tire speed rating vs tire longevity

[friendly_jacek]

I learned something new today.

Quote:

The NHTSA tire aging field study also indicated a strong correlation of the speed rating with tire durability, with higher speed-rated tires losing the least capability with increasing calendar age. Drivers living in hot climates may want to consider purchasing higher speed rated tires than those that came as Original Equipment.

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=183 Considering that trailer tires are only rated to 65 MPH, that would explain a lot.

 

[leeharvey418]

Uh huh. I get all smacky when I hear people say that they never get anywhere close to the 'rated speed' reflected in a speed rating. Age, elevated temperature, and low inflation pressure all lower the safe speed on a tire below what's supposedly safe per the speed rating.

 

[Benzadmiral]

Elevated temperature ages tires? I presume you mean ambient temp, not the natural heating of the tires from driving? In that case I'm gonna be running through tires awfully fast.

 

[leeharvey418]

Yeah, I might have clarified that... Elevated temperature meaning anything higher than the ambient temperature in the laboratory when a speed rating test is conducted.

 

[Texan4Life]

Originally Posted By: leeharvey418

Uh huh. I get all smacky when I hear people say that they never get anywhere close to the 'rated speed' reflected in a speed rating. Age, elevated temperature, and low inflation pressure all lower the safe speed on a tire below what's supposedly safe per the speed rating.

yep +1 I have also found this to be true with load range/load index ratings. no matter the brand the simply last longer.

 

[Nyogtha]

I've always bought tires with higher speed rating than the vehicle manufacturer supplied OEM, wherever I've lived (mostly fairly deep South Texas with some Northern Ohio and Southeast Louisiana thrown in). Down south anyway, some days I get nearer the tire speed rating than others but the vehicle manufacturer's tires were always the junkiest tires I ran on vehicles. I'm glad when they hit their end-of-life so I can justify replacing them. I typically buy T or H speed rated tires for my vehicles.

 

[Quattro Pete]

Ok, but higher speed rated tires also generally wear out faster. But if you dont put on a lot of miles then buying higher speed rated tires does seem to have benefits.

 

[Nyogtha]

I used to drive at least 100 miles a day on weekdays, often more on weekends. Ambient temperatures well over 100°F some summer days - highest I've driven in was 125°F. The road surfaces were of course higher than that. I do always look at the tread wear and mileage ratings along with traction & temperature ratings. I'd have to say Bridgestone has worked best for me over the years. YMMV, MDN

 

[friendly_jacek]

Full NHTSA report mentioning it is here: http://www.litigationandtrial.com/files/2012/03/Tire_Aging_NHTSA.pdf I'm still looking for the raw data. One additional unexpected finding for me. NHTSA used increased temp (65C) and increased oxygen concentration inside tires to artificially age tires in their studies. By doing that they can age tires 36 fold faster compared to "naturally" aged tires in Phoenix AZ. My conclusion is inflating with nitrogen can slow down tire aging. This is the first conclusive evidence that I saw that nitrogen is beneficial for tires.

 

[friendly_jacek]

Originally Posted By: Nyogtha

I used to drive at least 100 miles a day on weekdays, often more on weekends. Ambient temperatures well over 100°F some summer days - highest I've driven in was 125°F. The road surfaces were of course higher than that. I do always look at the tread wear and mileage ratings along with traction & temperature ratings. I'd have to say Bridgestone has worked best for me over the years. YMMV, MDN

Actually, I had good experience with them too. If you google a study titled:

Quote:

NHTSA Tire Aging Test Development Project Phase 4: Oven Aging of Tires Followed By Testing to Failure on a Roadwheel

you will find that some tires didn't fail the test despite lab aging. Those tires were from Toyo, Bridgstone, Michelin, Continental, Dunlop and Yokohama. The ones that failed a lot were no brand or private brand tires from tire chains.

 

[fdcg27]

Or maybe they just determined that using 40% O2 NITROX to inflate tires and running the tires at ambient temperatures of 150F or so will produce more failures? I'm not surprised that some name-brand tires did very well, but I also see plenty of people running tires of no brand name I recognize underinflated with 79% nitrogen air getting those tires down below the wear bars with no failures. I wonder whether the tires that failed lacked a cap ply?

 

[Nyogtha]

The articles referenced show 50% EAN was used, oven temperature of 65°C (149°F), and well replicated ageing on tires retrieved from service in Phoenix, AZ after 3 to 5 years service. Down South, where the sun shines many more hours of the year than Ohio, you don't want to touch pavement, sidewalk, automobile bodies, or tires of vehicles sitting in the sun with bare flesh. Some vehicle interiors (vinyl) are problematic as well. But you don't have to care about snow performance of your tires, unless you're going on a significant distance road trip in winter.

 

[fdcg27]

2.4X the amount of O2 that's found in the ambient air? Wonder what that does for oxidative decay? I'm not sure that this test replicates anything other than what happens when you expose a tire to it. We get plenty of sun and heat here as well, as you already know. We then get the darker side of the equation, where we see long months of cold, ice and darkness. You know it's winter when you drive both to and from work with the headlights on and the snow brush is more than a precaution.

 

[Nyogtha]

You can read the articles yourself - replicating oxidative decay in an accelerated process was an objective from what I saw. There were even some references to the should-be-still-familiar studies of Firestone tires. I went through the introduction & setup and conclusions in pretty short order, but I'm a quick reader. I was last clocked at 2 lines per second with excellent retention & comprehension, but that was back in my school days. I haven't been officially clocked in years. You get nowhere near the sun & heat as points South of San Antonio, where I spent most of my life. Your yardstick is quite different from mine. I've worked & driven in 125°F ambient temperature there - can you say the same of Ohio?