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20" wheels on 26" MTB

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20" wheels on 26" MTB

Old 08-27-19, 01:09 PM
  #1  
keepontrikin
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20" wheels on 26" MTB

curious to replace the 26" wheels on my mountain bike with 20" wheels.
anyone done it?

pics?
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Old 08-27-19, 02:58 PM
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55murray
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You first.
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Old 08-27-19, 07:23 PM
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You’ll need some really short crank arms .
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Old 08-27-19, 07:43 PM
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Your brakes won't reach unless they are disc brakes.
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Old 08-27-19, 08:21 PM
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kirby999
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Originally Posted by pinholecam View Post
Your brakes won't reach unless they are disc brakes.
Coaster brake rear .
How about a 20” rear and a 26” front wheel. That’ll get your pedals off the ground with some ape hanger bars ?
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Old 08-28-19, 08:37 AM
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Philphine
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i've kinda half thought about it, but i can weld a bit and i'm thinking to get it right some welding will happen. like adding about 3" to the bottom of the frames streering tube to keep the pedal to ground clearance the same, and to switch to a 20" fork so front brakes can still be used (unless disc brakes happen). something would need to happen with the rear triangle too, but i haven't figured that out yet.
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Old 08-30-19, 05:09 PM
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Many years ago , when I was in my early teens .
We didn’t have a lot growing up . We’d build bikes from parts others would throw away in their trash . We’d drag them home and piece them together.
Some would saw off the arms of one fork and would hammer wedge them onto the arms of another fork to raise the front of a bike to make a chopper style bike . Usually had a 20” up front and either a 24” or 26” in the rear .
I can remember seeing front wheels and fork arms flying off when some kid would attempt a wheelie ! Haha ! Man , that’s a long time ago .
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Old 09-07-19, 06:19 AM
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some times you just have to do it and see how it turns out
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Old 09-08-19, 03:55 AM
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20" to 26" is too large a difference.

not only bottom bracket height is lower but also the too small trail for the front wheel.
Bicycle Trail Calculator | yojimg.net

having the next lower size rims in it can work and some people do it without knowing that possibly the main benefit is in regards to their taste of having an easier to work with front wheel by that trail getting to a lower value. some are using large tire on 24" size rims. having not so wide tires on smaller wheels is not so fun.

the trend is with bigger than 26" wheels. people woke up to the benefits but they still stick to suspension forks for mtb. not too many are able to service their forks as often as recommended.
gravel/CX bikes are more appropriate for regular street riding/commuting. lower than 26" is only useful for kids or people who are really low height.
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Old 09-09-19, 03:44 PM
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I did build a MTB many years ago with 20" wheels off a BMX, front forks were old ones that got replaced of my 26" wheel MTB so I had to lower the brake mounts, rear triangle was from the BMX with the rear shock unit from the MTB that had been replaced. I built the frame to suit so I could get the bottom bracket up to a good height, also built in a 3 speed hub into the BMX wheel, (not Sturmey Archer, the other one) no pictures of it anymore but it was neat riding it around town, not so good off road because of the smaller wheels, but still good fun.
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Old 10-29-19, 11:22 PM
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I did it to a cruiser once and all I gotta say is make sure the crank is horizontal when you turn.
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Old 12-26-19, 11:47 PM
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are you try to build a minivelo? better start from scratch or find your self a good ol steel frame and 'lower' the rear drop out about 2,5 inch
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Old 09-09-20, 03:48 AM
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That's what i was thinking.... The minivelo concept... I would love one for Urban commuting.. Or públic transportation long distance travel.. Train or plane

Last edited by MMonde; 09-10-20 at 03:52 PM.
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Old 09-09-20, 05:14 AM
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Things I have done:
20" frame with 26" forks, 12" front wheel, 16" rear wheel. Feels always on the edge, but still gets over 40mph
20" frame with 16" wheels
20" frame with 12" wheels
16" frame with 12" wheels
16" frame with 20" forks, 16" front wheel and 16" rear wheels.
The longer the wheel base the better, optimum seems to be a long BMX with 12" wheels.
You need the cranks that go with the wheel size, so ashtabula cranks are great, just watch out that there are two different size bottom bracket shells and two different ways the crank engages with the chainwheel.
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Old 09-10-20, 01:27 PM
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20" rear . 26" front ? or 20" front 26" rear? NB: there are cargo bike frame designs using both of these...
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Old 11-27-20, 11:01 PM
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16" wheels on a 27" road bike with 3.5" crank arms just barely clear the ground if you don't lean. have one. I'll try to add photos this weekend. 3.5" crank arms are not easy to get.

had a 20" on a 27" road bike that had a bit more pedal clearance.

i've built a few 24" wheels on 26" bikes. those ride pretty good. You can usually fit fatter tires when you downsize. Swaping out crank lengths can give you a little more ground clearance. This is one I built a couple years ago. Ground off the canti brake mounts and cable stops/guides and the 2 chainrings that were riveted on. Coaster brake rear hub.

Last edited by rickpaulos; 11-27-20 at 11:11 PM.
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Old 11-29-20, 03:52 PM
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This was parked out side during business hours at the local bike coop. The right crank broke at the pedal threads after getting blown over for the upteenth time. The poster advertising blew away in a 50mph wind. But it was rideable. The builder welded on a couple of auto muffler clamps for fender mounts. The generator works. 16" wheels on a 27" road bike.
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Old 12-21-20, 07:39 AM
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This seems like a good place to post this:

A 20" wheel on a 24" fork will allow one to run a U-brake. The pads will be at max height and the pivots will be sloppy but it could work out depending on your expectations.


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