When I installed Grip Puppies on my last bike, I actually ruined the first set I got trying to install them. They were SOOOO tight, I tore them.
Here's the trick.
Run your tap water as HOT as it goes.
Fill a small pitcher with the hot water and let the GP soak for a while, maybe 20 minutes. This will really help them soften up.
Lube them on the inside with dishwasher soap and slide them on as fast as possible after taking them out of the hot water.
They are designed to be tight, so don't give up.
You'll love them!!!