cyclocross conversion

Originally Posted by Fignon le Grand

Hello

Iwant to convert a steal cyclocross frame to siingle speed ideally with a flip flop hub for cog/freewheel. What do I need to start with and will I need to convert a track hub to a wider axel?

Originally Posted by alfeng

Since you have a steel frame, you can simply respace the rear triangle to the appropriate 120mm width by squeezing the stays together ... you can do this manually. Just hold the frame from behind, a hand on each stay (rear wheel removed) and gently flex the stays inward about an inch. There will be some rebound. Measure, and repeat as necessary.

FWIW. I reduced the spacing on a steel road frame to 120mm so I could use it with a 3-speed hubbed wheel.

Similarly, I reduced the width on a 135mm steel frame to 130mm, for example, so it would accept regular 130mm rear wheels. I could certainly reduce it to 120mm if that had been the objective. I had to realign the dropouts; however, you don't need to realign the rear dropouts since you won't be using a rear derailleur; but, you may want to ...

There are 135mm solid axle hubs for single speeds, BTW.

You may need a chain tensioner ... some BMX riders prefer to use a HALF-LINK (and, BMX bikes have track-type dropouts!), which you may find to be more satisfactory (if only aesthetically) than a chain tensioner.

Other than the rear spacing OR wider hub, you obviously remove all the extraneous "stuff" ... leave the front brake ... leaving the rear brake is probably a good idea.

You MAY want to figure out what rear cog size & chainring combination you think will work best for you before you buy three-or-four different cogs & chainrings.

You'll need/want shorter chainring bolts if you don't use a chainguard ... again, a common BMX component.

Originally Posted by Fignon le Grand

Thats greats thanks for all the info. The frame is from the early 80s and has nice long almost horizontal drop outs, would I still need to use a tensioner?

Originally Posted by alfeng

You won't need a chain tensioner -- a chain tensioner is the usual KLUGE/(KLUDGE) when a frame has vertical drop outs.

... Basically, you're good-to-go!

BTW. The chainline MAY-or-MAY-NOT be of some concern, depending on the crankset & BB ... ideally, you want the chain to run as close to parallel to the centerline of the bike as possible. Consequently, most people run the single chainring where the inner ring is normally situated ... but, you'll have to just see what works best for your bike.

BTW2. In-a-pinch, if you don't have ready access to BMX/single chainring bolts (and, don't feel like grinding the nut shorter ... kids, don't try this at home! if you aren't real handy & familiar with power tools), then you can mount the barrel nut BACKWARDS, with the "brim" nesting inside the chainring's recess and the barrel facing the frame. Not pretty, but it will work.

Originally Posted by Fignon le Grand

I live in holland and have easy access to lots of track stuff, whats best for the chain line, a converted double chainset or a track chainset? Id quite like an old campag pista version. Also would bending the stays or moving the spacing on a hub be best for chain line?

Originally Posted by alfeng

Since you have a steel frame, you can simply respace the rear triangle to the appropriate 120mm width by squeezing the stays together ... you can do this manually. Just hold the frame from behind, a hand on each stay (rear wheel removed) and gently flex the stays inward about an inch. There will be some rebound. Measure, and repeat as necessary.

FWIW. I reduced the spacing on a steel road frame to 120mm so I could use it with a 3-speed hubbed wheel.

Similarly, I reduced the width on a 135mm steel frame to 130mm, for example, so it would accept regular 130mm rear wheels. I could certainly reduce it to 120mm if that had been the objective. I had to realign the dropouts; however, you don't need to realign the rear dropouts since you won't be using a rear derailleur; but, you may want to ...

There are 135mm solid axle hubs for single speeds, BTW.

You may need a chain tensioner ... some BMX riders prefer to use a HALF-LINK (and, BMX bikes have track-type dropouts!), which you may find to be more satisfactory (if only aesthetically) than a chain tensioner.

Other than the rear spacing OR wider hub, you obviously remove all the extraneous "stuff" ... leave the front brake ... leaving the rear brake is probably a good idea.

You MAY want to figure out what rear cog size & chainring combination you think will work best for you before you buy three-or-four different cogs & chainrings.

You'll need/want shorter chainring bolts if you don't use a chainguard ... again, a common BMX component.