1991 Marin Pine Mountain B/B specs wanted

[ginsterdrz]

Can anyone give me the exact specs off a 1991 Pine Mountain bottom bracket please?
Shell measures 68mm but don't know correct model/axle length that should be fitted.
Thanks in advance folks.

 

[ginsterdrz]

Think I've established it's a Shimano UN54 with 110mm axle. Can anyone confirm?
There's also a 107mm axle version. Would that cause alignment/clearance issues?

 

[marc two tone]

pine mountain bb

according to the gallery and archive above( full of good stuff) a DX bottom bracket was fitted. probably the cup and cone type with seperate lockrings.

are you looking for exact replacement or, something 'as near as damn it?'

i would fit a sealed type of 1992 spec say, un70 or un 72 (xt) but a un 53/54 would do just as good of a job, slightly heavier.

as for length, this can depend on the chainset you intent to run with. if you are going with the original DX i think 115-118mm would be fine.if something else (which may have a thicker or thinner spider) then its a trial and error job. if you have any other bb's laying around......try them til you are happy. keep the arms a good 3mm from the stays then, ask in the wanted section on here once you are satisfied with your choice.

good luck.

 

[hamster]

It depends hugely on the chainset - you buy a BB to suit the chainset, not the frame. BB shell width is the only time the frame comes unto ut, unless you have dishless wheel back end, 145mm OLN back end or similar.

If you fit a 110pcd chianset, a 110mm BB is a minimum as anything else is likely to cause the ring to hit the chainstay.

 

[FluffyChicken]

Think I've established it's a Shimano UN54 with 110mm axle. Can anyone confirm?
There's also a 107mm axle version. Would that cause alignment/clearance issues?

It cannot be UN54 as that's a modern bottom bracket.


hamster, not true. M900 was 107mm so where a few other superlowprofile designs, RaceFace iirc....
It's not the rings that decide (unless they do actually hit and you have it on fat tubes or a compact chainset (42/44) designed frame), it is the design of the crank arms.

But in 1991 nothing really in mass production would be down at 110 or 107 as far as I know.

If you just want to fit and forget and do it easily
http://www.chainreactioncycles.com/Mode ... elID=17473 UN54 122mm from here, easy though you'll need the fitting tool which is a few quid and a V.large spanner or socket set.

Deore DX was 122.5 and this was the common length for Shimano chainsets as well as many other normal profile cranks

Deore DX cup & cone mated to a DeoreDX chainset was what was speced.
Model number BB-MT60 and length 122.5mm*


(*though there where also longer versions 127.5mm and probably 125mm (?) as well, but it'll not be these lengths)

It should be stamped on the bottom bracket you have taken out if it was the original, either a length or a code on the axle.)


Though if your not actually after the original one and your not using the original cranks, then please do say, but you asked for original ?

 

[ginsterdrz]

The frame came without a bottom bracket unfortunately but I've sourced an original DX chainset.

A few questions answered thanks.

I'm happy to use a modern replacement and read on another thread a restoration had used a UN54 110mm. Seems strange if the original was 122.5mm or was that the shortest option made available by Shimano at that time?

 

[FluffyChicken]

The frame came without a bottom bracket unfortunately but I've sourced an original DX chainset.

A few questions answered thanks.

I'm happy to use a modern replacement and read on another thread a restoration had used a UN54 110mm. Seems strange if the original was 122.5mm or was that the shortest option made available by Shimano at that time?

No that was just the length you needed to keep everything where it should be, it's how the cranks was designed. 110 would place it 6mm further in, you might get away with it but the rings would be out of alignment.

 

[Xesh]

The frame came without a bottom bracket unfortunately but I've sourced an original DX chainset.

A few questions answered thanks.

I'm happy to use a modern replacement and read on another thread a restoration had used a UN54 110mm. Seems strange if the original was 122.5mm or was that the shortest option made available by Shimano at that time?

No that was just the length you needed to keep everything where it should be, it's how the cranks was designed. 110 would place it 6mm further in, you might get away with it but the rings would be out of alignment.

Agreed. The chainset on that build couldn't have been a '91 DX. It may have been a more modern Deore or equivalent.

I have used an M730 chainset with a 118.5mm axle, which was the shortest ATB BB that Shimano produced at the time, but it was at the limit of adjustment for the f/mech. There was literally no way that anything shorter could have been used as the large chainring was about 2mm away from the chainstay.

 

[gradeAfailure]

My '92 Eldridge has its original DX chainset and I'm running a 68x122.5 Shimano BB on it - aligns perfectly.

 

[ginsterdrz]

Thanks for everyones input-especially the last post. UN54 in 122mm it is then.