jbird

I thought that a speed rating was achieved by running the tire on a big roller (dyno type thing) under load and weight for a certain speed and a certain amount of time. Someone said z rated tires should hold 150mph for 2hrs. Speed and weight cause extra friction that causes extra heat. Z or better rated tires are supposed to be able to take more heat, or generate less heat within the tire, in order to stay reasonably safe from a heat or pressure (given they are directly related) blowout. Someone correct me if I'm wrong.

--J.Bird

IROC-T

So which kind do you run on the front?

IROC-T

I believe you are correct,or at least close enough in the way of testing. Which kind of brings us back to why do I need to run Z-rated tires? If I was going to run in the Canonball , or the Silverado where the tires would see high speed (100+mph)for an extended period then by all means Z's or better,but in normal everyday driving they are overkill,wouldn't you think?

trackbird

Speed ratings are not "a load of crap". The loads placed on a tire at high RPM are extreme. If the tire is does not have the correct combination of belts and materials in the carcass, it can (and often will) fail (high speed tire explosions are not fun). Many tire shops will not mount a "H" rated tire on an F-body to avoid the lawsuits after someone has one fail at 150+ (such as your self). The shops are there to make money, avoid lawsuits and, as a side benefit, protect you from yourself. If speed ratings were not "needed", we wouldn't have them. They were designed as a way to classify the tires to match the capabilities of the vehicle.

To put this in perspective.

A few years ago there was a Ferrari Testarossa that showed up for the Nevada Silver State Challenge (open road race in Nevada). This car was entered in one of the high speed classes (150+ as I remember) and only had "H" rated tires (or less) on it. The event organizers made the driver (a doctor and his wife) sign a release form stating that the car should not be run as is and they are not liable for the results. The good doctor signed the form and left the starting line.

About 1/2 way through the 90 mile trip, a tire failed (exploded) and the car flipped into the desert. HIs wife was killed, and he nearly died in the wreck.

This may be interesting reading.

http://realbig.com/pipermail/detomas...ne/013778.html

IF they were "crap", the tech guys wouldn't care, would they?

I'm pretty sure he thought speed ratings were a load of crap as well. Sometimes people are too smart for their own good.

I just want to see everyone live to drive another day.

Have fun!

P.S.

THe reason that VR rated tires are recommended (even if you only drive 75) is that due to the stiffness of the tires carcass and the design of that tire, they are usually stiffer and more responsive. This allows the car to handle as the engineers designed. The handling characteristics of the various speed rated tires can be quite different and this can cause unpredictable handling as a result.

Do you have to? No. But is is a good idea.

(Someone mentioned the "W" rated Sumitomo HRZ+ tires, they work well and are about $83 each from www.tirerack.com).

SirChandlr

If i could afford a ferrari I sure as #$ would have z rated tires on it. It's a shame about that guy, but with so many factors, whose to say his tires weren't just plain defective. Maybe they were ATX?
Either way, you take me too seriously. I'm just saying that I have driven like hell on h rated tires and not had a problem. For street use, uber z rated tires just aren't nessecary. H rated stand up just fine for the occasional high speed blasts. Even if someone wanted to drive around at 150+ all the time, the cops sure aren't gonna let them

trackbird

You've not had a problem so far. Good luck.

As for defective, he was running 175 mph on a 130 mph rated tire. BOOM!

SirChandlr

And again, I feel terrible for the poor guy, but I would NEVER exceed 90-100 with my girlfriend in the car.

trackbird

I'm not really trying to bust your chops or pick on you personally. I crew for a NASA American Iron Extreme car (the team is building a Grand American car for next year) and autocross, etc. I spend lots of time at the track and have seen most anything that can break, break. I think safety is an issue that gets taken too lightly by most (not just the 150 mph blasts and such, but having the car prepped with correct air pressures, etc) and I don't want to see anyone hurt. This is a fun hobby and to see anyone hurt in a preventable accident is no fun. So, I try to explain the reasons for various things in an effort to increase safety for everyone.

Live to drive another day.

If my "lectures" (ramblings?) save one life, it is all worth it.

Keep the shiny side up!

Kevin

SirChandlr

To everyone interested in the original topic,, I apologize for jacking the thread!!!

Don't worry about it kevin, I never felt like i was being attacked (just a little ) I happen to be in a particularly cocky mood when I said speed ratings were crap. Obviously they have some meaning, just like speed limits One of the things about the internet is there's no emotion. You can read one thing in a good mood and not be bothered by it, then come back after a hard day and get really pissed off. I just throw down my 2 cents and take everything I read with a grain of salt. It's too bad we have to take the time to explain it. Thankfully we are making progress, with these great little smiliys!

PS: safety IS important!

-rich-

IROC-T

Thanks for returnning the thread,I was just going to post a "Lost & Found"for it. Thank you to all that did give the proper info that was requested.

After reading all of the post here and elsewhere I have come to the conclussion that I will be going with a V-rated tire ,as it seems to fit my needs,as far as Saftey,Affordability,and Availability. Again Thank to all!!!