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atombikes 05-08-09 05:07 PM

Cheap BMX minivelo
After studying this for a week or so, I took the plunge and started to build up my homebuilt minivelo from junk bike parts. I started thinking that I wanted to build a bike that could easily be put in a suitcase by using sleeves as referenced in another thread, and I still intend to do that. But I decided I would build it up this way first just to make sure I like the ride before I cut the frame.

Here is where I'm at now. It will be a 52 chainring/16 freewheel single speed bike with front and possibly rear caliper brakes. I figure the less stuff I add to it the easier it will be to pack. I know the handlebars will probably have to be dropped some more.

Lalato 05-08-09 11:53 PM

I like it.

That's an impressively long seat post. And is that a quick release on the stem?

caotropheus 05-09-09 12:27 AM

First of all, lucky little me, I would not need such long seatpost and stem. And this build is giving me ideas!...:D
Second, a question. Do you consider 451 mm wheels?


griftereck 05-09-09 05:18 AM

you might want to put the saddle as far forward as you'll be more over the cranks then
will be steadier to climb then

have you got a close up of the stem?
did you cut the quill tube from a stem and then clamp a plain tube onto it?

atombikes 05-09-09 08:03 AM


Originally Posted by Lalato (Post 8884848)
I like it.

That's an impressively long seat post. And is that a quick release on the stem?

Yes, it is a seatpost clamp and quickrelease.

atombikes 05-09-09 08:04 AM


Originally Posted by griftereck (Post 8885188)
have you got a close up of the stem?
did you cut the quill tube from a stem and then clamp a plain tube onto it?

Yes, I did exactly as you said, clamped as scrap seat tube cut from a frame onto a quill that had the stem cut from it, then filed flush. Works beautifully. And allows use of a quick release.

rench123 05-09-09 06:45 PM

Does the seatpost flex much?

atombikes 05-10-09 07:16 AM


Originally Posted by rench123 (Post 8888023)
Does the seatpost flex much?

Not that I have noticed- I have only ridden this bike for a short distance but I have not noticed that seatpost flex would be an issue. The wheelbase seems a bit short but nothing insurmountable.

The way I see it, this seatpost is no longer than a Bike Friday and some folders?

The wheelbase could stand to be a bit longer, that would open up the "cockpit" for easier standing sprints and hillclimbing, but again, it's usable as-is.

rench123 05-10-09 11:46 AM

i was thinking of the cockpit as well. the top tube seems too short for someone with legs long enough to justify that seatpost. of course its a scrapbike project, so understandably you use what you lay your hands on. please update us on how it goes!

atombikes 05-19-09 08:35 AM

updated pics
I added chain, front brake, and am now able to take this bike on short rides. I think this will be quite a nice little bike for short trips. It took a short while to get used to, but nowhere near some other bikes (like some recumbents).

I am still waiting for the chain tugs to arrive in the mail. I used a cheap v-brake lever for the front brake, I was able to expand the plastic clamp enough to fit over the larger diameter handlebars. I will add the rear brake later for safety. The foam grips are not permanent, eventually if/when I decide this one is a keeper I will strip it all down, remove the decals, clean everything up and paint the currently painted parts. I think I will leave the chrome as-is since it is so durable.

There's alot to like about this bike- low step over height, extreme portability, very nimble handling, low weight (for what it is).

alecw35 10-14-14 02:59 AM

cool bike. Ive modified some kids bikes, and rode them.

marxmini 10-14-14 04:06 AM

1 Attachment(s)
very nice build. i have been toying with the idea of building a formula 1 BMX too. this diamondback BMX will be the guide.

DVC45 10-14-14 09:52 AM

Nice build!

I've been hunting Craigslist for a 24" tire BMX for a good price for the same project build. No luck so far.

fietsbob 10-14-14 10:04 AM

Put a straight edge, on that seat post.. so you are able to compare it as it bends a little bit at a time.
to plan replacing it , before its too bent.

Is that one using chromoly steel ?

atombikes 10-15-14 06:21 AM

Hey, that's my bike! haha. Well, it WAS my bike. This thread is 5 years old, and many things have changed during that time.

As I recall, the bike's handling was very nimble. It was simple, relatively lightweight, and fun to throw around.

My plan was to keep the frame intact, but braze in a second top tube and second set of seat stays along with a seat tube extension to stiffen the seat area. Similar to how some F1 bmx bikes were designed. In the end, I disassembled the bike and stored the frame and other parts for years, only to have recycled them about a month or two ago.

Here's what I like about the concept: compact frame, bottom bracket in "correct location" for 20"wheelset, if you get a bmx frame with a long enough top tube (~21") the bike is OK for adult size riders.

The challenges: the seatpost (as already discussed), need a riser for the handlebars, rear dropout spacing not correct for geared wheel.

I say if you can find a geared 20" mountain bike with a 21" or longer top tube, you might have something. Similar to the F1 bmx bikes that marxmini is using.

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