Lodi

Sean (sgroer) and I played hooky this morning and made a run to the GA mountains in our GT3s. Headed out at 6:30 a.m. and drove great roads for a few hours. Behind my desk by 11:00. Perfect morning, except.....

Two or three times on tight twisties my backend kicked out when I was accelerating out of the turns. A real eye opener! I've never had this happen in this car before. I have driven these roads a fair amount and we were well within the limits of the cars. Plus, Sean had no issues. He was on brand new MPSC2s. My Dunlops have 5K miles on them with a reasonable amount of tread - 50% plus. I know the Dunlops are not favorites here but I have never had an issue with their performance. Last week the dealership adjusted the air pressure and brought the rears up to 36 psi cold. I was probably at 33 before that. Too much air? Could they be heat cycled out from street driving?

LexVan

What are your rear tire pressures?

5,000 miles. They could be shot. Look at the tread way inside under the car. Need to poke your head under there and really look.

consolidated

36 psi cold starting pressure on a hot GA day could be the problem if you were driving hard.

sgroer

I was also at 36 psi in the rear and had no issues. Was actually fairly cool this morning. High 60s when we started and and maybe mid 70s when we left the mountains. I wasn't used to leaving Lodi behind after his very strong performance on the tail of the dragon in the spring. ;-) I think his slops are done.

hfm

Agree. 36 psi cold will probably rise to over 40 and will result in smaller contact patch. I think OEM settings are about where you had them before the dealership at 33 psi cold, if not lower. I'd try 31 cold.

rc512002

My dunlpos totally craped out 5500 miles. At the track we adjusted tire pressure and checked temps but tires became very slick.

morsini

The difference between your tires is profound. Go to tire rack and compare compounds, most notably wear rates and you'll see the difference.

Seth Thomas

What were your pressures hot during the run?

I made the mountain run up to Blairsville one night last week in my 997 RS. My tire pressures went up from my starting point about 4 PSI. I believe the rears were at 32 when I started and I remember seeing 36-38 in the heat of the curves. I would bet yours did the same and became over inflated. This sounds small but makes a big difference in the behavior of the car, especially on a 911

sgroer

I saw 39 at one point. Not sure if Lodi was watching his gauge.

reidry

I was on new MPSC2s at the Spring Smokies event, above 38 psi hot I felt the rear slide a bit here and there. I dropped the hot pressure below 38 psi before we jumped on the Tail of the Dragon.

Ryan

Petevb

Absolutely. You lose grip well before you run out of tread even on the street, both because the compound is hardening due to heat cycles and because you've got less rubber thickness, meaning it can't conform to the pavement as effectively.

My Dunlop SMR were like ice skates just before they corded (right around 5k I think), but they were down on grip far before that. Swap to new tires (either Dunlops again or better the MPSC2s) and you'll be amazed at how much more grip you'll get.

I've been moving towards dumping my tires at half tread depth largely for this reason. Pilot Super Sports, MPSC2s etc are all well past their best at half tread, even if you haven't overheated them.

Lodi

That's because you had GT Silver back then and both cars were equally matched. The Rivera Blue is obviously much faster!

I will drop it back 32/33. Service manager told me to only use the TPMS to fill the tires and ignore the pressure. Strange!

How many track days? I'd like to get to the fall on these tires but I'm considering just changing to PSC2s and maybe painting wheel satin black at the same time.

I saw 38 at one point. It may have gone higher but I was not watching the tires the whole time. You should join us next time. Shoot me a pm with contact info. We will keep you in the loop.

Thanks everyone!

sgroer

Dave and I were talking - we should make this a regular event - the first Tuesday of every month, we meet near the outlets. Each month someone else gets to pick the route with the goal being we are back in Atlanta by around noon.

Riviera blue is much, much faster...

rc512002

I had 4 days at Road Atlanta and 2 days Barber. The rest of the miles just normal street driving I noticed a big difference after 4 track days.

rockitman

Yes I heard from another participant I met last weekend that you are pretty tough to keep up with, especially on public roads..