SIK02SS

iTrader: (11)

When it comes to road courses, not completely no.

Things to consider:
-tires have there own spring rate (similar to your suspension springs) based on sidewall stiffness and rubber compound
-cars of the same weight can have drastically different cross weights and different camber/caster causing different wear and likewise will build tire pressures differently
-track surface temperature and outside air temp

and then as I mentioned before: every different tire has it's own sweet spot for every driver. Only the driver can be the judge; is the car over steering, under steering, etc..

Let's just say Hoosier Tire and I do not agree on tire pressures (hot and cold) with my Corvette. Likewise I've ran tire pressure similar to a Panoz GT2 (in this situation we were similar weight) car that worked for him, but were not even close to working for me. I could immediately tell the difference in just the first race lap and it got progressively worse

I'd be willing to bet that 90% of novice drivers who think they need to buy new mods to make the car do something different, really just need to learn there tire pressures and how they can affect what the car does

Big Bu Bu

iTrader: (4)

Great thread. It's tough to tell a gear head not to modify his car when so much of the enjoyment comes from the tech aspect of motorsports. That being said, there is plenty of great advice dripping out of this thread about looking at the big picture on how to go faster and enjoy it more. Skill and experience along with a well thought out mods make all the difference. Tires have always been a contentous debate. The real reason I moved to dedicated track tires was because I was tired of gobbling up $1200 a year in street tires taking my car to 3 ot 4 track weekends a year. As soon as I was ready, (and I asked for lot's of advice first from my advanced buddies and instructors if I was ready) I started to pick up some R comp scrubs for about $400 a set. One thing for sure is that I was glad I spent a couple years on street tires because R compounds are a game changer.

SVThuh

iTrader: (2)

Let me try to help a bit here.

Track surface, car weight, cross weight, brake bias, track temp, tire compound and drivers skill/style all come into play.

I went to Buttonwillow raceway yesterday and after I learned the lines and started getting faster and faster, I quickly noticed that while my front tires were dialed in pretty well and were offering up loads of grip, the rear tires were overinflated and slipping pretty badly and needed to be deflated a bit.

I was running the exact same pressures that I run at Willow Springs big track, but because Buttonwillow is a lot tighter and more technical, and the surface is patched quite a bit in spots, its a bit more slippery. The Offramp especially was bad. I would brake hard, hit the apex and get back on the gas only to have the rear end step out on me.

Once I dropped the rears down a total of 7 hot PSI, it was a whole different ballgame and corner exit felt much more balanced and controlled.. I was able to get on the gas a tad sooner and harder which means my corner exit speeds were increased and my laptimes decreased.

Now I know what tire pressures to run at Buttonwillow, and will use that information as a baseline. It does not necessarily mean that I will run that pressure, but it gives me a good starting point for when I go back.

Even at Willow Springs big track, I am constantly adjusting pressures throughout the day to get it dialed in. I know where to start now and I adjust as I go. Checking tire pressures and temps.

qwikz28

iTrader: (12)

All great info, but I doubt I am anywhere near the point where a few psi differences would make a noticeable difference. Still very interesting stuff though.

SVThuh

iTrader: (2)

You might be quite surprised. Take a tire pressure gauge with you next time and if you feel the front start to push a bit or the rear start to walk out on you, adjust accordingly.

Remember hot pressures are a lot different than cold. With my NT-01's I can hit the track with a cold temp of 35psi and come off the track (after a cool down lap) with my pressures in the 40-45psi range.. That makes a BIG difference!

qwikz28

iTrader: (12)

I notice it on the streets for sure. I have Falken Azenis 615s and despite having very stiff sidewalls, the car doesn't turn-in as predictably if the tire pressures fall below 35psi hot. I bumped up my tires to 38 hot before the HPDE. Although I can tell the difference in turn-in, I don't think changing the tire pressures would affect lap times just yet. Hopefully when I get better.

I have to say though, those Falkens grip like mad when they warm up. I can't imagine what stickier tires feel like. You guys seriously have some ***** to push your cars as hard as you do.

SVThuh

iTrader: (2)

A lot of us are on tires that dont really fall off in terms of grip when the tires get hot like your Falkens eventually will.. NT-01's and Toyo RA-1's wont heat cycle out like a street tire will and will offer better grip longer, which will allow you to go faster.

SIK02SS

iTrader: (11)

typically it works the other way around, if you are struggling to get the car to turn in (the front end wont turn..understeer), you drop a couple pounds of front pressure. If you have a lot of tread on good tires and your rear end starts coming out a lot in corners, drop pressures.

qwikz28

iTrader: (12)

Sik- It isn't so much that the car doesn't turn in, but rather it feels unpredictable like you could feel the sidewall flexing. That's when I pump up the tires. I never thought to drop the tire pressures to avoid understeer, I usually just take that to be me taking the turn to fast for the car's grip.

SVThuh- I haven't reached that point, but I hear these Falkens get greasy after getting too hot on a heavier car like ours. I see what you are saying though. Interesting stuff. Do you, personally, run those dot-r's on the street?

JimMueller

iTrader: (9)

Since the topic sort of turned towards tire temp/pressure, I seem to have encountered conflicting opinions on how to set the pressures. Books seem to indicate to use a pyrometer to get the temps linear/even across the surface. Others with experience have said they've done better adjusting the pressures effectively by the seat of their pants.

While I prefer the ease of using a probe pyrometer, is there more to it than blindly trusting the pyrometer? My current process is to park the car absolutely as soon as safely possible, note in/ctr/out temps on all tires, then take pressure readings in the same order. I try to adjust center temps by using the rough formula 1psi=3*. Although I think I should be beginning on a specific tire based upon track design, I usually forget to do it.

SVThuh

iTrader: (2)

I use a pyrometer, but only to get an idea of how hot the different portions of the tire are. I may use that info to adjust pressure, but generally will use the info to get an idea of how hard I am on the tires and then adjust my driving style accordingly.

The tires will cool off WAY too much to get a good idea of running temps after the cooldown lap. Even 2 minutes at a cooldown pace (60% or so of lapping pace), the temps can fall off as much as 30*. Running your car hard, getting everything up to temp and then just shutting down and stopping to check temps is a good way to break stuff.