Tread Depth

[wantin150]

How has this "standard" come to be? I have seen new depths of 6/32 (DOT legal racing), 10/32 (performance tires), 11/32 (standard), 12/32 and 13/32 (off road and a/t), 14/32(? - Mud).

Unless they are really "specialty" tires, most seem to come with 11/32's tread depth when new. Who came up with this number and why? I have my own thoughts on the matter but would like to hear from those in the know. I understand the hydroplane resistance as well as snow or off road traction but what is preventing us from having a new tire at 15/32 with interconnecting ribs and such to reduce squirm and improve handling?

 

[alreadygone]

When I first started selling tires in the early 70's they were all bias belted with 13/32 of rubber. Average tire life was 18-20k miles. First 2/32 would be gone in less than one thousand miles (made low mileage warranty replacement a hazzardous duty). First radials I sold were Mobil (Had a Mobil service station at the time). Best memory serves, they came with 12/32. Mobil rep. said improved mileage more than made up for less inital tread depth. Probably would have if they hadn't all separated at approx 25-30k with 1/3 to 1/2 of tread left.

Now we're seeing 11/32 initial depth lasting 60-70 thousand plus. Don't personally want to go back "good old days"!

While 11/32 is pretty well standard, I do sell light truck load range C (6 ply rating) tires with 14/32 and severe mud service tires with 17/32. All Cooper built.

Bob

 

[XS650]

quote:

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Originally posted by alreadygone:
First radials I sold were Mobil (Had a Mobil service station at the time). Best memory serves, they came with 12/32. Mobil rep. said improved mileage more than made up for less inital tread depth. Probably would have if they hadn't all separated at approx 25-30k with 1/3 to 1/2 of tread left.


Bob

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Were they made by Firestone? Firstone has big problems with their earlier radials soing an unscheduled automatic disassembly while running down the road. Goodyear had problems with their early radials too, but not as bad as Firestones.

They both tried to cheap out and make radials on equipment that was designed to make bias belted tires instead of buying the right equipment.

 

[alreadygone]

Kelly Springfield. Yea, they're a Goodyear generic, but I believe at that time still built in different plants. Allways seemed kinda odd, Michelin was there giving better mileage than they do now with 2 RAYON body plies and 2 steel belts. Tried to sue everybody attempting radial construction even though patent had expired. U.S. companies attempted radial construction with polyester,nylon,steel,ALL IN THE SAME TIRE!! Sometimes as much as 7 tread plies in a standard load (4 ply rating)tire. IMO early failures were the result of internal heat/friction buildup. Or they just couldn't glue all that sheeet together!

Yes it was Firestone's "Firestone 500" that prepared them for Bridgestone ownership!

Bob

 

[toocrazy2yoo]

Quote:

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Now we're seeing 11/32 initial depth lasting 60-70 thousand plus. Don't personally want to go back "good old days"!

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Yeah, well, getting that mileage from such a thin tread requires such a hard compound, I'm not interested from a traction standpoint, especially in wet weather..

 

[Dominic]

I go through tires about every 25,000 miles. 11/32" of tread to wearbars.

 

[ebaker]

Quote:

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Unless they are really "specialty" tires, most seem to come with 11/32's tread depth when new. Who came up with this number and why? I have my own thoughts on the matter but would like to hear from those in the know. I understand the hydroplane resistance as well as snow or off road traction but what is preventing us from having a new tire at 15/32 with interconnecting ribs and such to reduce squirm and improve handling?

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Thicker tread build more heat and are more prone to blowout at high speed. Dry cornering is less due to the flexing of the thick tread. I think 11/32" tread is just a good compromise figure for average passenger cars.