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If the bearings have some lube and are spaced correctly, they should last you forever.......... unless you exceed a couple of Billion miles.

Duane Ausherman wrote:If the bearings have some lube and are spaced correctly, they should last you forever.......... unless you exceed a couple of Billion miles.

As this bike's only for riding when the sun's shining (and I live in the UK) it sounds like it could be a year of two before Plan B gets put into action! I must admit I wasn't looking forward to having to strip out the bearings so I reckon if I can turn down a nice piece of stainless to fit right into the 17mm leg it will be nearly invisible. This also means that should a nice 14mm r/h slider show up I'll be able to put the whole front end back to original (Plan C).

Thanks one and all.

Your original 14mm hub needs the center web to be drilled out to accomodate the 17mm axle.

Pull out the spacer (number 3 in the reference drawing) in there and you'll see what you need to drill; it's not very much. In fact, I didn't have a drill big enough so I filed the opening after using the largest drill I had. You must make the hole big enough to clear the spacer assembly or you'll never get that to pre-load correctly.

The only other change is to replace the 14mm ID left spacer (number 9, between the outers side of the bearing and the slider) with a 17mm ID spacer.

Each of your bearings have a 14mm ID adapter (number 3) lightly pressed in that you can pop out easily (the bearings for the 17mm and 14mm axles are the same).

You probably won't even have to cahnge the "wedding ring" spacer asumming your pre-load was good before.

Teo

Thanks to one and all for the advice - typically, as soon as I made a plan things changed:

I found a local engineering outfit who agreed to turn down an old 17mm spindle to fit the 14mm hub (while retaining the large diameter end that fits the 17mm slider). This struck me as an easier (for me) fix than the making up a new shim to space out the original spindle. No sooner did they call me to say it was ready than I located a nice condition 14mm slider...

I now have the option of returning the whole front-end to original configuration when I next strip the forks and in the meantime I'll run the machine with the mis-matched sliders and the machined spindle.

While BMW increased the spindle diameter for sound engineering reasons I'm hoping I won't see any major handling weaknesses by retaining a 14mm spindle!

Teo - can I ask why you decided to swap a 14 for a 17?

Daniel,
The reason for the cahnge was frugality, cheapness, practicallity, or fun. I was in the process of converting my '74 R75 to dual calipers (with a set of 1977 forks with the 17mm axle). I bought a very cheaply priced bent wheel with the intention of salvaging it; it had a later hub for 17mm axles. After studying the "new" hub, I found it would be easy to convert the /6 hub to 17mm and I would then have two wheels for whatever (I love extras!!).

I'm no genius but am practical. After my experience I saw a note that Duane posted a few years ago about converting /5 and /6 hubs to 17mm.

Teo