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Building a BMX bike for my 2.5yo?

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mtnbkr:
A high end bike builder I know of has a few of his BMX frames on clearance for $50 (normally over $200).  I have a crazy idea to buy one and slowly build it up into a complete bike for my daughter who's just now learning how to pedal a tricycle.  Why bother?  Well, if I do this, she'll have a unique, high quality, light bike.  However, at this point I don't know that she'll even want a bike when the time comes (I ride, wife doesn't), or will ride it enough to justify the expense.  While the frame's discounted, it'll take a bucketful of money to buy the wheels, cranks, etc to complete it.  Of course, I'll have plenty of time to do this, so I won't need to spend it all at once.  

Of course, I could ride it, but there's nothing more flattering than an adult on a BMX bike.

Opinions?

Chris

Harold Tuttle:
i build bikes and used to manage the repair shop at the fools gulch Bicycle Exchange on Route 7 in yer neck of the woods

i bought my kids Aluminum, 20 inch, single speed, coaster, hand brake bikes at Target on clearance for 36 bucks
they grow so fast, they rapidly fit a 24 inch mountain bike
i think my older daughters was a couple a hundred at Performance

a cheap frame is a fun project but by the time you buy worthy rims and hubs and a nice crank...

Now, i still have my Redline RLII freestyle bike
but that ones a rare bird...
Back in my prime, i used to skoot about on it alot
quite the aerobic workout

what my kids really love, is our drag behind trailabike
http://www.trail-a-bike.com/interface/adams.php

K Frame:
That sucking sound you hear is money flying out of Mtnbkr's wallet...


How about this?

Why not buy the frame, and hang on to it since it's such a bargain.

As the miggit gets bigger, you'll be better able to gauge just how intersted she'll be in biking.

If it turns out that she doesn't want to bike (my luck she'll want to study martial arts), sell it on EBay.

zahc:
I'm a 20" riding adult. My shoulder is too bad to ride much anymore, though. Since I am bored at work, prepare for a wall of text.

If you intend her to get into freestyle riding, a 20" bike is actually too big for her. Of course it would make a fine bike for here to ride around, though. Building bikes up is fun but pretty expensive, depending on how high quality you want to go. Mine is worth almost $2, which not many people expect in a little kid's bike!

I suggest you get the lightest frame you can, such as a racing frame, probably the shortest (20" TT or less). The kind of light bike I'm envisioning would have a lot of 'race' bmx parts on it, rather than freestyle parts on it.

You will not find a better headset for cheaper than an FSA pig. I've been riding mine for 5 years and three frames. Before that I got at most 6mo out of a headset. It is a bit heavy, but if I wanted something lighter the only thing I would get is a King ($$). Most any aheadset can be used with good results however. There are no sealed headsets cheaper than a King that are worth a damn.

36 spoke wheels, if it's for her, and this isn't just an excuse for you to get into shredding :). Any rims would be fine as long as they are light and cheap! Buy decent spokes, though. I refuse to use anything but DTs, they are not expensive. Do not use aluminum spoke nipples. You definately want sealed bearing hubs. 3/8 axles would be best for a light bike. The kind of light bike I'm envisioning would have a lot of 'race' bmx parts on it.

Buy light, skinny (not 2.1") racing tires, and use regular (not thornproof , heavy duty, slime, etc) innertubes. Do not use a rims strip, use fiberglass stranded packing tape or duct tape. It's lighter and doesn't move around.

Cassette hubs are popular but they are too expensive and complicated. You can get what is called a 'flip flop' hub or one with the smaller threads so you can use 13-15t freewheels. Traditional threads only allowed down to 16t freewheels which require larger, heavier and more dangerous front sprocket. Another option is to just use 16t freewheels with smaller (~36t) front sprocket anyway, which gives easier gearing which is probably better for the most part anyway. We adult freestyle bikers run tall gearing for speed, and so the cranks spin slower when you roll backwards, so 36-16 or even easier would be fine for a kid. I know adults that run 36-16 out of preference  anyway. G-sport hubs are simply the best, at any price, just FYI.

3/32 chains are standard for racing and weight weenies, and I can't reccomend a brand because I've never used them. 1/8" are stronger. KMC Z510HX is the chain of choice if you really don't ever want to break or stretch a chain, but it's pointless if it's not running on 1/8" sprockets. You can do it, but it's probably not worth the system weight to go 1/8. If you lube the chain, use something like progold. Personally I think oil attracts more grime than the lubrication is worth. The chain should always be wiped dry.

Tradition dictates a single rear brake with a straight cable. Freestylers use u-brakes, racers use caneliever brakes or v-brakes, and u-brake posts are unique so pay attention when you choose a frame. If you want to run sprockets smaller than 44T watch for break-to-chain clearance. u-brakes also require matched levers. Canteliever brakes would probably be the lightweight choice.

Cable detanglers add weight and hassle, but your cable never wraps around the frame and breakes, and they feel much stiffer, a tradeoff I gladly make. Front brakes can be routed through the fork making them tanglefree, and of course they also stop much better. They are not very popular and finding forks with mounts is probably not an option. But I would rather ride with only my front brake than only a back brake. Still the canteliever brake and straight cable is probably they way.

Whatever grips you use, you have to do something to prevent core samples of either dirt or flesh. Simply sticking grips on lets the bars eventually pop through. So you can just drop a nickle in the grips or use bar ends, preferably light ones. Some grips come with plastic ones that don't last very long, but they are light, and  possibly last as long as the grips.

Cranks are complicated. 1 piece cranks suck in every way, but 3-piece cranks are expensive. It's up to you. Just don't buy 175mm+ cranks for a little kid. Also pedals don't fit both, 1 piece cranks take 1/2" pedals. Speaking of pedals, cheap is fine. I think you can get cheap welgo aluminum platform pedals for like 16 bucks.

Albes.com and Danscomp.com, in that order, are good mailorders.

garrettwc:
I don't know about one of those exotic metal framed bikes. They can be a bear to weld on.

How are you going to mount the crossbar so she can "joust" with Mike if he happens to wander onto your street?

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