Is there a cure for tire cupping?

[reecebike]

I changed A lot of tires & they seem to cup or add more air they wear out in the middle!!

 

[motorcycle-ed]

For sure you need more air pressure. Run 39front 40rear minimum. If you are heavy guy or carry "stuff" in the bags, bring the rear up to 42. These are cold pressures.

Ed

 

[Checkswrecks]

No attempt to hijack the thread, but at what point does increasing the pressure change the contact patch enough to alter the amount of traction available?
If the pressures are specified by the manufacturer and are exceeded, wouldn't this make the contact patch smaller and reduce available traction due to the tire not deforming enough to grip the road surface properly?

I would rather change the tire earlier than lose the margin of traction that correct (?) inflation would provide.

Please feel free to bump me or just point me in the correct direction. I did search, but the results were lacking in specificity.

HRZ's answer is pretty good, but note that the whole thing is counter-intuitive to an implication in the way your question was asked. The static contact patch does increase with reduced pressure as you mention. But the dynamic contact patch can decrease when there's movement between the surface of the tire and the road. (Which hopefully isn't moving, especially outside of California.)

The friction we want is provided by solid contact between two materials. (Each of those has a coefficient that can affect the total but let's just figure that the coefficients of friction never change.) Flex, squirm, whatever you want to refer to it as, is description of a process that reduces the actual total number of square inches of contact area betwen the two materials at any one instant. This is because any one small bit of the tire's rubber contacts the road, loads elastically, and then the reduced tire pressure reduces the stiffness of holding that bit of rubber in place and against the road. Basically, the rubber is allowed to pull away from the little bit of road it was trying to stick to, hence the term "squirm" while another little bit of rubber goes through the same process in the next millisecond. The net is that the overall tire has less traction because the instantaneous total number of square inches of area is less. The reduction in traction is also how some of the really experienced track guys can get pretty close to telling you their current tire pressures just from their cornering performance.

I once got to see a tire run against a "glass wheel" at one of the tire manufacturers and the high-speed video we saw of the same test was eye-opening in how much movement the rubber goes through. (Engineer-geek stuff)

Obviously a simplification and it omits all sorts of chassis dynamics that are also affected, but I hope this helps.

Bob

 

[daddyman]

Thanks for the info.

Good stuff!

B)

 

[monk69]

'Bearly Flying' To establish the tire pressure for Your Bike, with the load you normally carry at the speeds you ride...........

Take the cold tire pressure.

Ride the bike normally to heat up the tires...

Take the Hot Pressures of your tires.

You should be looking for a 5 % to 10% increase from cold to hot.

If you have more than 10% increase,,,, add air.

As much as I like your concept and have copied/paste it to my mc file info page I keep....I'd like to know where you got that info....or is it something that you worked yourself(which is ok with me).

I stole some info from a 4 wheel tire solution,in that I draw a line with chalk across the tire and drive a block,then check the line to see where the line is wearing Middle,or sides.( tire temp. warm).Works great,for years.

To bad it doesn't work for bikes,but yours seems to make since......More input please!!!!

 

[MartyO]

I run the 39 and 42 on my 06. I've had 3 sets of Storms with no cupping. The Metzlers, B220's and my new Roadsmarts are cupping. I'm disappointed in my front Roadsmart, significant cupping. The back is doing well. I may try a Storm on the front and the Roadsmart on the back next time. I might be doing this soon. I have a still good front Avon in the rafters and the cupping is bugging me, I don't like the noise and vibration. After reviewing this thread, I may go to 40 and 43, give it a try.