It could be any number of things. I'm guessing the brake structure is not beefy enough. Also, I notice mine are grabby... when I apply the brakes they don't really grab initially, then all of a sudden they're grabbing too much.
It's a bit of an annoyance, but the good news is they have absolutely stopped the vehicle in every emergency - when I've needed them.
Here's my latest mod. I ordered this leather wheel skin and sewed it onto the wheel over the weekend.
I had the choice of colours and types of leather(perfed or solid), this is what we came up with.
If anyone decides they want to do on for theirselves I'll give you a run down on how to install........ it's more involved than most would think......... having a background in these things is helpful.