Let's talk tyre pressure

Now, we all know that tyre pressure is very important. To my understanding it's even more important than getting the right rubber on the wheel. You might have a perfectly dimentioned wheel & tyre combi, but if you are running the wrong tyre pressure, you won't have the contact patch that you need to stick to the road in the situations where you want it to.

• Toyota recommends 32psi on stock tyres but is this also applicable if you are running 18" or (god forbid 19" and larger )?
  
• How about if you are running wider tyres, is 32 psi also the correct pressure?
  
• Does a suspension change warrent a tyre pressure change?
  
• How about keeping the correct pressure when actually using the car on track?
  
• Should you lower the pressure for a blast on the autobahn?
  

So, lets hear!

I have tried different pressures on 18s and always resort to 36psi front and rear

when i recently had my tyres changed, 245.40.18 and 275.35.18 they would not put anymore in them than 29! said anymore was too much. The car felt awful until i could stop at the nearest garage. I put 34 all round and it felt much better.

To get a decent tyre pressure you really need to be measuring temperatures across the tread widths.

Hotter in the middle compared to the outer edges suggests too much pressure.

Hotter on the outer edges compared to the middle suggests too low a pressure.

Each suspension change or geo alignment or change in car weight etc. will result in the tyre making a slightly different contact patch, and this patch may shift relative to the tyre. Therefore any change in the car setup should really have a check on tyre temps.

(Doing this in the real world without the correct equipment is a little tricky however...but there are some dedicated motorsport devices available - but they don't come cheap!! - http://www.demon-tweeks.co.uk/products/ProductDetail.asp?cls=MSPORT&pcode=BET017600380&vat=inc )

34 all round works well for me

34 all round for moi

Apparently according to a fitter at Elite in Rainham, for every inch larger than stock, up the tyre pressure by 2psi.

I'm running 18's, so 34 sounds about right.

Toyota recommends 32psi on stock tyres but is this also applicable if you are running 18" or (god forbid 19" and larger )?

I think it's 36psi that's recommended for stock tyres.

To get a decent tyre pressure you really need to be measuring temperatures across the tread widths.

Hotter in the middle compared to the outer edges suggests too much pressure.

Hotter on the outer edges compared to the middle suggests too low a pressure.

You will find however that the OB edges will be cooler than the IB, this is down to the camber and toe. You should see a linear fall off of temperature from the IB to OB.

i think the tyre has alot to do with it. my old pirellis worked verry well with 32 front 30 rear but the continentals i am currenty using seem to be happyer a bit harder 34 front 32 rear

The tyre wall and tread stiffness have a massive impact, so what will work for one model of tyre for a particular size might not work for another.

However, you can be too anal about these things....

To get a decent tyre pressure you really need....

This sound about right Aji. When going to trackdays or driving the Ring, you also notice people measuring and in/de flating their tyres constantly.

I have seen IR themometers down to roughly 30£. They are probably crap, but hey, it is possible to get them cheap.

I think it's 36psi that's recommended for stock tyres.

Right.. 2.5 bar. Miscalculated a bit earlier... 36psi