tyre speed rating

sibbat2 · 05-01-08, 07:59 PM

I am doing a track day at silverstone this month where on a couple of straights my CAV GT40 may reach speeds of 140 mph. The car has 295s Goodrich T/A radials with S speed rating. I have done a couple of track days before with these tyres where maximum speeds were in the range of 100-120 mph. Is it safe to use these tyres at silverstone?.

Rune · 05-02-08, 01:00 AM

My opinion is no The producer have testet those tyres to far above the 100-120 mph .but to be absolute safe so the speed will not be the reason to blow a tyre they set this speed. I vould recomend to change to code VR at least. If You blow a front tyre in 140mph, I belive the repair cost on the car is higher than a set of tyres.

Rune

Ian Anderson · 05-02-08, 04:22 AM

Rune

I hear what you say but have a look at TYRESAVE: Tyre Speed Ratings

The word "sustained" is always in these ratings and I am sure on a track like Silverstone you will never sustain over106mph for very long

I know in Zimbabwe we raced on retreaded / remolded tyres (got a deal through a retreading company if we carried decals and as they sponsored the series they were a must!) - these would probably be someithing like a P rating and we did 130mph plus on the long straight (From memory about 1.25 miles) Never saw a tyre blow other than for a reason like running it flat through a puncture. But also know we only got about 100 mile race life out of the rear tyres on a Formula V and less on a saloon racer.

That said a higher speed rating would be a great idea and will always be a safer option

Ian

EGLITOM · 05-02-08, 04:43 AM

If the tire holds up is also always a question of total stress you asking from.
So on a race track not only the average speed is putting load on the tire. Moreover the heat brought into by braking and fast cornering is stressing the tire as well.
Personally i would trash them and by a set of AVONS Cr 6 ZZ or something similar.

Besides the speed rating discussion my main concern would also be grip levels which you can achieve with the TR compared to track purpose tires.

TOM

Cliff Beer · 05-02-08, 06:32 AM

Sibbat, the BF Goodrich's are horrible on the track - I have some experience with them and they're just not what you want for a track day. As Tom mentions above, it's not just the maximum speed v. speed rating, it's the fact that a track day puts a lot of heat into the tire and this will lower the safety cushion so that even going a little beyond the speed rating invites some material chance of failure. Tom's suggestion of switching to the Avons is a good one - I'm in the process of doing that right now.

Malcolm · 05-02-08, 08:22 AM

I would not expect the tyres to explode. I suspect you may get to 130 mph (ish) at the end of Hangar Straight and that will be your highest speed. You will likely average between 65 and 80 over a lap.
On the tyres you have you will find they overheat far quicker and lose grip ie go off and that is far more of a concern than exploding to me. When it happens, back off and cool them down sensibly. Of course there are no guarantees......

Use these tyres up as fast as you can and then get some good ones eg Avons as mentioned here.

I am surprised that CAV are selling cars with an underrated tyre for the performance of the car.

Brian Hamilton · 05-02-08, 10:36 AM

Having worked in the Tire industry for about 4 years, I can tell you that the tires speed rating is determined by testing it at that speed for a sustained period of time. That period of time, believe it or not, is 24 hours. They (Firestone/Bridgestone at least) put the subject tire on a loaded roller and bring it to that speed and monitor it for 24 hours for things such as heat, wear, and structural integrity. If you're going to a track day, I'd suggest the highest speed rating you can find. Speed rating is also a notation of the tread compound (also wear indicator or rating depending on what you wanna call it) and generally the higher the speed rating, the higher the grip from the tires. Just a little infor for ya.

Laters,

Brian

sibbat2 · 05-02-08, 07:52 PM

Thanks guys for your advice. Looks like I'll have to bite the bullet and spend £1000 for a set of Avons.

Chris Headon · 05-20-08, 06:53 AM

Sibbat
MDA put Kumho tyres on mine, rated a W which I think is up to 170mph (someone correct me if I'm wrong). I use mine for the road and have never done a track day, but they have performed very well so far. Speak to Mark at MDA about suitability for track use and prices, but I'm sure they are less than Avons. Mine are 255/50ZR15 and as said, W rated.
Chris