tire pressure

[Fitz]

Thanks a lot for that., Richard. Good to hear!!

[Dag-Henning]

- anyone racing with CR 65 out there in 4.50 -13 ?? - if so, at what pressure do you run them ??

Dag / S1

[Fitz]

Hi Dag

We use 25lb/sq.in (cold) for 4.50 M profile Dunlops mounted on 5.5 inch rims for Classic sports car racing (FIA series cars). I hate the bl***y things, but all of my much more competent friends tell me what a hoot they are as they slide so nicely. Can't see it myself.....................

Incidentally, a very good friend who drives a pushrod Anglia extremely fast, reckons he puts his CR65 tyre pressures up to 35 in the wet, as he says he gets better adhesion through the water with stiffer tyre walls.

Anyone else heard of this logic? I think it is extremely suspect, but as he goes faster in the wet than I go in the dry, am a bit fearful of contradicting him!

Fitz

Fitz

[Dag-Henning]

Thanks Fitz, - 25 lbs. is what I have been using, with, - I guess -, reasonable results. They do slide (!),which is kind of fun, but that doesn't produce good times, does it ?!
35lbs. in the wet requires some serious thinking on my side........Can't really see the logic, unless the high pressure would sort of open up the tiny drain-channels .... (?) Stiffer walls..- yes could well be. All in all the tires must be seen together with the suspension set-up, so.......
Rgds Dag

[rgh0]

I used to use historic dunlops but since modern Yoko A032R's were approved for our historic racing class I use these as they work much better and are about half the price and last longer. I ran the dunlops around 25 to 28 psi on most track in normal dry conditions.

Typically in wet weather I increase the cold tyre pressure by around 5 psi. This is because the normal cold to hot pressure rise of around 5 psi does not occur in the wet due to the cooling of the water. Thus to have the same tyre pressure as when dry you need to increase the cold pressure.

I have also been told the higher pressure helps kep the tyre tread open better but I have never seen any quantified demonstration of that such as via photos

Rohan
Rohan