Tyre width

[stuart928gt]

Would a brand new tyre's width be smaller off the rim of a wheel to when it is on the wheel inflated to the correct pressure, i know this may sound silly but can anyone comment on this please.


stuart

[deltaf]

Yes it will be thinner.

[stuart928gt]

so i guess the sidewalls will fillout but the tread width wont increase ????????.


stuart

[deltaf]

Yep!

[stuart928gt]

Right so why is a 225 tyre bigger than a 245, 245 aint gonna grow much more fitted and blown up.


stuart

[GreenV8S]

stuart928gt said: Right so why is a 225 tyre bigger than a 245, 245 aint gonna grow much more fitted and blown up.

stuart

You are right the nominal tyre width (245 or whatever) doesn't mean very much. In theory (for a road tyre) it's the overall width of the tyre at its widest point on the recommended rim and at the recommended pressure.

Change the rim or pressure and the actual width can be very different. For example, the standard 7.5" TVR rims are really too narrow for these 245 tyres. Also, the width of the contact patch, which is what really matters, is quite a bit less than the nominal width and again, how much less will depend on the rim width and pressure.

Also, all these vague relationships vary a lot between different types of tyre. For example I have compared an S02 245 and an S03 225 side by side, the S03 has a wider contact patch.

Bottom line is you can't read much into these numbers except a general trend that bigger numbers mean a wider tyre.

Cheers,
Peter Humphries (and a green V8S)

[stuart928gt]

I've got SO3's too the front 225 tyre is wider than the rear 245, they have not been fitted yet, i'm just a little worried buy the skinny 245, have 245 avon's on the rear and they look wide but offer no grip, my rear rims are 9 inch wide, am worried that the skinny looking 245 wont fit, but 245's is the standard size or have brigdestone cocked up, when moulding the tyre or am i making a mountain out of a mole hill.


stuart

[Farmer]

once bought a set of 205 50 15 Fulda Y2000s and one of them was noticeably smaller and had shallow tead, it was actualy a 195 50 carcass that had jumped in a 205 mould by mistake got it changed pronto

[clubsport]

As stated the actual widths can differ from what you might expect.I assume you have a 928,,,,check with your tyre supplier that you have the correct N number for fitment to a Porsche...Whenever I have bought tyres for my porkers I always have to do this & have never had any problems.