Tire Question for our track experts

[PAvenomRT/10]

I am relatively new to the track and high performance driving having only started a year ago. My question relates to tire durability and safety and when they should be replaced. I have searched the forums and found several posts relating to how many heat cycles one can expect from track tires. However, that seems subjective as different tracks will heat tires differently along with different weather conditions, etc. My question is what is a more objective method for determining when track tires need to be replaced? Is change in durometer measurements the best method and is there an "absolute" durometer reading when a tire should be replaced?
I am currently running Michelin PSC's.
Thanks for any and all input.
PAVenom RT/10

 

[Paul Hawker]

Difficult to have a hard and fast rule here.

Fresh, scrubbed tires stick the best. Each heat cycle will degrade the performance, and tire wear is also a factor.

Some wear out the tread before heat cycles become an issue, while others tend to change them out even with some rubber left because they are too slick.

Some keep an older, worn tire to "use up" on practice days, then switch to fresh tires for mortal combat.

With track experience you will know when they are going away, as the durometer is not the final answer.

Busy track guys usually end up with a trailer full of somewhat used tires to throw on, as well as a fresh set for the finals.

 

[Chuck 98 RT/10]

They lose grip but that doesn't mean there's a safety issue, you can track them to the wear bars just like on the street, your laps times just won't be as fast. For any guy that drives a fresh tire like he drives a tire that has a dozen cycles the safety issue isn't with the tire it's with the idiot driving.

 

[viper067]

Since we have a tire question post, I'll add to it ...

What constitutes a warm tire? Just playing with toys, and my new TPMS has a temp sensor ... on highway speeds, the tires would warm to about 120 or so. At the track they would get up to about 170's. The TPMS is preset to alarm at 180 .... so what temps would you expect good tire grip at and what is the real alarm temp for a Z rated tire? I have Kuhmo XS's.

For the tire pressure question ... if I generally run 30psi on the street (sidewall says max psi 40) what should I do at the track? add a few psi, remove a few psi? Starting at 30 psi, the last track day they would increase to about 35 psi

 

[Chuck 98 RT/10]

You probably already know this but for the sake of those who don't, immediately after lapping take three temp readings across the face of the tire. Outside, middle, inside. If the middle is 10 -15 degrees higher than the outside and inside then there is too much pressure. If it is 10-15 degrees lower there is too little pressure.

Sorry about that annoying TPMS. Sports cars should have been exempt from that government mandate.

 

[Shandon]

Get a good Pyrometer and measure the temps accross the tire (NOT the surface temp!) Keep a log of tire temps, pressure cold/hot etc. With any tire just work up to the limit of adhesion on the track. Don't go 100% on lap one but work up to it and let the car and "sotp" tell you if its not holding like you want it too. I have a set of Hoosier R6 im going to burn up next wednesday. They are a bit old but hardly have any heat cycles on them. So im not sure how well they will stick but I will work up too the limits they give me.

 

[Leslie]

What Shandon said is what I do as well!

I don't race, just HPDE's.....but this is what I do...If you need to, have someone standing at the grid so they can take your temps.

Outside weather, which track, heat cycles, all of that play a factor.

Keep a log book.

Listen to your 'seat gauge'.

 

[witz323]

I was going to post some tire wear questions this morning, but someone beat me to the puch. Great thread, and thanks for some of the info already. One question to Shandon...Can you explain how to measure the tire temps across the tire versus the surface temp?

My next question relates to tire wear, and when the tires should be replaced. I installed a new set of PS2s on my '04 last summer. I ran 3 track days (HPDE's, no wheel to wheel racing), 3 autocrosses. Overall I'd say the tires have 3,000 miles on them between track days and street driving. Can I expect to get another track day or two out of these? Is there a specific tread depth I should have? A good rule of thumb would be great to know. Am I crazy to think that I should be getting more than 3 track days and 3 autocrosses out of a set of PS2s?

 

[Shandon]

I was going to post some tire wear questions this morning, but someone beat me to the puch. Great thread, and thanks for some of the info already. One question to Shandon...Can you explain how to measure the tire temps across the tire versus the surface temp?

My next question relates to tire wear, and when the tires should be replaced. I installed a new set of PS2s on my '04 last summer. I ran 3 track days (HPDE's, no wheel to wheel racing), 3 autocrosses. Overall I'd say the tires have 3,000 miles on them between track days and street driving. Can I expect to get another track day or two out of these? Is there a specific tread depth I should have? A good rule of thumb would be great to know. Am I crazy to think that I should be getting more than 3 track days and 3 autocrosses out of a set of PS2s?

Us a Pyromater that has a small pin that goes into the tire just enought to give you the internal temps at or near the belts. I have seen some people use the laser temp readers and they do the surface temps and not all that accurate in my book unless its right in the pit. When you come off the track and into the paddock you loose temp off the surface and if you go through a puddle of water etc. before you park you are screwed with a surface temp. With the pyrometer you take three temps accross each tire. Right them down take air pressure readings etc. adjust accordingly with temps and or alignment setup.

Can you get more than 3 track days and 3 Autocross out of a set? YUP and NO hows that for an answer heheheh Depends on how hard you are on them or how rough the track is on them? I have PSCups and I have gotten nearly 5 track days on them. Two years ago those same tires would have lasted me through 12 track days since I was not nearly the driver I am now (and im not anything to talk about just improved over what I was). Im sure some day I may only get one or two weekends or less out of a set of tires and I might need to sell a kidney or something to keep doing this

 

[witz323]

Is there a tread depth I should not go below for a track day? Once again, general rule of thumb.

 

[SoCal Rebell]

10 years of heavy track experience has led to a few basic conclusions regarding tire wear on a Viper, Hoosier R3s are good for about 16 sessions normally 4 track days. But you can run them until they cord but you will have slower lap times, check front tires after every session after 12 sessions for cording. A course surfaced track will cord faster then a smooth surface. On PSC on a Gen IV ACR I got between 16-20 sessions on the fronts at Willow Springs then they cord, rears will another track day and then they are dead.

 

[witz323]

SpCa; Rebell...any input on the PS2s?

 

[Dom426h]

If the middle is 10 -15lbs higher than the outside and inside then there is too much pressure. If it is 10-15lbs lower there is too little pressure.

Chuck, you must have some sort of special tires with 3 separate chambers in them if your getting a diff psi across the tire, lol

One question to Shandon...Can you explain how to measure the tire temps across the tire versus the surface temp?

My next question relates to tire wear, and when the tires should be replaced. I installed a new set of PS2s on my '04 last summer. I ran 3 track days (HPDE's, no wheel to wheel racing), 3 autocrosses. Overall I'd say the tires have 3,000 miles on them between track days and street driving. Can I expect to get another track day or two out of these? Is there a specific tread depth I should have? A good rule of thumb would be great to know. Am I crazy to think that I should be getting more than 3 track days and 3 autocrosses out of a set of PS2s?

Use a probe, Not an Infrared/Laser sensor:
http://www.longacreracing.com/catalog/catlist.asp?catid=7

I got 2 years, over 10Kmiles, 4 trackdays, 3 autocrosses out of my Nitto Invo tires. I would expect the same out of most Performance/Summer street tires. However, the INVO's kind of **** for performance events as they have a soft sidewall that rolls over if you dont have enough psi in em but then that screws with the contact patch. Recently switched to the NITTO NT05's for the NJMP ViperDays event this past weekend and felt more secure around turns. Also, now running a more agressive alignment with 1.5deg camber front, and 1.0 rear. I recommed you tweak to similar specs if your still running the stock alignment.

Is there a tread depth I should not go below for a track day? Once again, general rule of thumb.

Not sure, but i would personally take a set of street tires on the track untill there is No tread left on the inside several inches. Especially if they are only a couple years old.

 

[SoCal Rebell]

SpCa; Rebell...any input on the PS2s?

I ran the Pilot Sports the first year I raced and at Viperdays. If I were to guess I'd say 10 track days but it's hard for me to be exact because I tracked a 2000 Viper with no ABS and I would occasionally flat spot the fronts and have to have the tires shaved. They got through 3 Viperdays events in 2002 and the Nationals at TWS which was about 8-9 track days and they lasted well until I had a major lockup at TWS and had to trash them and buy a new set from Archer.

A good indicator is the treadwear rating, the higher the number the harder and longer lasting the tire is:

Hoosier R3S06 = 40 rating
Michelin Pilot Cup = 80 rating
Michelin Pilot Sports 2 = 220 rating

I also heard good things about the new Michelin Super Sports

 

[ACR steve]

Brand new R6's and brand new cups will be shot (no rubber left) after 1 weekend on my car. (Stock ACR) for me heat cycles mean nothing

 

[SoCal Rebell]

Brand new R6's and brand new cups will be shot (no rubber left) after 1 weekend on my car. (Stock ACR) for me heat cycles mean nothing

Are they corded after one weekend? I can usually milk them for 2 weekends (4 days) but that was on a slow Gen 2. I never ran Hoosiers on the ACR just the Pilot Cups.

 

[ACR steve]

SoCal- Yes I was very surprised the fronts were gone. The wear was even across the whole tire . On my race car I can get 2 X 30 min races and qualifying and 1-2 practice sessions and it still has tread just heat cycled out. I figured on the Viper I would get good wear I was shocked when I looked at the tires Sat. night when I went to rotate front tires.

 

[Magnus_]

When measuring tire temps you really need to exit during a hot lap session and try to get to your pit asap to get good readings.

Cool down laps or too much time will skew your readings.

I actually posted some good tire readings here:
http://forums.viperclub.org/threads/646174-My-Road-America-results-more-2-26-s..

 

[witz323]

Hey Magnus, that was a very interesting thread on tire pressure, temp and set up. RA is my favorite track in the country mostly because it's in my backyard. I'll be running there in August w/ the Shelby Club, really excited about that.

Do you have any experience with the PS2 tires? If so, what kind of pressures were you running in those?

 

[JonB]

LOTS OF GOOD ANSWERS ABOVE....

I have to add: taking the 3 temps and a pressures as Chuck suggests, and doing it MID SESSION, is the abslute best way to assess correct inflation pressures.

If you DONT have a performance alignment, you WILL eat up your outside shoulders much sooner....ESPECIALLY PS-2 !! That PS-2 tire is track and autocross vulnerable to an OE 'flat-footed' alighnment. GOTTA HAVE NEGATIVE CAMBER to make a PS2 endure on track....yes, your inner shoulders will wear out, but they can be sacrificed for faster cornering. Theyll wear out when the rears do!

Have Fun and Be Safe

 

[Chuck 98 RT/10]

Chuck, you must have some sort of special tires with 3 separate chambers in them if your getting a diff psi across the tire, lol

You got me there. Hey, it was 7 AM.

 

[witz323]

JonB, of course I have a track allignment...You're the one who gave me the specs when I purchased the PS2s from you. Car handles amazing by the way. Do you have a good tire pressure suggestion, hot & cold, for road racing?

 

[ACR steve]

36-39 hot see what feels best to you. I like the lower side but some guys like the higher side of those numbers