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What if road gears is on a MTB bike frame and 2.1inch MTB wheels?

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What if road gears is on a MTB bike frame and 2.1inch MTB wheels?

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Old 07-12-18, 04:19 PM
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Quintessentium
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What if road gears is on a MTB bike frame and 2.1inch MTB wheels?

Iím very keen to get much larger custom chainring as a road chainring for my 29er bike,
such as 53T or even 58T, 60T.

(Iíd be most happy to put 3x10 60-42-26T or 58T-40T-26T or alternatively 53T-38T-26T or alike, and/or 3x9, 3x11, 3x12)

but I learned that I just canít put those on MTB gear system.

(I also learned that Shimano offers 48T MTB chainring, but I couldnít content with it.)

so the idea popped up later was just putting road systems on a MTB frame and my 2.1 inch wheels.

( I didnít get a frame yet because I couldnít determine one with what kind of BB specification I should get among B30 or BSA for most common Shimano stuffs in my country, South Korea.)

so concerning pedaling force regarding bigger and heavier wheels,
usage in rough terrain and hills as for riding a usual MTB,
and comparibility with a frame and other components such as m

Iím enquiring what downside and problems I might have to face or risk.

Thank you deeply in advance for this unusual, odd idea.

Last edited by Quintessentium; 07-12-18 at 04:29 PM.
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Old 07-12-18, 04:54 PM
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Start with making sure you have at least a 11T sprocket on the rear, or perhaps 10T. That is the easiest update for higher gearing.

A few issues occur with the monster chainrings on a MTB frame. First of all, the chainstays may be angled in such a fashion that a big ring may not fit properly and may hit the chainstay. Road cranks may also hit the chainstays.

Newer road cranksets have a fixed width. Older ones have a little more adjustment with choosing appropriate bottom brackets.

If you have a braze-on front derailleur mount, that will likely be in the wrong spot.

If you install a very long bottom bracket, your front derailleur could also have issues reaching that far to the right.

Keep in mind, the curvature of MTB front derailleur cages may also be designed for smaller rings.

Your front derailleur may not have the capacity for a 60/26 or 58/26.

Your rear derailleur may also not wrap enough chain for a 58/26 in front, and a wide cassette in the rear.

Anyway, you may be able to work around some of these issues, but it will lead to many headaches.
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Old 07-12-18, 05:10 PM
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The other issue that people will argue until they are blue is whether you really need the 60T rings.

I like my big gears on my road bike, but realistically, I really only hit the high gears on hard fast descents, > 40 or 50 MPH. Most of the time, I land somewhere mid-cassette.

Soon, I'm building a 29er touring bike, and it will have a reasonably wide gearing range, but realistically speaking, I will rarely be hitting > 20 MPH on the bike, so there won't be a need for anything extreme.

As far as power, it isn't as simple as just adding bigger gears. The human body realistically can't increase power indefinitely without also increasing cadence. Which means that you may well be in the same gears at 30 MPH as 20 MPH.

Think of an old car with a manual transmission. 5 speed? Can you start driving in 5th gear... maybe, but it will struggle with it, with slow acceleration, especially on a hill. Say you are cruising along the freeway at a fairly high power, and wish to accelerate up a hill, what do you do? Just mash the pedal the the metal? Nope... downshift, at least until you get up to speed.

The same thing is more less true on a bike. You can't just use an infinitely high gearing.

The amount of force you can repeatedly put into a pedal is limited to some fraction of your weight. In some cases on a hill, you can push and pull for a little more. However, standing and mashing big gears on the flats isn't particularly efficient either for a number of reasons including wind resistance.
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Old 07-12-18, 05:18 PM
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I have a Shimano 5500 road triple with 52/42/26. I wouldn't go for a bigger spread than that.

When I ride MTBs I'm perfectly happy to coast after I spin out my 44x11, and that's on 26ers. on 29er that's an even higher gear.
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Old 07-12-18, 08:41 PM
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Would you run into clearance issues with your driveside chain stay?
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Old 07-13-18, 05:18 AM
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thank you for considerate replies, everyone!


I think I didn't clarify that I'm thinking to put entire road gearing groupset or such combinations on the frame.

shifter/brifter, derailleurs, crankset and cassettes for road bikes

and 29er MTB frame + a thick MTB wheel set as 2.1inch + a drop bar or preferably a flat bar. (if there are fully compatible flat bar shifter/brifter with mechanical lever.)

or did most people already regarded so?

Last edited by Quintessentium; 07-13-18 at 08:57 PM. Reason: more detailed and correct writing
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