Tire speed ratings...

[Edmond]

Hey all, I'm going to get 4 new ones next week and I'm debating on what to get.

I don't go out to the track at all and I very rarely drive the car hard. I don't want something too expensive and I came down to two tires:

Firestone SZ50's-ZR rating, $186

and

BF Goodrich f-Force T/A KDW's-YR rating, $159

anyone have any opinions on those?

do I really need a ZR rated tire for my driving habits?

are the speed ratings only based on how fast the tire can go or is it also a measure of it's ability to last?

 

[maxrevs85]

They are speed ratings....wear factor is rated like for example , 200, 300 etc. Tire Rack has a complete breakdown of all the tire info.

 

[coolvette]

To the best of my knowledge, the speed rating is a measure of how fast one can safely drive on a particular tire. Check out

http://www.tirerack.com/tires/tiretech/general/speed.htm


Paul

 

[Ken]

The speed rating of the tire is an indicator of the tire's performance capability. Improving the tire's performance capability will normally benefit an automobile's performance. Conversely, decreasing the tire's speed rating generally lowers the tire's ability to contribute to the automobile's performance.

From the Tire Rack web site:

In Europe, where selected highways do not have speed limits and high speed driving is permitted, speed ratings were established to match the speed capability of tires with the top speed capabilities of the vehicles to which they are applied. Speed ratings are established in kilometers per hour and subsequently converted to miles per hour (which explains why speed ratings appear established at “odd” mile per hour increments). Despite the tire manufacturer’s ability to manufacturer tires capable of high speeds, none of them recommend the use of their products in excess of legal speed limits.

Speed ratings are based on laboratory tests where the tire is pressed (to reflect its required load) against a large diameter metal drum and run at ever increasing speeds (in 6.2 mph steps in 10 minute increments) until the tire’s required speed has been met.

Speed Ratings:

• N=87 MPH, 140km/h, Spare Tires
• P=93 MPH, 150km/h
• Q=99 MPH, 160km/h, Winter, LT Tires
• R=106 MPH, 170km/h, LT Tires
• S=112 MPH, 180km/h
• T=118 MPH, 190km/h
• U=124 MPH, 200km/h
• H=130 MPH, 210km/h, Sport Sedans
• V=149 MPH, 240km/h, Sports Cars
• Z=149 MPH, 240km/h and over, Sports Cars
• W=168 MPH, 270km/h, Exotic Sport Cars
• Y=186 MPH, 300km/h, Exotic Sport Cars

*Today, the Z-speed rating is the only speed rating that is still branded “within” the tire size, as in P225/50ZR16. All other speed ratings are shown in the tire’s service description.

When Z-speed rated tires were first introduced, they were thought to reflect the highest speed rating that would ever be required. Since that time the automotive industry has found it necessary to add W- and Y-speed ratings (indicated in the tire’s service description) to identify the tires that meet the needs of new vehicles that have extremely high, top speed capabilities.

_ken

 

[rrubel]

Really the speed rating is indicative of how stiff the sidewall is which affects how well the car corners (and rebounds from bumps, etc). A stiffer sidewall won't fold over at higher speeds or harder cornering.

Really you shouldn't change speed ratings DOWN. The suspension is *supposed* to take that into account. That said, I honestly don't think there's a lot of difference between W, Y, and Z rated tires - except you can sometimes get a treadwear warrenty in W ratings and not above that .

I bought four Kumho Ecsta Supra 712s from Tire Rack; they averaged about $100 each. So far in the 1000 miles I've had them they've seen hard dry track use, wet track use, wet roads, dry roads, and gravel. I like them a lot so far; their rain handling is awesome. They do have wide treads, though, so they tended to pick up a lot of gravel chunks... not that I often drive gravel roads in a Vette...

They're Z-rated, btw, though Tire Rack sometimes calls them Z and sometimes W.

[RICHR]

 

[vms4evr]

Edmond,
I have the SZ50s (not the newer run flat version). I have nothing but good things to say about them. My only experience is with these and the factory GSCs. In comparisson I can assure you I won't spend money on Goodyear tires again.
Given your driving habits you may want to consider the Khumos that Rich is referring to. I have heard a number of people comment on how good the tires are especially at the price.
A friend has them on his Mustang and he is quite pleased with them. He also doesn't race and rarely messes with the car. He's been running them for a year now and they still look good.
I'll be curious to see what Rich thinks about the Khumos after he has about 10,000 miles on them.
My SZ50s are approaching 25,000 miles. And I still have a good chunk of tread on them. So obviously I'm not an overly aggressive driver and don't autocross (yet). They still handle well in wet and dry and don't hydroplane on me. They are a little hard first thing in the morning in colder weather is probably the only negative comment I can make.
Graham

 

[MoeJr]

The Avon ZZ1's I just got for the 84 are 255/50ZR16 99W which makes em good to 168. I don't think I will be goin that fast anytime soon. Nice to know I got good tires. The ride nice and the car really corners well.

 

[rrubel]

I'll be curious to see what Rich thinks about the Khumos after he has about 10,000 miles on them.

Given how much I don't drive the Vette, check back in about 5 years .

[RICHR]

 

[Edmond]

Graham,

It's that kind of feedback that I read which made me go with the SZ50's. I placed an order at Tire Rack and should get them Monday or Tuesday.

 

[vms4evr]

Edmond,
As long as you can you live with the price I'm quite confident you'll be happy with the tires. I searched all kinds of forums and looked at the tire rack surveys and the SZ50s just stood right out above the rest. I actually bought mine at a local Firestone dealer at a comparable price and got lifetime rotation and balancing included. Like I said, no complaints after 25,000 miles.

Rich,
I think I'll pass on waiting for your review in 5yrs :L

Graham

 

[Eric]

...I searched all kinds of forums and looked at the tire rack surveys and the SZ50s just stood right out above the rest....Graham

That seems to be the case with all Firestone performance tires. The Firehawks on my Shark, Z24, and Monte were the highest rated performance tires for all three sizes and I love 'em.

By the way, speed rating also indicates the tires ability to disipate heat, thereby resisting tread separation. Any tire will fail when driven beyond its stated limits for a long enough period of time. We all remember the Ford Explorer story - the underinflated tires caused the tires to heat up more than would normally occur, causing separation. I buy the highest rated tire I can afford for my cars, wether the car can perform at that level or not. Anything to improve safety is worth it IMHO.

 

[rrubel]

Rich,
I think I'll pass on waiting for your review in 5yrs :L

You sure?

Actually, it should be quite a bit less than that now - we're doing the 2003 National Corvette Caravan next June and that should put about 1500 miles on the car right there.
[RICHR]

 

[Edmond]

By the way, speed rating also indicates the tires ability to disipate heat, thereby resisting tread separation. Any tire will fail when driven beyond its stated limits for a long enough period of time. We all remember the Ford Explorer story - the underinflated tires caused the tires to heat up more than would normally occur, causing separation. I buy the highest rated tire I can afford for my cars, wether the car can perform at that level or not. Anything to improve safety is worth it IMHO.

Eric,

thanks for that information. Someone told me something about the heat disipation, but I wasn't quite sure on it.

Graham,

I was going to bring my business to a local dealer like Firestone or even Goodyear. I looked at the Goodyear F1 somethings and they wouldn't match the price of Tire Rack.
It was the same thing with my local Firestone dealer, they couldn't come close to the price and he also said a few other things:

1. If I bought from the rack and had them installed at the shop, they would charge me extra than if I bought the tires from the shop.

2. He tried to convince me that Tire Rack would charge me 14 bucks shipping on each tire.

In all, I wasn't very satisfied with his service and attitude so I'm not giving him my business.

I did place the order yesterday and since I'm only 1 1/2 hours away from Tire Rack, the big Brown truck should drop them off on Monday or Tuesday. It feels weird spending 775 bucks on tires for some reason.:eek but I know it'll be worth it.

Thanks for the feedback Ya'll.