Thread: Trex250 Manual
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Old 12-10-2008, 12:59 AM   #20 (permalink)
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Join Date: May 2007


To answer your last question, it's my understanding that preloading (or lack of it) was never an issue with the tail, and didn't lead to the tail hub redesign. After all, as you point out, the original hub setup didn't have any preloading, nor does the new hub Align's sending out with the single 2mm bearing.

Instead, the binding issue stemmed from really crappy 1.2mm bearings that couldn't handle the side (lateral) load. That is, once up to speed, some tails had binding issues simply because of the side load put on the bearings due to centripetal force. It's possible the new 2mm bearings will be better with side load issues, simply due to the bigger balls and larger races. However, if the 2mm bearing is crappy, too, it may still bind when dealing with heavy side loads.

Heim's 'sandwiched' techique for preloading will better tolerate side load issues, because the side load fights against the preload, instead of pulling against the bearing races. By the way,that's why Heim recommends you actually preload the bearings before you do the Chinese weight mod. Those weights are going to add a butt-load of side force that a single (or non-preloaded set) probably won't handle. Consequently, Align's new tail hub assembly isn't going to be ideal for the Chinese weights. You may want to go back to a good pair of 1.2mm bearings and preload them. I think he's going to offer the preload kit, as well as the Chinese weights, exactly for that reason. Neall
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