Temperature grade vs Speed rating

[wbwanzer]

I don't need tires right now but am always researching the next set of tires. Currently I'm looking at the Firestone Destination LE3. It has a traction grade of A and a temperature grade of B. I don't believe I've ever had a tire with a temp grade of B before. So I looked into it and it seems that a temp grade of B means that the tire can withstand some amount of time running between 100 and 115 mph. What is confusing to me is that this same tire has a speed rating of H which means it is good to 130 mph. Does it make sense that it can have a speed rating of H but a temp grade of B?

Just curious. Thanks for any input.

 

[skyactiv]

Member @CapriRacer is a retired tire engineer and has a website named barrystiretech.com. The site is educational and worth a look.
From the main page, scroll down and click on Uniform Tire Quality Grading (UTQG) Ratings

 

[eljefino]

The H grade means you get 10 minutes at the high speed rating. I could only muse that the temperature rating has a different standard.

 

[CapriRacer]

Let's compare the 2 tests:

........................................UTQG..................Speed Rating
Test Room Temperature 95F ............. 77F
Inflation pressure............... 25 psi .......41 psi
Load .......................................88%.............100%

So, yeah, the results are going to be different and the UTQG test should result in a lower value.

 

[CapriRacer]

Opps!!!!

I made a mistake: The testing pressure for the UTQG Temperature test is supposed to be 32 psi. I misread a chart.

The good news is that it doesn't change the conclusions! The UTQG test will generate a lower speed!

 

[krzyss]

25 was quite underinflated.

Krzyś