kdm123

I posted in a longer thread elsewhere, but I'm posting it here to get other opinions. What do these tire temperatures tell you, and what do you guys think of these alignment specs?


This is from a test day at Willow yesterday, 6/15. I drove my ’03 Z06, which has most of the spec Corvette suspension on it (coil overs, sway bars, but stock bushings) with mid-level brake mods. I just had a new alignment put on the car, and I noticed that it understeers more.

Conditions: 80 degrees.
Tires: Federal RS-R (285 18s, stock 10.5 inch wheels) with a few heats cycles, and Hoosier R7s (298 18s, and 315 18s, both on wider wheels) also with a few heat cycles.
Alignment specs: Front: 2.6 camber, zero toe. Rear: 1.6 camber, zero toe. I should know my previous alignment, but I’ve forgotten. But I had did have toe front and rear. I told the alignment guy at a race shop to set the alignment to whatever he thought best. I was surprised that he took out all the toe.
Important note: before taking these temperatures, I came in hot off the track, with the last two corners (Turns 8 and 9) being fast right handers.
Subjective impression: on Federals, the car felt more understeery than in the past, but I was able to get power oversteer. With the better traction of the Hoosiers, the car felt even more understeery, and I was not able to get much power oversteer.

Run #1: Federal RS-R’s
Cold pressure (set at 70 degrees ambient temp): 27 psi front and rear.
Hot pressure: 35 psi on the front and rear tires on the right side of the car, and 36 psi on the front and rear tires of the left side of the car.
Left front: 208 outside, 193 middle, 187 inside
Right front: 147 outside, 152 middle, 179 inside
Left rear: 199 outside, 195 middle, 188 inside
Right rear: 142 outside, 155 inside, 170 inside

Run #2: Hoosier R7’s
Cold pressure: 28 psi front and rear (set at 80 degrees ambient temp)
Hot pressure: forgot to take hot pressures
Left front tire: 160 outside, 175 middle, 199 inside
Right front tire: 138 outside, 148 middle, 175 inside
Left rear tire: 143 outside, 164 middle 189 inside
Right rear tire: 143 outside, 162 middle, 173 inside

kdm123

FYI the Federal tires are a very cheap tire. They cost $500 a set. Both the Federals and the Hoosiers that I ran had a few heat cycles on them.

SocalC5Z

I'm very familiar with WSIR and run a 02 C5Z as well. Your tire temps seem to coincide with what I've seen running Nitto's and Maxxis R comps square with stock bushings. Speaking of the 1st temps, the left side would benefit from more negative camber based solely on the temps you posted. Like in my car, the control arm bushings compress and you loose negative camber and the outside of the tire does most of the work in 8-9 and the temps validate that. I would leave it for now. Running much more than 2.5 neg camber impacts front grip under straight line braking and made my car unstable for turn in. I personally like a little bit of toe but I don't think that is causing your understeer.

It's important for anyone else reading this tread unfamiliar with WSIR to understand that the right side tires coming in hot off of turn 9 have had nearly a mile to cool down from T5, so those temps are not going to give much data.

IMHO, I'd step back from tire temps and alignment for now and try to get the car balanced. The coil overs and sway bars is where I'd start. I'd either soften the front bar, stiffen the rear, and if that didn't produce an improvement, talk to others running the SPEC coil over package about spring rates and consider going to a lower (softer) front spring. Just typical advice I know...but it's where I'd start. .

Hi Volts Z06

Your really talking apples and oranges here trying to compare a street tire to an R-comp. As you see from you tire temperatures there is radical difference in how the two tires behave with the same setup. You really have to perfect your setup with ONE tire package before trying to compare. Tire pressures are going to dictate a lot but the one thing you seem to state is that the Federals are a square setup whereas the Hoosiers are a stagger setup which by nature is going to make the car push. Pick one tire and optimize the setup by experimenting with tire pressures. Just a one or two pound difference will show in the tire temps. You don’t make any mention of shocks so I’m assuming your non-adjustable so you might be better off staying with a square setup to keep the car neutral.

Your alignment settings aren’t too radical for an occasional street car that sees track duty but at the expense of accelerated tire wear from street driving.

kdm123

Thanks for your responses.

The Hoosier temps make sense to me. The Federals' temps are weird though. On the Hoosiers, the inside temps are highest across each tire, which makes sense due to the negative camber. But on the Federals, the outsides of the tires have the highest temps. Is this because the tire is rolling under?

Hi Volts Z06

Correct. The Hoosier is built as a purpose built, track specific tire that's intended to run around 3 degrees of camber and it's construction is that it doesn't roll over. The Federal is a street tire which despite it softer compound is still intended for street applications. A street tire is always going to roll over like that hence your unusual tire temps. You might experiment with tire pressures on the Federals to see if that has any effect. Move in one to two pound increments and log the temps to see if you can effectively shift them a bit but honestly- you're really not horrible where you are at. You might find that every tire needs it's own pressure.

On the street tire you probably need a little more pressure. That 208 number is getting past the limit of what I think a street tire will tolerate. More pressure will bring down temps. While the left rear looks just about perfect- you might try seeing what happens with another few pounds (in terms of both high temp and temp across the face).

Jfryjfry

kdm123

Looking only at the Hoosier left side tires (since they are not doing weird stuff like the Federals doing rolling over, and since I'm coming off two long rights), it seems like I have too much negative camber since my inside edge temps are about 40 degrees hotter than the outside edges.

However, Hoosier recommends 2.5 to 3 degrees of negative camber for their R7's. This is what has me confused.

Robert R1

What pace are you running relative to cars of similar nature? Is this the same car setup that Oli and the other guys are running in their spec corvette series?

If you're not loading up the tire aggressively enough, it won't generate heat/temp and if your temps are too low, the car will probably feel nervous when trying to push.

Atleast poly bushing are probably a safe bet as the stock bushings in the C5 and C6 are pretty awful. A camber kit is also advices so you don't get movement and keeps the settings locked in place.

Your hoosier temp disparity was the first thing that popped out.

kdm123

The temperature of the inside of the outside (left sided) tires is right in the correct range. Disregard the inside (right sided) tires because the car is coming off two long rights before coming hot into the pits.
Looking only at the Hoosiers, and looking only at the left-sided tires, I don't understand why the inside edge is running so much hotter (40 degrees) than the outside edge of the tires. It's the same on the front left and the rear left tire. According to Hoosier, you're supposed to run 2.5 to 3 degrees negative camber when using their R7s.

fatbillybob

At this hot pressure you need less air pressure LR (try -3lbs) and need more lateral loading. That will balance out the temps on all 4 tires. Do you have any lat G data?

kdm123

I posted this thread back in May. It was my old set up, prior to doing more to the suspension and getting a proper alignment and corner balance.

fatbillybob

Not sure how my post got here. Was ment for other thread.

strano@stranoparts.com

With negative camber as you roll around the track the inside will stay hotter than the rest. Also how are you taking temps? IR isn't a great way to do it unless you are doing so at speed (read fancier setups). There is a reason you see tire techs @ IMSA, Indycar, etc using probes to take temps immediately upon the car getting into the pits. Also notice they tend to run as hard as they can until they have to slow down to keep the tire working as hard as possible to get the most accurate temps. In other words, your LF might be, dynamically, more even than it looks.

My question would be wear. How are they wearing? That's a better, easier way to see what is happening if you can't get the most accurate temps you can. If a tire truly runs hot somewhere you will see it in accelerated wear.