SSTHO

After the alignment from Fordahl, I took the 7.2 3 to Pacific Raceways for a track day. First lapping day was perfect. Happy as can be.

The next day with PCA, en route to the track, was not. I had a completely flat rear RHS tire. I did not re-flat my tires after the track day. Dumb - I know. But on the morning of the second track day, my pressures were low. I thought it was due to bleeding air from the track. TPMS showed 28 psi in moe colder morning. 30 min of Hoggan driving and I was on 3 wheels.

The rear RHS was replaced. However, when I got back to the track, I noticed it was losing pressure again. To the point where you could hear it. Then we had the valve stem core torqued. The sound went away. After one horrible track session with no confidence in the car, I drove home to Vancouver. It was a 3hr drive. My pressures went from 38psi when I left to 15 psi when I arrived home. Got it checked out at the tire shop and they told me it was the valve stem gasket creating the leak.

Now I have a set of brand new rears. I go to the track day in Seattle this past Saturday and drive back. Everything is good. Then, I went to Mission (local track) just a few days after, everything good.

Then, this morning, I noticed my tire was low. 2psi low...

Any advice on what to check? I just want to know what's going on. Is it bad luck? Should I not bother with RE 11's anymore? Not sure what to make of things except I am losing confidence in the car again. TIA

24Chromium

Ah, I just gotta show some love for Gielse's twin sister. She's hot too! LOL

As to your specific issue... well, strangely enough, I've had the exact same problem. I was at a 3 day event with new wheels and tires. I kept loosing air in the RR tire. The track has a tire shop, so I took it to them for analysis. They couldn't find anything wrong (sprayed the valve stem and both beads with soapy water while the tire sat flat on the ground). But I kept loosing air. Mind you, the tire never went completely flat, just very low, at worst 12 psi in the morning after sitting overnight.

Once back home, I took the tire to my race shop. They too did the exact same soapy water sprat test and found it had a loose valve stem. They figured that since the tire was cold at this time, it showed bubbles now, but did not at the track when it was hot.

I've had recurring leaks with this same rim. I've just tightened the nut on the valve stem each time. I found it to be surprisingly loose every time.

Hope this helps! Be good to your girl! LOL

SSTHO

If it were as easy as tightening the value stem caps, I'd LOVE that! However, I've checked and they all seem fine.

What tires are you running 24Chromium? (Your avatar is just too much!)

24Chromium

My avatar is Gisele Bundchen. I named my car Gisele, 'cuz she's a German supermodel! LOL

The tires are not the problem. It's the valve stem. I only had this problem with my track wheels. They are GMG wheels fitted with the Porsche TPMS sensors. As for tires, I had Hoosiers R6s on when I first got them. Most recently, I had Pirelli Trofeos.

24Chromium

Here is the story of how we met...

https://rennlist.com/forums/997-gt2-...irlfriend.html

mdrums

24Chromium, do your tires spin on the rims with the GMG wheels?

24Chromium

Yep. I think pretty much they all do, assuming you're getting to threshold braking.

I did see some wheels recently that had radial fluting (knurling) where the tire bead seats. I thought that was a great idea to reduce or maybe even eliminate spin. Unfortunately, I can't remember what brand/model of wheel it was.

LehmanZ06

I think I have your answer.

This happens on my rear tires ALL the time. Now this isn't on the sport cups, but on Hoosier A6's. Leak is from the bead of the tire. Tire looses sometimes 5-6 lbs a day. Happens more to the fronts.

I believe it's the 19" tires, and the 19" wheels. Note this doesn't happen to the stock Sport Cups. Just keep an eye on your pressures at the track, or other driving event. over inflate tires when putting on trailer so that tire won't be flat when you get home

24Chromium

I've heard that the Hoosiers are prone to leak. As I stated prior, the initial incident was when I had Hoosiers on. However, I had the identical problem on the exact same wheel when I switched to the Trofeo tire. Again, a simple tightening of the valve stem cured my problem.

None the less, LehmanZ06 provides excellent advice!

tcsracing1

it has to be the stem/valve nut assembly.

im sure the tires are fine.

If you do go for new tires, lap per lap the MPSC work for a street tire. ( let me know what you do with your old tires )

If you want to have a better street tire that supposedly keeps up to MPSC on the track then try the Michelin Super Sport.

mdrums

I figured when I looked at the ultra smmoth seat at the bead area of the GMG wheels when I visited there shop back in January. My CCW's spun a little too but I had the seat/bead area blasted and roughed up and tires mounted dry and no more spinning on the rims.
While at GMG they had some BBS wheels with a very rough surface at the bead area. I wonder if those were what you saw?

SSTHO

I was on MPSC on the '07 7.1 GT3 RS - I did enjoy them, but the rain really makes me think twice.

I might consider going R6's during track season and RE 11's for all other times.

Agreed it is very unlikely it is a tire issue. Same damn problem really ticks me off,...

mdrums

SSTHO, how do you like the RE11 on the street and track compared to the MPSC. The RE11 sure do cost a lot less. thanks!

997gt3north

3 of my 19" R6s would lose pressure slowly - 1 would basically hold the pressure
I just refilled when necessary - this was on 19" Volks

SSTHO

Living in Vancouver,... the RE11's are FANTASTIC!

It's the rain. I remember I used to be able to do 85km/hr in the pouring rain out to Mission on HWY#1 with the 996.2 GT3. With the RE11's and the 997.2 GT3, I am able to do 125km/hr in the SAME conditions (standing water).

Compared to the MPSC's, they are less grippy. How much? I can't quantify, but enough for me to notice. However, they are a great value and fits what I am looking for. FWIW, the Tire Rack ratings were top notch too.