Singlespeed & Fixed Gear - converting road to fixed

I've done my best to look around here at all the newbie questions, I've also spent some time at sheldon brown's site looking over his instructions.

so far I've gathered that in looking at some used cheap frame to convert, it must have horizontal dropouts and a moderately high bottom bracket. my questions is, how does one measure this bottom bracket height, and could someone give me an idea of what is a low, med or high bracket height?

also, is there anything else someone with conversion experience would suggest in looking for an appropriate frame?

thanks

i found mine behind a dumpster. i'm slowly converting it and dealing with the joys of school at the same time. i think a swap meet or trash hunting might be your best bet. if your near a college, you might be able to find stuff just laying around. that's how i found my beauty, errrrr..... project.

ride the bike you're thinking about converting. make some tight turns and if you scrape the pedals an excessive number of times, the BB is probably too low... however i've yet to ride a road bike that had a BB that was too low to used as a fixie... i've really only come across that problem with a couple cruisers...

when you're testing for pedal scrape, take into account the cranks you'll be putting on the conversion. i dunno about anyone else, but i don't see any reason to go any bigger than 165. a lot of road bikes will have 170+ cranks.

-alex

Bottom bracket height addresses handling issues more than anything else. Don't concern yourself with B/B height.......just find yourself a nice frame. Keep your cranks under 170 and you'll do just fine.

Well...a low BB could be around 70mm. My road (and most road bike I think) has a 60 drop. Typical track sprint bikes have 40-45mm drop.

I'm riding a converted Bridgestone with 170mm cranks and have no clearance problems.

Grant Peterson, who designed Bridgestone bicycles and is the founder of Rivendell, is known for "longlow" designs. True to form, this bike has a loooong wheelbase relative to it's standover height. It rides very well with no hands. I haven't measured the BB drop or BB height, but would estimate the BB to be "average" for a bike with 27" wheels.

You might also consider the issue of toe overlap with the front wheel. While this condition would only affect very low speed maneuvering... since you won't be able to "ratchet" the pedals, a lot of overlap is probably not best.

thanks for the tips, i guess BB height isn't really as important as I had gathered. a few more questions though...

what is ratcheting your pedals at low speeds? and also, in looking at old used frames at junk stores, garage sales, goodwill, how can I tell if a frame is warped or bent? will that be obvious (to the untutored eye) or should I be doing some sort of test on the frames? thanks again.

onespd can correct me if i'm wrong, but i believe he's talking about the fact that when you're turning at slow speeds without a freewheel, you can get into trouble where your toes hit the angled wheel. with a freewheel you can ratchet the cranks/coast/pedal backwards/whatever to keep your toes from hitting the wheel. can't ratchet the cranks on a fixie, so be careful.

chances are you'll be looking at old steel frames. i'd start by looking for the following things:
1) any obviously scary flex in the frame
2) cracks in the paint/frame near the bb (and other joints)
3) serious scratches/stripes in the paint (could mean rust and thus a weakened joint or tube)

for bent/warped frames, i'd ask someone else, cuz i can't help. sorry... ;)

you're in seattle, so if i was you i'd check out recycled cycles down on the north side of the montlake cut. they've supplied the frames for several local fixies that friends of mine have built.

best of luck,

-alex