# Would this be worth it for a 24" build?



## Venturewest (Jul 13, 2007)

I can pick this Trek MT 220 up for $50 right now. It is really beat up, but I was just going to use the frame and maybe the wheels as a base for an ultra-light 24" build. On another thread I read that the MT 220 frame only weighs 1420 grams. That seems hard to beat.

Obviously the bike has seen some abuse, but since I am planning on basically replacing everything, I can't see paying more for a nice bike.

I would strip the frame and wheels and have them powder coated some outrageous girly color scheme. I would ad an old SID, sinz cranks, 1 x 10 drivetrain, cheap carbon cockpit, bmx seat, and build the wheels with light hubs, and a light spoke pattern.

What do you think? Is there any disadvantage to using an old MT 220 frame like this one?


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## Jordan300 (Jul 26, 2008)

Especially for what your using it for, I think that's perfect. I'd pay that much just for the frame alone.


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## joe_bloe (Nov 18, 2010)

That's a great frame - quite light. I think you'll be pleased with the results. I know my 8-year-old loves his MT 220 that I built for him.


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## GrayJay (May 16, 2011)

I recently aquired a bare MT220 frame from local bike co-op and I am planning a similar lightweight rebuild project for my daughter, the frame itself looks to be a great starting point, a bit lighter than the 4 pound Novara aluminum 24" kids frame I previously acquired. Pretty pathetic that Trek managed to build such a nice frame up into a bloated 28 lbs kids bike. 
The frame has good (low) standover clearance but the effective top-tube length is fairly long (around 52cm if I remember right?), not much shorter length than a typical XS sized 26" bike. For a small kid just starting out on 24" size, it might be adviseable to use a very short stem and forward seat position to keep the reach from getting too long.


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## Venturewest (Jul 13, 2007)

Thanks for the input. If these Alpha white aluminum frames only weigh 1420 grams, I wonder how much the nicer MT 240 frames weigh. According to the Trek website, the 240 frames are Alpha Black aluminum. I think the "white" is just straight walled tubing and the black is maybe double butted. So I wonder if they are noticeably better in any way?


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## Venturewest (Jul 13, 2007)

GrayJay said:


> I recently aquired a bare MT220 frame from local bike co-op and I am planning a similar lightweight rebuild project for my daughter, the frame itself looks to be a great starting point, a bit lighter than the 4 pound Novara aluminum 24" kids frame I previously acquired. Pretty pathetic that Trek managed to build such a nice frame up into a bloated 28 lbs kids bike.
> The frame has good (low) standover clearance but the effective top-tube length is fairly long (around 52cm if I remember right?), not much shorter length than a typical XS sized 26" bike. For a small kid just starting out on 24" size, it might be adviseable to use a very short stem and forward seat position to keep the reach from getting too long.


Did you ever have a chance to weigh the frame you picked up? It does make you wonder how heavy components can be that much cheaper to manufacture.


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## GrayJay (May 16, 2011)

I will try to weigh the bare MT220 frame later today.

Looks like Trek went from white/black/red alpha tubing designations to a new scheme of silver/gold/platnium, this from 
Trek FAQ :: What are the differences between all the materials you use in your frames? (and pasted further below)

After bit of reasearching, It looks like the last year that alpha-black (butted) tubing was used fro the MT240 was around 2009, the MT240 model was discontinued for several years and then starting in 2012 the MT240 (and even the more expensive kid 24" superfly models) use alpha-silver (strait gauge) tubing. Given that the frame tubes are so short, there is probably not as much potential for weight savings with butted tubes as you would get on a larger adult frame with longer tubes.

Probably would be entirely possible for a custom framebuilder to produce an optimized kids 24" frame from butted tubing that weighs less than 2 pounds but it would also be somewhat fragile, prone to getting dents when crashed/dropped. 
3.1 pounds is probably a fine starting point that gets you some extra ruggedness, still plenty of room to build it as a very lightweight complete bike with careful component selections, particularly with fork selection which is likely to out-weigh the frame as the single heaviest part of the bike.

Another point of comparison to look at are the Scott scale RC and JR 24" bikes, two pounds difference listed in the complete bike weight, one is plain gauge frame, other is butted however I would suspect that most all of the 2 pound weight gain is due to cheaper parts, not the frame tubing difference. 
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Trek Mountain Aluminum

Alpha Silver - Our proprietary blend of lightweight aluminum alloy is continuously cold extruded to a single wall thickness. Frames built with Alpha Silver feature mechanical forming and are finished using Trek's smooth-weld finishing process.

Alpha Gold - Our high-performance lightweight aluminum alloy is continuously cold extruded and butted for weight reduction and superior strength. Frames built with Alpha Gold feature mechanical forming and hydroforming to create more complex industrial designs for even lighter weight, and are finished using Trek's smooth-weld finishing process.

Alpha Platinum - Our premium, aluminum alloy is continuously cold extruded and butted for weight reduction and superior strength. Frames built with Alpha Platinum feature extensive hydroforming to create the most complex industrial designs for the lightest weight, and are finished using Trek's smooth-weld finishing process.


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## GrayJay (May 16, 2011)

Venturewest said:


> Did you ever have a chance to weigh the frame you picked up? It does make you wonder how heavy components can be that much cheaper to manufacture.


Weighed my bare MT220 frame this evening. It was 1415 grams with no seatpost binder clamp and it was missing the rear derailleur hanger which is probably around a 20gr part. 
I am not sure on the year but the label looks to be alpha-silver so probably made within past 3 years. While it may not have originally been made of butted tubing, the downtube is hydro formed into a fairly complex oval-round-square profile and the top-tube had an flared "trumpet" shape (bigger at the headtube). Definitely seems to be more complex than just a strait gauge round tube frame and feels like fairly thin tubing.

The actual top tube length is 51cm center to center, effective top tube length measured from top/center of headtube horizontal back to the seatpost is 52cm.


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## tigris99 (Aug 26, 2012)

man I would be all over a deal like this if my son was ready for a 14" I got him a 2009 mt60 for $20 off craigslist. replaced the BB with sealed square taper, had a chain on hand and new 7s freewheel, so bought a shifter, almost new alivio linear brakes and derailleur all on hand for it, have like $40 in it and I was like a kid on xmas, not to mention my son when he saw a TREK for his bday present,lol. Even got lucky on forks working and being abuse, forks after some work and tlc, actually work at his weight,lol. SO HELL YA BUILD IT AND KEEP US UPDATED,lol.


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## Venturewest (Jul 13, 2007)

*Found a 26" Fork.*

I found a 2003 Manitou Skareb I can pick up cheap. It is a spring/ air fork. 80mm. I am not sure if it is an elite or comp yet but they are both pretty light. about 1400 grams to 1500 grams.

What do you think? I wonder if I can lower it even further. I will try to find an extra light spring kit for it and rebuild it with new seals. I guess these were super plush forks. I will also powder coat it the lowers to match the frame.

Were all the 80mm forks of that era about the same axle to crown?


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## snowbeaverking (Nov 9, 2009)

The trek kids bikes compoents are so heavy because they are all intended to get a large range of cockpit change as your child gets bigger. for example the crank arms have 2 sets of pedal holes to extend the arm length as your kids legs grow they call it dialed geometry great idea and even with them the are fairly competive with other manufactures weights. Kids bikes are just heavy unless you are willing to drop a grand or more for a bike that will be grown out of in a couple of years and for the majority of parents out there that just seems wastefull

You are going about it the right way if you want my 2 cents


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## GrayJay (May 16, 2011)

Skarab tuning/sevice manual list the lowest rider weight for the lightest springs as 100 pounds. To go even softer for a kid, if this is a dual coil spring fork you might try to completely eliminate one of the springs, just run one in one side, this would also shed some weight. 
Nice thing about air spring forks for kids is that you can easily tune them jut by changing air pressure, no need to source custom springs.


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## GrayJay (May 16, 2011)

snowbeaverking said:


> The trek kids bikes compoents are so heavy because they are all intended to get a large range of cockpit change as your child gets bigger. for example the crank arms have 2 sets of pedal holes to extend the arm length as your kids legs grow


Extra set of pedal holes should make the crank lighter, not heavier! 
Actually, the MT220 came with a junky, heavy steel arm crankset (with dial-fit holes). Should save a bunch of weight to replace it with a suitably short aluminum arm & ring crank, set it up as 1X chainring and ditch the FD too.


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## snowbeaverking (Nov 9, 2009)

Gray Jay to have the hole in it that is not beenig used the arm has to be beefier or it would break there is also the second set of steel threaded sleeves that add to it's weight. If it had no structual impact all the wieght weenies would be drilling holes in their crank arms to lighten them up


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## GrayJay (May 16, 2011)

snowbeaverking said:


> Gray Jay to have the hole in it that is not beenig used the arm has to be beefier or it would break there is also the second set of steel threaded sleeves that add to it's weight. If it had no structual impact all the wieght weenies would be drilling holes in their crank arms to lighten them up


Trek offers two dial-fit crank options (can be ordered as relpacement parts through a Trek dealer). The 140mm/120mm cranks is the junky one made of steel, probably 50X stronger than would be needed for a 70 pound kid. The 152mm/127mm crank arms are made of aluminum and are reportedly much lighter. 
I dont think I have ever had an aluminum crank that came with threaded steel inserts for the pedal spindle thread, the threads are most typically tapped directly into the aluminum, certainly wouldnt be required to deal with the torque of a 70 kid. I think the steel 140/120 crank is just an example of using grossly overweight & cheapest possible parts, not due to a strength requirement.

Trek part W292771 140mm/120mm pedal positions 
Trek part W298798 152mm/127mm pedal positions

more info on these at;
Dialed dual-hole cranks [Archive] - Unicyclist Community


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## Venturewest (Jul 13, 2007)

GrayJay said:


> Skarab tuning/sevice manual list the lowest rider weight for the lightest springs as 100 pounds. To go even softer for a kid, if this is a dual coil spring fork you might try to completely eliminate one of the springs, just run one in one side, this would also shed some weight.
> Nice thing about air spring forks for kids is that you can easily tune them jut by changing air pressure, no need to source custom springs.


I picked up the Skareb for $15, so for the price and weight of the fork, I decided it would be worth it to make it work. I figure I maybe can pick up a custom spring if I need to. It looks like it is a single spring fork, because the air spring does the majority of the work. The spring is just for small bump compliance. I may even experiment with shortening the spring. I will have to see once I disassemble it.

I did end up getting the frame, so I am $65 into the project with a frame and fork. Should be fun. This will be about a one year build. I am going to take my time finding great deals. I was messing with a weight spreadsheet today and it seems possible to get sub 20 lbs for under $500 maybe under $400.


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## joe_bloe (Nov 18, 2010)

Venturewest said:


> I picked up the Skareb for $15, so for the price and weight of the fork, I decided it would be worth it to make it work. I figure I maybe can pick up a custom spring if I need to. It looks like it is a single spring fork, because the air spring does the majority of the work. The spring is just for small bump compliance. I may even experiment with shortening the spring. I will have to see once I disassemble it.


Don't shorten the spring. That will make it stiffer. When I wanted to make a coil-spring fork softer for a kid, I just went to Home Depot and browsed the springs in the door hardware section. Found a nice soft one that would fit inside the fork, cut it to length, and it worked great - for about $10. You can get more advice on how to revive the fork in the Suspension forum.


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## xc71 (Dec 24, 2008)

joe_bloe said:


> Don't shorten the spring. That will make it stiffer. When I wanted to make a coil-spring fork softer for a kid, I just went to Home Depot and browsed the springs in the door hardware section. Found a nice soft one that would fit inside the fork, cut it to length, and it worked great - for about $10. You can get more advice on how to revive the fork in the Suspension forum.


Correct, shortening the spring will make it stiffer.


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## NYrr496 (Sep 10, 2008)

I did exactly what you're doing with a 24" GF Tyro I got from Craigslist for 60 bucks.
The bike ended up lighter than it was when I got it with the cheapo triple and junk fork, but not as light as I would have liked. 
I used a Manitou 26er coil fork and got the softest spring I could. Built wheels with Sunringle Rynolites, 1 x 10 drivetrain with a Sinz crankset and a Salsa ring. Ebay stem, handlebars and seatpost along with a seat, pedals and grips from the parts bin. 
It did work as the perfect go between for my son. He was way too big for his 20" bike but way too small for a 26er. 
I'm building a 14" 26er for him now.


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## shupack (Nov 28, 2012)

xc71 said:


> Correct, shortening the spring will make it stiffer.


~~incorrect, shortening a spring does not change the stiffness of the spring, of the spring is pre-loaded, that will make it softer overall...~~

I had it backwards, I stand corrected.


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## xc71 (Dec 24, 2008)

shupack said:


> incorrect, shortening a spring does not change the stiffness of the spring, of the spring is pre-loaded, that will make it softer overall...


Talk to any suspension tuner/shop - shortening a spring makes it stiffer.


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## Venturewest (Jul 13, 2007)

I picked up the bike tonight. It is actually recently tuned, and despite the rough shape it works great. I had my daughter try it out and it is way too big. I would say she will be 10 by the time it fits her.

A couple of observations. I weighed it on a crappy scale and it came to 27.5 lbs. I weighed my daughters Hotrock 20 and it was 24 lbs, so the weight is probably fairly accurate. The wheelbase is almost identical on the Hotrock 20 and the Trek 24". The chainstays on the Hotrock are really long. 

I did a rough spreadsheet on a potential build tonight and it is amazing how fast all the little things add up. I will have to compromise somewhere. Like I said, this will be a build that happens over time. Maybe even a couple of years.

I am looking forward to tearing into the fork soon though. In the meantime, I have a new BD fatbike being delivered tomorrow!


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## TigWorld (Feb 8, 2010)

Spend $$$ on stuff you can use on future builds. Good brakes, hubs, forks, bars, shifters, derailleurs etc. can all be used on a 26", 650B or 29er build as your kid outgrows the smaller bike.


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## shupack (Nov 28, 2012)

I looked it up, (since they're closed right now) seemed backwards to me, but I stand corrected, now that I understand why. 

probably not the place to get into the details though.


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