Tyre Pressures

[Pug620]

Hi

Currently running a stockhatch rallycross car Pug 205 on Yoko AO48's and have been running them low at f 20psi r 16psi the car weight is around 850kg
just wondering if this is too low?

I know the tyre pressure will increase when racing due to heat but we only do 3-4 laps per race

I am planing to check tyres when comming in from a race this year but wanted a tech veiw on were i should start from

Also is it bull that if you fill tyre with Nitrogen you don't get such a temp change?

Cheers

marty

[Adam43]

Your pressures seem a little low to me, but I can't really comment as I use different tyres and a different car.

As for Nitrogen, over your race distances I wouldn't worry, but yes it can help. The tyre performance can be much more consistent. It is not that Nitrogen has magic properties rather you can purge your system of things that do effect it (water, etc...). Some tyre places can fill your tyres with Nitrogen.

As with all these things it is difficult to notice a difference. unless you can back to back a couple of equal sets! However if you can get it done cheap, why not.

[Slippy Diff]

I used nitrogen in Dunlop L sections in historic racing. It made a huge difference to those tyres (crossply) over a race distance whether it be 10 or 100 laps. Simply put, the tyres did not 'go off ' or start to degrade as quickly.

[Chris Y]

My car currently uses the 032Rs (the predecessors of the 048s), and most of my fellow competitors use around 23-26psi. Mine used 24 front, 26 rear (helped dial out some understeer)

Now the 032Rs may vary, as they have a 'crossover' tread section in the middle, which can lead to the middle of the tread being too soft, so with that in mind, you'd probably have to run the 032Rs with more pressure to support the soft middle.

However, I still think 16 is a little low! Check the shoulders of the tyre for wearing more than the centre.

[Mackmot]

Just something I learned a while ago from some historic touring car racing. Try really high pressures around 45-50psi it seems illogical but it seems to work, you get better tyre wear, less tyre roll, and the temperatures are pretty even.

[pitcrew]

You want to start this with 20psi, after a race you would come back with about 23-25psi (was used last season)

hope that helps!

Pitcrew

[Carlos]

OK im waiting for the laughter but I know of at least a couple of competitors doing the same thing. I run the same car in rallycross so marty you probably know me. I run with a stiff setup, ie bigish braces top and bottom with bilsteins and run 16 front and 18 rear (keeps the tail loose if higher at rear). I find the temp rises quicker because of the increased flex so with the short 3/4 lap races the heat gets in the tyres quicker and helps in the gravel with softer tyres. Feel free to ignore me but it seams to work well for me, and when I was first advised this I was very sceptical about trying it. P.S I know of someone running 14 front and 16 rear but havnt been brave enough to try that.

[Peter Horsman]

Slippy Diff, what car was that; a heavy or light one?

[Pug620]

Thanks for all the info

Cheers

Marty

[Slippy Diff]

Originally Posted by Peter Horsman

Slippy Diff, what car was that; a heavy or light one?

Healey 3000 around 1040 kg's without driver and fuel.

[Peter Horsman]

Thanks. Not light, then (even before driver considerations.........)

[Slippy Diff]

Originally Posted by Peter Horsman

Thanks. Not light, then (even before driver considerations.........)

Not particularly light, but then it is a proper car

[kartingdad]

Maybe talk to the tyre manufacturer.......

[Peter Horsman]

No doubt about it being a proper car, and probably stresses tyres with the tail-out attitude they seem to be like to be driven

[Slippy Diff]

Originally Posted by Peter Horsman

No doubt about it being a proper car, and probably stresses tyres with the tail-out attitude they seem to be like to be driven

Tyres did tend to go through it a bit. I occasionally ran Avon ZZ's in the wet. They were great until it started to dry when they would just disintegrate.