Rear Bearings and Spacers

#22
Here are some pics of mine I have two rears just like yours and the hole is actually bigger than 5/8th to fit the spacer thru then it is necked down to 5/8th at the end to fit in the bearings and the axle must be a half inch. The front I have uses a 5/8ths axle and it just has a spacer inside the bearings with a 5/8ths ID. It fits between the two bearing centers. You must have the spacer or the side thrust on the races will ruin the bearings.




I can’t understand why you can’t just have the bearings stuck in each end of the wheel. I just don’t see why the spacer is needed. They are almost impossible to get out if you want to replace them. I just went through this. I don’t ever remember the spacers being in there from years ago. I guess I must be thinking of other wheels other than Rupp….. we’re all you need is a big screwdriver to stick through and pop the other side bearing out. These are horrible to remove and I’m sure they weren’t meant to be removed. You basically have to destroy the bearing and get as much out of it as you can and then drive it down inside to drive the other side out… It’s really a PITA
 
#23
The reason for the spacers is that ball bearings are not good with having a big sideload on them. When you have two ball bearings with no middle spacer as you tighten the axle bolt it will push the inner races inward toward each other putting a sideload on them. Depending on how much you tighten the axle bolt it could cause the bearings to wear slightly more than no side load or with tightening the axle bolt so the axle does not move on the swingarm the bearings could fail in less than an hour. Riding mower wheels have no spacer because the wheel is held on with a c clip and there is nothing to press the bearing inner races together. Hope this makes sense.
 
#24
Ole, respectfully, when a bearing fits tight into the wheel bore, the center spacer has to be absolutely precise, otherwise torque applied to the axle nuts will force the inner bearing to interfere with the outer race because while the outer race is resistance to movement: Pressure is being applied to the inner race to "crush" the center "spacer," but the outer portion of the bearing is not being pulled in. I spent a long time removing .001 at a pass trying to get this perfect fit with tight bearings, and it takes a long time.

What about when bearings are seated in a wheel bore. Theoretically there is zero tolerance between bearing centers and the ends of the bearing spacer. How do you achieve that without leaving some fraction of bearing out of the seat? Who is achieving a zero tolerance interference on these spacers? Wheels that use bearings with flanges are even more difficult to get perfect, because the bearing may or may not be bottoming out within the wheel bore.

Yes, my motorcycle restorations use these spacers, but they are precise lengths. They are also a heck of a lot less robust then what some of these people recommend be used on mini bikes, and the bearings in my vintage dirt bikes are a lot less robust than what we use in mini bikes. When mini bikes start doing 65 MPH, weigh 400 pounds, and encounter leaning turns commensurate with a motorcycle, I'll start using center spacers. Most, and by most I mean every mini bike I've restored, save one- did not have center spacers. I don't know why this continues to be in issue here, since the vast majority of mini bikes never had them, nor needed them in the first place.

For those that are concerned about tightening axle nuts, use a lock nut and double nut the opposite side to get it snug, then repeat for the other side. Now loosen either of them, and spin the wheel, then apply torque until there is no lateral movement, but so as not to restrict the bearing movement. Very easy, and this is how vintage mini bikes for the most part were assembled.
 
#25
This old thread popped up at the perfect time

Ok shined up this old yard cart new everything but bearings jumped on and went around the block and the inner right front wheel bearing took a dump pulled both sides apart and no spacers so I got new bearings and some spacer material was inch and a half thought my tape measure said thats what I need but actually about 1/8th shy of what I need after hammering in the new bearings I can't get to the outer race to hammer them back out

But now I'm wondering if the. Nut tightened up on me and crushed it causing it to fail with no lock nut rotation must of tightened it up enuff to cook the bearing im gonna leave it alone go get some locknuts and se what happens because it is a tractor hub I bet it had a c clip not a nut
Thanks guys you answered my question before I asked it
 
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