Hi. I have a solid rear axle cart with a hydraulic disk brake. When assembling the axle I followed the tightening directions properly until the axle froze in the bearing as it was supposed to. However, now that I have been throwing it around a bit the axle slips back and forth about an eighth of an inch until the brake disk hits the caliper and stops it. I tightened the bearing mounts, but that didnt help, and I'm afraid of over tightening them. Is this a serious problem? If so how do I fix it? thanks