# 20" bike build, based on Trek Superfly 20



## oren_hershco (Mar 11, 2006)

This project started based on another frame and fork, therefore I purchased all the components seperatly. Had I planned using a Superfly, some of the original components would have been used.

The bike was stripped, leaving only the frame, headset, fork and stem:









The original bottom bracket was hardly spinning. If you plan to purchase this bike, do pay attention (it's a cup-and-cone type, so bearing tightness can be adjusted)

The wheelset:

https://www.aliexpress.com/item/New...32621769662.html?spm=2114.13010608.0.0.qe60Ag

These wheels can be customised: hubs, spoke, nipples and rim colors, plus a selection of 24 or 28 spokes on the rear wheel (front is 20)

Although I'm a big fan of hydraulic discs, I decided to use v brakes, for the following reasons:

1. Weight
2. Robustness (rotors can be bent easily, especially on a small-wheeled bike)
3. Safety: the rotors have a potential of causing a serious injury, if a curious kid sticks a finger in the wrong place at the wrong time.

These are the actual weights, without QRs:

















Skewers are titanium Aliexpress stuff (The wheelset eventually came with steel skewers, I wasn't sure at the time of order)

https://www.aliexpress.com/item/Ult...32323491151.html?spm=2114.13010608.0.0.qe60Ag

The brakes came from the same brand (Litepro). The levers

























While truly 'ultralight', I cannot recommend them, yet. They have very tiny bolts, which I covered with Loctite fearing they'll fall off. I even have to grind the cable heads a little, so the cable can spin freely into its groove. So far, they work fine. The reach adjustment fits my 6 YO boy, and the operation is smooth.

The brakes:

























These come without brake pads. Original KoolStop didn't work (the armes touched the tire), but Avids had a slightly higher profile, which gave a good result.

Crankset was purchased from "Flow Cycles":









It's a two-piece design, with the left side that matches ISIS standard. The arms are 130mm, and it comes with 32T chainring. Weight is 200g lighter than the original Superfly crankset+BB.

Cassette is Sunrace 10 speed 11-34, with the 11T cog removed (in order to avoid severe chain angles, caused by the short chainstays). Sunrace's next-small cog, the 12T, is knarled, so can be used as the final cog, but you need to install a 12T lockring:









Shifting was tasked to Shimano Zee system (FR derailleur version):

























The clutch mechanism in Shimano derailleurs can be adjusted. I tried to tune it s light as possible, but so far decided to use the system without the clutch engaged (it requires more thumb force with a working clutch)

The selection of this gearing system prooved right: unlike "normal" 20" bikes, with cheap revo-shifters which kids struggle with, my kid succesfully switches between all the gears, from day one.

The final result:

















Final weight is 7.75kg (17.3lb)

Other components:

Toseek carbon handlebar and seatpost (Aliexpress). Handlebar was cut to 50cm.

VP junior pedals.

Schwalbe Black Jack tires.

Original Superfly saddle (altough I purchased a nice one from "Flow cycles")

Last few touches:

The frame was covered with 3M "helicoter tape", a clear decal which protects sgainst scratches, and can be easily removed when worn.

Black 3M reflective decals.

And, of course, front and rear lights, and a bell.


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## MTB Pharm (Mar 10, 2007)

Nice build. 

Did you start with a used Superfly? 

What do you think of the Black Jack tires? Looks like a good tread.


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## oren_hershco (Mar 11, 2006)

MTB Pharm said:


> Nice build.
> 
> Did you start with a used Superfly?
> 
> What do you think of the Black Jack tires? Looks like a good tread.


I started with a new bike. Used ones are hard to find where I live (Israel) and if on sale, too-high prices are asked.

Maybe some of the components will be used for a 24" bike build, two years from now.

The Schwalbe Black Jack is a good off-road kids tire. It's light, it has good grip on the loosed gravel roads we have here, and has a protection layer. I have it on the boy's 16" bike, and even purchased a 12" pair for his sister's Specialized Hotrock 12.


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## RMCDan (Feb 28, 2008)

MTB Pharm said:


> What do you think of the Black Jack tires? Looks like a good tread.


For 16" wheels the Blackjacks are the best you can do. For 20s though I'd recommend the Maxxis MaxxDaddy. The claimed weight is actually about 70g lighter than the Blackjacks, but they're significantly wider and have beefier tread. I'm very happy with the ones on my son's bike. Despite being Maxxis they're only $17/ea on Jenson.

Maxxis Maxxdaddy 20" BMX Tire > Components > Tires > Dirt Tires | Jenson USA


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## RAKC Ind (Jan 27, 2017)

What's wrong with bontrager xr1 kids tires. Light weight, fast rolling. Unless trying to corner hard in gravel their plenty for most kids. And extremely light (even set up tubeless ok)

Sent from my XT1565 using Tapatalk


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## GrayJay (May 16, 2011)

Oren-
Very nice build. I completely agree that rim brakes are appropriate for a little kids bike, both for weight and safety.

Probably too late to bother changing, but for anyone contemplating a similar build;

When I built up my kids 20" bike a few years back, schwalble's 20" moe-joe tires were 330 gr each, nice supple casing and good weight saving. I think the moe-joe was replaced by the little-joe tire which might weigh more but the weight of the original mow-joe is worth trying to find something similar.

For further weight savings on the wheels, a 20" kids bike is fine with custom12 spoke wheels; http://forums.mtbr.com/families-rid...-wheel-build-40lb-rider-need-help-891768.html


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## oren_hershco (Mar 11, 2006)

RAKC Ind said:


> What's wrong with bontrager xr1 kids tires. Light weight, fast rolling. Unless trying to corner hard in gravel their plenty for most kids. And extremely light (even set up tubeless ok)
> 
> Sent from my XT1565 using Tapatalk


Again, I already had a complete set of parts, so I used the Black Jacks. The original Bontrager tires look good as well, and I have no way to decide which of the two is better.


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## oren_hershco (Mar 11, 2006)

GrayJay said:


> For further weight savings on the wheels, a 20" kids bike is fine with custom12 spoke wheels; http://forums.mtbr.com/families-rid...-wheel-build-40lb-rider-need-help-891768.html


Thanks. I have read this thread several times, and considered wheel custom building. I have a friend who is a professional wheel builder.

However, components availability is not very good for 20", and we assumed any result we'll get will not be as good as those Litepros.


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## baltik (Nov 16, 2005)

Oren - thanks for the inspirational build. I just purchased a stock superfly for my 5.5 year old and wanted to lighten the bike for him. Based on your writeup it seems like the crank/bb is a pretty good place to start. Can you share the link where you purchased them as well as what they weighed in as?


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## Danimal (Nov 18, 2004)

So you bought a new frameset only? The stock build on the 20" Superfly is definitely adequate for my boys, and is ~18lb. For the age range they're at on a 20" though, 1x7 and rigid makes good sense and dropping weight from the reasonable stock build would probably bring fairly minimal returns on the $$$.

Dan


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## baltik (Nov 16, 2005)

I bought a complete bike, the stock build is great, I was planning to swap out a few things for fit - so was going to do the cranks and stem. Figured I'd get the lightest option if I'm buying the cranks anyway


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## hobiesmith (Mar 1, 2008)

oren_hershco said:


> 3. Safety: the rotors have a potential of causing a serious injury, if a curious kid sticks a finger in the wrong place at the wrong time.


spoken like a true veteran. if its a bad idea to put anything, anywhere, a kid will do it.


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## oren_hershco (Mar 11, 2006)

baltik said:


> Can you share the link where you purchased them as well as what they weighed in as?


The first thing I would change on a stock Superfly is the final gear ratio. 7 speeds give an adequate range, but the original low gear is not low enough.

Now that I think of it - the way to solve this is also on the crankset.... So, this is where I ordered the crankset:

https://www.flowkidsbikes.com/product-page/flow-crankset

You can also order Sinz cranks on Ebay. They fit square tapered BB, and come without a chainring. Just pay attention: they have a 5-bolt 110mm bolt circle, so you wouldn't be able to attach a 30T or even a 32T chainring.

And, there's the Spawn Cycles crankset:

https://spawncycles.com/spawn-cycles-alloy-cranks-127


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