cyclocross conversion

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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?

Any other tips v welcome :)

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?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.

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.

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?

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?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.

BTW3. Those in the know say that ACS BMX single-cog freewheels are considered the best-for-the-money ... you can get them at DAN'S COMP (~$17US) http://danscomp.com/ OR eBay.

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.
Thank you, Yeah I thought it would be ok, thanks for confirming.
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? I certainly wont be reversing the barrell nuts BACKWARDS!! :cool: But its certainly a resourceful solution. thanks again for all the assistance

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?Oh, the Pista crank would certainly be the best ... AND, exquisite! It should be perfect ... you just have to be sure to get the correct length spindle (Pista BB cups are NOT well suited for road use ... because they apparently have a slightly enlarged spindle opening through which dirt/etc. can enter the BB shell).

An obvious difference is that the Pista cranks don't have the inner shoulder because the chainring is mounted on a shorter BB spindle (~103mm? ~108mm?) and the ring is mounted in the otherwise outer position ... 144BCD is common, so a 42t chainring is the smallest you can use. There may be other differences ...

You should be able to mount a contemporary/symmetrical(?) 135BCD Centaur crank on a 102mm Record/Chorus BB ...

If you're using an ISIS or Shimano Octalink crank, then you'll probably want the shortest (109mm?) BB ... and, you will probably need to mount the chainring on the inner shoulder of the crankarm.

You do NOT want to change the symmetry of the rear stays because it would preclude being able to use a flip-flop hub ...

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.
Thanks for all the help but here is the question I have no clue about. What r u measuring when people talk of a 42mm chainline?? Many thanks

Thanks for all the help but here is the question I have no clue about. What r u measuring when people talk of a 42mm chainline?? Many thanksI believe the 42mm reference is to the chainstay length (the distance between the center of the BB and where the rear axle is theoretically located) ... with a longer stay (~16.5 inches), it will be easier to ensure that the chainline is closer-to-parallel.

The chainline is the angle of the chain when viewed from above vs. the centerline of the bike's frame -- 0º (parallel-to-the-centerline) is ideal for single speed bikes because there is usually nothing to otherwise prevent the chain from being pulled away (vs. deflected by a derailleur) from the teeth on the cogs or chainwheel other than the chain's tension.

I do not know how many degrees off parallel from the centerline that the chainline can be when setting up a single-speed bike before the chain is incapable of staying on the cogs/chainwheel.