Hi Folks, Who runs slicks for trackdays and what pressures do you use? Tubs? GVK? Who else? My are 15" on a mk1. Cheers Ian
Aurok motorsport who run the Clio cup cars recommend 2bar cold for the Michelin 19/57x15's we use. I find the grip to be more consistent throughout the session by aiming for about 30psi hot. (23-24psi cold) bear in mind the NS tyres get a lot hotter and the OSR is hardly ever on the road) Wether I'm doing the 'right' thing or not is open to question and what suits me and my car may not suit YOU , but how I do it is. Set them all to 24 cold, go out for 10-15 mins then when they're still hot bleed them to 30 all round. Go out for the next session ( tyres are a bit squidgy for a couple of laps) then they're fine for the rest of the day. Obviously the ideal way is to do the temps with a pyrometer, but that's really getting serious Some people (book a track and castle combe for instance) Don't allow full slicks, but there are exceptions if you've an FIA approved cage. Edited by: G_V_K
Cheers Gary, I've got some 19/57x15's too, I used them yesterday at Snetterton for the 1st time, the grip was just amazing. I started with them at 30psi cold, which went upto 37psi hot, but i spoke to a couple of people there running similar weight cars on slicks who said they run them as low as 18-20 psi hot, so bled them down to 20psi hot, but even after a few laps to get some heat in them the turn in was very sloppy. So i upped it to 28psi hot, which sharpened it up a treat. Thou by the last hour the grip was started to drop off, and the back left tyre has been cooked there are big smeary dobs of rubber all over it. I assume this is overheating? Is it due to too high or too low pressue? Is just that they have got very hot? Also did you get any oil surge probs? I have a roll cage, so most of the trackday organizers are cool with slicks. Ian.
The blobs are likely pickup as the tyre is too cold - often seen on rear left. Its wierd, but if a tyre is working right, at the right temp (namely hot) and running square to the ground, there is very little 'blobs' - only get these if too cold but warm enough to pickup Rear drivers side doesnot pickup so bad as it really gets very little heat and is off the ground much of the time Try and get about 30 hot on all wheels but this will be difficult on rears. If you take temps, I have had 70C from mine in the past and they were working well and not blistering at all - 50-60C is more typical, F1 tyres go well over 100C. Cheers Rob Edited by: RobT
2bar cold? ~29psi Hmmmm. more like that hot I would have thought. Not tried mine yet. Will have to see.
Rob, The tyres were all wearing evenly across the tyre, which i suppose is a good sign. My golf's set up very stiff at the back, so now doesn't really understeer, accordingly i think the rear tyres are working quite hard, obviously around Snetterton the rear left more so, but the rear right was quite warm too. But on the rear left it wasn't so much blobs, but more like the rubber had melted and smeared across the tyre before setting again. Does that make sense? All in all, next time i think i'll try around 30psi hot and keep a eye on them.
I did get oil surge at Mallory, big ends went *clatter clatter* [:^(] around Gerads one lap, took it 'a bit steadier' after that. Grip was amazing though Jim who works for Aurok was at Mallory, I asked him and questioned "hot or cold"? when he said 2 bar cold. Edited by: G_V_K
Yes - this is usual and is due to the tyre getting just hot enough to pickup rubber off the track - this happens less the hotter the tyre gets. Its very hard to get the rears up to proper temps in a FWD car Cheers Rob
