Tire Cupping?

[CNY Fizzer]

Over the years on this forum I have read about peoples tires developing some cupping but I was never sure exactly what it looked like. Today checking over my tires and air pressure I noticed an odd pattern on the rear tire. The center is 2 1/2 inches wide, on each side of that is 1 1/2 inches below the center level, with 1 inch chicken strips on the edges slightly elevated. Is this cupping? ----_____----------_____----
The tires have good tread depth still and about 3,500 miles. The tire is kept at the recommended 42 lbs. I do believe this is caused by riding almost exclusively 2up on a heavy bike (FJR), on a tire with too weak a carcass. These are not the GT tires that I have discovered most run on these bikes.

 

[TownsendsFJR1300]

The worst cupping I had was on the OEM Bridgestone on my 04 FJR. It had about 6,000 miles on it.

The cupping generally occurs at the edge of a tread. You can feel an adjacent tread flat, then the cupped tread, literally lower.

The more cross treads you have, the more cupping you'll get as they age.

When I rolled my FJR backwards out of the garage, tilting it some, I could literally feel the cupping coming thru the handle bars(at the end of the tires life). It felt like a knobbie tire. There was still a fair amount of tread down the middle but it got replaced..

Now that's with the appropriate tire for the heavier bike. Make sure, when replacing, you get the appropriate tire from the manufacturer as some have slightly different tires (heavier duty-the FJR, Goldwing, would fall into this category) depending on the application..

 

[FIZZER6]

You described cupping.

I have found that it has as much to do with tread design as it does with load and tire pressure.

Seems that tread grooves that run a closer angle to parallel to the direction of travel cup less. Tread grooves that run closer to a 90 degree angle from direction of travel tend to cup worse. So far Michelin Pilot Power tread grooves cup the least of the 4 different tires I've used on this bike.

Example:

This tire

Will likely cup worse

Than this one

 

[TownsendsFJR1300]

You described cupping.

I have found that it has as much to do with tread design as it does with load and tire pressure.

Seems that tread grooves that run a closer angle to parallel to the direction of travel cup less. Tread grooves that run closer to a 90 degree angle from direction of travel tend to cup worse. So far Michelin Pilot Power tread grooves cup the least of the 4 different tires I've used on this bike.

Example:

This tire

Will likely cup worse

Than this one

+1 ^^^ 100%.

I have a PR2 on the front and PR3 on the rear(they didn't have aPR 2 instock and I needed it ASAP).

My next set will be PR2's front and rear for this exact reason. I currently have well over 13,000 miles on the front PR2 and is about 2/3-3/4 worn...

I already have some slight cupping on the rear PR3 with 3,000 miles on it, none on the PR2 FRONT with 13K...

 

[FinalImpact]

Damping rates or lack of damping/excessive damping can also cause cupping.

Over pressure = wear out the middle, loss of traction
Under pressure = tire damage, cracks, excessive flex = heat damage
Rebound too fast = trailing edge of tread is raised
Rebound too slow = leading edge of tread is raised

Some light reading... Race Track Motorcycle Tyre Wear Guide - Types and Causes

Notice leading edge of rear BT023 is raised. I'll reduce the rebound damping (its adjustable in this case) and see if goes away.

 

[Solarservant]

Dude. Thank you. I've been seeing leading edge raising on my rear PR3 since my last track day. It's been getting worse. Appreciate the info.

Of course, don't know what to do about it... No ability to adjust stock suspenders. Should I play around with tire pressure a little?

 

[FinalImpact]

Dude. Thank you. I've been seeing leading edge raising on my rear PR3 since my last track day. It's been getting worse. Appreciate the info.

Of course, don't know what to do about it... No ability to adjust stock suspenders. Should I play around with tire pressure a little?

Checking the pressure is never bad thing. The difference in running pressure from cold check at ambient 50°F vs tire in the sun and 70°F is huge when for example both are set at say 36PSI. Once warm check them and where they really are... A firm carcass rolls easier but pressures can shoot up pretty high as temps increase.

Just an observation but lots of highway miles with no corners can make some tires scallop even if everything is near perfect....