In article
<66fb4701-54e7-4cc0-8db9-9c805fef9b48@y77g2000hsy.googlegroups.com>,
"Rik O'Shea" <
[email protected]> wrote:
> On Mar 6, 4:45 pm, [email protected] wrote:
> > I kind of like bicycles with twenty inch tires.
> >
> > I once had a Bike Friday NWT and found it rolled fast
> > and was not as cumbersome as a full size wheel bike due
> > to its 20" wheels. The small wheels made the bike easy
> > to handle even when not folded. Easy to pick up.....
> > carry up stairs.... into house..etc.
> >
> > BUT.... the reality of it was that I didn't NEED the
> > folding aspect of the NWT frame.... and in fact found
> > the added complexity of the hinge and al a nuisance
> >
> > Having said that.... how feasible is it to build a
> > touring bike out of a good BMX frame? Could have 20"
> > wheels without the folding aspect.... just use long
> > handlebar and seat post extensions
> >
> Your best bet is something like a moulton http://www.alexmoulton.co.uk/
>
> I have a bmx, its great for "messing around on" with my childer in
> the local park.
> As a converison to a touring bike - no way! The frame is very robust
> (read heavy) and
> the fork only accomodates a bmx ahead style headset and stem, the rear
> dropout is for a
> single speed and you can only use 15 mm axles... I could go on but I
> think you get the idea.
Sir! I would direct you to the lighter end of the BMX racing frames,
where frame weights dip below 3 pounds:
http://www.bikemania.biz/ProductDetails.asp?ProductCode=FMF_Frame_CarbonP
ro5
For a normal seating position, you're going to need a long seatpost.
Recent BMX frames tend towards MTB seatpost diameters, so long seatposts
are available, at least if you're not too tall or too heavy. Getting the
bars high enough may or may not be a problem: a low road-style bar
position isn't going to be much higher than the normal place where BMX
bars go, and a high bar position can use either a tall stem or a
BMX-style riser bar.
BMX frame ends or not, there are derailer claws that will allow you to
hang a derailer off the back. I did this myself in converting an old
Kuwahara to a 6-speed, but a derailer drivetrain will also require a
frame respacing, which is only practical with a steel BMX frame.
For non-steel frames, you could use a hub gear system, of which the
obvious choice is the Sturmey-Archer XRF-8, which has 8 speeds, can be
as narrow as 115 mm, and has gearing especially suited to small wheels.
http://sheldonbrown.com/harris/sturmey-archer-hubs.html
Note that 115 mm is a bit wider than the stock width of 110 mm for BMX
rear ends, but it shouldn't matter.
This is a fun project, and I think the variant with a hub gear makes for
an interesting and very practical small-wheeler. The combined markets of
serious folders and recumbents mean there are some very nice wheels and
tires available if you want to spend some money on upgrades.
S-A claims 1840g for their 8-speed hub. Roughly speaking, add that to
the bike weight of a lightweight BMX, wave your hands a bit, and that's
probably what your finished bike would weigh, though there's a lot of
room to replace BMX-oriented parts with lighter bits if bike weight is a
real issue for you.
That said, I'd be flabbergasted if you could make the bike weigh more
than 30 pounds, and I think that 25 pounds would be possible with enough
money and parts changing.
A Norco Pro BMX weighs about 23 pounds:
http://www.norco.com/bikes/bmx/race/norco_pro_bmx.php
These are not heavy bikes, and they're cheap. Go for it!
--
Ryan Cousineau
[email protected] http://www.wiredcola.com/
"In other newsgroups, they killfile trolls."
"In rec.bicycles.racing, we coach them."
