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      03-05-2013, 12:42 PM   #7
ben@tirerack
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Drives: 740i
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Quote:
Originally Posted by sonic03inSC View Post
I don't understand how a 220 wear rating has less grip than a 300 rating. The wear rating is just like how soft a compound it is. The lower the number the softer the compound.
I personally am swapping out the stock worn rears for the PSS and will do the same with the fronts when they are worn. I don't track the car or I would get a much softer compound.
This is one of the most common sources of confusion. The wear rating does not tell you anything specific about grip. It tells you about wear. You might make a guess that a tire with low wear will have high grip. But you would often be wrong.

A few examples:

1) Low rolling resistance tires. Tires that are built for low rolling resistance have very poor traction compared to a max performance tire. But optimizing for low rolling resistance can give a tire shorter tread life. So you could have a tire with low grip AND low treadwear. For example, the OE tire on the first gen Honda Insight has a 260 wear number and isn't even average for an all season tire in terms of grip. Such is the price of maximizing fuel economy.

2) Better technology. As tire manufacturers improve technology, they are able to add both durability and traction. So a newer tire, like the PSS, may both outgrip and outlast an older tire like the PS2. For any given level of technology there is often a direct tradeoff between grip and life, but technology is always advancing. Just like the engines of today often make more power AND get better fuel economy than equivalent engines of yesteryear.

3) Inaccurate numbers. Treadwear numbers are fairly arbitrary. Different tire makers use different scales. Some manufacturers deliberately interpret their test results toward higher or lower numbers depending on how they want to portray the tire.

Sorry for the rant, but so many people put so much stock in such a misleading number that I feel the need to try to educate.
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