Scroched..
Picked up my last set of grip puppies from Triclid.com. Since the prices have gone up since my last buy in 2008, I bought two pairs for around $20 total. Folks at Triclid are very friendly and their customer service is great.

 

Could also be the position the bars are holding your hands at.

 

If you have big hands, using grips that are too small or too soft (so you have to grip them too hard to have control) can cause cramping on long trips. For me, the answer was H-D Get-A-Grip magnums. They fit my hands well and give me good control with a relaxed grip.

As several have already said, if you don't have cruise control, a throttle control type cruise control can also give your hand a rest.

 

Any thoughts on the Kuryakyn ISO grips or the Avon Air Cushion grips?

 

I've had both the Kuryakyn and the Avon Air Grips. I prefer the Avons, Now running the Avon Custom Contour grips and love them. I have small hands.

Ed

 

I had some aftermarket Chrome grips and my hands would cramp and fingers would go numb. Diameter was a tick too small. I just received the Avon Air Cushioned AR-90 TB. These are a larger diameter than my existing grips and larger than the Avon model AR-93, same grip but it is a narrower diameter. the AR-93 is 1.60" diameter and the AR-90 is 1.625" diameter. Also the 90 TB has the throttle boss.

 

My problem was much as the OP's. The cure was using the skinniest grips available with a throttle rocker. H-D grips come in different diameters, try the smallest ones.
I'm getting ready to try some Performance Machine Contour Grips that have Renthal tacky rubber around them. But right now I simply wipe the shine off of the grips with lacquer thinner - makes the rubber very tacky and easy to grip.
You can also use acetone (fingernail polish remover) and get the same results and you won't believe the results. Combine that with a throttle rocker (definitely not 'crap') and you should be good for many miles of un-cramped hands.

 

Forgot, Throttle Boss also

Ed

 

Everyone's hands are made differently...to a point. That said, the chrome and rubber grips on my bike are great for me.

What I did discover is that it's very important to ensure that your wrists remain relatively straight when you are operating the clutch and brake levers. A twisted wrist, and it don't have to be twisted much, can cause ligament and circulation issues.

The level of issue varies from person to person, but try to adjust the brake and clutch levers to where your wrist is fairly straight when you stretch out your fingers and lay them on top of the levers while resting the inside of your hand on the grip.

This is an important adjustment that will make a difference. I find that fatter grips are less stressful then the skinny grips found on sport bikes. Those guys use the grip puppies to increase the diameter of their grips so they don't have to curl their fingers so tightly around the grip. Been there done that.

 

I just bought a cramp buster, seems to help, for $11.00 if I don't like it, I'll pitch it, or give it away