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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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Old 09-13-18, 02:27 PM
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Your knees will thank you for much, much lower gearing.
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Old 09-21-18, 04:32 PM
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If you are only going to go as wide as a 2.1 inch tire you may want to consider looking at some of the gravel or monster gravel bikes. There are some that will take that wide a tire and come with dropbars and brifters and few can accept a 100mm suspension fork.

Good luck
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Old 09-24-18, 02:56 PM
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Quintessentium:
Could you explain what you want the bike to be able to do for you, and why you think you need uncommonly high gearing? I don't want to be too dismissive--some people have physical problems that restrict them to very low cadences, or perhaps you have some exotic needs regarding land speed records.

To put things in perspective, average cyclists pedal about 60-80 rpm on average, and professional road cyclists average around 90rpm. Assuming the low average range of 60rpm, this means a top speed of 43.3 KPH on a 29x2.1 tire on 175mm cranks with a 60x11, and 38.2 for 53x11, and 36.1KPH for 50x11. These speeds are higher than noncompetetive athletes cruise on flat ground, would mostly be reached via hard efforts in a draft or down hills. Cyclists reach higher speeds sprinting on flats commonly, but that's almost always accomplished at high cadences usually in excess of 100rpm.

On a personal note, I'm a moderately fit cyclist who rides steep descents often and rarely want more than the 50x11 on my road bike (hitting speeds up to 50MPH), and spent a fair amount of time riding with a high gear of 46x11 in similar terrain. At extremely high speeds I loose interest in pedaling because I can go faster for less effort focusing on making my body more aerodynamic rather than pedaling more. On the 46x11 there were times I would've kept pedaling if I had a higher gear, but I don't think it effected my solo ride times in any meaningful way. If I road raced competitively I would consider higher gearing, predominantly given the competitive importance of sprinting which I rarely ever do on solo or non competitive rides.

If you do want to run road drivetrain components with a flat bar setup, there are definitely shifters that will work for this. For the pure compatibility concerns of fitting, say, a road 53/39 crank on a 29er bike your main concerns are:
-The chainline is 2.5mm outboard for mtb vs road bikes. This is sometimes no big deal, but given the additional clearance problems you're likely to have, it's probably better to get a 3 piece crankset with a square taper, octalink, or ISIS bottom bracket that you can use to bring the crank outboard.
-Chainring clearance is usually pretty tight to designed cranksets on most mountain bikes, so usually much larger chainrings won't fit. You may have better luck in general with steel frames and those designed more towards touring use. I would definitely check the specs for a given frame and contact the manufacturer. I did a quick search and failed to find anything that'll work for you.
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Old 10-31-18, 12:52 AM
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Originally Posted by LesterOfPuppets View Post
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.
Hey LesterOfPuppets, what MTB are you riding that allows you to clear a 44t chainring? I'm in the market for a new MTB and am struggling to find anything higher than 30 or 32t up front. I'm not looking to put anything like a 50t road crank on there, but are there any bikes/frames you know of that could clear a 36, 38, or maybe even a 40 up front? Thanks in advance!
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Old 10-31-18, 08:21 AM
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^^^ Hoov, check out some from Surly, I have my older karate monkey set with a 3x9, 22, 34, 46 chainrings up front. Lots of the high end full sus are 1x only, look at at say some of the steel/touring stuff for 2x, Salsa and Surly come to mind. 27.5 plus or 29er/ 29er plus with a front sus, if that is enough for off road for you.
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Old 10-31-18, 10:54 AM
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Originally Posted by hoovbikes View Post
Hey LesterOfPuppets, what MTB are you riding that allows you to clear a 44t chainring? I'm in the market for a new MTB and am struggling to find anything higher than 30 or 32t up front. I'm not looking to put anything like a 50t road crank on there, but are there any bikes/frames you know of that could clear a 36, 38, or maybe even a 40 up front? Thanks in advance!
I have a few olde bikes with triples with 44T big rings on. Many MTBs that can fit a front derailleur can fit a 44T big ring on a triple.

Are you talking about in a 1x setup?
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Old 10-31-18, 11:14 AM
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Originally Posted by LesterOfPuppets View Post
I have a few olde bikes with triples with 44T big rings on. Many MTBs that can fit a front derailleur can fit a 44T big ring on a triple.

Are you talking about in a 1x setup?
Ah, gotcha. Yes, I was looking for a 1x set up. I just made a separate post about it actually: Best Chainring clearance bike or frame
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Old 10-31-18, 11:22 AM
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Originally Posted by Leebo View Post
^^^ Hoov, check out some from Surly, I have my older karate monkey set with a 3x9, 22, 34, 46 chainrings up front. Lots of the high end full sus are 1x only, look at at say some of the steel/touring stuff for 2x, Salsa and Surly come to mind. 27.5 plus or 29er/ 29er plus with a front sus, if that is enough for off road for you.
Thanks! As I mentioned to Lester, I was in fact looking for a 1x set up if I can manage. But if not, maybe I'll just bite the bullet and go 2x. I was almost sold on the Karate Monkey but after test riding a few bikes yesterday I realized the speed issue. I just made a separate post about it actually: Best Chainring clearance bike or frame
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Old 11-05-18, 12:55 AM
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Well, for all concerned, after looking around as thoroughly as possible (including but not limited to all the primary notables in this category- ie Surly, Salsa, Kona, All City, etc), the winner for largest 1x chainring clearance on a hardtail goes to (wouldn't ya know it) the new Ritchey Ultra frame. 38t clearance on that steel beauty. Sadly, more than I'm looking to spend at the moment, but hey, kinda nice to know it's at least out there.
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