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markaliquo
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portsmouth nh
Joined: 03/16/2006
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I believe I need new steering bearings on my bike. I ordered the bearings and am looking to put them on. I took off the handle bars and now just have the top triangular shaped section that is attached to the top of the front forks and to the steering column. There is a bigger screw in the middle, a smaller screw on the side and both are screwed into a nut which sits on a large washer holding the triangular part in place. I have checked online for help about this but could not find a good source for explain the front fork assembly. Should I just unscrew that big nut or will I forever be throwing something out of adjustment. FYI the big nut I am referring to on the top of the forks is about an inch and a half standard socket wise.

Mark

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i have a 1937(or so) BMW R35 and need advice.

Darryl.Richman
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VBMWMO #6285
Surf City, USA (Santa Cruz, CA)
Joined: 10/27/2006
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r35 front fork/steering bearings question

Mark, I don't have, nor have I worked on, an R35. Although most of BMW's fork designs are similar, I'm having a hard time visualizing what you're looking at. The best advice I can give you to start with is to obtain a parts manual for your bike. It will make everything easier. Craig Vechorik has them:

P23 51 8 079 90--$45.00--parts book R35 German

Typically for a bike of this era, there is a top triple clamp and lower triple clamp that align the fork tubes on the outside of their reach and contain the steering stem in the center, which is the "axle" on which the forks pivot within the steering head at the top front of the frame.

There are two steering head bearings, one for the upper and one for the lower openings of the steering head. The bearings' outer races seat in the top and bottom of the steering head and the inner races and balls or rollers on the steering stem.

All of this is clamped together at the top triple clamp center with, from the top bearing upwards, a dust cap that goes over the top bearing; a special nut that sets the bearing preload; the top triple clamp; and a jam nut that holds the top triple clamp and locks the setting of the preload nut.

On top of this will be some pieces associated with the steering damper. They are: a round piece that locks onto and covers the top of the steering stem; a stamped, cross shaped piece; and the steering damper knob or wingnut.

(Below the lower triple clamp there are several pieces that make up the steering damper proper, and a rod passes up from here, through the steering stem and out the top. The damper knob screws down onto this.)

Beware that the damper knob possibly has one or two spring loaded ball bearings in the bottom to act as detents against the cross shaped piece. These sometimes escape upon disassembly!

I wouldn't worry about disassembling the steering head, so long as I took digital photos or made DETAILED notes with drawings about every step. If your bike is set up slightly differently, don't worry. Just be sure to note how it comes apart so you can put it together again the same way.

Block up the frame under the engine to get the front tire off the ground. Be aware that when you loosen the preload nut, the forks are going to come free from the frame. When you go to reassemble this, you may need a friend to hold the forks in place while you get the preload nut back on and snugged up.

Upon reassembly, besides getting the order right for the parts, the only critical issue is setting the preload properly. You will need to set the preload (lower) nut tight enough so that the forks just lean on their own to either side with only a nudge. There should be NO play in the steering stem in the steering head. Once the lower nut is set, the upper nut has to be tightened to lock the setting, without changing the setting.

If you get the preload too loose, the forks will bang over bumps and judder when you use the front brake hard. This is very hard on the bearings. If the preload is too tight, the bike will tend to weave back and forth, even on smooth, flat roads.

Good luck!

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markaliquo
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portsmouth nh
Joined: 03/16/2006
Posts: 9
thanks for the reply

I think I can follow that. I have the parts book but it does not show a blow out of the forks. I included a picture of what my bike looks like. I was wondering if the preload nut is that big metric 27( inch and a half) i have circled in blue, and, do i have to first unscrew that screw that on top and circled in red. I am just asking because I tried to back off that big nut that is in blue, and i felt tension like it was attached to some spring or something. Can I just back off that nut, pop off that sort of triangular brace that holds the two forks, and sits on the steering column.

For me at least, if i can get those nuts off, and the washer under the support should just come off and i can replace the steering bearing.

then deal with the bottom one.
Mark

Ok, so i dont know how to add a photo here, I uploaded the picture to this site though

http://www.flickr.com/photos/69859413@N00/171093043/

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i have a 1937(or so) BMW R35 and need advice.

markaliquo
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portsmouth nh
Joined: 03/16/2006
Posts: 9
r35 front fork/steering bearings question

This is an attempt to get the photo in.

[/img]

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i have a 1937(or so) BMW R35 and need advice.

Darryl.Richman
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VBMWMO #6285
Surf City, USA (Santa Cruz, CA)
Joined: 10/27/2006
Posts: 2185
r35 front fork/steering bearings question

Great, thanks for the photo, now I can see what you're talking about.

When this bike came out, BMW was still working on the telescopic forks design. The forks they put on the R12 were changed quite a bit for the R5, and I believe they changed them again after the war.

The triangular piece, with the wingnut in the center and the two large SW27 nuts on either end, is the triple clamp. The preload nut is under the triple clamp, and below the wingnut.

You will have to remove the steering damper pieces under the big wingnut in the center. You will have to loosen the pinch bolts across the front of the upper triple clamp on either end that hold the fork legs.

Your goal is to remove the top triple clamp, so you must investigate how it comes off. If just by loosening the pinch bolts and by removing the jam nut you'll find buried under the wingnut, you can remove the triple clamp, you're in fat city.

If not, then I believe you will have to remove the SW27 nuts (blue). I am guessing that the smaller nuts (red) are holding a through-rod, which keeps the internal springs and fork sliders in place, and this is why you feel the spring tension on the larger SW27 nuts. However, as I've said, I have never looked at or worked on this model.

Anyway, I would disassemble as little of the fork legs as necessary to get the triple clamp off.

Once the triple clamp is off, you'll see the preload nut in the center, and under that, the top steering bearing. When you release the preload nut, the forks will come free and, by removing the entire unit, you'll be able to access the lower steering bearing.

Take pictures, and once you learn the secrets of this fork, please post your information back here. BMW made 14,000 of these bikes, and the East Germans made more after the war. There will be other people interested in what you're learning!

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brown7185
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VBMWMO #7185
Baltimore, MD
Joined: 10/12/2006
Posts: 9
r35 front fork/steering bearings question

markaliquo:

The plates in older R35 parts manuals are indeed laid out seemingly at random. But if you find one from the EMW R35/3, they made new parts-plates around 1952 which are 'exploded' views, i.e. the parts are laid out in order of their assembled positions. Of course, the lists are all in German. The later forks are somewhat different, but still may be of some help.

An indespensible source is the book "Eisernes aus Eisenach;" it will allow you to identify pre-war vs. post-war parts and features, & has parts lists and manuals, the complex history of the model, serial numbers, etc.

I've got a pretty-well-restored 1950, and am now in the process of removing all the post-war parts from a bike put together from legit pre-war frame, fenders, hubs, tank, and headlight, with the rest being way late 50's or repro junk. Its frame # is 301073. By sheer coincidence, another guy in town has an R35 which has motor & drivetrain # 300997 (but the frame etc. are crap), meaning his motor was built THE SAME WEEK in 1937, more or less, as my chassis. Now I just need to talk him into selling his to me, so I can combine the legit parts.

Good luck with your forks, although by now you've probably got them back together. Always willing to talk about R35s.

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