Have seen a set of goodyear eagle f1 gsd3's in 215/40/17 Y 83 (so)
The Y is the speed rating, is 83 the hardness of the tyre compound?
I have seen the same size tyre but with ZR on the end. Are these two tyres different. Obviously the tread pattern will be the same and a slightly different speed rating.But are they a different compound/ sidewall stiffness to the ZR?

 

I cant comment on the chemistry of the actual tyres but the Toyo site is good for explaining all the markings on the side of the tyre. http://http://www.toyo.co.uk/index.p...car.speedindex for the speed index and http://http://www.toyo.co.uk/index.p...=car.loadindex for the load index.

In your case I think it was actually probably 215/40/17 83Y - the '83' is the load capacity of the tyre. So, the tyre you mention has a load index off 487kg going of Toyo's table.


ZR is an old speed designation (the change must have been quite recent as I think ZRs are still in circulation - mine are ZR - probably old stock). Now it is just one single letter (well, for us anyway).

There is actually a better site detailing the ZR/Y etc business - I will see if I can dig it up.

John

 

I can't find it now - maybe tomorrow.


Basically, it's that ZR is simply rated to over 150mph, but the top speed wasnt really specified. I guess, as cars have got faster they have had to specify exactly what speeds over 150mph the tyres work to. So Y has been tested to 186.4mph.

I doubt there is really any difference between the two in terms of the chemistry - other than tweaks and changes that happen to every product over time.

John

 

Thanks john very heplfull :-)

 

Tyre marking info is on Michelin UK site.

Andy.