I last built-up a 20" Novara frame into a bike for my daughter, Novara Pixie 20" project
She is turning 8 yrs old this week and ready for a 24" bike so I have slowly been working on building up her next bike.
My philosophy is to keep it light as possible without splurging on any really expensive parts. I found the Trek MT220 frame at a bike co-op for free, it was a donated frame still in great shape, undamaged but had been stripped of all parts and the co-op didnt want to bother with sourcing all the components to put it back together as a complete bike. The Trek frame is made with hydro-formed aluminum (quasi-rectanglular downtube) and weighted 1420gr, almost 1 lbd lighter than another Novara 24" frame I had previously sourced for this project. Most expensive cash outlay I made on the project was for a set of new Schwalbe Rocket Ron 24" folding bead tires, 440gr each and very supple. I re-used the Alex singlewall 36 hole rims from the Novara, 404gr and 420gr each and re-laced them to some much better quality (& quick release) non-disk hubs as I am staying with V-brakes to keep weight down. The rear hub was an older shimano with a 7-speed cassette body. The hub itself was not particularly light (cheap steel cassette body) but the shorter 7-speed cassette helps to keep the spoke dish more even, makes for a good wheel build geometry. I laced the rear with 12 crossed spokes on the drive side and 6 radial non-drive spokes, producing a 880gr rear wheel. Front was built as a 12-spoke radial wheel using just every 3rd spoke hole. 12-spoke front makes for a completely symmetric wheel with the spokes correctly oriented in the angled rim holes to each side. I have ridden the wheels around under my own 200lbd weight and they hold up fine so I feel confident they will be reliable for my much lighter daughter as the 400gr rims are complete overkill for her weight. I used a lightweight (253gr) XT 9-speed 32-11 cassette with aluminum carrier that I shortened to 8 cogs (32-12) in order to fit on the 7-speed body. Also used a XT rear derailleur and a deore push shifter that I had all sourced cheap from a swap meet.
I found a late 90's manitou spyder 26" fork at the co-op that was fairly easy to shorten into a 24" fork by carving up the fork tip ends, see 24" air fork . The fork has aluminum steer tube & stachions and it uses combine coil springs and elastomers and had a simple oil-bath dampener that is easy to service and tune. I re-worked the internals to provide 70mm of travel and eliminated the spring & elastomers from one side to soften the compression for my daughter. Once shortened and reworked, the spyder fork weighted 1300gr, a very nice weight savings compared to the currently available 24" forks (RST first air, Spinner, suntour). With the fork sliders shortened, the rim brakes work perfect on the original bosses and the A-C height is nice and low so the front end is not jacked up excessively.
The crank is a 5-bolt Bulletproof brand 145mm length that I setup 1x with an outer bashguard and a 34t inner ring (581gr crank weight) on a reasonably light (270gr) shimano UN71 bottom bracket.
Despite the good standover clearance, the frame has a somewhat long 51cm effective top-tube length so I bought a new shorty 5cm stem and found some swept-back riser bars that help keep the seat-to-bar extension reasonably comfortable for my daughter.
The V-brakes are generic caliper arms with small tektro levers, they work great and provide a light touch with plenty of braking force and control.
I have spent perhaps $250 altogether on the build. Most of the parts were sourced lightly used but I did need to get a new chain, derailleur hanger, tires, cables, stem, and a cheap kids saddle ( Bell saddle from wal-mart!). As it stands now, the bike weighs 20.5 lbs ready to ride, just above my goal of a 20lbd bike. The frame, fork, tires, wheels and crank are all fairly lightweight parts that I want to keep. The inner-tubes are fairly heavy at 150gr each so I am thinking I can drop some more rotational weight by going to a tubeless setup. I didn't use any carbon fiber parts for the stem, bars or seatpost. I could likely drop another 150gr by using a lighter rear hub with alloy cassette but that would also involve re-building the wheel (again) and I like the 8 of 9 on 7 cassette & shifting.
My daughters birthday is this weekend so I plan to give her the bike then, have her test ride it a bit if winter conditions allow but hopefully I can re-work it further to drop a bit more weight before springtime riding really starts!
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Thread: Trek MT220 24" mod build