On Sun, 22 Apr 2007 20:11:00 +0100 (BST), "Dave Liquorice"
wrote:

On Sun, 22 Apr 2007 18:38:55 +0100, Autolycus wrote:

I'd inflate them a bit over pressure, check the tread and sidewalls
carefully for any bumps or distortion, and if they're OK drop them back
to pressure and tow away.

I'd also under inflate and squish them to see if any cracks open up in the
side walls. One of my trailer tyres loks fine inflated but when it's a bit
soft the crack open up...

Ok, another good test thanks.

A thought though, just what percentage of the strength of a tyre
(especially the sidewall) is down to the rubber rather than the
'ply's'?

I mean the rubber 'inside' the fabric would tend to keep the air in
(these tyres are tubed in this case though) and the stuff on the
outside helps give the sidewall it's 'stiffness' and protect the ply
from abrasion etc?

I guess what I'm trying to ask here is is it possible that a crack (or
cracks) in the sidewall *might* not actually increase the risk of the
tyre deflating or delaminating etc?

I have a very old trailer (in itself very tidy) with equally old tyres
with lots of very fine cracks in the sidewall but it only gets used
for a very rare slow trip to the local dump etc (and wouldn't be
'noticed' unless inspected very closely). I probably first spotted the
issue 10 years ago but they seem to have survived?

All the best ..

T i m

p.s. I would very probably fit new tyres 'anyway' if they were on our
cars or motorbikes and especially if they were going to be used
regularly or at any speed / distance.