Tyre pressures for slicks??

[hazy]

I have a BMW E36 track/race car which I have managed to get a few sets of brand new Michelin slicks for, rough size is 225/55 x 18, what tyre pressures hot/cold should I be running, got Oulton and Anglesey coming up next weekend.

[Racefan_uk]

Err, whatever works best with the set-up on the car I should think.

It will vary according to temperature (gonna be cold!) and how the suspension is working.

But, I'm not an engineer, so don't listen to me! :P

[thunderbelmont]

Start around 24psi cold.

You then need to go out, do a few laps, get them hot, then come in and see what the temps are like across the width of the tread.
Also see what the pressure is when they're up to temp.

Michelin motorsport dealers should be able to provide with ballpark figures for cold/hot pressures, and max tyre temps too.

If you have them too soft, you'll cook them on the outside edges - hence checking the temp across the tread.

[flemke]

Also, keep in mind that tyres will go off for any of several reasons. One is total mileage, a second is if they get overheated. A third is if they go through too many separate heat cycles, which is an easy thing to do on a track day when you might be inclined to do six or eight tennish lap stints with nice breaks in between.

[Animal]

flemke said:

Also, keep in mind that tyres will go off for any of several reasons...A third is if they go through too many separate heat cycles, which is an easy thing to do on a track day when you might be inclined to do six or eight tennish lap stints with nice breaks in between.

Flemke - Is there a way around this problem?

Thanks,

Animal

[hazy]

thunderbelmont said:

Start around 24psi cold.

You then need to go out, do a few laps, get them hot, then come in and see what the temps are like across the width of the tread.
Also see what the pressure is when they're up to temp.

Michelin motorsport dealers should be able to provide with ballpark figures for cold/hot pressures, and max tyre temps too.

If you have them too soft, you'll cook them on the outside edges - hence checking the temp across the tread.

Cheers mate, I had them at 26psi so not far off really!!

[flemke]

Animal said:

flemke said:

Also, keep in mind that tyres will go off for any of several reasons...A third is if they go through too many separate heat cycles, which is an easy thing to do on a track day when you might be inclined to do six or eight tennish lap stints with nice breaks in between.

Flemke - Is there a way around this problem?

Thanks,

Animal

None that I know of, although I know so little about tyres that there could be six ways.
There are certain chemicals that are used to make finished tyres' compounds softer. In most series they are illegal, but you can obtain them. For example:
http://www.demon-tweeks.co.uk/products/ProductDeta...
Perhaps that would help.

Also, in some series there will be a spec tyre that is intentionally long-life. I wouldn't know the heat-cycle tolerance of any of them, but I'm sure that some of them would be able to endure a number of heat cycles before any meaningful deterioration develops. Having said that, there is going to be a correlation between a tyre's sustainability of grip and its initial grip. It is difficult to get something for nothing.
The underlying problem is that slicks are usually meant to be consumables that will be discarded as often as feasible. Heat cycles are not an issue for most racing tyres.

The OP and others would probably be best off by consulting tyre-makers to get their advice on longer-life compounds.

Cheers.

[custardtart]

You might be lucky and find someone in your race series who will help (usually with slicks, tyre pressures are a closely guarded secret)otherwise testing really is the best way to find out what works best for you. As previously said though, make sure you put them through the right heat cycles when they're new.

The other is to contact Michelin and ask their advice, I know AVON/Yoko are pretty good at this.

[fergus]

As already stated, get hold of a pyrometer, NOT the IR ones though, they're ste. Also check for graining on the tyres. Make sure you bed them in properly, unless you intend to use them for just the one day, otherwise you will ruin them!

The setup on your car will dictate the pressures. If you've not driven on slicks before, be *very* careful until they are warm - they will slide with little warning and on an E36, you will swap ends very quickly indeed with probably little chance of recovery!