So the rear tire (Dunlop OEM) started cupping on my 15 Limited Low at about 5k miles. This is the first time I've had a tire cup on any bike I've owned and based on the searching I've done here it seems like this is not unusual and typically caused by poor tire pressure management. But something I've not been able to find much information on is whether a cupped tire is safe to ride on.

It seems reasonable to think that safety could be a concern. The amount of surface contact between the tire and the road has got to be less than optimal due to the cupped surface of the tire. Also the slight vibration caused by the cupping would also seem to compromise the traction of the tire.

Am I wrong in thinking this or worrying to much about it? I'm trying to decide whether or not I should replace the tire or attempt a warranty claim.

Also, while I'm asking, has anyone recently requested a warranty replacement for a cupped tire. It seems that the MoCo is generally not willing to do that anymore and I'm wondering if anyone has had a recent experience with it.

Thanks in advance.

 

Mine cupped at about 9,000 or 10,000. I rode it until I replaced the tire at about 17,000 or so. I hummed a little in the turns, but I didn't notice any loss of grip.

As far as why it cupped, that's anybody's guess. I am all over my tire pressure and check it at least weekly, so it wasn't pressure related.

I mentioned the cupping to my dealer and the local indie...both had the same reaction. I'll replace it for ya, but it won't be free.

 

I thought the general consensus was that the ESP w/ tire was basically bogus.

Anyways, my OE Dunflops were cupping bad (front and back) and I rode them past the wear indicator. Should I have... probably not, but I don't have a money tree in the backyard. The did hum quite a bit and its amazing how one gets used to the noise.

 

Back in 09 I had a electraglide classic with 4 k miles and on a trip to the Black Hills I noticed my front tire cupped badly. Went to Rapid City HD and they got it covered under warranty.

 

I check my tire pressure at least once monthly or every other ride... depends on how often I get out. I have never had to add more than a couple pounds. I call BS on bad pressure management causing the cupping. Seems Dunlop has had problems with the 407s/408s since 09. Just saying, but I'm not bitter.

 

The Dunlop cupped on my WG, but I rode it until the end without issue.

 

Keep an eye on our tire pressure. As mentioned, should be checked regularly.

 

My bike has about 80,000 miles on it so I've been through a few tires and every one of them has cupped. I'll concur with others and say that air pressure does not seem to be the issue, at least in my case.

While the humming that results from the cupping can be annoying to some, it really doesn't bother me. The thing that is more concerning is the squirm you can feel when going into a turn. I seem to feel it more on slow speed turns (think parking lot speed) and not so much when riding aggressively. The squirm sure isn't confidence inspiring, but the on the other hand, I don't freak out over it either and I've ridden every one of my cupped tires to depletion.

As for a reduction in traction. I'd suspect that does occur under certain conditions, but maybe not all. It's quite possible that under whatever condition caused the cupping that you may actually have better traction as the highest pressure points have been worn down and you now have a more uniform force within the contact patch. I'm not saying this as fact, I'm simply thinking aloud.

Now here's some more food for thought for those analytical nerds like me... My theory on what causes cupping. I have no proof for this theory and it's really just an opinion being presented for the sake of discussion.

When the tire rolls along the road surface it flexes to some degree. Some of that flex is in the structure of the tire and some of it is in the tread that contacts the road surface and it is directly proportional to the loads imparted on the tire based on the conditions. As the tire flexes certain areas of the tread are subject to higher forces with the road surface and therefore wear quicker than other areas of the tread. There is also a scrubbing action taking place as the tire loads and unloads at the edges of the contact patch. As the tread grooves reach the edge of the contact patch, the void created disrupts the consistency of the scrub. Those two items, the isolated higher force areas of the tread and the inconsistent scrubbing action between tread grooves, are the cause of the cupping.

While air pressure does play a role, it will primarily control the amount of structural tire flex. Flexure of the tread is less dependent upon the air pressure and is primarily controlled by the physical properties of the rubber itself. Therefore, air pressure levels cannot be the sole cause of cupping.

To validate that point even further, our bikes see a multitude of varying conditions. The optimum pressure for a tire rolling down a glass smooth interstate is different than the optimum pressure for the same tire rolling down a washboard surface, or a surface riddled with cracks, bumps, tar snakes, etc. Or the optimum pressure for going through the same curve at 40 mph vs. 80 mph is different. There's other examples but these should sufficiently identify the point I'm making.

Then you also have to define, "what is the optimum pressure"? Is it the manufacturer's recommendation? The pressure that gives the best fuel economy? The smoothest ride? The best reaction to steering input? The best high speed traction? And so on. Recommended air pressures are simply a compromise value and as such cannot control the tire performance equally as well across the entire spectrum of use.

So! My conclusion is that the tire's design, especially how the structure and the tread behave as a unit, along with the conditions it is subjected to play a much greater role in tire cupping than a few psi one way or the other.

Anyone else want to chime in?

 

Wow, you're serious? TP is key.

 

I agree that it plays a role but not as much as you may think. My logic, even though as previously stated is not fact, says there's a lot more to it than simply tire pressure.