I hope this is the right section to post this - if a tyre is H rated ie up to 130mph I was just wondering how fast it will actually go before coming apart? There must be some manufacturing tolerances, anyone know what they are?
Sensible answer (since it is actually a sensible question);
There are both testing AND manufacturng tolerances... the one is intended to more than cancel out the other.
So when testing a tyre design, it will be run up to significantly more than its official speed rating.
... but this is because not each and every tyre is tested before it leaves the factory, and manufacturing tolerances mean that some will be
'stronger' than others. The testing tolerance is intended to ensure that even the worst of of the production tolerances will give a tyre
that can sustain the rated speed.
As to what the actual testing tolerances are, I must admit that I don't know - I leave that to the tyre manufacturers - but if you really want to
find out, contact ETRTO (the European Tyre and Rim Technical Organisation, or maybe speak to the technical section of one of the UK's tyre
manufacturers (Avon are usually pretty helpful).
its also worth mentioning that the tyres are only meant to withstand there rated max. speed for 10min at a time...
Cheers for the replies guys.
I was asking because my tyres are rated to 130mph which is fine for the 70mph limit on UK roads (I don't do track days or drag racing) but
we're going on a trip to Germany next year and if we end up on the unrestricted stretches of autobahn we'll really need to go a lot faster
to keep pace with 'normal' traffic.
I didn't know the max speed was only for 10 minutes, its lucky I asked because if I'd just sat at 130mph for miles and miles it sounds like
I would've been really pushing my luck!
I've been looking for higher speed rated tyres for when they need replacing but so far haven't found any in my size (275/60-15) so I'll
contact Coopers and see what they say.
Have you been on an autobahn? Speed of normal traffic is less than you think!
You're quite right, lots of it do now have speed limits, 80mph or less but the unrestricted sections have an advisory but not compulsory 80mph
limit. The last time we were there it was all on bits with limits between 50 and 80mph, we didn't see any unrestricted bits but thought it'd
be a good idea to be prepared this time, just in case.
I've a few friends who've been on some of the unrestricted sections and they reckoned it got a bit scary when overtaking at 100mph and
suddenly a Merc or a Porsche appears behind you, almost out of nowhere.
The speed ratings are for 10 minutes at the tyres maximum rated load at the correct pressure. The rated is usually well above the maximum corner
weight in the real world. With a lighter car there is less heat build up so the time is less of problem provided the pressure is correct for the
speed and load conditions.
The other factor that comes into consideration is centrafugal force causing the tread to separate but provided the maximum rated is not exceed by
huge margin this should not be a problem,
My Autobahn experience was something like 80miles at around 140mph over a few different sections.
Yes there was traffic at about 80mph and there was some fast AMG at 180+ the rear view mirror is your friend, as is a limitless supply of fuel 
enjoy the drive, always better to be prepared
quote:
Originally posted by britishtrident
The speed ratings are for 10 minutes at the tyres maximum rated load at the correct pressure. The rated is usually well above the maximum corner weight in the real world. With a lighter car there is less heat build up so the time is less of problem provided the pressure is correct for the speed and load conditions.
I suspect that if you did have a problem and you were over the speed limit of the tyre (and it could b e proven) then you insurance would be invalid.
The fundamental problem here is that your car is capable of a higher speed than the tyre is rated for and therefore should not have passed IVA
You are right in looking at your proposed high speed holiday in more detail as I would want tyres rated at a good few mph more than my car can
achieve
Don't forget the speed rating is but one part of the story and as described in the wheel & tyre bible the tyre speed and load ratings give an
indication of the braking and cornering loads the tyre is capable of.
Slowing from 130+ puts as much strain on the tyre as continuous high speed
quote:
Originally posted by nobrakes
...if we end up on the unrestricted stretches of autobahn we'll really need to go a lot faster to keep pace with 'normal' traffic...
My tyres are rated for up to 130mph and I have absolutely no intentions of exceeding this, either in the UK or abroad even though I easily could. I
value my licence and my life!
Insurance - yes, this would definately be a problem if exceeding the tyres speed limit. Also, German courts can hold you partly responsible if
involved in a crash at over 80 (130km/hr to be exact) on the unrestricted sections even if it isn't your fault.
I was concerned that if the rating is a nominal speed, for instance 130 plus or minus 5% then 124mph could be too fast - I had a puncture at 50 and
that was scary, I'd imagine a blown tyre at 130 would be pretty much uncontrollable...
quote:
Originally posted by prawnabie
Have you been on an autobahn? Speed of normal traffic is less than you think!