Optimum Pressure With Stretched Tyres

[conan7772]

Just checked my tyre pressures for the first time with my new tyres.

I have 235 40 18 KU36's on the front and 255 rear, fitted to 18 x 9.5's all round.

I was surprised to see 38 psi in all 4 from Jax tyres fitters.

Is it normal to have high psi for stretched walls ?

cheers

[blind_elk]

It's not a matter of having stretched tyres. It's that the tyres are quite low profile, and the pressure is required to keep the sidewall stiff enough to support the weight of the car.

Generally, the smaller the profile of the tyre, the higher the pressure required to keep the tyre in the correct shape.

[boiracer]

^^^^^^^^^^ like he said

[KiwiRS4T]

The sidewall is designed to be perpendicular so with "stretched" tyres they can in an extreme case be almost at 45deg so they would need some extra pressure to stop them from collapsing or slipping off into the rim and deflating suddenly and dangerously.

As you can guess I am not a fan of stretched tyres although those on the OP's car are not an extreme example.

And while I'm at it I don't see why a low profile would require a higher pressure - less sidewall to flex . Its already going to give a harsher ride. Low profile is a trade off - better handling, less comfortable ride.

[blind_elk]

less sidewall to flex .

And less sidewall to support the weight of the car.