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Old 02-01-07, 02:14 PM   #1
Gotte
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Bottom bracket query.

Can someone explain which bottom bracket/chainset I need, I'm having problems getting anything to wor.
Let me expplain.
I have an old MTB with a tange frame that I always thought rode quite well. I fancy turning it into a tourer/road bike. Trouble is it has a small Acerta x chainring. It's way too low for real road use. I've tried changing it, though, and nothing else seems to fit properly - or rather, I cant get the deurailier to move to the outside ring. It runs out of travel. All the newer chainsets I've tried seem to have the chainrings further out than the original one I have.
Anyonew know if it's fixable. I've tried a wider BB (one I had hangong around, and it's not much wider) but it still doesn;t work.
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Old 02-01-07, 02:57 PM   #2
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Have you opened up the upper limit screw on the front derailleur?
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Old 02-01-07, 03:19 PM   #3
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The width of the bottom bracket will depend on the make and model of the crankset you are trying to fit. Go the your LBS and ask them for the right size bottom bracket to fit the crankset- Or answer the question====

What make and model crankset are yoiu trying to fit? and someone here may be able to answer you.

I was lucky last year in that I had a no name double crankset to replace a Triple STX on a bike and one of the old BB's in my spares box fitted. The STX took a 115mm and the Double road crankset took a 127mm.
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Old 02-01-07, 05:30 PM   #4
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Turning a mountain bike into a road bike is a waste of money. Just buy a cheap road bike.
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Old 02-02-07, 07:36 AM   #5
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It's an old MTB which is actually well suited as a road bike - long wheelbase, relaxed angle, 42" stays, brazeons for racks and fenders. It's not the lightest, but it's chromo, and I like steel over aluminium.

As for the chainset. I'm pretty sure it's Acerta. The rest of the groupset is. It dates from the mid-90s.
The bottom bracket is 4cm, and the smallest chainring is not flush with the back of the crankarm. It is closer to the bike, like a road chainset (or rather, like the chainsets on the two roadbikes I have - both two ring).

All the three ring chainsets I've tried are flush with the back of the crank arm, and are further out on the biggest ring. This means the changer cannot push the chain onto it (I've checked, and yes I have it at it's full extension; little screw out as far as it will go).
I can go with a road chainset, but I'd rather have a three ring affair.




The bottom bracket is shimano and measures.
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Old 02-02-07, 09:43 AM   #6
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Quote:
Originally Posted by Gotte
42" stays
I think you mean centimeters ..........Seriously, I think an older mtb converted to a tourer makes a lot of sense-

Last edited by well biked; 02-02-07 at 09:50 AM.
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Old 02-02-07, 10:22 AM   #7
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Maybe Sheldon's page on chainline will have the info you're looking for:

http://www.sheldonbrown.com/chainline.html
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Old 02-02-07, 11:27 AM   #8
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Quote:
Originally Posted by well biked
I think you mean centimeters ..........Seriously, I think an older mtb converted to a tourer makes a lot of sense-
You know, I'm forever doing this kind of stuff. Yes, you're right, 42 cm.
They do make a lot of sense. Even the weight is marginal. I have a dedicated tourer, put together from a Coventry Eagle frame. It's 531,a nd when which racked up weighs in about 30lbs. The MTB I'm converting (mainly for use by wife and a friend) weighs pretty much about the same. It rides well, also. I fitted 700 wheels and shimano road brakes (the longer armed ones), and it rolls along really nicely.

If only I could get the chainring sorted.

Hopefully the link Nick Burns put up will sort that out. Thanks all.

Phil
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