Do you dive into the corners, grab the brake and then power out?
If the front forks are not setup correctly for your weight, the side will cup as the tire bounces off bumps in turns. Also tire balance can cause it.
Roy, after you run a BT-021 you won't be suggesting that guys can't ride or their suspension ain't set up ....this tire really sucks --trust me.
John,
I'm not saying that "guys can't ride or their suspension ain't set up" My point is regardless of the tire, if the suspension isn't doing the correct job, the tire is going to wear faster, and the more aggressive you ride, the more important it is for the suspension to keep the tire in contact with the road. If the tire is a POS, it will go faster and as it wears, riding style, road surface and weather, and suspension will cause it to go faster.
I had BT020Fs on my bike when I got it. And it looked bad after 2,000 miles (of riding in the "flat lands of" the Sierra Foothills. Got the suspension adjusted and it slowed the decay. I changed them several thousand miles 'cause I didn't want deal with them on a 5,000 mile trip to Colorado.
Roy