What's the shortest Square Taper BB?

jimmy5willy

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I've got 113mm fitted at the moment and the front mech wont reach the large ring. Is there like 100mm bottom brackets out there?
 
For mountain bikes, the shortest I've known is 107mm. If you go the road bike route you can go down to 105 or even 103mm.
 
Sheldonbrown's site shows recommended lengths for most usual cranksets. Actually the 103mm one is used on one series of Dura-Ace cranks (and few others, not really common ones, not even sure if some mtb ones use that). So I would be afraid the cranks will need more not to touch chainstays.
(unless it is a FD issue, such as when using road shifters and mtb FD, it also usually doesn't reach)
 
Re:

I hear what you're saying but it's not a shifter issue. Theres no shifter connected, I'm just pushing the front mech to full reach.

The chainset is just a shimano chainset, middle of the range. LX maybe? Outer chainring is 42t compact drive so not massive.
In any case I'll whip it out again at the weekend (the bike) and measure the distance from the back of the crank arm to chainstay. That should tell me how much shorter I can go yes?
 
107 is the shortest tipple on an MTB, used for super low profile crankset like the M900 XTR. similar counter part is the 110, that just gives a bit more on the none drive side.
113 gives a 2.5 mm further out chainring (chainline) at 50mm
every other crank style would push the rings and arms into the chainstays more.
THAT should be capable for any triple MTB front mech.

Quick question... have you screwed the limit screws out.

take a picture and make and M number on the mech, crank etc.
 
Quick question... have you screwed the limit screws out.

take a picture and make and M number on the mech, crank etc.[/quote]

This is a ton of info and I love it!
What is 50mm though?
Limit screw is currently half way out but now you mention it, I could take it out and see what the absolute max is. Good shout. ;)
 
Re:

How far does a chain need to move across for the ramps to flick it up onto the next ring? At the moment and by sight, this front mech isnt moving much past middle ring.

...but then on second thoughts, the derailleur is going to need to be almost centre on the big ring so it doesn't rub?
 
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