Tyre pressures for larger diameter wheels

[SonicShadow]

Easy PH,

Does anyone have a link to a proper source that goes over the correct way to calculate suitable pressures for a non standard wheel? From my limited knowledge, I would think the volume of the tyre and it's load rating will change the required pressure?

[Red Devil]

Tyre pressure is dependent on the gross weight* of the vehicle and the load rating of the tyres fitted (wheel rim size per se is not relevant).
See here - http://www.uklegacy.com/forums/index.php/topic/985...

n.b. the method outlined above has one major flaw. It fails to take account of front/rear weight distribution. For an accurate calculation you need to do each end separately. So you need to know the front/rear percentage split of the total vehicle weight.

 * This is why manufacturers usually recommend upping the pressure when heavily loaded - e.g. an estate car with 4 up crammed full of camping gear.

Tyre pressures also need to be adjusted for driving at sustained high speed. The reasons are explained here - https://www.tyreleader.co.uk/tyres-advices/adjust-...

[PositronicRay]

That's interesting. So why do manufactures recommend higher PSI on driven wheels?

i.e. Front engined Merc SL with around 50/50 weight distribution has 29f/34r recommended from the manufacturer no staggered tyre set ups or anything else.

Edited by PositronicRay on Monday 15th February 07:41

[SonicShadow]

Thanks Red.

Trying to work out what the best pressures will be for my MR2 with 17inch wheels, and of the people I've asked so far, everyone seems to be running different pressures. Looking for a more scientific way to get a good base point rather than 'it feels alright'!

Will have a read through those links above.