Tire speed ratings

[RedNigel]

OK
Here's one for all the tire wonks to weigh in on:

The NT comes with ZR rated tires
I was just looking at a site that explains speed ratings and they say never to mix speed ratings between your front and rear tires
I am looking at an H rated tire to put on the back to help finish off the PR3 in the front

Anyone here who understands tire speed ratings and why you wouldnt mix speed ratings front to back???

 

[Phil Tarman]

If you could get to the 149+ mph that the Z rated tire is good for, you wouldn't want an H rated tire on the back. The H is "only" good for 130mph. I think you'll be safe.

 

[DirtFlier]

["...The NT comes with ZR rated tires.."]

The Z is the speed rating while the R means radial construction.

 

[RedNigel]

That make sense Phil

 

[karl]

Speed ratings on tires are about the tires ability to deal with heat. The faster you go the more heat you generate with flex. What you can do by mixing tires is have a tire reach operating temp while the other is still warming up. Tires need a level of heat in them to work "as advertised" too much kills them again. Life is a compromise, enjoy.

 

[charlie b]

But that means we should all dump our z rated tires and get v or h rated tires since none of us venture near z rated speed on NTs

 

[Phil Tarman]

I think you'll be OK with the Z-rated tires, Charlie. And I'll bet you're not about to dump them for H-rated ones.

 

[charlie b]

Phil,

Yeah, I was just kidding.

I think the point is that if they are mismatched and ridden hard an H rated will be hotter and grip more at a lower speed than the Z rated which may cause a problem in handling. At least that is what I get from mfg recommendations.

 

[Rmcapozzi]

Speed rating is a bit of a misnomer nowadays. It means more than how fast the tire can go (it original intent). It also relates to the handling characteristics of the tire. Higher speed rated tires are "sportier" performers offering better grip. The concern with mixing speed ratings (as is the concern with mixing differing construction types like bias v radial) is that the front and rear tire will not offer similar grip levels.

A grippier rear could introduce understeer which could result in a low side crash. A grippier front may introduce an over steer and result in a high side. Death and carnage isn't guaranteed but this is the concern.

A Z rated tire (all things being equal) offer superior grip to an H rated tire.

I suspect most of the tire manufactures websites discuss this.

 

[karl]

How fast can it go without damage. Infer what you will from the marketing department. They do this test running on a drum run for x time at X speed and then inspect for damage. The aroma is not part of the evaluation that I can find anywhere.

 

[DirtFlier]

I would venture a guess that most riders, including me, are not able to ride hard enough on the street to cause problems related to different grip levels because of mixed speed ratings for F & R tires. If you had several hours of private time on a race track, that might be a different matter.