Re: How safe are our tyres?

["Christopher A. Woodward" <cwoodwar@bellsouth.net>]

The W and Y ratings have (or will) supposedly replaced the straight Z rating,
as they are a more precise system.  The Z is a 150MPH + rating, but as more
cars are able to break this barrier (i.e. you no longer need a 911 turbo to go
170 in the U.S., just a suspended license), a more precise system was needed
to know the limits of a particular tire as far as sustained speed goes.  Ever
since I became interested in automobiles, I've always thought the Z rating was
a bit ambiguous, of course most people just said "who's gunna go that fast
aneeway?"

Adding 5psi means adding to what your vehicle calls for, NOT the max pressure
indicated on the sidewall (adding 5psi to that might be disasterous).  The
vehicle's recommended pressure is of course labelled usually on the door jamb
or gas filler cap or sometimes in the glove box.

My $.02,
Chris
'97 A4t
'90 CQ

Todd Phenneger wrote:

> >BTW, an H rating is for 112 mph.  The ZR rating refers to tires above the
> >Vrating.  The speed rating is molded on the tire with the load index*
> >(together these represent the service index of a tire) after the size.
> >ZR tires will have a W or Y in the service index and if it's a W or Y
> >tire,
>
>         Great report Richard.  One correction.  H rated is for 130mph.
> 112 mph is S rated I think but not sure.  There are like 3 ratings in the
> 110 to 116 mph group.  T,S and one other.  Q is below that at like 89
> mph???  H is 130.   V is 149 etc on up the line like you said.
>         One question, W and Y rated tyres are still Z rated.  Z is better
> though as it is still unlimited?d  That would make sense.  So a W rated
> tire is still Z rated but limited to what you said but a straight Z can be
> higher?  I didn't know that.
> Thanks for the write-up
>         Also, your part on incrasing tire pressure.  What pressure is that
> from???  Adding 5 psi if you want to sustain 150 mph is great but add 5
> psi to what, NOT the Max pressure I am assuming, that doesn't make sense.
> Can you explain that a bit more.  Thanks
>
>         Todd Phenneger
>         1984 4000s quattro / modified/ awaiting Turbo Transplant.
>         1985 4000 quattro / Silver / Fixing it Up.
>         1987 4000cs quattro / Saphire Metallic Blue/ Girlfriend's
>         1996 A6q / Volcano / Dads Car
>    *****1985 5kt / PARTING OUT!