puppypilgrim

I'm toying with an idea of building a road bike using 451 wheels based on a BMX frame. The idea being a small frame, stiff and good for a little guy like me 5'6" with short legs.





Has anyone done this and how would something like this ride?

Any issues and things I should look out for?

pibach

one problem, at least, is to find a seatpost that long with that small diameter that still is durable enough. The BMX comes in different geometries. Use a "flatland" frame as these are lighter. Still most are above 2kg. But better buy might be a stock minibike, lets say an Ultegra equipped Dahon Hammerhead 7.0 which sells now cheap for $599,-.

puppypilgrim

Thanks. Not coming from a BMX world, I am unfamiliar with what the issues might be.

ChiapasFixed

get a minivelo (like the one in your first pic), save yourself a million headaches and a world a grief, AND have yourself a really nice roadbike!
smoothhound or hamerhead are good options..

pibach

As you intend it as a single speed/fixie I don't know of any minibike with track ends. So you would need a Trickstuff Exzentricker for bottom bracket or an ENO excentric hub.
BMX frames are mostly too heavy.

But I think your Helios is just fine. It is the lightest frame in the Dahon range.

LittlePixel

First bike is a converted F1 bmx - so technically not a mini-velo in the modern sense

I think a normal lightweight bmx converted for road use is a perfectly reasonable idea; 451s should fit fine (they will raise the bb by about 25mm) and you'll likely be able to fit some nice roadie calipers. Can't really think of any issues beyond finding a good handlebar setup and as mentioned, a seatpost that's long enough - but neither of these are that taxing I'm sure.


I'd have a look at Mr Rentschler's lovely handmade minibikes for ideas; it's also worth noting the amount of Raleigh Twenty's that get converted - they aren't bmxs but are solid little 20" bikes and proof that a diminutive retro bike can be brought up to date in terms of wheels, gearing and components - so why not a bmx?

https://www.tonyrentschler.com/Bicycl...Minivelos.html

Lastly - have you thought about 24" wheeled so-called 'cruiser' bmx bikes? They might be nice platform to fit some skinny iso520 airnimal wheels...

puppypilgrim

Thanks for the ideas everyone! Google led me to Tony Rentschler as well as a slew of Mini-Velos in Japan. Very interesting fashions and very interesting concepts.

After having done the research, I ultimately think that a folding bike is still the way to proceed forward for my cycling needs. The portability of a folding bike to travel by car, train or transit is an indispensable feature for my urban riding.

griftereck

mini BMXs. those that are raced by young kids have 451 wheels
sometimes in sprint rim form

of course the frame will be smaller too.
the PK ripper BMX had and adjustable brake mount. So could use either size of wheel.

I built a BMX with 3 speed 406 alloys from a shopper bike.

I made the seat pin out of a long tube of metal from a garden frame. I put another tube inside it. That bike had 180mm cranks. Im 5 foot 8" I have since got a long BMX seat pin. Heres it on my Puch Mini sprint. Its 22.2mm diameter tube

A lot of BMXs are using thicker seat tubes these days. 25.4mm is common. Which is also a common size on normal bikes. Ive got a long Kalloy seat pin in my Gold bike. A 1970s Raleigh Phaser. Thats a 25.4mm post, and quite long.


I did manage to build a BMX. An 1980s Raleigh Wildcat with a 451 5 speed deraileur gears. With out widening the rear stays. Just messed with the axle spacers and the spoke dishing. I dont have a picture of that bike in 5 speed form. But here it is with mags on. Those old Raleigh BMXs had the R20s thick seat tube. So I cut out a seat tube from an old road bike and inserted it into the frame to extend it to my size.


you might have to run the saddle in the furthest forward possition. As small bikes have a lazy seat angle. So the seat lays way back when on a long post.

OrangeClownBike

If you want a mini velo with track ends try a Sillgey Picollo. It uses 451 rims. Unfortunately the rear chain stays are just too narrow for a 50mm big apple tire. If they had been I would have been all over that.....

LittlePixel

Those Sillgeys are lovely! How to import them to the UK!?!?!?!?!

pibach

Here' s another thread with BMX conversions:
https://www.bikeforums.net/commuting/535216-bmx-commuting-hub-gears-vs-singlespeed.html

And this is the lightest BMX frame:
Supercross BMX ENVY, 2.75lbs
https://www.supercrossbmx.com/envydetail.html

Could be fitted with Trigon 20" carbon fork:
https://www.bikeforums.net/showthread.php?p=8839888
Still don't know if there exist a long enough seatpost.

stevegor

My son used R20 451 3 spd wheels in a GT bmx, some work to get the brakes right but it worked.

griftereck

yes bmxs commonly have brakes that are 890 to 1080
with larger diameter wheels you would need 810 or even 730
the sidepull brakes add a zero onto the reach.
If you have U or V brakes you might have to make pad drop brackets or something

pibach

Like this Tyrell mini: