your tire after a session can tell you how to tweak air pressures as well as tell you if your suspension is set right. Typically toe and camber settings, and air pressures, can show themselves in how (and where) the tire is wearing as well as their temperature. The average person going out once or twice a year may not need this level of information but for people that are advancing to higher levels will want to know.


Instead of copying a bunch of material here are a couple links that explain it in greater detail.
http://www.elephantracing.com/techtopic/tiretemp.htm
http://www.turnfast.com/tech_handling/handling_pressure

This chart from the first site is probably the most concise representation of the information.
Symptom & Diagnosis (ok so the chart format didn't work at all)
Center hotter than edges
--Tire pressure too high. Reduce 1 psi for each 5' F delta.
Edges hotter than center
--Tire pressure too low. Add 1 psi for each 5' F delta.
Inner edge hotter than outer
--Too much negative camber.
Out edge hotter than inner
--Not enough negative camber or too much toe-in.
Tire below ideal temperature range
--Tire pressure too high, tire too wide, or springs/sway bars too stiff at that axle.
Tire above ideal temperature range
--Tire pressure too low, tire too narrow, or springs/sway bars too soft at that axle.
Front tires hotter than rear
--Car is under steering (pushing). Too much front spring/sway bar, not enough rear spring/sway bar, front pressure too low, rear pressure too high, front tires too narrow, rear tires too wide.
Rear tires hotter than front
--Car is over steering (loose). Too much rear spring/sway bar, not enough front spring/sway bar, rear pressure too low, front pressure too high, rear tires too narrow, front tires too wide.

[Synner]

Reading your temperatures. While some people will consider using an IR gun that you can get for cheap they're not ideal for getting readings. They're only looking at the surface and they also measure an average temp over the surface area. So you will get an average based upon how far away from the tire you hold it. Not ideal when trying to get inner/middle/outer temps with clarity.

The correct solution is a tire pyrometer. It will read the subsurface temp using a small temp probe that goes into the tire about 1/8-3/16". Their price for base models isn't unreasonable. The ones that have memory functions are ideal but you can get cheaper ones that don't. But consider this, getting the temps as fast as humanly possible after a session will give you the most accurate temps. So instead of trying to unhook your harnesses, find a notepad and pen, and going around taking and recording temps why not get one with memory? It will be far simpler pulling a temp probe out of your console and getting 12 temp readings fast. Don't take an overly long cooldown lap either on the sessions you want to record temps, they will only reduce fidelity

My next purchase will be a decent pyrometer. Here is an example and the one I'm considering as of right now:
http://www.jegs.com/i/JOES+Racing+Pr...55016/10002/-1

Another example but it doesn't mention memory capability so not a front runner:
http://www.jegs.com/i/Intercomp/541/360012/10002/-1

If anyone has models to recommend let me know and I will add them to this thread.

[Synner]

So here is my brand new Michelin Super Sport (295/35/20 ferrari spec on 20x10.5" rim) front tire after my most recent track session. The rear tires were even worse but tougher to get a picture of. Partly because of a lack of camber and partly because I prefer driving with some oversteer. The tires both front and rear were warm enough that I could deform the tire with my fingertip, you can see that they began to melt from the heat. Letting out air from my front tire gave me a burned fingertip, those suckers were HOT. For perspective I was keeping up with, and passed, a Ferrrari 430 Scuderia, in the advanced run group. My fluid coolers and brakes were working excellent until I threw a belt towards the end of the day. I'm hard on the car but it was dealing with it very well after overcoming my consistent brake issues. The tire tells me 2 things. I was fighting too high of tire pressures and at -3.25 degrees somehow I could probably use a tad more camber.

1) The center has more wear than the outer portions. I was taking out 5psi of air like I had done with my Pirelli's however I was seeing an increase of up to 9psi due to how much harder I was driving.
2) The outside was clearly much hotter than the inside and I could pick pieces of tire off with my fingers. I will see what I can do to get more camber as I don't see this as a toe issue. I was surprised that -3.25 wasn't enough. I will be able to learn more when I take temp measurements. Visual inspection isn't ideal but clearly I have some issues and is the "entry level" of reading tires to adjust your suspension. The stock tires on -1.2deg were losing chunks on the outside and worn down badly. Insides looked brand new.

Hopefully my dialing in my cars suspension will help others understand what their tires are telling them. If you have any info or pics please share with your tire type, suspension settings, and how you're changing things to make an improvement.

[White_SS/RS]

Great thread idea. Interesting that your tire looks like that with 3.25 deg of camber, What pressure are you running up front?

[Synner]

I was trying to keep it 35-36 which I've found to be the sweet spot but because of learning the new tire and driving it at the limit it was getting up to 41. Far from ideal, and what I attribute the center wear to, so I will be starting out around 27-28psi and go from there on the next day. I was surprised by the 10 degree temp rise but I was driving very hard.

The pirellis were ok starting at 31-32 and taking out 3 psi at the end of each session.

[NJ Drive]

The wear you're seeing is indicative of a non-shaved tire with wide siping. I'm certain you'd see better results with either shaving or choosing a better tire for track day use. Unfortunately the lack of options in 20" for the moment kind of suck.

[Synner]

At this point I'm avoiding pure track tires that are closer to slicks due to cost and longevity.

Although I find it interesting that Discount tire offers that as a service. If only they had the sizes I use. I haven't seen anything on tire rack about the service.
http://www.discounttire.com/dtcs/tireSiping.dos

[NJ Drive]

Tire Rack it's $25 per tire shaved and you have to call in your order to get it. I've talked with them multiple times to offer it as an option during checkout. Not sure why they haven't yet.

Just to be clear, shaving and siping are two different things.

[Synergy SATX]

OH EM GEEE

This is thread I have been needing for a year...Now I need to take more time off to study. Can I post tire pics for surface level interpretation of what I have going on?

I just stare at the tires and try to figure it out...this is so sweet a thread.

[Synner]

Thats why I made it, to learn from each other. Just post enough detail about suspension, wheel/tire, and alignment.

Too many people worry about tire brand when they should be asking am I using what I already have effectively.

[Nor Cal ZL1]

I was surprised that -3.25 wasn't enough.

Is your car lowered?

[Synner]

Prior to corner balancing my drop was only 3/4". There was no significant changes to ride height afterwards but I don't recall the exact change so I don't see that as the issue.

[Nor Cal ZL1]

Please check your lower control arm positioning. The ball joint end must be lower than the bodymount pivot point in relation to the ground. If not your geometry is reversed from desired.

[cornerspeed92]

I just took these pictures after cleaning the rubber off from Sun. Does anyone know what this wear says?