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Old 06-13-10, 04:02 AM   #1
graytotoro
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MTB-Road parts interchangability

Hi all,

I have an older gas-pipe road bike that may need a bottom bracket - the chainrings keep dropping the chain even without any sort of pedaling - even if it's not broken, the pedals themselves sound as though they're about to snap off. So I was wondering if it was alright if I could source a cheap MTB crank and/or bottom bracket and use it as a replacement. I don't want to buy a potentially expensive road crankset and chainrings and see them go to waste.

Would there prove to be any difficulties? I plan to run this as a single-speed with as little cost as possible; I've been treating it as one every since I gave up on making the front and rear dérailleur work.

With that said, what other parts can I interchange between the MTB and road bikes? I know that Surly equips the LHT with a XT RD and I've heard vague rumors about interchangeable road parts with MTB shifters or something like that.

This isn't my primary bike, in case you're wondering. This is just a summer project to do in my spare time.

Thanks for your help!
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Old 06-13-10, 06:09 AM   #2
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The devil is in the details.

Shifters and rear derailleurs can be mixed and matched unless you have a wide ratio rear cassette in which case you need a mountain bike rear derailleur.

Shimano says not to mix and match shifters and front derailleurs but many manufacturere used to spec mountain shifters with road bike front derailleurs. Within a range, your front derailleur has to match the size of your front chainrings.

Cranks are pretty much interchangable but your bottom bracket has to match your bike frame and, again within a range, you need to be aware of the chainline.
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Old 06-13-10, 04:02 PM   #3
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I don't know ALL the MTB parts that are interchangeable, but have used MTB cranks, cassette's and RD's on my road bike. I have even gone to the extreme of (gasp) using a Campy BB with my XTR crankset! I liked the idea of cartridge bearings in the BB, and even using ceramics for it.
Like Retro says, your BB has to match your frame (68, 70, or 73mm width), but beyond that, you can mix 'n match to your hearts content. Of course, your BB has to be the type your intended crank will fit (square taper, ISIS, etc.).
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Old 06-13-10, 04:08 PM   #4
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Your best bet if you want to do it on a budget, is find a donor bike. Remove any/all parts that you want to use, then recycle what is left through a local co-op or whatever. Best to reuse the bottom bracket and crankset as a pair.
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Old 06-13-10, 06:14 PM   #5
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Quote:
Originally Posted by graytotoro View Post
Hi all,

I have an older gas-pipe road bike that may need a bottom bracket - the chainrings keep dropping the chain even without any sort of pedaling - even if it's not broken, the pedals themselves sound as though they're about to snap off. So I was wondering if it was alright if I could source a cheap MTB crank and/or bottom bracket and use it as a replacement. I don't want to buy a potentially expensive road crankset and chainrings and see them go to waste.
Cheap road cranks are available if you look around: http://www.bikepartsusa.com/bikeparts/item/01-98916/ , but I agree with WRK: find a suitable donor bike and Frankenstein 'em together. You'll learn more that way.
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