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Is there an MTB double that can be put on a road bike?

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Is there an MTB double that can be put on a road bike?

Old 08-14-07, 11:48 AM
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Is there an MTB double that can be put on a road bike?

I have a long ride in a bit over a month that has 29K of climbing over 2 days. Problem is that I'm having issues with my knees. Currently, I run a compact crank with 34/27 as my lowest gear. I expect that much of this ride will be spent grinding in first or standing.

If things go well, I might be able to make it with my existing setup and have moderate pain that could be recovered from in several weeks (this is an acceptable outcome to me). It could also turn out much worse, so I'm rethinking my gearing.

Are there MTB doubles, and if so, can I just swap out my current compact crank, lower the FD and have a nice light bike with some crazy low gearing? I couldn't care less if I'm spun out all the time on the flats and the downhills. This is just a ride and I don't care if speeds are low.

Alternatively, I have a 28lb touring bike that has a 30 ring and an MTB RD, and I even have an old 11-34 cassette that came with my trike (and was immediately removed but not thrown out for some reason) which could also be ridden. But something that heavy really sounds like a lot of extra work. I've taken that bike on rides with over 10K feet of climbing before (but not with that cassette), and it was significantly more difficult than taking a racing bike.

Touring bike is 9sp and racing bike is 10sp, so moving touring bike components over doesn't make sense because I'm not willing to swap out entire transmissions. What would you do in my shoes?
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Old 08-14-07, 11:56 AM
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Just in the throes of deciding myself as I plan to ride some mountains next year- Did one this year and I have got hooked. I do not know of an MTB double crankset.

If you are 9 speed- then an MTB cassette of 12/34- or 32 is a straight swop but you will require a new rear derailler and chain.

10 speed and two ways- Down to a triple with new front and rear derraillers involved aswell. R.D. is required to take up the extra chain from dropping to a 30 and still trying to run a 50. Or There is a 10T MTB size cassette that is available-12/34 I believe from Sheldon Brown. Same rear derrailler and chain required though.

Failing that and it is get out and build up strength- Which I will have to do in any case- but those Multiple steep hills will need lower gearing for me.
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Old 08-14-07, 11:57 AM
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I'd probably buy another bike.
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Old 08-14-07, 12:05 PM
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The only mountain bike double crank that I ever knew about was the Ritchey 2x9 set-up. But as far as I know, it was a 110mm bolt diameter anyways, so that wouldn't be any different than what you've got. Can you just move your long cage derailleur and the 11-34 cassette to your lighter bike? That would give you a one to one ratio, which is better than the 1:1.25 you've got now.
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Old 08-14-07, 12:09 PM
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Originally Posted by redtires
The only mountain bike double crank that I ever knew about was the Ritchey 2x9 set-up. But as far as I know, it was a 110mm bolt diameter anyways, so that wouldn't be any different than what you've got. Can you just move your long cage derailleur and the 11-34 cassette to your lighter bike? That would give you a one to one ratio, which is better than the 1:1.25 you've got now.
The problem is that the lighter bike has a 10 speed tranny while the 11-34 is 9 speed. I suppose I could move the front shifter as well, but I'd prefer to keep things simple if possible.
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Old 08-14-07, 12:22 PM
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How bout 650cc wheels?
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Old 08-14-07, 12:54 PM
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Originally Posted by bbgobie
How bout 650cc wheels?
Just so happens my bent has some nice light ones. Is there a way to make the brakes reach the rims since the wheels are smaller?

Also, will I be able to mount a 10sp cassette on since them? They have a 9sp mounted.
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Old 08-14-07, 01:01 PM
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ok...here is what I know about your setup. it is 10 speed. I am guessing Shimano.

Honestly, ANY MTB crank can be made into a double but I would keep it a triple. Here is what I would "suggest". There used to be some 94 BCD MTB cranks floating around. I'd try to find one if I could. I have some 110 BCD MTB cranks and I used to own a 94bcd.

Yes, your FD "SHOULD" still work on it. I know many MTB racers that use ultegra level front and rear derailers.

What I might consider doing is keeping your rear shifter intact and friction shift on the downtube the front with the MTB crank. Just keep your current brifter on there for the bracke and put a friction downtube on it.

Have you also thought about having a custom Miche rear cassette made? You can get those up to 29 tooth I think in Shimano and still be 10 speed. 13x29 just like the campy setup.


Originally Posted by banerjek
I have a long ride in a bit over a month that has 29K of climbing over 2 days. Problem is that I'm having issues with my knees. Currently, I run a compact crank with 34/27 as my lowest gear. I expect that much of this ride will be spent grinding in first or standing.

If things go well, I might be able to make it with my existing setup and have moderate pain that could be recovered from in several weeks (this is an acceptable outcome to me). It could also turn out much worse, so I'm rethinking my gearing.

Are there MTB doubles, and if so, can I just swap out my current compact crank, lower the FD and have a nice light bike with some crazy low gearing? I couldn't care less if I'm spun out all the time on the flats and the downhills. This is just a ride and I don't care if speeds are low.

Alternatively, I have a 28lb touring bike that has a 30 ring and an MTB RD, and I even have an old 11-34 cassette that came with my trike (and was immediately removed but not thrown out for some reason) which could also be ridden. But something that heavy really sounds like a lot of extra work. I've taken that bike on rides with over 10K feet of climbing before (but not with that cassette), and it was significantly more difficult than taking a racing bike.

Touring bike is 9sp and racing bike is 10sp, so moving touring bike components over doesn't make sense because I'm not willing to swap out entire transmissions. What would you do in my shoes?
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Old 08-14-07, 01:13 PM
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I did some research and a 94 BCD crank is definately what you are looking for. Suntour made them in triple and they were called microdrives. they were 94/58 BCD cranks. The smallest 94 is 29 tooth and they are hard to find. The next size is 30 and is pretty common.

Ritchey also made a 94 bcd crank and I also believe at one time Race Face might have.

Ebay. They will all be square taper for the most part but hey...it is for one event right?

I am serious about the friction downtube on the front though. Won't have to worry about swapping brifters.

Heck, you could even keep them triple and have that lovely 20 tooth granny gear.
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Old 08-14-07, 01:54 PM
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Originally Posted by Rutnick
Honestly, ANY MTB crank can be made into a double but I would keep it a triple. Here is what I would "suggest". There used to be some 94 BCD MTB cranks floating around. I'd try to find one if I could. I have some 110 BCD MTB cranks and I used to own a 94bcd.

Yes, your FD "SHOULD" still work on it. I know many MTB racers that use ultegra level front and rear derailers.
By this logic, could I take the triple from my touring bike, remove the other ring and use it as a 30/42 double after adjusting the FD?

The custom route does sound tempting. 29 teeth would be a noticeable improvement.
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Old 08-14-07, 02:06 PM
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Just ride it with what you have. 34/27 is already pretty low.
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Old 08-14-07, 02:30 PM
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The good news is that it's do-able. The bad news is that you can almost never change just one part on a bicycle. In this case, depending on what changes you decde to make, you will find yourself replacing the bottom bracket, chain, front derailleur and maybe the rear derailleur. They'll be a debugging process too.

Have fun!
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Old 08-14-07, 06:28 PM
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yep. All it take is just giving it a try. Take the inner off and get a shorter BB. Adjust the limits on the FD and give it a try. I doubt it would index shift properly the way you would want it but it would friction. The only concern I would have is the width of the 10 speed chain.

Originally Posted by banerjek
By this logic, could I take the triple from my touring bike, remove the other ring and use it as a 30/42 double after adjusting the FD?

The custom route does sound tempting. 29 teeth would be a noticeable improvement.
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Old 08-14-07, 08:54 PM
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The best crank would be a Shimano LX trekking crank like this one. It's cheap and good. Remove the inner ring to make it a double giving you a 48/36 compact. You might need to change the bottom bracket, although these take a narrower bottom bracket than you think. In some cases narrower than a double road crank...go figure

I run the XT version on a road bike with an Ultegra front derailer without issue. You shouldn't have to do more than move the derailer down to the proper height. Since you are already running a compact, I assume that it's a 50 tooth outer. You won't even have to monkey with the chain. Additionally, this is a 104BCD crank and there are lots of 44 and 42 tooth outers out there if you want something lower.
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