Sealed Swing Arm Bearing Question

[88bmwjeff]

My 1988 R100 RT has sealed swing arm bearings. I think I know the answer to this, but I thought I'd ask. I had the swing arm bearings replaced about 15,000 miles ago and I didn't expect them to be bad. But, when I checked them, there was a lot of side to side play. That would be a side to side (left/right) with the swing arm on the bike. If you were staring down at the bearing in the swing arm, it would be an in/out or up/down play. I hope I explained this well. I don't there should be any play whatsoever. I really thought the bearings should last more than 15,000 miles, but if they're bad--they're bad.

 

[20774]

Maybe they need to be retorqued? There's a special sequence to do that.

 

[52184]

Definitely should last more than 15k miles. Pop off the swingarm bearing caps on both sides of the frame and check the locknuts and pins for looseness—one may have loosened and backed out a bit. If they need adjusting, the procedure is covered fairly well in the Clymer manual.

Best,
DeVern

 

[88bmwjeff]

FYI, I'm checking the bearings with the swing arm removed from the bike.

 

[52184]

Those are sealed tapered roller bearings, and the only function correctly when installed and torqued to the correct setting. Without any preload on the bearings they will always feel somewhat loose and sloppy, and if they are the unsealed variety the inner race and bearing assembly pop right out in your hand.

With the swingarm out, you could press and turn on the bearings to see if there’s any obvious roughness or brinelling, I guess. So long as they are still sealed with no obvious damage to the exterior seal I’d install the swingarm and set the pin adjustments, then see how the swingarm feels with no shock installed. If it moves freely and smoothly, ride on!

Best,
DeVern

 

[88bmwjeff]

Those are sealed tapered roller bearings, and the only function correctly when installed and torqued to the correct setting. Without any preload on the bearings they will always feel somewhat loose and sloppy, and if they are the unsealed variety the inner race and bearing assembly pop right out in your hand.

With the swingarm out, you could press and turn on the bearings to see if there’s any obvious roughness or brinelling, I guess. So long as they are still sealed with no obvious damage to the exterior seal I’d install the swingarm and set the pin adjustments, then see how the swingarm feels with no shock installed. If it moves freely and smoothly, ride on!

Best,
DeVern

Yes, they are a bit loose and sloppy, but they feel good when I apply a bit of pressure on them turn. To really test them I may put the swing arm back in and preload them and check the movement. It makes sense with everything apart to replace them now if need be. I have a bit of time as I will be shipping my drive shaft off for a replacement U-Joint, and that will take 2-3 weeks.

 

[88bmwjeff]

I reinstalled the swing arm and preloaded the bearings. The up-down motion was smooth with no notchiness; however, there seemed to be a minute bit of side-to-side play, which reminded me that the rear seemed a little loose a few times since I brought it out of storage. As such, I think it's best to replace the bearings since thing are apart. FYI, there's no play in the final drive (I had it rebuilt about 10k miles ago), so I'm sure that's not the issue. Thanks for everyone's help.

 

[88bmwjeff]

Long story short, it ended up being a good decision to replace the bearings. They were brinelled.

 

[stevenrankin]

Thanks

Thanks for the solution. It is nice when people follow up. St.