tire pressure for track tires?

[silver]

i am tracking my V8 using Toyo R888 tires. What tire pressure should I be using? Normally its 39psi all round but is it less for track tires? My rims are 19inch. Thanks

[KfabR8]

Mothertucker had a post about pressures.

He was running 36 psi once the tires were up to temp.

When I ran at Road America a little while back, I set up my tires at 29 psi cold, which brought them up to 36 on the track. I had a little bit of a push (understeer) and dropped the fronts down to 34 and it made an impressive difference.

With the R compound tires I could be off on suggested pressures.

[desperado]

I've tried low pressures (low 30's hot) and I've tried high pressures (high 30's to low 40's hot). The lower pressures cause the R888 to wear noticeably faster on the outside edges. At the higher pressures the tires wear much more evenly across the entire tread. Either setup shows excellent pyrometer temperatures across the tread face. I don't time my laps (and don't drive consistently enough, yet, to draw much conclusion from lap times if I did ). So it's difficult to say which is better. I'd start with hot pressures in the mid- to high-30's and then make adjustments from there.

I've attached a couple of setup guides for the Toyo R888. While the one by Toyo is specific to a much lighter car (the spec Miata), the paragraph with the recommended tire pressure range of 32-38 hot is intended to apply to all vehicles. Typically the heavier the car, the higher the pressure within that range. Also, for many DOT R-compound tires the higher pressure can be faster when handled properly, but using a little bit lower pressure will give the average driver a more confident ride at the expense of somewhat faster wear.

Don't over-drive the tires. If you are getting understeer in the corners, slow down your entry speeds. Use the power of the car to accellerate once you are able to unwind the steering. Even though this doesn't "feel" fast, your lap times will decrease compared to roaring into the corner and then understeering around the turn which just scrubs speed. Plus your tires will last an entire session instead of going off after 3-6 laps.

Edit: Link to Toyo website http://toyotires.com/tire/pattern/proxes-r888, click on Set-Up & Care.

[desperado]

I meant to mention that I usually use up two sets of fronts for one set of rears. I guess I'm not very good at following my own advice about avoiding understeer . It is so much fun to slide the car around, but not very good technique.

[silver]

thanks guys.

there seems to be such variation in psi. I think i will aim for a 43psi (hot) as suggested by Toyo for the weight of the R8 (and this should help with longevity I hope!!)

thanks again

[bz888]

Michelin Cups for Track Day on my R8V8
******************************

Hot (PSI)
32 Front
33 Rear

Cold (PSI)
23 Front
25 Rear

[desperado]

Looks like you are in the sweet spot for the PSC.
Michelin guidance for the PSC: http://www.michelinman.com/media/en-...p_Brochure.pdf
I liked this thread, it gives some idea what pressures the serious P-car guys are using for the PSC: http://forums.pelicanparts.com/porsc...ack-tires.html

[desperado]

thanks guys.

there seems to be such variation in psi. I think i will aim for a 43psi (hot) as suggested by Toyo for the weight of the R8 (and this should help with longevity I hope!!)

thanks again

43 psi seems pretty high. I think the Roger Krause recommendations err on the high side.

[harrison]

Silver, Your track temps would be a whopping 10 lbs too high. You will be out of controll and passed up by Honda S2000s. Make a freind at the track. He will help you lower your lap times. I get great satisfaction from helping the fellows pitted next to me. Sort of like a good big brother. And I am always still looking for help in lowering my lap times as well.

[dailydriver]

I ran my car at Autobahn Country Club several times this year and had kept the pressures on the higher end since my previous cars all experienced mostly outer tread wear which is usually due to pressure that is too low. I have nice gauge with a bleed valve so I can be pretty accurate in dialing in the desired pressure. I was running 39 pounds hot and the car seemed to handle really well but at one point I noticed some unusual tread wear - pieces of the center tread just pealed away from the tire. I took some pictures and sent them off to my dealer (he also races competitively and is very knowledgeable) for his opinion/assessment. He ended up forwarding to some folks at Audi and here is the feedback we got which I thought was very useful information (I was aware that the chunks of excess rubber were just picked up off the track):

• I have seen this many times at the track over the past 15+ years. This is blistering from too high PSI usually. When the heat expands the tire, it will run only on the center- then it overheats because your contact patch is narrowed down to the size of a motorcycle tire. A track that has a few high speed right hand turns will do this, or if he trail brakes into a long right hander.
• If he is getting serious about track driving, the tire PSI in a street car needs to be controlled much closer than what an open ****pit car are.
• IE; Starting temps for Limerock Park with nitrogen are LF- 27 RF- 31 LR- 28 RR- 32 Target temps were 240 across tire surface and PSI would be about 36 on all four corners after a 15 lap session. Track is predominantly right handers.
• These don’t look all that bad considering that they have 10 sessions on the track.
• I see two things on the tires:
• Rubber from the track. It is typical that the tires pick up rubber from the race track surface and from exiting the track. The tires are hot and pick up rubber that has been shed. This is normal and not a concern. See picture attached.
• The little pits in the center band of tread: I believe this comes from the tread block moving around and scrubbing on the track. Tire pressures and driving style play a key role. The type of turns and the skill of the driver also plays a key role. Many racers will adjust tire pressure different on each track and sometimes on each tire, depending on the track in use, the temperature of the track and air temp. You also have to remember that you are using a street tire on the track. Also the left front has to support the driver, so it takes a little more of the load. 39 PSI sounds a bit high for the pressure.
• I have been told that tires get replaced after about 2 track days on our Driving experience vehicles.
• I would normally recommend that the customer talk to a tire guy at the track for on the spot analysis.
• Also track vehicles usually have much higher camber adjustments to have the tire sit flat on turns.
• I also know that many times when a racer is using a street tire on the track, he will shave down the tire tread about ½ way to minimize tread movement and to help with the handling.

In addition to the above comments, I would personally concur that 39 hot is probably too high and that they don't look all that bad for 60 laps. The front left tire takes most of the load at Autobahn, particularly on AWD car. I would certainly consider an exclusive set of track wheel/tires. You may also consider getting a laser heat gauge to make sure the temps are even across the face of the tread, which will help dial in the PSI.