Moving from a single front chain ring to a double - help!

[sheggers]

I'm putting together a mixte that was once a claud butler majestique. It used to have single ring crankset but I want to upgrade it to a double. I've got a nice Shimano 600 and attached it, but the inner ring is so close to rear triangle of the frame, a chain won't fit on, never mind go round!

Is this an unsolvable problem and am I going to have to resort to go back to a single front ring, or is there a workaround?

Cheers

David

 

[Midlife]

You need a longer bottom bracket axle, any idea how long the axle is on yours? Might be easier to get your LBS to put in a suitable Shimano UN55 bottom bracket for you.

Shaun

 

[sheggers]

Re:

I've got a UN55 sealed BB fitted - can I put spacer in?

 

[hamster]

Work out how much further out you need it, double it and add to the existing bb length. UN55 has a large variety of different lengths available.

 

[Midlife]

As far as I am aware you can't space it out, if you did the non drive side will be too short.

New bottom bracket needed I fear.

Shaun

 

[sheggers]

Re:

Ah, different lengths of un55 exist! I shall seek out some others. Thanks all.

 

[Midlife]

Have a look at the usual suspects, Wiggl, Evans, SJS, Merlin etc as one of then usually has a special offer on Shimano BB's for some reason.

Shaun

 

[WilliamC]

Re:

You can use a spacer, even Evans have them, but not sure how far you can go. Google "bottom bracket spacer". A longer BB is probably the best solution.

William.

 

[twosheds]

Re:

If you look up your chainset on velobase.com, the specifications tell you the length of bottom bracket required. There might be 2 figures, one for a 68mm BB shell and one for a 70mm BB shell.

Bruce

 

[Steelframeman]

Without a doubt take out the axle measure it, buy the next longer one, remember half the extra length goes on the N.D. side so if you buy one that is 2.mm longer your crank will only move out 1.mm, you don't want to go too far as it will pull the chain line out to the rear wheel.

I have used a spacer before to pull out the drive side, OK the offside reduces no worries, but unless you have a selection of the threaded cups on the non drive side you will be pulling the bearing out by the width of the spacer, I was lucky I had a few threaded cups & put a longer one in.