I would try using a wrench on the tool itself instead of pulling on the crank arm. I've never had a problem removing the arms using that method. The first time I ever used the crank puller, I tried it without and could not get the crankset to budge at all. Now, every time I just use the wrench to hold the base while I spin the arm of the puller. They pop off super easy every time. The advantage, too, as someone else mentioned is that you can re-position the wrench for optimum leverage.