[baruffir]

I haven't ever used the 6" ones, but I've had the same issue with the 8" ones. First of all, it does make a significant difference, especially if all the rollers on one wheel are tight, while the other wheels are loose. To fix this, simply loosen up the bolts on the wheels. It will seem like they are too loose, and that the wheel will fall apart, but it actually works quite well.