Driving Above Required Speed Rating

[vevro]

Can someone tell me what can happen if I drive above my speed rating? I have a 99 ls400 and to accommodate my city driving, I've wrapped my wheels with T rated Pirelli tires for ultimate comfort. Originally I've never though I'd be able to drive over 100mph in the city. However the other day I drove upstate and decided to test what my car was capable of. So I floored the gas paddle until the speedometer hit 115mph, a second later I realized I was riding on T rated tires which according to specifications is 118mph tires. Now, can the tire actually shred if I would have hit 120mph that day, or is there a safety margin?

[chips229]

Dont quote me but i think they down rate the tyre speed for safety.

In the uk if say the top speed of the car is 160mph you must have that spec tyres on them or its againest the law

Even though our motorway speed limit is 70mph. :(

[Lexusfreak]

You would have to be doing that consistant speed for a long time before the tire would fail vev. If you do it once it's not going to do anything.......just don't get pulled over or you'll be asking the bus driver what speed rating his tires are!

Love the pic btw! :) wearing an F.D.N.Y. shirt over here actually! :)

[vevro]

Thanks guys. That's what I though as well, so next weekend I'll be back on the NY throughway and kamikaze driving. ;)

My only concern is that I was driving in the range of 100 mph for roughly 1 1/2 hours and when I finally arrived I looked at my tires and water vapor was steaming of them. Freaked me out a little.

[MrSypher]

That's funny.. I remember when I was young seeing that on my car..

But as for the speed rating if your gonna do 100+ it's good to have tires that capable of handling those speeds.. You see with bigger profile tires the car tends to bounce at high speeds which in turn makes it dangerous.. Also cornering the tires tend to give away a roll..

[Lexusfreak]

Agreed! If one were to do that kind of speed for a long period of time I would suggest to equip the car accordingly (assuming one still has a licence & not in jail going at those speeds) A tire that's not rated for those speeds could fail & then it's the "phone call from the horizontal telephone booth". :(

[SKperformance]

It is only a problem when contionious for usually over 1-2 hours before the belts shift, which is what the rating is for

[Lexusfreak]

vev mentioned he did that consistant speed for about 1 1/2 hours at that speed. He was lucky by the sounds of it 2 ways. 1 his tires didn't fail & he is still alive, & 2 he still has a drivers licence by the sounds of it lol

[vevro]

Yeah, Yeah, Yeah, I'm still here with all limps attached. I doubt the tires would have failed that day. The car was sailing at 110-115 mph without any vibration. I almost rear-ended a van that was going around 65mph, the SOB changed lanes without signaling. On a sad note my typical speed around NY is 19 mph, so the T rated Pirelli’s are perfect for my everyday needs.

[MrSypher]

Don't sweat it that much.. Before when I was wet behind the ears I used to fly around all day at speeds of 120mph with non mod'd cars.. Now if I'm not in a mod'd car I don't feel safe enough to keep a steady pace above 90 or so.. But when I'm in my car that's a different story, I'm always around 100mph cruise'n speed..

[tds]

Your 99 LS400 came standard with V rated tires. This is because the top speed is around 150 mph and V rated tires can handle 150 mph continuous.

Here are speed ratings of other tires:

S rated: 112 MPH

T rated: 118 MPH

H rated: 130 MPH

V rated: 150 MPH

Now, you should keep in mind that the handling characteristics of your LS400 are based on V rated tires. A T rated tire also has a much softer sidewall than a V rated tire, so your handling will deteriorate with T rated tires.

On my LS400 I installed H rated tires. It is a good compromise between tire cost, handling characteristics and safety. I would never run a T rated tire at 115 MPH, but I would run an H rated tire at that speed.