Thursday, December 17, 2009

That's not a downtube...










...THIS is a downtube!

Yes, I am building myself a track bike. Yes, it has a 44.5mm BMX downtube. No, there's no good reason for it, except that I'm using only orphan tubes for this and it seemed like it would *probably* be stiff enough. It will also feature some tandem chainstays that I bought on a whim (for cheap) and can't find a use for, as well as the horrible double taper seatstays I purchased by mistake and a toptube that I mis-mitered for Eszter's 29er... should be just as wacky as the 24" dirtjumper that I built from orphans that already lives at the track!

13 comments:

Rob Young said...

Beautiful!

Anonymous said...

Is there a Velodrome near you? Wood, cement, other?
Or is this the uber-hip townie fixie? Sew-ups?

Walt said...

Anon -

There is a wood (plywood) velodrome about 1 mile from my house. So it will be a track-only bike. I already have a townie.

Cellarrat said...

sick!

Dave said...

Orphan tubes aside, would a track bike need a downtube that big/stiff? Wouldn't the same be true for a SS 29er? Have you built 29ers for big dudes with that beefy of a DT?

Ok, sorry for the barrage of questions. When my mind works at all, it's usually in bursts like that.

thanks. :-)

Walt said...

Hey Dave -

For this bike, for me (145#, about as much power as Ashley Olson) the downtube makes no sense at all. I could ride a 32mm downtube and be just fine.

For really big folks (ie, 300# or something) I have used 45mm downtubes many times.

For normal sized people, a 38mm downtube is about as big as you'd ever need. You can do some ovalizing at the BB to make things even a big stiffer (long axis up to about 42mm) if someone is a serious lateral stiffness snob, but generally speaking, humans just don't generate enough power to generate significant flexing in a 38mm downtube, so it's not usually necessary.

Dave said...

Cool, thanks for the explanation.

One last one... is that the diameter of the tube or circumference?

Either way, that DT in the pic does look beefy... way burlier than most steel track bikes that I see ridden by 200 pounders.

I *dare* you to flex it while pedaling. :-)

Llama said...

That awesome! A nice bit of offset on the BB as well.

Eszter said...

Remember back in the day when you said track bikes were stupid and you were never going to ride one?

Just sayin'.

Walt said...

YOU'RE OFF THE TEAM, ESZTER

Anonymous said...

Are you replacing her? Should I send a resume??

Feldy said...

@Dave: that's a diameter.

@Anon, "uber-hip townie fixie?" For Walt?!?

evan said...

Dude, sounds like a messenger's bike....totally hip!