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Old 07-24-2014, 04:36 PM   #1
knary OP
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/7 rear wheel bearing stack and race issues

A couple years ago when I started on this thing ('77 R100S), I noted that the rear wheel bearing stack appears to use a homemade spacer (43.7mm long) in place of the stock spacer and "wedding band" (if I understand the arrangement). In addition, the bearing race can move around in the hub. It all spun at some point. Back then, I put it all back together, noted a little bit of movement in the wheel and told myself to deal with it later as the engine was the priority. Well... "later" is here.

What I've got:


A quick video to show how the race fits into the hub:


The bearings are 30203A, the stock size for this application. But they should be a press fit requiring heat. There's a bit less than .08mm of wiggle room. At this point, I'm assuming that the movement in the wheel, which is modest, is primarily a product of the race being able to move.

The questions, oh dear denizens of the adv airhead forum...

1. with that amount of movement and space, I would assume that I'd "glue" the race in - Loctite 640 (or permatex equivalent). Opinions?

2. Getting the right amount of preload on these bearings. With a homemade spacer is less than ideal. Suggesting?


A new hub is not going to happen and seems unnecessary at this point.
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Old 07-24-2014, 05:13 PM   #2
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I'd glue it in. I'd use a pipe nipple to simulate the spaces taken up by the forks so I could use the axle to hold the bearing race in place. Tightening the axle should insure the race is centered.

It should not be hard to find the OEM parts for the insides of the wheel. I get the idea of the custom part but if you don't have a lathe and the inclination to make another custom spacer then you are better off getting back to the wedding band.

If you ever sell this bike you should tell the new owner the bearing race is glued in place. If both bearings not in perfect shape I'd use a new bearings. Looks OK from here.
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Old 07-24-2014, 05:45 PM   #3
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A couple other options; use a section of a long .04mm feeler gauge to take up the slop OR, make a series of small punch marks around the hub to raise the surface slightly... no glue required. If the preload was OK with what you had, I buy the correct part and a wedding band that was slightly smaller and use some of Duane Aushermans shims to set it exactly.
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Old 07-24-2014, 07:55 PM   #4
knary OP
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I'm inclined to use the loctite as it would give me a little more control vs trying to create an interference fit with muscle.

I've been looking and can't find the length of the stock spacer to compare. Assuming this one is close to the right length I could use that number to figure out which wedding band to get.

Anyone know the length of that part? It would be #8 below:
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Old 07-24-2014, 08:12 PM   #5
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You have an early snowflake, which are famous for losing their interference fit at the bearing bores. Later wheels have a steel sleeve captured inside the hub. Many of these early wheels have been repaired by Loctiting the race in place.
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Old 07-24-2014, 08:12 PM   #6
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It was a completely different application, so I'm not able to comment directly, but I have used the loctite 640 on a spun bearing race. Successfully. No problems. And rated to 400 degrees F. Fwiw.
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Old 07-24-2014, 08:32 PM   #7
Stan_R80/7
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1. IMO, loctite 640 will aid the fit.
2. Preload is described here: http://w6rec.com/duane/bmw/wheel_bearing/index.htm
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Old 07-24-2014, 08:33 PM   #8
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Quote:
Originally Posted by bmwrench View Post
You have an early snowflake, which are famous for losing their interference fit at the bearing bores. Later wheels have a steel sleeve captured inside the hub. Many of these early wheels have been repaired by Loctiting the race in place.
Fwiw, it's a spoked wheel, not a snowflake.
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Old 07-25-2014, 12:29 AM   #9
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I think we're on the right track.

Instead of taking a chance in ordering the correct wedding band spacer, Duane (and Cycleworks) sell sets of "supplemental" preload shims that can be used to fine-tune the preload using an undersized wedding band.

The Duane wheel bearing page link was given in Stan_R80's post and those shims will be near the bottom of the page.

And Duane's page has a section on damaged hubs:

Quote:
Originally Posted by Duane_Ausherman_webpage
A hub with a spun bearing is evidenced by you being able to lift the outer race out of the hub, without the use of heat. The usual bearing to spin out is the one on the left side, but the inside one can spin out too. If the race just barely slides out then one can get away with Locktite to hold it. The only disadvantage of a glued in bearing race is that it is hard to remove for servicing the bearings in the future. Proper spacing and it should never again need to come apart.

http://w6rec.com/duane/bmw/wheel_bearing/index.htm
On that Spacer #8: that part new is only $16 or so (/5 part) so it's not a big issue. No idea of the length. Duane's wheel bearing page has a section on modifying the /5 inner spacer so that it can be removed with the bearings in place. Not a bad idea to CYA since you are "gluing" your bearings in.

Quote:
Originally Posted by Duane_Ausherman_webpage
.
/5 BMW wheel bearing modification

At this point you have the perfect opportunity to modify the inner spacer so that it may be removed without removing the whole stack. I highly recommend this. You will need a lathe, grinder or a file to do it. You only need to remove a bit of metal from the centering ridges of the inner spacer.

http://w6rec.com/duane/bmw/wheel_bearing/index.htm
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Old 07-27-2014, 01:08 PM   #10
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I went cheap for the moment. Surprised? I'm not.

I used Permatex High Temperature Sleeve Retainer. It's essentially their version of the Loctite 640 (3000 PSI sheer strength, for up to .007” gap, etc.). Might even be the same stuff. Same company? I can't remember.

I also reused the DIY spacer. It seemed almost right in a stack, but when in the wheel, there was still a little bit of lateral movement. With a tiny bit of material removed from the spacer, everything is smooth and laterally rigid. MUCH better than it was. As this is a first for me, I'll keep an eye on it. It's easy enough to pull the wheel and inspect it, and I will.

Side note: I would assume that inadequate preload on these rear wheel bearings would contribute to wear of the final drive output splines by allowing the wheel to rock back and forth on those splines.
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Old 07-27-2014, 01:52 PM   #11
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Quote:
Originally Posted by knary View Post
I went cheap for the moment. Surprised? I'm not.

Side note: I would assume that inadequate preload on these rear wheel bearings would contribute to wear of the final drive output splines by allowing the wheel to rock back and forth on those splines.
Not usually mentioned, maybe a factor, maybe not such a big deal.

With the wheel bearings themselves. They will live with too little preload. Rapid destruction comes from too much preload. But too little preload and the wheel wobbles, you'll know it. Too much preload and the bearings can be trash in a few miles. They get so hot they can weld themselves together and have to be removed with a torch.
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Old 07-27-2014, 01:57 PM   #12
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I am aware!

As measured at the rim, I went from 1/4" of play with the loose bearing race, to about 1/8" with it glued in place, to essentially zero with a whisper of material removed from the spacer. I will be checking it regularly.
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Old 07-27-2014, 03:44 PM   #13
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Permatex and Loctite are intertwined. You probably got the same as the 640 sleeve mount, rebranded.

Being a little nitpicky, you can get a little more (or less) wheel bearing preload with the tightness of the axle nut. When I shimmed my wheel bearing stack, I shimmed it for the "proper" preload at an axle nut torque of 30 ft-lbs. And from testing, I know that I can get a little more bearing preload by going a little tighter on the axle nut torque and a little less bearing preload by going a little looser on the axle nut torque. The axle has a little stretch under load (tension) and the bearing stack (hub, spacer, outer races) has a little compression under load (compression). You get a little springiness in the system and carefully adjusting the axle nut tightness you can fine-tune the preload to suit (within smallish limits), so if you find that the bearing preloads are a tad tight or loose, you can tweak them. The distance between the two outer races isn't going anywhere until you heat and pound them out.

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Old 07-27-2014, 04:15 PM   #14
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I have (unintentionally) removed a component held with loctite 640 after applying Kroil. I think it took the Kroil ~ 48 hours to get between the cured adhesive and the metal.
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Old 07-27-2014, 08:21 PM   #15
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Quote:
Originally Posted by knary View Post
I went cheap for the moment. Surprised? I'm not.

I used Permatex High Temperature Sleeve Retainer. It's essentially their version of the Loctite 640 (3000 PSI sheer strength, for up to .007 gap, etc.). Might even be the same stuff. Same company? I can't remember.

I also reused the DIY spacer. It seemed almost right in a stack, but when in the wheel, there was still a little bit of lateral movement. With a tiny bit of material removed from the spacer, everything is smooth and laterally rigid. MUCH better than it was. As this is a first for me, I'll keep an eye on it. It's easy enough to pull the wheel and inspect it, and I will.

Side note: I would assume that inadequate preload on these rear wheel bearings would contribute to wear of the final drive output splines by allowing the wheel to rock back and forth on those splines.
This job is fresh in my mind.
You've achieved the desired result, well done.
Keep a weather eye on the "wobble".
After your first decent ride a quick removal of the rear axle and a pinkie finger check on the "repaired" bearing for overheating will measure your success.
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