tyre pressures and bigger wheels?

[anonymous-user]

[redacted]

[Hoover.]

no idea what pressure should be in the bigger rims.....

but if you inflate your tyres to that of a normal car and then try driving it that will answer your question. It's all over the place, directionless, and you don't feel in control.....

[Colin RedGriff]

I think it's because the car is so light. With a heavier car you need higher pressure to get the right contact and stop the tyre deforming , a lighter car needs less pressure to do the same.

With bigger wheels and lower profile tyres I guess you might need even slightly lower pressure. Depends on the tyre though and how stiff the tyre walls are

Just my thoughts not based on any real knowledge.

[gammav]

I'm running SP12 rims, 17" fronts with 24 psi and 18" rear with 26 psi no problem with rim crash (yet).

Feels a lot more planted than the 15/16 Estorils, both set of rims have Toyo T1R..which I assume to be due to the fact that the SP12 wheel/Tyre weighs a few kg less than Estoril wheel /Tyre, so un-prung weight is dramatically reduced.

[SSPPGG]

start around 22, and work up and down 2 psi either way and see how it feels.

the sidewall stiffness had a great effect on the feel and pressure required, so it really is a case of trying it

[500dread]

In the interest of safety....

They'll very likely need a higher pressure to maintain the larger tyres stability at contact patch due to a larger contact patch area requiring MORE air pressure to plant it and prevent it from deforming.

[jesfirth]

Road tyres have relatively soft side walls. If you reduce the pressure too much they deform under heavy cornering and reduce the contact patch. B list Ypres such as R888's are much stiffer(and heavier as a result) but can run much lower pressures. When I ran standard road tyres I used between 26 and 28psi. But on the b list tyres I run them at 22

[500dread]

Thank you for bringing this topic to my attention. It's always a concern when there is no guideline readily available so I've done a bit of Internet fishing and found some interesting information on this U.S site.

I've linked it to the page I hope is relevant to the OP'S concerns as there is a formula at the bottom of the page that might be of some use. The rest of the site appears to have some sound information too.

http://www.tirerack.com/tires/tiretech/techpage.js...

[UKAuto]

500dread said:

Thank you for bringing this topic to my attention. It's always a concern when there is no guideline readily available so I've done a bit of Internet fishing and found some interesting information on this U.S site.

I've linked it to the page I hope is relevant to the OP'S concerns as there is a formula at the bottom of the page that might be of some use. The rest of the site appears to have some sound information too.

http://www.tirerack.com/tires/tiretech/techpage.js...

I very nearly lost my Griffith last week as I spun on a wet wood bridge - many discussions about my @##$%! tires followed. I find my tires are poor in the dry, but awful in the wet. Thanks for the link, one link off of that page did answer one of my questions about tire pressures in the wet ( http://www.tirerack.com/tires/tiretech/techpage.js... ).


I would be intereseted in comments from people on their experiences with specific tires on their Griffiths, particularily with respect to changing road conditions. I will try to change the pressure a bit - but suspect I will be scrapping them and moving on to a better tire.

Cheers,

Rob.