Marin 90s BB / chainline question

[tweedi]

I took out of a team marin 1994 a M900 crankset and it was mounted with a 107mm spindle UN71 Bottom bracket.

I would like to mount the set (cranks + front mech m900) on a 1993 eldrdige grade frame, and possibly reuse the UN71 BB with 107mm spindle.

Now those frames are all 135mm OLD, and I read this normally means 50mm chainline and a spindle of 113mm.

What is the correct original set-up to get the proper chainline on a 135mm OLD and m900 crankset? I wonder if I may have to buy a new bottom bracket.

Thanks!

 

[bikeworkshop]

If that setup was working on one 68/135 bike (same 28.6 seattube?)
Then it will work the same on the other... although...

You might find that the drive side bb axle projection on the 107 and 113 are the same, so the only change would be crank/stay clearance on the NDS.
Alloy frames have fatter stays,

This, combined with accomodating fatter tyres, required a longer bb axle to push the chainset out, increasing q factor and worsening chain line.

 

[minor_LEGEND]

Typically a crankset determines it's ideal b/b length by design. Funnily enough my own Team Marin has chainline issues, cobbled together using parts I had, the octalink XT (9) setup has awful chainline but I don't have axle lengths to choose from. (well I do but it's already on the shortest)

 

[bikeworkshop]

Typically a crankset determines it's ideal b/b length by design. Funnily enough my own Team Marin has chainline issues, cobbled together using parts I had, the octalink XT (9) setup has awful chainline but I don't have axle lengths to choose from. (well I do but it's already on the shortest)

Those octalinks supported the fatter tyre at the expense of chainline.

It seems worse if fitted on early mtbs - shorter chainstays increasing the angle perhaps?

Often you have to fit all the spacers on the nds if using ht2 on 90s mtbs, and sometimes that's not enough.

 

[minor_LEGEND]

Those octalinks supported the fatter tyre at the expense of chainline.

It seems worse if fitted on early mtbs - shorter chainstays increasing the angle perhaps?

That's the exact problem, the chain angle is too acute & it just doesn't feel right (or sound happy). It's getting a tapered square UN71 & an early 90's crankset. Cheers for the advice!

 

[Tootyred]

I use 113 on that set up. Done it on several early 90s marins with xtr m900 over the years. No issues with chainline.

Did try 107, found it a bit too tight.

 

[Janners BJJ Clunker Rider]

Just following along out of curiosity.

 

[DrDaveTampa]

Familiar with Sheldon Brown's website? Spindle length is part of the crankset spec, he has a halfway decent database here. More on chainline here

 

[Tootyred]

Spindle length is part of the crankset spec

Kinda......but not entirely. Most cranks have a from / to distance. So i think m900 is 107 to 113. But it depends on the frame its going in too. If the frame has over built chain stays for example, that can change the size needed.

Tbh...if the op has the 107, screw it in and see..... if its clearing ok....its ok. If your not happy with the stay clearance, chain line or front mech swing....pop in a 113mm or at least measure from that point.