Introduction: Top Banana Bike

Picture of Top Banana Bike

Convert a small kid bike into a fun sporty looking silly riding adult bike.

Kids outgrow their bikes so fast but here is a way to put even the smallest 12" wheel kid bike back into action as a cool-goofy adult bike.

Re-uses/repurposes old items from the dumpster:
small kid bike,
old steel tube,
wood mop handle.

Visit a good primer on Dumpster Dipping

Only had to buy the banana seat and a 5" long 1/4" bolt.

Step 1: Parts Needed

Picture of Parts Needed

12" or 16" kid bike
Banana seat
Steel tube to fit in steering tube and support seat nose.
Steel tube that accepts kid bike stem
caster wheel from cart, furniture etc to form swiveling seat nose bracket
1" or 7/8" wood dowel (about 8" long) to connect caster threaded post to steel seat nose support tube.
Crutch to support back end of seat
3/8" bolt to bolt seat nose to caster bracket
1/4" by about 5" long bolt and 5-6 nuts to bolt seat back to crutch

Step 2: Pull Stem From Kid Bike and Make a New Tall Seat Support Tube Instead

Picture of Pull Stem From Kid Bike and Make a New Tall Seat Support Tube Instead

Take stem from kid bike and measure tubing diameter needed to replace the stem and slip snugly into the fork's steering tube.

Slip it into steerer and determine length needed to get eat to right height for you.
Cut to length remembering to subtract height of caster frame that goes between tube and seat nose bracket.

Shave dowel down to fit snugly in top of stem tube. Pound it in at least 5 inches. Cut off protruding excess dowel. Drill snug whole to let you force thread the caster bolt into the dowel.

Attach stem tube to bike either slipping it directly in fork's steerer tube or using an intermediate tube in the steerer and slipping the stem over the intermediate tube. fit with aluminum can strip shims if needed for snugness.

Step 3: Miter and Weld Stem

Picture of Miter and Weld Stem

Cut and miter (mitering means to cut or grind joint to fit together snuggly for welding) stem extension onto stem upright.

I used a tube with an inside diameter that the bike's stem fit inside (just like the fork's steerer tube).

Weld in place with goopy weld. I use a MIG (Metal Inert Gas) welder with flux core wire and no shielding gas. This really helps me avoid pretty welds.

Step 4: Gently Squash Crutch Arms

Picture of Gently Squash Crutch Arms

Cut armpit brace off of upper crutch arms.
Gently semi-squash aluminum crutch arms into ovals so the bike's rear wheel bolts can reach through after proper sized axle whole is drilled in each arm.

Step 5: Assemble the Seat Nose

Picture of Assemble the Seat Nose

With caster screwed tightly into wood dowel in stem, now you can assemble (bolt) the seat nose bracket to the caster bracket.

Step 6: Proto Type Testing

Picture of Proto Type Testing

Take rear wheel axle nuts off and put drilled crutch arms on axle and re-tighten nuts (gently so as not to crack the aluminum).

For testing purposes the rear of the banana seat can be suspended by rope from the crutch while you finalize seat height desired.

Yes, it's already fun to ride.

Step 7: Cut Crutch and Assemble Seat Rear Mount

Picture of Cut Crutch and Assemble Seat Rear Mount

Cut crutch to length.
Drill hole for bolt (1/4" or largest bolt that seat eyelets accept.)

Assemble with nuts to keep parts in desired locations.

Step 8: Enjoy the Finished Product

Picture of Enjoy the Finished Product

Rides slow because of very low gearing on 12" bikes. (helps parents keep up with the little rascals)

The feeling alternates between:

Recaptured youth and your first bike ride or

It feels like the circus is in town or

you need to be wearing a Shriners' hat.

This bike was a proof of concept experiment for building a successor to my compact triangle bike


wizcling68 (author)2011-06-15

This thing rocks. I place this right up there with the Barfly. A bar stool with a small gas engine and a steering wheel with the gas and brake controlers on it.

unaffiliatedperson (author)2011-06-14

thats no lowrider thats a high rider lol

TheMadTinker (author)2011-02-12

This is pretty brilliant. If the parts are on hand, I might have to try this next time there's down-time in the shop I work in.

Woodenbikes (author)2010-10-08

This "Seat Support Tube" fits in the fork's steerer tube (I welded it in there instead of using an expansion bolt) just like the stem would on a normal bike. So the Seat Support Tube is conceptually a modified overgrown handlebar stem that now holds the handlebars (by holding their stem) and supports the nose of the seat.

mooseface97 (author)2010-10-07

I know your pretty spacific but I don't quite understand. Does the tube go inside the same spot the fork is or does it get welded to the top.

Tinworm (author)2009-09-09

I think this is a really neat idea....this use of a caster. It did worry me how you would keep the seat from slewing when you turn the handlebars. I can't help wondering how stable the seat will be, however. How did you find it, in practice?

Woodenbikes (author)Tinworm2009-09-09

The seat is fairly stable and only wiggles because some hardware is loose after hundreds of riders at Maker Faire(s). In practice the bike rides funny with the very short cranks. and long tiller dimension (~stem length). When you ride the bike it feels like you are getting in touch with your inner circus clown. From bringing my wide variety of bikes to Maker Faire I notice most people test several and find one that hooks them somehow more than the others. People who enjoyed silliness, enjoyed this bike. See others at

Tinworm (author)Woodenbikes2009-09-10

well, I really like the idea...and you'd have to have something of the clown about you to even consider building one (as I am). I think I might be tempted to raise the crank centre and have longer pedals or even put a cog further forward, just beneath the word "speed".

fosho4 (author)2008-04-23

Thats amazing!!! I'm a big fan of wacky bikes. One question though. Where were you able to find a banana seat? It seems like they are pretty hard to come by.

Woodenbikes (author)fosho42008-04-25

I got it via the web from lovely lowrider

SirJoey (author)2009-02-10

This is so kool, I had to build one! Thanx for posting another of your unique creations, Tom! :)

airborne325 (author)2008-08-05

THis is amazing. I think Ill build one and ride it at the next critical mass!!!!!

Woodenbikes (author)airborne3252008-08-06

I'm glad you like it. to keep up with Critcal mass ride speed >3 MPH, you may want to put a larger chainwheel on the front and/or a smaller rear cog to give you a higher gear ratio driving the 12" rear wheel. The store bought bike is designed with a low gear so your little kid can't outrun you. Happy Trails!

Luuke (author)2008-08-04

does it turn easily? with the weight of the rider... wont it affect the turnability??

Woodenbikes (author)Luuke2008-08-05

The handle bars and stem turn easily because the rider weight is supported on the top ball bearing race that is part of of a shopping cart caster wheel fork assembly, (You normally see this piece other end up on a shopping cart.) The bike handle funny ( like the circus is in town) because of the tiny cranks.

finnster (author)2008-05-07

dumpster diving is for hobos not for civilized people with PCs

Is it though? Many people make a decent living finding scrap metal and things other people didnt want at dumps, and can keep the good stuff for themselves if they need to.

no they do that at garage sales

shooby (author)finnster2008-08-05

Davethescubarock uses the word "find" in terms of discovering something and acquiring it at no financial cost. You are using the word to describe your discover of a purchase opportunity. This makes you sound like a 13 year old Mall Rat. Additionally, you might want to consider the hundreds of thousands of people that own a PC only because they found one scavenging through the trash. In many third world countries, this is the case. So....scavenging is for hobos and civilized people with PC's.

Genius. What a brilliant way to get some fun out of something that otherwise has such a short shelf life.

olson_224 (author)2008-05-30

i think it would be cool to have a wheelie bar off the back of one of these then you could just pull back + go

f3 (author)2008-04-23

Have you seen a similar project. Make a recumbant bike, this is one where you sit in a comfy chair, out of a kids bike. I would like to make one but can't remember where I saw it on the net. Like your bike. Think you could try and make it more obvious that you used a crutch by adding crutch foot poking out of seat and under arm support at bottom.

Woodenbikes (author)f32008-04-25

Is it this one? Office Chair Bike

incorrigible packrat (author)2008-04-18

Hey Woodenbikes, how come you didn't use a wooden crutch. I'm only asking 'cuz I only tend to see wooden ones in dumpland. It could just be that the scrap metal drunks thieve the 'looneymum crutches before I can get my own grubby paws on 'em (the crutches that is, I'd be loath to prod some of the scrap metal drunks with a 10' pole). Dumpland (that's the landfill site where I "work", I've recently taken to calling it "dumpland") sees it's unfair share of wee kiddies bikes and crutches. I should make a bunch of these. It would amuse me greatly to see a cadre of delinquents, tooling around on these vehicles... Great job, by the way.

I'm saving my wood crutches to someday make a
Dursley Pederson

What a fascinating site. Thanks. I knew nothing of this fellow. The bit about cream separators was particularly interesting. I couldn't help but wonder if he ever got his big ol' beard caught in the spokes of one of the racing models; those handlebars are placed pretty low. The hammock seats look darn comfortable, ever ride one? I'm thinking that a Pedersen constructed of bamboo, would be a marvel to behold and would probably weigh next to nothing.

dolabil66 (author)2008-04-16

That is a riot ! Nice Job

bedbugg2 (author)2008-04-16

too many bad puns! lol, i did something like this when i replaced the seatpost on my cousins bike with a longer one, then made the handlebars longer...nice idea

killerjackalope (author)2008-04-16

This thing is obscenely ridiculous, I love it, are they hard to ride?

It's ridiculous and easy to ride. The short cranks allow for a low bottom bracket that allows for a low seat height above ground with full leg extension. the net result is high rider confidence since both feet can reach the ground while you butt is on the seat. The speed is under 10 mph pedaling. Downhill would be scary as the angle between the front tire road contact point and the rider center of gravity (belly button) is steeper than on traditional safety bikes. The long tiller dimension (radius from steering axis to hand position ahead of steering axis) makes you swing the bars more than twist them to turn.

Sounds fun to ride... I may go make one...

Kiteman (author)2008-04-16

Oh, we definitely need to see a video of this being ridden...

messeis (author)2008-04-16

Nice way to recycle and have fun.

LinuxH4x0r (author)2008-04-16

nice! Looks like it would be hard to to ride

About This Instructable




Bio: Long time bicyclist, bike commuter, bike tourer, recent bike builder/experimenter. I'm an energy consultant for hydro electric, solar and other renewable energy generation.
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