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 Post subject: Crank arm clearance??
PostPosted: Wed May 23, 2012 12:13 pm 
retrobike rider
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Location: Looking at my bike from the comfort of my sofa!!
Due to financial constraints, my new Voodoo Bizango is having a lot of the parts from my Kilauea fitted to it for the moment!

I'm kinda figuring that as it is designed by Joe Murray, most of the geometry must be pretty similar.... :shock:

So I have transferred over the bottom bracket and the cranks and noticed there is hardly any clearance between the crank arm and the stay..maybe 4mm The chain line is roughly sitting at 49mm, (middle ring to centre of seat tube)I tried a shorter bottom bracket got the chain line down to an almost perfect 47.5mm but the arm was only about 2mm from the stay!!......not good.

So.....my question is this:

Are modern cranks designed so the arms have a bigger clearance due to, what I presume as, more modern frames having bigger tyre clearance between the stays??

If you know what I mean!!!

The photo is with a 113 bottom bracket, 110.5 gives a better chain line but the arm is even closer.


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PostPosted: Wed May 23, 2012 12:56 pm 
Old School Grand Master
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Location: Behind you with the duct tape pulled out.
Always thought 50mm from centre of seat tube is correct? Thats what it says on sheldon b.


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PostPosted: Wed May 23, 2012 1:48 pm 
retrobike rider
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Location: Looking at my bike from the comfort of my sofa!!
poweredbypies wrote:
Always thought 50mm from centre of seat tube is correct? Thats what it says on sheldon b.


Recommended is 47.5.- 50mm dependent on tube thickness!!!

Apparently!!! :?

From Sheldon B:


MTB Triple 47.5-50 mm Shimano spec, measured to the middle ring.
47.5 preferred, but for frames with oversized seat tubes, the longer dimension may be needed, because the fat tube places the derailer mechanism farther to the right.

Im within the recomendations....more worried about the closeness to the stay to be honest!!


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 Post subject:
PostPosted: Wed May 23, 2012 1:57 pm 
Old School Grand Master
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Joined: Tue Oct 04, 2011 4:15 pm
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Location: Behind you with the duct tape pulled out.
I wouldnt worry to much anything to bend the cranks over that far is likely to bend something else first. Or get an e-stay no probs then :lol:


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