Norton928

Hi all,

I have recently purchased a set of 17" Cup 2 rims for my '87 S4, but haven't had a chance to run them on the track.

What have the track crowd found to be a good starting point in terms of hot tire pressure for dry and rain conditions?

I'm running Yokohama Advan AD08 tires (225/45 fronts, 255/40 rears):
http://www.yokohamatire.com/tires/advan_ad08.aspx


Thanks.

Norton

Erik N

I run the same size tires as you do. 36F/34R psi on the track. I've found that less pressure gives an uncertain wallow to the car, and more makes it slippery.

On the other hand, ...

AO

35.2F/36.7R Adjust for barometric pressure as needed.

GlenL

My car (me) likes cold pressures at or below 30 psi. 28 front and 29 rear.

I drive pretty hard and find that too high pressures lead to a thermal runaway condition where the tires get hard, start slipping, get hotter and then get really greasy. Haven't run the Advans but that's my experience with 4 other brands/models of DOT competition tires.

You'll need to work this out for yourself. Ask for input at the track you frequent from owners of similar cars (E.g., 944s).

Gary Knox

I try to keep the pressure on High Performance street tires at about 39-40 psi when exiting the track after 5-8 hot laps, with either 17 or 18 inch rims. Probably about ~34 cold, depending on ambient.

Gary Knox

Norton928

Interesting observations, and a good starting point for me to adjust based on weather, track, personal preference, etc. Thank you to all that have responded.

Most seem to be running with a hot pressure lower than my previous sweet spot of roughly 38psi in the dry when I was on the stock S4 dish rims when using Toyo RA-1s.

FUSE69

I run Advan AO48's and agree with GlenL's input.... cold pressures below 30psi.

First time I used these tires I had the pressures way too high.... and almost lost it at 'Flugplatz' (High speed right hander over a crest at the 'Ring')

It became obvious how over inflated they were, once I pulled into the parking area.... the dust that stuck to the tires showed a very small contact patch... so to begin with I adjusted the pressure until that contact patch 'looked right'... these tires have very stiff side walls, so the low pressures seemed to work well.

Norton928

The 'Ring' eh, very nice What kind of lap time does the shark have on the Nordschleife?

FUSE69

Well that largely depends on the size of ***** you can squeeze into a race seat

Best I've done is somewhere around 8min 30sec, Bridge to Gantry...

IMO the car is certainly capable of better...

Here's a pretty crappy video (only one I have) that is around 9min 13sec BTG, fair amount of traffic on this lap.... you will also notice that I get a little 'out of shape' over Flugplatz in this video too... (tire pressures still a bit high)

Norton928

Thanks for posting the video. That certainly is a lot of traffic!

Do car clubs ever rent the track for a day so it's a smaller group of vehicles to deal with?

KLVA

Yep...that about right for Yokohamas... you want to end up with a hot tire pressure of between 38- 39 psi...so a starting point on a balanced car, like a 928 would be about 34 all the way around.

there are also arrows along the sidewall..very small and at the right pressure at the track, you should be noticing wear right up to those arrows.

If the wear line is way back up to the tread , then you are running the pressure too high..tire cannot flex enough..

If you are getting wear beyond the arrow, then your hot tires are flexing too much and creating a high friction. high heat condition.

After your 1st really hot track run...dry conditions..quickly check the HOT pressure and notice the wear line along the upper sidewalls toward the arrows and play w/ it some...hotter track= slightly lower psi....wet or cold track = something like 36 psi...
Just my experience with my Yoko AS 100 ZR tires...Good Luck

GlenL

I use a chunk of kiddee sidewalk chalk to mark the sides. Helps to see where you're wearing now.

This approach is a bit misleading as the tires will roll over more until they're hot. Then again, tire temps and pressures in the pits aren't accurate either.

The best evaluation is from the driver's seat. Is the car handling well especially late in the session?