Part number on forks?

[GTRider]

Helping a friend clean out his shop area. Years ago he bought a set of new, OEM take-off fork tubes from a new R1100RS that was having a leading-link fork installation done for sidecar use. There is a number cast on the slider (2 339 445)that looks like a portion of a part number, but it doesn’t match the 31 4 22 314 627 or 31 4 22 314 628 part numbers for the forks. Are those numbers just casting or production numbers unrelated to the actual part number, or?
Thanks,
DeVern

 

[20774]

I think you answered your own question. BMW doesn't stamp part numbers on their parts.

 

[AntonLargiader]

Those are part numbers, but they are intermediate work-in-process numbers rather than final production/retail part numbers. For instance, in the case of a front wheel there could be a part number for the raw casting, others for any machined variants of that casting (with/without a speedo drive, tall vs. short rotor mounts, etc), and then more for painted versions of those parts. Maybe even another for the assembly including wheel bearings and seals, which is what is sold as a replacement part at dealerships. Since these numbers are mostly generated at the time of design, they tend to have sequentially close part numbers.

I just looked at the fork sliders on our '98 R1100GS. They show the casting numbers 2 311 983/984. The retail part numbers are 2 311 981/982. The fiche shows them to be the same as on the R1100RS, so I don't know what is with the different casting number you see. My Showa part numbers are B004-L and B004-R. Can you post a pic of the whole fork slider? Maybe BMW updated that casting to accommodate some R1150 variant and issued a new number for it.

Needless to say at this point, BMW DOES mark parts with the part number. They do it all the time. It's just not always the retail part number, because it might be the unpainted fairing panel, the plastic seat pan rather than the upholstered seat, or the raw final drive casting that hasn't been drilled for the optional ABS hole, speed sensor hole or possum scraper mounts. But sometimes it is, like on the windshield and the air filter cover from that same GS. And FWIW the seven digits are the real part number. The 11-digit sequence you usually see are the unique part number preceded by the main group (31 in the case of front suspension) and subgroup (don't remember what 42 is but I think I have a chart at work).

 

[20774]

Anton -

While it might be a "part number", most lay people don't know anything about internal or casting numbers used by BMW in the process of manufacture. Since those internal numbers don't help an end user, I wouldn't really call them a part number in the classic sense of the word. An owner can't go down the store and ask for that part with that cast number. Just my 0.02.

 

[AntonLargiader]

I think the number on that fork leg might be 2 333 446. 445 and 446 seem to be the left and right fork slider castings for the bikes with the EVO brakes (based on the brake mounts on some fork legs I have here at the shop, having Showa numbers B023-L and B023-R). This would mean your fork sliders are from an R1150RS rather than an R1100RS. In this particular case the finished fork leg part numbers 31 42 7 651 477/478 are nothing like the casting numbers, but it looks like BMW skipped from 2-xxx-xxx to 7-xxx-xxx for a lot of parts in that time frame.

Part number geek stuff: my part number guide lists subgroup 42 as the only subgroup for MG 31, explaining why practically everything in the 31 MG starts 31 42 x xxx xxx. HOWEVER... I have one inventory item, swingarm pivot seal 31411233252, that is an exception to this. Looks like my info is incomplete!

 

[GTRider]

More pics:











Maybe these will help with the identification?

Thanks for the help!

DeVern

 

[AntonLargiader]

The numbers nailed it; they are EVO forks. If you want to use them on a classic R1100 you will need EVO calipers and 320mm rotors.

 

[GTRider]

Thank you, Anton! I take it these would be the correct part numbers, then?:





Best,
DeVern

 

[AntonLargiader]

MAX shows those part numbers as being the complete fork legs (sliders, tubes, seals, etc.) for the RT only. The sliders themselves (the 477 and 478 part numbers I cited) seem to go to the RS, R, and RT.

What are you trying to figure out?

 

[GTRider]

MAX shows those part numbers as being the complete fork legs (sliders, tubes, seals, etc.) for the RT only. The sliders themselves (the 477 and 478 part numbers I cited) seem to go to the RS, R, and RT.

What are you trying to figure out?

These are complete fork legs that will be listed in the Marketplace, so I’m just trying to make sure we’re calling out the right fitment. The legs were removed from a new or nearly new bike that was being fitted with a leading link for sidecar use, and were intended to be used on a local fender-bendered RS. But, the RS forks checked out ok, the paperwork on the purchase of these legs has disappeared, and these legs have been taking up shelf space for too long…

Best,
DeVern

 

[AntonLargiader]

Aha, got it. I was focused on the sliders and forgot these were complete. The 1150 models all had different fork leg assemblies. Same slider for R/RS/RT, but different fork tubes. If there is a threaded post on top, it's either R1150R or RT. No post, it's an RS or even possibly a K12. Post a pic.

From my notes:
R11xxRT - 349mm bottom to hole, 628mm bottom to seam at cap
R1150R - 373 and 617

 

[GTRider]

Pic:


I take it your dimensions are for the forks tubes alone, sans sliders. Rather than disassemble the forks, I’ll get an overall length measurement for a potential buyer to compare to.
Thanks!

DeVern

 

[AntonLargiader]

That should work. If my notes about the tube lengths are right, the fully compressed R1150RT fork should be 29-3/8” overall (measured using a tube I had that measured 628mm) and therefore the R1150R fork would be right around 29”. When you compress that one fully, what is the overall length? The pic shows them not fully compressed; it would be easier if you bled some air out of the bleed screw to compress them.