IsleRide

I'm thinking of building up a frame with horizontal dropouts into a single speed (not fixed) bike. I've seen several conversion kits employing spacers for freehubs but I'd like to use a really nice wheelset I have with a freewheel hub.

I've haven't come up with any info with searches regarding this. Are there specific spacers available? Don't want to do anything that would screw up the threads on the hub.

mack_turtle

you can thread a singlespeed freewheel onto a hub that was designed for a multi-speed freewheel. however, the cog of the freewheel will be difficult to line up with the front chainring. (I'm guessing you know this and that's why you asked.) you can put just a few millimeters of spacers behind the freewheel, but I would not think it safe to put more than 5mm because there are not enough thread on the freewheel after that. that's most likely not going to be enough to get the chainring and freewheel to line up.

you can try moving the chainring in by using a narrower BB spindle and/or moving the chainring inside the spider if it's not already there. the limiting factor will be the point at which the chainring makes contact with the chainstay. again, that's only going to get you so far in your quest for an adequate chainline.

lastly, you can probably re-space the axle. if this is a conventional cup-and-cone hub, there will be a cone nut, wide spacer, maybe some washers, and a lock nut on the right side of the hub. you can remove the axle and rearrange those spacers all you want until the freewheel is closer to the drive side dropout. just make sure the overall spacing is the same when you're done so the axle fits in the frame correctly.

the next problem you need to tackle after the axle re-spacing is the rim dish. effectively moving the hub laterally on the axle means the rim will come with it and the tire will be off-center in the frame—maybe even bad enough that the tire will rub the stays. you MIGHT be able to mitigate this by adjusting spoke tension until the dish is correct. however, this will likely mean that some of the spokes will be engaged all the way in with spoke ends sticking out into the rim, and the other side with nipples that are barely engaged on the spoke threads at all and likely to strip out and or break. ideally, this means the best way is to completely unlace the wheel and rebuild it with the spokes on the opposite side from where they started: longer spokes on the drive side and shorter ones on the NDS. if you have any skill with wheel building and the wheel is in decent shape, you can do this in less than an hour for $0. I've done it several times.

if that sounds very complicated, you can find a singlespeed wheel with a thread-on freewheel hub pretty cheap.

DrIsotope

Wouldn't the easiest way be to just mount the single cog on the freehub, and adjust spacing of the chainring to set the chainline?

IsleRide

I think both answers are right. I have done simple truing but this is a nice wheelset that I just had rebuilt by a pro. Mavic MA40 with Mavic 550 cartridge bearing hubs. I also want this to be reversable should I use them with a geared bike one day. That was my original plan but I have other multi geared bikes.

Searching the web I just found this. Looks like it would make it easy to set up the chainline. Not cheap but comparable to the kits for free hub bodies. Made for motorized bikes.

(Yes my Mavic hub is English / ISO threading)

https://www.ebikekit.com/products/fr...er-for-1-speed

ofajen

Interesting! That might get you in the neighborhood to line up with the outer chainring of a double crankset. Assuming it works, it might keep you from having to space the hub over and re-dish the wheel.

Otto

acoustophile

The problem with freewheel hubs like the Mavic 550 is that you'll have to redish the wheel to get a straight chain line with the front chain ring. You could also adjust the chain line by rearranging spacers on the axle, though this is also requires the wheel to be redished. I've generally found that an offset chain line matters less on a single speed than it does on a fixed setup. That adapter seems like a good solution if your chainline is 12mm off though. If it's just a few mm off, that adaptor would cause even more offset.

TugaDude

I agree that SS is less critical than fixed and would add that if it is 3/32" chain, then it shouldn't be a big issue, just get it close as you can.

IsleRide

Thanks for all your replies. Of course it will also depend on what I can come up with on the front chainring position but I think the offset with the adaptor will get a SS freewheel close to what would be a midway position (or more) on a 6 or 7 speed freewheel. The concept is the same as the free hub kits. (but without the adjustability)

I'm not interested in re-spacing and re-dishing this wheel. If it can't work I'll get a dedicated wheel.

mack_turtle

I think the point of this thread is that this is not an option. OP has a hub that is threaded for a freewheel, not a splined freehub.

this is friggin cool. that could save a lot of people a ton of hassle when converting older road bikes into singlespeed. not sure of the spacing, but it should get the chainline much closer. chainline does not have to be perfect, but just threading a freewheel onto an ordinary hub designed for a multi-speed freewheel usually results in a chainline that is pretty lousy. this should help gett it to be "close enough" to not be lousy and cause premature wear on the teeth.