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Discussion Starter #1 (Edited)
I know other board members have already given good reviews to these tires, but I wanted to post a quick question anyway, so I'll add a few of my own observations.

These are the Dunlop Super Sport Race competition tires, size 265/35/18 on 9.5" OEM wheels. I bought them from Tire Rack at $130 each; they were not shaved or heat cycled. I've now run them at three DE events at Lime Rock Park: 11 sessions, 20 minutes each. Some sessions were slow due to traffic, but I think I have enough time on them to make some observations.

These are the first competition tires I've tried. I found them to be predictable; no unpleasant surprises. They still squeal quite a bit as they slide, as I've run them at full tread depth. My front camber is -1.5. The tread wear is greater on the shoulders, but not as bad as I initially thought. I've rotated the wheels for each event. Ambient temps in the 50s-60s.

My question is about pressures. I was shooting for 41 psi hot. Starting at 32 psi cold, I found my left front tire pressure (after a cool down lap) to be around 43-45 psi. The left front tire takes the biggest beating at Lime Rock because the track is nearly all right hand turns. So I would bleed the left front to 41 (and the other tires as well) and go from there.

I think this worked pretty well, but can anyone confirm similar cold/hot temp numbers? I'm reluctant to run less than 32 cold, even though 32 brings me a little higher than where I want to be hot. Thanks for your input.
 

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most tires (except PS Cups) are pretty happy at 42-44 PSI. I've had recommendations from Porsche guys that i should run RA1s at 40 hot, but they're looking at a very different tire/section-loading than the M5. And i agree that running less than 32 cold is not nice until the tires are warm -- if you think you can get some clear laps, change the pressure by 2 psi and see if you feel a difference and see a change in lap times. At your level of experience, i wouldn't screw with tire pressures if it feels good




EdP said:
I know other board members have already given good reviews to these tires, but I wanted to post a quick question anyway, so I'll add a few of my own observations.

These are the Dunlop Super Sport Race competition tires, size 265/35/18 on 9.5" OEM wheels. I bought them from Tire Rack at $130 each; they were not shaved or heat cycled. I've now run them at three DE events at Lime Rock Park: 11 sessions, 20 minutes each. Some sessions were slow due to traffic, but I think I have enough time on them to make some observations.

These are the first competition tires I've tried. I found them to be predictable; no unpleasant surprises. They still squeal quite a bit as they slide, as I've run them at full tread depth. My front camber is -1.5. The tread wear is greater on the shoulders, but not as bad as I initially thought. I've rotated the wheels for each event. Ambient temps in the 50s-60s.

My question is about pressures. I was shooting for 41 psi hot. Starting at 32 psi cold, I found my left front tire pressure (after a cool down lap) to be around 43-45 psi. The left front tire takes the biggest beating at Lime Rock because the track is nearly all right hand turns. So I would bleed the left front to 41 (and the other tires as well) and go from there.

I think this worked pretty well, but can anyone confirm similar cold/hot temp numbers? I'm reluctant to run less than 32 cold, even though 32 brings me a little higher than where I want to be hot. Thanks for your input.
 

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Discussion Starter #3
Thanks. They felt pretty good except when traffic allowed me to get in 7 or 8 consecutive fast laps, and at that point the rears started to get slippery. I'm guessing that's going to happen regardless of what pressures I'm starting with if I run them hard enough? Otherwise, they felt good to me.

Does anyone use a tire pyrometer when they track their M5? I've read and heard different opinions on their usefulness in a DE environment. And since front camber is not adjustable, I haven't given it serious consideration.
 

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We run our Dunlops at 45-47psi hot, as that was recommended by a competitive autocrosser and fellow track junkie I know. Seems to work well for these tires and the wear is pretty even.

A pyro comes in handy because it helps you even out the tire pressures even if your suspension is not adjustable. I forget the rules, but you want even temps from inside, to middle, to outside of the tire. If they are not even, that tells you which way to go with the pressures to try and optimize the best possible way without touching the suspension.
 

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Redshift said:
We run our Dunlops at 45-47psi hot, as that was recommended by a competitive autocrosser and fellow track junkie I know. Seems to work well for these tires and the wear is pretty even.

A pyro comes in handy because it helps you even out the tire pressures even if your suspension is not adjustable. I forget the rules, but you want even temps from inside, to middle, to outside of the tire. If they are not even, that tells you which way to go with the pressures to try and optimize the best possible way without touching the suspension.
 

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oops, hit the wrong button

if you use the pyrometer, you want to come in hot and take temps immediately - not do a cool-down lap

because the M5 suspension is less than optimum for track, you won't be able to acheive equal readings across the tire and will spend a lot of time recording data and puzzling over what they really mean -- as long as your tire pressures are reasonable, i'd reccommend concentrating on keeping them consistent throughout the day (which generally means letting a little air out after each session as the ambient and track heat up) so that the car is predictable. until your driving can deliver consistent lap times (which of course need to be measured) tuning tire pressures is not going to be terribly productive
 
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