Mine seemed to cup more after a trip to Fuel Moto. so I think how much power you are trying to put to the ground is also a factor.

 

....along with the fact that Harley doesn't give good enough guidance on them IMHO! The pressures in the owners manual should only be taken as a guide. If you are heavy, or ride 2-up a lot then add more air, according to taste. I use book pressures when solo, for 2-up I add 2F/4R and when fully loaded in touring mode I use solo plus 4F/6R.

 

It's pretty much low air pressure that does it. My back tire was pretty badly cupped when I replaced it at 16k miles even though it has less wear than the front tire.

 

My tire pressure is checked once/week, both front and back. I have MC2's and go with 40PSI in both just so I don't forget which is which. No problems yet. I used the same method for my stock Dunlops and ended up with 15000 miles and no cupping issues. It's all about the pressure I think.

 

I run the same 40/40, and have tried other combos. Seems no matter what I do I get cupping, more so on the left side. Some say it's the crown of the road, who knows, I typically get 10K out of a set of tires, then they need replaced due to them cupping.

 

I'm on my 5th Harley, I have always run 36 psi in the front and 40 psi in the back. Check the pressure prior to riding almost every time I ride, especially if it has been a few days since the last ride. I have never had a tire to cup.

 

On Dunlops I've had great luck running 2psi over the recommended pressure.

 

Besides tire psi being some of the issue, I believe the forks and rear shocks play a bigger issue causing cupping. Usually cupping on an auto is from weak shocks and the tires dribble up and down going down the road, the same theory holds true with the rebound/compression of the forks and shocks.
How many HD's have precise suspension adjustments? Not too many, throw in the fact that majority of folks dont adjust their air properly and it goes down hill from there. FWIW, once a tire wear pattern is started (even when you cant see it starting) it only accellerates wear and theres nothing one can do to stop it.

 

Good article on common motorcycle tire wear patterns.........

http://www.rattlebars.com/tirewear/index.html


.........martin

 

Just changed my back tire because of cupping. I'm keeping a closer eye on tire pressures this time and see if that changes anything.