Well Worn Tires and Grip

[rjundi]

I understand on wet and winter conditions that tire grip lessens considerably as tire wears down.

I noticed when I pushed my 2004 WRX with 80k around a sharp corner it squealed quite a bit under power. In the past it would not do this that I can recall with its newer RE960 tires that were installed on car at 30k miles.

Currently the RE960's are 6+ years old and have 3/32" tread left. They also have very small cracks at tread/sidewall edge.

Does dry traction also lop off as tread wear is gone too?

 

[CapriRacer]

I think what you are encountering is that rubber changes properties as it ages - and heat accelerates the process.

 

[sciphi]

Dry traction should increase as a tire wears, up to a point. The tread blocks aren't as tall so they don't flex as much. And with the channels worn down, there's more rubber meeting the road surface to give more grip. Both of those should theoretically increase dry grip at the expense of wet grip.

It's why autocrossers will have brand new autocross tires shaved to 6/32" or some low number, and why pretty much every on-road race series runs semi-slicks or full-on slicks that are useless in the wet. Look at an F1 car's dry tires, and compare to their wet tires. Slicks in the dry for maximum grip, channeled tires in the dry to move water.

 

[rslifkin]

The cracks indicate that the rubber has hardened, which is why you have less grip. Less tread doesn't hurt (and can actually help) grip in the dry, as long as the rubber is still soft.

 

[brandini]

Originally Posted By: rslifkin
The cracks indicate that the rubber has hardened, which is why you have less grip. Less tread doesn't hurt (and can actually help) grip in the dry, as long as the rubber is still soft.


Your tire compound has now heat cycled out, so you need new tires. A tire can lose grip even when not worn physically to replacement.

 

[dparm]

If the tire is cracking, it's old and needs to be replaced.

 

[TallPaul]

3/32 tread is pretty low. I would think that you are down to the wear bars. I have about 5/32 on the front tires on my Aerostar. They are not high performance tires, but they hydroplaned in a heavy rain the other day, so they are being replaced tomorrow. Also, get fresh tires with a manufacture date of this year if you can, because they are supposedly not very good after six years.

 

[rjundi]

Thanks the age of rubber/degradation/hardening makes sense.

These tires have only had 10k miles placed on them over the last 2 years with a large drop recently in traction with limited tread wear.

 

[TallPaul]

Slicks have the best traction--on both dry and CLEAN pavement. It also helps for the pavement (and tires) to be hot, so I would guess blacktop is better.

 

[CapriRacer]

Quote:
I'm glad CapriRacer answered this. I too was confused why safety advocates show an increase in stopping distance with worn tires, yet racing tires are slicks.

I think you'll find they are talking about wet traction.

 

[Volvohead]

Cracks are very bad. Very dangerous. 45 years ago we called it "dry rot". Seen 'em cracked to the belts. Mr. CapriRacer correctly described it as compound aging. Either way, it's time for new tires.

Time is often a silent tire killer. Compounds are much better now than in 1970. But after 5 years from production, more frequent inspections are needed to watch for the signs. Nothing past 10 years no matter what, I was just told by one manufacturer. That's still pretty darn good, considering.