R80 Mono Caliper Alignment V2.0

[Rob Frankham]

Hamstring injuries are a real pain (Hah!). I hope Mrs H has a quick and successful recovery.

Rob

[New Haven Neil]

Hamstring injuries are a real pain (Hah!). I hope Mrs H has a quick and successful recovery.

Rob

Thank you, Rob.

It has been very troublesome, turns out she didn't get the follow-up treatment it needed/should have had at the time, we have now raided the piggybank to pay for private physiotherapy (a very skilled lady who deals with the TT riders). This is now finally sorting it out, but it would have been much quicker if etc etc. And here's me an at-one-time NHS Outpatients manager. #sigh.

Space spacer ordered to play about with - more next week!

Neil

[New Haven Neil]

'Holding' post!

I have a spare spacer now and will be machining a metric smidge (1mm should do it, but a touch more is a possibility, it's hard to measure in the depths of the caliper) off it tomorrow, and have taken the opportunity to overhaul the caliper whilst it is apart, only to find the packet of seals and dust seals doesn't have the caliper half O ring in it - must have used it for something. So I await a replacement to arrive, hopefully early next week but post is weather dependent here, as it comes by ferry now not air, and the boats are often off at this time of year.

More next week!

[New Haven Neil]

It's done!

First attempt we did cut too much off, while the disc was dead centre on the caliper, the bottom of the caliper was just catching the disc rivets, by a metric teeny tiny smidge. Could hardly hear it, but very slow rotation of the wheel I could just hear something rubbing. So 0.75mm is the dimension we were looking for, second try did the job, new pads in and brake tested. Whew!

Now for that back brake lever.....

[Rob Frankham]

Glad you got there in the end... what's up with the rear brake lever?

Rob

[New Haven Neil]

You gave me some advice about the travel stop quite some time ago, as I couldn't find it, and when setting it up to my wife's liking (having moved the footpeg a bit) it is too high, and it needs the brakelight switch adjusting too. Some health issues for us both stopped progress dead on that, but now I'm back into sorting it.

TBH the brake has never felt right, it isn't very effective in comparison to the ST I had some time ago (one I wish I still had - sigh) despite new shoes etc. I've just got a new hydraulic bench so the BM is next on it so I can drop the wheel out (it has pannier frames which get in the way) and have a good look around to see what I can do.

[New Haven Neil]

You gave me some advice about the travel stop quite some time ago, as I couldn't find it, and when setting it up to my wife's liking (having moved the footpeg a bit) it is too high, and it needs the brakelight switch adjusting too. Some health issues for us both stopped progress dead on that, but now I'm back into sorting it.

TBH the brake has never felt right, it isn't very effective in comparison to the ST I had some time ago (one I wish I still had - sigh) despite new shoes etc. I've just got a new hydraulic bench so the BM is next on it so I can drop the wheel out (it has pannier frames which get in the way) and have a good look around to see what I can do.

[New Haven Neil]

That's....odd!

[zjacker]

On a 1990 BMW R80 Monolever the single front disc should normally be on the left, with the axle orientation matching the factory setup, so if yours has the disc on the right and the spindle inserted from the opposite side it strongly suggests the front end has been rebuilt at some point using parts from another model or assembled incorrectly; before machining 1 mm off a wheel spacer I’d strongly advise confirming you have the correct fork sliders, hub, spacers, and axle arrangement for that exact VIN, because altering spacer width will shift the wheel relative to the fork legs and could affect alignment and wheel bearings preload, as well as caliper positioning, and the proper fix is to identify and refit the correct components so the disc naturally centers in the caliper rather than compensating for a mismatched setup.

[Rob Frankham]

On a 1990 BMW R80 Monolever the single front disc should normally be on the left, with the axle orientation matching the factory setup, so if yours has the disc on the right and the spindle inserted from the opposite side it strongly suggests the front end has been rebuilt at some point using parts from another model or assembled incorrectly; before machining 1 mm off a wheel spacer I’d strongly advise confirming you have the correct fork sliders, hub, spacers, and axle arrangement for that exact VIN, because altering spacer width will shift the wheel relative to the fork legs and could affect alignment and wheel bearings preload, as well as caliper positioning, and the proper fix is to identify and refit the correct components so the disc naturally centers in the caliper rather than compensating for a mismatched setup.

AS has been covered earlier, some monoshock machines with a single disc had the disc on the left, some on the right. The axle is inserted from the same side on both. As far as I can tell (unless someone can tell me different), there's not rhyme or reason to which side it was fitted but i've seen numerous examples with them on each side. Doesn't make any operational difference and, as the two disc variants are readily available, there are no unique parts for either setup.

As Mono front wheels all have ball bearings, wheel bearing pre load isn't an issue. The axle can only be fitted from one side due to the diameter being stepped.

Rob