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Old 05-19-11, 12:54 PM   #1
divtag
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SRAM MTB Double?

There has been talk on the board about compact doubles for light touring or even the VO 46/30 vs a traditional triple. However, I haven't read anything in regards to a MTB double like the ones from SRAM: http://www.sram.com/sram/mountain/pr...ram-s1400-2x10. With 39/26 and 42/28 they could even work for loaded touring or century riding.

Since I am a novice in regards to mechanics/components, I could be missing a perfectly reasonable explanation for why it won't work. Shifters? What am I missing? Seems like the advantage of a double with a low enough gear for climbing.

Last edited by divtag; 05-19-11 at 03:12 PM.
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Old 05-19-11, 01:21 PM   #2
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I run a double on my Brompton 3 speed folding bike,
its a planetary low gear,
they make an overdrive one too 1.6x and the 2.5x
that the mountain drive is the inverse of..
my 16" wheel Has a 54t chainring, the low is like 21.6t,
so the 3 speeds have 2 ranges,
the gears in the hub are used twice .. 4th is low in high gear ,
3rd is high gear in low range.
still no derailleurs at all..

Quote:
Since I am a novice in regards to mechanics/components, I could be missing a perfectly reasonable explanation for why it won't work. What am I missing? Seems like the advantage of a double with a low enough gear for climbing.
do the math, and see if the ratios are suitable,
http://sheldonbrown.com/gears/internal.html
http://sheldonbrown.com/gears/


A touring companion 20+ years ago rode a French TA crankset,
2 rings 50t and a 28t.
14-28 or 32 tooth freewheel.
bail out low.. big upshift right at the crest of the hill,
where the pedal forces
were let up as much as possible.

triple cranksets work out well for most people ,
thats why there are so often OEM bike specs including them

But buy what gear suits your curiosity ..

What works out best for me at present,
is Rohloff's speedhub..
those are a 7 speed hub used twice..
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Old 05-19-11, 07:37 PM   #3
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Quote:
Originally Posted by divtag View Post
There has been talk on the board about compact doubles for light touring or even the VO 46/30 vs a traditional triple. However, I haven't read anything in regards to a MTB double like the ones from SRAM: http://www.sram.com/sram/mountain/pr...ram-s1400-2x10. With 39/26 and 42/28 they could even work for loaded touring or century riding.

Since I am a novice in regards to mechanics/components, I could be missing a perfectly reasonable explanation for why it won't work. Shifters? What am I missing? Seems like the advantage of a double with a low enough gear for climbing.
That's definitely a good setup. A lot of people criticize 10 speed chains, but I've used them fine on my road bike and when I raced cyclocross. A large friend of mine has a 1x10 setup on his mountain bike and it works fine too. Just note that you won't be able to use a SRAM road shifter to control a mountain front derailleur. It doesn't pull enough cable (trust me I tried). You'll want to use the SRAM mountain shifters, either the twist grip or thumbies.
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Old 05-19-11, 09:31 PM   #4
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divtag, When one considers all of the drivetrain options available all one needs to do is have a low gear and a high gear comfortable enough for the intended purpose and terrain and the intermediate gears for your 'working' cadence. How you go about it is all up to you.

Brad
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Old 05-20-11, 07:16 AM   #5
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I've thought alot about this. The only way it makes sense for touring is if you really have a problem with your front derailleur. If you use your bike also unloaded, then with a triple you just rarely, if ever, use your grannie. 10 speed components are more difficult to find and more expensive than 9 speed components. I just haven't read a compelling reason to give up the greater range of a triple.

Can one make a compact double work for loaded touring? Probably.
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