Tyre size markings

Both of my sets of tyres are 205.70r15 but side to side the more worn-out Bridgestone are taller than the new renegade yet the renegade are noticeably wider especially in the tread. Is there any sort of formal regulations that specify a percentage of variance of tyres marked as the same?

BS AU 50-2.7B:2017 is the relevant standard, but it costs £150 ish and I am not sure if it specifies the tolerance. You might be able to find an older copy online.

There must be a tolerance, possibly at least 1%, but may be up to 3%.

I'm not sure there is any specific tolerance requirement. I bet they only have to list the size in certain places on the tyre.

Many remould tyres are often very far off from what they should really be.

Also thinking about it. It would be really hard to dictate definitive sizes and measurements.

e.g. would you measure height from the top of the caucus or from the outside of the tread? A track tyre might only have 5mm of thread, while a serious off road tyre might have over an inch.

Hmmm, I don't think I will chance 150 quid it's not that important. I know remould tyres are all over the place size wise which is why I avoid them.

The internet suggest that a 3% manufacturing tolerance is accepted by manufacturers. Also tire section width is not the width of the physical tread, but a measurement of the tire width from sidewall to sidewall, and it is implied that the tire is fitted on a rim under inflation pressure when measured.So two "205" tyres can have different tread widths, but should be roughly the same sidewall to sidewall (fitted and inflated), +/- 3% to add more discrepancy.

So yes the same size can look different.

 

So by that token it's possible to have a situation where a big 205.70r15 is virtually the same size as a small 215.75r15 given the mathematical difference is approximately 5% in terms of overall height obviously the opposite can also apply meaning a significant difference in height.

Very interesting.