I have recently come into a set of tires that I intend to use and I started looking at the numbering system on them. My 15" Goodyear RSA's (stock size) have a rating of treadwear 'A', load range 'A', and compound '260'. The ones I recieved (16" 60 series) have a compound number '340' on them.

Anyone know the meaning of all this? I did a search and didn't come up with any sites that explained it.

I am assuming that the higher number is a softer tire, but I'm just guessing.

Hans

 

I beleive that is the treadware rating that you are referring too. I think that the lower the number, the stickier the compound and the shorter amount of time/miles the tire will wear out. I don't beleive that they are very comparable between different tire manufacturers( ei A BFG and a goodyear rating of 300 does not necessarily mean that they will last the same amount of time). The numbers are supposed to be used to compare different tires of the same manufacturer, although they can be used for a rough comparision between different tires of different manufacturers.

 

Zack has it right. Some racing tires do have codes or numbers to indicate the softness/hardness (relative durometer) but not street tires. The treadwear ratings are made by the individual makers and don't necessarilly correspond to those of other makers. Within a given make, a lower treadwear rating usually means a softer and grippier compound but not always. In many cases the difference in the treadwear rating has more to do with the construction of the carcass or the tread pattern. Typically, a tire with a higher speed rating will have a softer compound as it's intended use puts better traction performance above longer life or fuel economy.

The letter designations on a tire indicate it's wet braking traction, it's heat handling rating, (A being better than B) and the number is wear, not compound. A tire with "A" traction is expected to stop better than one with "B" traction. A tire with an "A" heat rating is expected to be more resistant to heat from high speeds or low inflation than a "B" rated tire. Tires with a 400 treadwear rating is expected to last twice as long as a tire with a 200 treadwear rating under normal conditions (in hard driving, the ratings may not apply). If the tires you got are also Goodyears, their higher tread rating would suggest that they would have a harder tread, not a softer one.

 

Yup. That's the treadwear index. Now...what does it mean?

Well, there's a 'reference tire' that's used for comparison. Everything is compared back to that reference tire. The reference tire had a treadwear rating of 100. And no, I have no clue what exactly the reference tire is. But the treadwear is relative to that baseline and thus all treadwear ratings should be relative to each other as well.

One more note. The 'traction' rating is for WET BRAKING traction. Don't get confused that it'll tell you how good the tire is for drag racing or anything of the sort.

 

"A" is the highest rating. Normally "A" tread is the highest adheasion wet and dry in forward and side loading traction. "A" temp is the ability of the tire to get rid of heat without tread to inner separation. Really needed in the hot pavement of the southwest.

The numbers like in most high performance tires is low like 180 ware rating - which is very sticky but the 180 or even a really high number like 340 stands for the number of miles that they expect it to last under normal driving. 180 is @ 20,000 miles or less 340 is 50,000 + miles.

340 is a hard high mileage tire. It will only be sticky until the first couple of heat cycles. I never get much more than 5-10 K miles out of sticky 180 Z rated tires.

 

SORRY dont mean to get all technical on you guys but ---

The Department of Transportation requires each manufacturer to grade its tires under the Uniform Tire Quality Grade (UTQG) labeling system and establish ratings for treadwear, traction, and temerature resistance. These tests are conducted independently by each manufacturer following goverment guidelines to assign values that represent a comparison between the tested tire and a control tire. While traction and temperature resistance ratings are specific performace levels, the treadwear ratings are assigned by the manufacturers following field testing and are most accurate when comparing tires of the same brand.

TREADWEAR
Treadwear receives a comparative rating based on wear rate of the the tire in field testing following a goverment specified course. For example, a tire grade of 150 wears 1.5 times longer than a tire graded 100. Actual performance of the tire can vary significantly depending on conditions, driving habits, care, road characteristics, and climate.

 

LIke ddecart said the traction rating is for wet braking performance...for example the Goodyear Aquatred 3 has a traction rating of AA! If you try to drag race with it you will just spin your tires because there isn't much rubber on the road...hence the treadwear is 640 for 11/32" of tread, plus the temperature is just B rated.

So, you need to consider all the ratings...traction, temperature, and treadwear. Another example is a Comp T/A Drag Radial which has a traction rating of B...mostly because it's just a slick...and treadwear of zero because there's just 5/32" of tread (minimum legal limit)...plus temperature rating of C which means they are a single use only...get them hot and they will give you excellent traction, but if you let them cool off then the rubber will form plastic bonds (instead of the desireable elastic type) and lose traction.

When I look for a tire I look first at the Traction rating, then I look at the temperature, then the treadwear and tread depth. The best tires I've seen will have something like A A 200 for a tire with 10/32" tread. Another number I look at is the speed rating...but since I rarely go over 90mph I usually just use this last number to determine the quality of the manufacturing process if there are more than one tire with my desired ratings


[Modified by Rockn-Roll, 12:58 PM 4/3/2003]