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1Back to top Go down    Shimming preload in the final drive on Tue Jul 17, 2018 6:26 am

halflive

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The problem.
I have a howling sound from my final drive on motorway speeds. Main suspect is the large ball bearing.
Easy way is to buy a new bearing and replace it. Two disadvantages, I do not have a thin enough puller, the bearing is expensive.
My solution:
I have another final FD lying around which is good. The new challange: It is a drum brake, I need a disk brake. Challenge accepted, change the cover plate.

Now my real problem starts.
To obtain correct preload on the tapered roller bearing i need to place shims between the large bearing and the cover plate. I expect the shims to be different in my two covers.
The official method is (short) to measure the difference between the bearing outher ring and the mating surface and the recess in the cover and the mating surface. adding 0.05-0.1 mm to the difference should give enough preload.
Not to difficult if you have a depth gauge. Sadly i only have a common caliper en not the BMW fixing ring.
Has anyone tried it by bolting the bearing down with M8 bolts and large washers? Is it possible to get relyable measurements that way?
Has anyone measured the cover depth by using two lying drills as compensation for the ridge in the cover plate and using a steel ruler as bridge to compensate for the depth gauge? Is this a relyable method?
Has anyone tackled this challenge before? I know people have replaced cover plates but cannot find any reports on the net. Does one of you have a link to a report or a video?

Secondly, i read about a method using solder wire to obtain the shim thickness. Is this a relyable method? If the lead is compressed does it stay in the shape or does it bounce a little and expand a bit from it's compressed state?

Yes, i'm aware this is not the easy way out.

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2Back to top Go down    Re: Shimming preload in the final drive on Tue Jul 17, 2018 7:12 am

MartinW

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Try an automotive specialist shop for a product called Plastigauge.
Regards Martin.


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3Back to top Go down    Re: Shimming preload in the final drive on Tue Jul 17, 2018 7:31 am

halflive

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@MartinW wrote:Try an automotive specialist shop for a product called Plastigauge.
Regards Martin.
Thanks.
I knew plastigage only from measuring thickness forb plain bearings, never knew it was available for play around a millimeter.

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4Back to top Go down    Re: Shimming preload in the final drive on Wed Jul 18, 2018 4:02 pm

Snod Blatter

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I have done this, I used the "DMAN" method where you check the amount of movement of the crown wheel bearing up and down in the case without any shims in it and then shim it out (plus preload) accordingly. This requires a dial gauge though, which you say you don't have..

I too came across the solder method but I'm not sure how it could work, the CWB can be a tight fit in the casing and you ideally want it hot so that you can be sure the casing has gone all the way on - if you melt the solder it would be a disaster! I also wonder if solder is soft enough for this, how could you ever really know if the bearing is as far in as it could ever go..

My thread - http://www.k100-forum.com/t13591-rear-wheel-wobble#160954


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1989 K100RS SE ABS 8v VIN: 0149214
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5Back to top Go down    Re: Shimming preload in the final drive on Wed Jul 18, 2018 6:27 pm

MartinW

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A dial gauge indicator is not that dear, around the $20.00 mark complete with a magnetic base.
Regards Martin.


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6Back to top Go down    Re: Shimming preload in the final drive on Fri Jul 20, 2018 3:38 am

halflive

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Thanks guys.
Sorry for the misunderstanding, BMW uses a depht gauge which i don't have. But I do have a dial gauge. Never thought of using it for this purpose.
Just having this discussion helps finding a solution. I can make a bar for my dial to make it into a depth gauge. I'll have to see if the reach is enough. But i also like the DMAN method. It sounds more accurate than squishing lead. It is a bit more work setting up stable enough so the FD does not wobble.

Question: Why is it called the DMAN method? I cannot find an explanation on the net.

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7Back to top Go down    Re: Shimming preload in the final drive on Fri Jul 20, 2018 4:41 pm

Snod Blatter

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I believe it is called the DMAN method as that is the Internet name/handle of the guy who first proposed it on a forum some years back. Now he's famous! Well, a bit.. Laughing

I like it too, as you saw in my thread I followed the procedure and it seems to be pretty good. Beware that this will all probably change how the crown wheel and the pinion mesh though, you are slightly changing where the crown wheel sits but not re-shimming the pinion to match. You'll probably get away with it but you'll make RickG nervous!


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1989 K100RS SE ABS 8v VIN: 0149214
Others: 1.5 x Honda CBX250RS-E, '94 CB250, '95 TRX850, '16 Z250SL
http://justbikethings.blogspot.co.uk/
    

8Back to top Go down    Re: Shimming preload in the final drive on Sat Jul 21, 2018 1:42 pm

halflive

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In my opinion the crown wheel does not move. I will not redo the shimming of the tapered bearing. It is just the end play prohibiting the crown wheel to float from the pignon.
I've been Googeling all over but cannot find any reference to the DMAN method, Is it an inside forum joke? Or does it come from another BMW forum?

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9Back to top Go down    Re: Shimming preload in the final drive on Sun Jul 22, 2018 8:44 am

Snod Blatter

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I think it comes from the BMWLT forum, though they may just be the ones who talk about it the most. Whoever DMAN was, the technique seems to have come about many years ago and now the origin appears to have been lost..

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10Back to top Go down    Re: Shimming preload in the final drive on Sun Jul 22, 2018 2:59 pm

halflive

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@Snod Blatter wrote:I think it comes from the BMWLT forum, though they may just be the ones who talk about it the most. Whoever DMAN was, the technique seems to have come about many years ago and now the origin appears to have been lost..
Yep, found it/him. The LT forum, not my cup of tea.DMAN PDF link

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11Back to top Go down    Re: Shimming preload in the final drive on Thu Jul 26, 2018 8:31 am

halflive

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Yesterday i have removed the FD from my sidecar combo. It was worse than i expected. You can wiggle the disc about a millimeter. But the pignon seal is also leaking. I have exhanged the FD with the one from my spare solo bike for the vacation. When i'm back i will start combining the drum FD with the cover plate of the leaking disk. I have decided not to take any risk and replace the large bearing and the seal.
No deed for a puller also, i will cut the inner ring.

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12Back to top Go down    Re: Shimming preload in the final drive on Fri Jul 27, 2018 5:36 pm

Snod Blatter

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1mm at the disc is an awful lot of play, may the gods have mercy on the FD innards

Also, you could tell us if the bolts holding the outer case halves are still tight? Mine were noticeably loose, I don't know if that is due to the failure or perhaps even partly responsible for it! Just for my own interest..

How do you plan to cut the bearing? Do tell!

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13Back to top Go down    Re: Shimming preload in the final drive on Fri Jul 27, 2018 6:42 pm

halflive

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As my bike does not have a center stand i never noticed the wheel could wiggle. There is no need for a center stand as the sidecar will hold the bike straight. I was also surprised by the amount of play. I suspect the tapered bearing would also had a bad life. I only wanted to get rid of the whining.
I will cut the inner race of the bearing with a Dremel copy with aTungsten carbidecutter. Maybe i'll have to cut the bearing retainer also. My intention is to cut about 90% of the race and convince it to break with a little tap. But it does no harm if i accidentally touch the stump a little. I have tried to pry the bearing off but it is very tight.
I will take notice if the bolts are very loose. The bolts of the drum version which inners i intend to use where very tight.

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