tire pressure

Proper air pressure in your tire can make a big difference.
It may not seem like that big of a deal, but not having the proper tire inflation can result in some serious problems.
The most common problem we see involves uneven wear or cupping. Low tire pressure isn’t the only cause for abnormal
wear but it is the most common one that we see. 
Abnormal wear can cause handling problems and/or a vibration from the tire that is cupped.
Rear tires will sometimes be where the tread has started to lift.
If the tire is not replaced, a bubble can form and cause a blow out.
Obviously, You don't want to have a blow out on your motorcycle.
it’s important to avoid all of these things. Having your tires inflated properly can increase the handling performance,
fuel economy and increase the longevity of tire life.
How often your tires should be checked depends on a few things.
For instance, if you are only riding your bike once every few weeks,
tire pressure should be checked every time you ride.
People who ride daily, or a couple times a week, should check tire pressure when ever you fill the gas tank. 

Some harley davidson dealers even recommend filling your tires with nitrogen.
When tires are nitrogen filled, the pressure bleeds out about four times slower.
This helps maintain the tire pressure and all the benefits that come with proper inflation.

http://thehawgpit.com/
catalog pages 1156-1166 you can find a variety of tires.
Avon Tyres, Dunlop, Metzeler,
Continental Twins,
Firestone Replicas.