Some question about converting a road frame to a fixed gear...

March 18, 2009 10:31 AM

Fixed Gear Conversion / Bike Question: 120mm rear hub. 130mm frame. Solutions? I also have a crank/bb question inside.

So I found a vintage frame that I like, but it's got 130mm rear stays. I like the hub that I have (Phil Wood), which is 120. Is there an easy fix?

Also, I have a 68mm Phil BB but the frame has 70mm Italian. Obviously, I can't make this work so will have to buy a new BB. However, I know nothing about road cranks... will my Sugino 75 crank connect to an Italian BB? Are the bolts that the crank arms attach to universal?

Anything else I should consider when converting a road frame to a fixed gear bike?

Thanks!

posted by You Should See the Other Guy to sports, hobbies, & recreation (9 answers total)

You can respace the stays. Usually that's done to make the stays wider, though. But I can't see any problems with narrowing the stays.

By 'vintage', I'm assuming you mean a steel frame. Other materials might not bend as well.

Alternatively, you could put the Phil hub on a longer axle and use spacers. Not a huge deal.

With an italian-threaded BB I'm pretty sure you'll end up with square-taper. Square tapers are universal, as far as I know. I've never read anything different. So your Sugino should be fine. Just be extra careful when determining the BB length; make sure you know exactly what chainline you're going for.

You've checked out the rear dropouts, right? You seem to know what you're doing, so I figure you have.
posted by iwhitney at 10:46 AM on March 18, 2009

iwhitney, thanks for the answer.

It's the same frame as this one, a 1985 Eddy Merckx. Those stays should be fine, right? I'm just supposed to avoid vertical stays, correct?

I was a bit concerned that the BB may be too low (my crank's 175)... any idea what a minimum should be?
posted by You Should See the Other Guy at 10:56 AM on March 18, 2009

You say you have a Phil BB so you should be able to use the same bb and get different cups.
See page 4 of this pdf:
phil wood BB pdf

If you find your BB part # in that catalog you should see "Campagnolo" or "JIS" in the description field. Your Sugino crank should be JIS, that is the taper on the ends of the BB spindle. That taper needs to match the taper of the square hole in the center of the crank. If your BB is Campagnolo you need a new BB.

Phil hub axles have shoulders so if you get a new axle you won't need spacers. Changing the axle on a Phil hub is very easy compared to any other hub.

Another thing you need to consider are your fingers. If you have the bike on a stand, and are turning the cranks, never put your fingers anywhere near the cog or the chain wheel. If she gets a hold of your finger the drivetrain will just keep going and crush them. This also applies to shoe laces and hems when riding.
posted by bdc34 at 11:35 AM on March 18, 2009

Info on BB taper: Sheldon Brown on Taper
posted by bdc34 at 11:37 AM on March 18, 2009

looking that the image ... I've got a Centurion conversion with similar diagonal stays, and it's ok, but just be sure to that your rear hub is tight against the stay, as there is still a chance of throwing your wheel at low speed if you have too much slack in your chain. I specifically replaced the quick release skewer with a non-QR allen key skewer after encountering this one day.
posted by bl1nk at 11:54 AM on March 18, 2009

I would be surprised if the dropouts of your frame from 85 were originally 126mm, and were cold-set to fit a modern 130mm wide drivetrain at some point. You should be able to press them right back to 120. Barring that, you can pay philwood for new axle shoulders, but they are expensive.

Also, please note the following -!YOUR SUGINO 75 CRANKS TAKE AN ISO TAPER!
ISO = Campy standard. This is counter intuitive, since most other Sugino cranks (including their lower end track/ss cranks) take the Japanese standard taper, JIS. But I assure you, the 75's are ISO. I've run them on both campy and phil ISO bb's for years. 109mm is the bb length you need for sugino 75 cranks. You dont mention what taper or length Phil BB you have, but you can get the 70mm cups (actually mounting rings) to fit.

To answer your question - the 8mm allen keys/14mm bolts that attach crankarms are universal, but it is the parts that interface (bb axle and crank hole) that differ. Using the wrong taper means your crank won't sit properly on the spindle, giving an incorrect chainline and possibly wear out the hole, rendering said cranks useless.

I can't tell what your BB drop is from here, but you might be fine with 175mm cranks -you just have to avoid leaning too far over while turning. Sounds funny, but the first time your pedals strike the ground will show you just how low you can go.
posted by stachemaster at 12:28 PM on March 18, 2009

should have opened with: *wouldn't* be surpised. Everything else stands.
posted by stachemaster at 12:29 PM on March 18, 2009

Thanks for all the answers, folks!
posted by You Should See the Other Guy at 1:28 PM on March 18, 2009

That BB/rear triangle angle seems like 175mm's may give you a bit of heartache at some point. And by heartache, I mean "wear a helmet."

10mm may not seem like much, but if I had the cash or an inflated local fixie market full of rare parts, you may be better off selling them for a halfway decent, non-fraudulent price and getting something shorter. Then again, other things can matter, such as pedal/clip length, tire size, etc. Without doing some math or building the bike up, you won't know for sure. I see people do things FAR more dangerous on a daily basis.

Otherwise, what everyone else said.
posted by onedarkride at 3:01 PM on March 18, 2009