Boxerworks.com

Yes, I only have access to Real OEM but the danger in working off obsoleted or non-updated systems is that they won't have the supersessions, e.g. from the examples you refer to;

'31429062419' Stanchion (04/09/1990 — 06/07/1991), superseded by '31421241655' (09/01/1980 — 12/06/2022), exchangeable retrospectively, found on 2477 vehicles (i.e. models by years).

Part 31421241655 was found on the following vehicles:

R 60, R 75 , R 80, /7, RT (76-85)   (04/1977 — 01/1985)
R 65 GS, R 80 G/S, R 80 ST (80-92)   (05/1980 — 07/1987)
R 100, /7, /T, CS, RS, RT, S (76-84)   (03/1976 — 11/1984)

Then looking at the bolt and what they called the absorber etc, it's all the same. Ergo, they'd fit although they make might some minor change in performance. Hopefully being refined or improved over the years.

Seems 31422000376 was the earlier number but also refers back to the same models.

I don't know if BMW keeps the current, official fiches updated for obsoleted models but if they did, from other manufacturers' parts system, I'd expect it to keep track of all the superceded numbers. Again, I don't know BMW specifically, which is why I am asking, but sometimes, e.g. part numbers changed because the part suppliers changed.

Similar/same but I find it easier to use...less pop adverts.

https://shop.maxbmw.com/fiche/PartsFiche.aspx

SteveD wrote: ↑Fri Dec 19, 2025 4:37 pmSimilar/same but I find it easier to use...less pop adverts.

Hear you on that. It seems to be a new thing they've just enabled, huh? I don't remember it happening before.

Has anyone ever put up just a part number search, i.e. for backwards compatibility? I see it actually lists the fork tubes as 35.95mm. It's still not really clear to me that the difference between the pre- (31 42 2 000 376) and post-09/1980 tubes (31 42 1 241 655) are.

I learned a new word a few weeks ago, it was "ensh*tification". It's a term coined by Cory Doctorow to describe the decay of online platforms where they first attract users with quality service, then exploit users to benefit business customers, and finally exploit both to maximize profits for owners, leading to a useless, "ensh*tified" state.

I'm really seeing it in my every day use of the internet these days, when every website wants you to click past 3 pop ups, or even the same pop up every page, for cookies, sign ups, offers etc. It's like the designers never got the message that we don't consult our lawyers over every copy and paste terms and conditions before reading a website. Why do they all do it?

Someone needs to make a browser extension called, "I really don't care and don't want to sign up to anything".

Thanks.

Todd wrote: ↑Fri Dec 19, 2025 12:44 pm Yes, I only have access to Real OEM but the danger in working off obsoleted or non-updated systems is that they won't have the supersessions, e.g. from the examples you refer to;

'31429062419' Stanchion (04/09/1990 — 06/07/1991), superseded by '31421241655' (09/01/1980 — 12/06/2022), exchangeable retrospectively, found on 2477 vehicles (i.e. models by years).

Part 31421241655 was found on the following vehicles:

R 60, R 75 , R 80, /7, RT (76-85)   (04/1977 — 01/1985)
R 65 GS, R 80 G/S, R 80 ST (80-92)   (05/1980 — 07/1987)
R 100, /7, /T, CS, RS, RT, S (76-84)   (03/1976 — 11/1984)

Then looking at the bolt and what they called the absorber etc, it's all the same. Ergo, they'd fit although they make might some minor change in performance. Hopefully being refined or improved over the years.

Seems 31422000376 was the earlier number but also refers back to the same models.

I don't know if BMW keeps the current, official fiches updated for obsoleted models but if they did, from other manufacturers' parts system, I'd expect it to keep track of all the superceded numbers. Again, I don't know BMW specifically, which is why I am asking, but sometimes, e.g. part numbers changed because the part suppliers changed.

I don't want to get into a war on this but the contemporary parts lists are normally the more accurate. BMW stopped supporting the airheads many years ago and so they are not designing or modifying the parts. Real OEM and MaxBMW reflect this.

The fork was completely redesigned for the 1980 year, In the first line you quote, the 1991 date and the 2022 date are the dates when BMW stopped supplying those items as spares, not the manufacturing dates dates of the machines they were fitted to. After all, machines after 1985 use another completely different set of forks, this time with different diameter stanchions. The fork stanchions are different and this is born out by the fact that suppliers still supply different stanchions now. To Todd, I would say... if you want to try it, go ahead but be aware the chance you'll be able to make them work is minimal. If you do, let us know the definitive answer.

Rob

Rob Frankham wrote: ↑Sat Dec 20, 2025 5:16 amThe fork was completely redesigned for the 1980 year ...

But they weren't "completely" redesigned.

The pertinent dimension remained the same, the yokes and stem remained the same, the internals remained the same ... as far as I can see, all that happened was the outside of the castings where changed to fit Brembo calipers.

But even there, the leading axle remained the same, the mudguard bolt holes remained the same, the external dimension of the boss at the bottom and where the seals/gaitors at the top remained the same, the seal remained the same, the bolt that hold the dampener remains the same.

That's a whole heap of same.

Circa 09/1980 is when they brought in the 17 digit VIN system. May be that is related to parts renumbering?

I've known other manufacturers to go through renumbering phases. Most if they improved a part would use a different number for it, but it would still fit or work. The advice just being to use the upgraded part.

I'm not interested in the later, post-85 38.5mm forks on the Monolevers. That obviously WAS when the largely complete redesign DID happen. But it's seems like the 36.5mm forks just went through an incremental change to the external castings.

Todd wrote: ↑Fri Dec 19, 2025 10:59 pmIt's still not really clear to me that the difference between the pre- (31 42 2 000 376) and post-09/1980 tubes (31 42 1 241 655) are.

OK, thanks to Euro Moto Electrics (EME), I've found out one possible difference. Although the basic dimensions are the same, the pre-09/1980 376 tubes have two holes drilled in them. I have no idea what difference this would make or why, presumably to feed the gap between the tube and slider?

They also say that "The [later] tubes will also fit on Pre-09/1980 models however you need to install the fork damping system from the Post-09/1980 models for these older models".

Ergo ... so far ... it seems the sliders can be swopped but the dampners and tubes need to match.

Does the dampner on the older forks screw in to place?

Todd wrote: ↑Sat Dec 20, 2025 1:13 pm

Rob Frankham wrote: ↑Sat Dec 20, 2025 5:16 amThe fork was completely redesigned for the 1980 year ...

But they weren't "completely" redesigned.

The pertinent dimension remained the same, the yokes and stem remained the same, the internals remained the same ... as far as I can see, all that happened was the outside of the castings where changed to fit Brembo calipers.

But even there, the leading axle remained the same, the mudguard bolt holes remained the same, the external dimension of the boss at the bottom and where the seals/gaitors at the top remained the same, the seal remained the same, the bolt that hold the dampener remains the same.

That's a whole heap of same.

Circa 09/1980 is when they brought in the 17 digit VIN system. May be that is related to parts renumbering?

I've known other manufacturers to go through renumbering phases. Most if they improved a part would use a different number for it, but it would still fit or work. The advice just being to use the upgraded part.

I'm not interested in the later, post-85 38.5mm forks on the Monolevers. That obviously WAS when the largely complete redesign DID happen. But it's seems like the 36.5mm forks just went through an incremental change to the external castings.

I can be absolutely certain that the internal components of the two different fork systems are NOT the same. I have both in the shed and I have rebuilt both so I know this to be the case.

VIN numbers were first used in 1954 and were not used by BMW except in the US till '83. They are simply identity numbers and have nothing to do with the physical construction of the vehicle.

Rob

It's best not to copy the entirety of previous posts, Rob. Anyone reading this discussion has already read what I wrote. Just edit out the pertinent section, e.g.

Rob Frankham wrote: ↑Mon Dec 22, 2025 5:03 amI can be absolutely certain that the internal components of the two different fork systems are NOT the same. I have both in the shed and I have rebuilt both so I know this to be the case.

Well, if nothing else, by persisting, we've discovered that the like of RealOEM parts fiches are not entirely accurate or reliable.

But, equally, that it's incorrect or misleading to state that the forks were "completely" re-designed.

EME state that "The [later] tubes will also fit on Pre-09/1980 models however you need to install the fork damping system from the Post-09/1980 models for these older models."

Hence, presumably, the later slider would also fit on Pre-09/1980 models if you stuck with the early fork damping system.

Is it that the earlier fork tubes have internal threads at both ends, and the dampening absorber has two washers and a spacer that screw into them and a circlip, whereas the later tubes don't and just use a push in unit and then the circlip?

(I haven't taken apart a later pair). See photos.

VIN numbers were first used in 1954 and were not used by BMW except in the US till '83. They are simply identity numbers and have nothing to do with the physical construction of the vehicle.

Now you're just being pointlessly obtuse because,

a) BMW certainly didn't adopt the VIN system in 1954. It only adopted it for 1981 year range, as I stated. And,

b) I never infered it had anything to do with the physical construction, which makes no sense at all. I was looking for an explanation for changes in parts numbering, which took place to the same time, e.g. 09/80.

I wonder what's going on with the fiches that RealOEM use then because they clearly state compatibility up until 1984.


• So why won't the post-09/80 Brembo sliders fit on the pre-09/80 tubes, if one uses the matching dampening absorber?

According to the fiche, both use the same M12 Fillister-head screw to hold the inners in place.

Todd wrote: ↑Tue Dec 23, 2025 2:15 am
But, equally, that it's incorrect or misleading to state that the forks were "completely" re-designed.

The stanchions changed, the sliders changed and the internal damping components changed... to me, that's a complete redesign.

EME state that "The [later] tubes will also fit on Pre-09/1980 models however you need to install the fork damping system from the Post-09/1980 models for these older models."

EME don't supply OEM stanchions which are no longer available. There is no guarantee that the parts they supply are the same as OEM.

Hence, presumably, the later slider would also fit on Pre-09/1980 models if you stuck with the early fork damping system.

That doesn't follow... even if the early slider will work with the later stanchion and dampiing components (which I'm not convinced about) that's not the same as saying that the later slider will fit with the early stanchion and damping components...

Is it that the earlier fork tubes have internal threads at both ends, and the dampening absorber has two washers and a spacer that screw into them and a circlip, whereas the later tubes don't and just use a push in unit and then the circlip?

Neither types of stanchions have threads at the bottom... both types have threads at the top and use the same screw in top plug. The push in plug with a spring clip is ony used on machines that have a cast auminium top yoke. One of the few common parts is the threaded plug that screws into the top of the stanchion and locates it in the top yoke.

Now you're just being pointlessly obtuse because,

Not Obtuse at all. simply stating that, in Europe, the VIN system was not universally recognised in 1981 and a simple look at the parts number list will show that BMW parts numbers in general did not change at 09/80 except where there parts themselves changed. This whole issue has absolutely nothing to do with VIN numbers which have to do with the identity of the vehicle, not the parts used to make it.

• So why won't the post-09/80 Brembo sliders fit on the pre-09/80 tubes, if one uses the matching dampening absorber?

According to the fiche, both use the same M12 Fillister-head screw to hold the inners in place.

Not so. The dampers in the early fork legs are attached to the sliders (or rather the screw in plugs at the bottom of the sliders) using an 8mm nut. the bottom part of the damper assembly has a threaded stud that goes though the bottom plug and is secured (with appropriate washers) by the 8mm nut. On the later assemply, the Fillister head screw is used.

I'm afraid I'm away from home at the moment and don't have access to most of my reference material to post more images.

Rob

Might help?

http://www.vintage-register.co.uk/libra ... 0Forks.pdf