Quick fixed/geared conversion

[dkel]

After posting something about how my Straggler does everything I want it to do except switch from geared to fixed really easily, I got to thinking: could I build a wheel that would let me switch to fixed by only swapping out the wheel and chain? Here’s what I’ve come up with:

The bike has rear spacing of 135mm, and uses a 10-speed road double with 43.5mm chainline, putting the outer (46T) ring at 46mm. A 135mm fixed hub would give me a 53.5mm chainline, which would be too wide for the crankset. A 130mm fixed hub, though, would give me a 47.5mm chainline, which isn’t far off from that 46T ring, and could be dialed in even further with spacers (which it could use anyway, being narrower than the frame spacing) and re-dishing. Since it has horizontal dropouts, chain tensioning would be easy, and if I have a quick-link in each chain, swapping them out would be easy.

Is this a totally cockamamie idea? Would it be dangerous or impractical in ways I’m not seeing? Obviously bumping the front derailleur while riding fixed would be disastrous, so there’s that. What am I missing here?

[DismalScientist]

I would think you would use the narrower wheel with spacers, but I don’t know how this would mess with the spacing of the rear brake rotor.

Shifting the front derailleur which riding fixed would hardly be disastrous, just embarrassing for you and hilarious for spectators. Why don’t you adjust the limit screws so that the front derailleur can’t be moved.

Oh… and don’t forget not to thread the chain through the rear derailleur.

[dkel]

@DismalScientist 113194 wrote:

I would think you would use the narrower wheel with spacers, but I don’t know how this would mess with the spacing of the rear brake rotor.

Doesn’t matter, since there would be no need for a rear rotor when riding fixed (and nowhere to put one on any of the 130mm fixed hubs I could find on the internet, anyway).

@DismalScientist 113194 wrote:

Shifting the front derailleur which riding fixed would hardly be disastrous, just embarrassing for you and hilarious for spectators.

I had envisioned this would be tantamount to dropping your chain, since the tension would go and something would get suddenly yanked on by the loose (and still moving) chain, but I suppose it could just result in ten teeth’s worth of play in the drivetrain without being a disaster. Still seems like a bad situation to me.

[TwoWheelsDC]

Why do you want to switch it back and forth? If you just want an all-weather fixed bike with racks, it’d almost be cheaper and certainly easier to pick up an N+1 from BD or Nashbar.

[Harry Meatmotor]

I think it could be done, but it’d be a large-ish amount of work to swap between setups with much fiddly-business inbetween. One thing of paramount importance: DO NOT run the chain through the rear derailleur if you try this. If you try to slow down using the fixed hub by applying backwards pressure on the pedals, it WILL yank the derailleur up towards the fixed cog and possibly rip the derailleur off or drop the chain from the cog or chainring. Big NO NO! Even if there isn’t any slack in the chain (like when the bike is in a big-big gearing combo) there’s a lot of force being exerted on the derailleur in ways no derailleur is intended to handle. And it’s also going to put a lot of strain on the B and knuckle springs, likely wearing them out prematurely.

Your best bet will be to remove the rear derailleur entirely, tho it might be worth it to check if there’s enough clearance when the RD is shifted into the position of the smallest cog on the cassette, just to get it out of the way.

As far as the front derailleur is concerned, you’ll likely be able to adjust the limit screws to lock the front derailleur in position. But then you’ll need to figure out what to do about the derailleur cable (probably best to just remove it, too).

IMHO at the end of the day, it’s too much work on a 135 spaced frame unless you can find a 135mm fixed/free flip flop hub. I haven’t ever looked for one, but I’d bet they exist.

[Phatboing]

1. Surly makes a 135mm fixie hub (disc compatible, no less), for exactly this sort of silliness, I believe.
2. Maybe you can switch to a 1x setup? When you want to go fixed, replace wheel, remove derailleur, begin party. Reverse when you want to be sensible again.

Though like TwoWheels says, it may cost less to just get another fixie from BD, depending on what you want to do with the fixie (Mercier Kilo WT comes to mind)

[dkel]

@Phatboing 113202 wrote:

1. Surly makes a 135mm fixie hub (disc compatible, no less), for exactly this sort of silliness, I believe.
2. Maybe you can switch to a 1x setup? When you want to go fixed, replace wheel, remove derailleur, begin party. Reverse when you want to be sensible again.

Though like TwoWheels says, it may cost less to just get another fixie from BD, depending on what you want to do with the fixie (Mercier Kilo WT comes to mind)

1. The 135 hub gives an MTB chainline that is too wide for the road crank that is on the bike.
2. No removing of derailleur…much too much work! Trying to devise a simple way of doing this while changing as little as possible of the original setup.

The cost of a new, custom wheel is not insignificant, but it’s less than the $450 for a Kilo WT. Like I said in the OP, though, this may be a totally dumb idea for reasons like you bring up. Still, switching to fixed easily is the only thing that the bike doesn’t already do that I would like it to do; when I think of the perfect FG commuter, I imagine the bike I already have, but fixed. I think the ultimate solution would be a Soma Wolverine as a FG commuter, and trying out switching the Straggler without disassembling everything or totally giving up a geared setup for an indeterminate amount of time might be the needed intermediate step before an actual N+1 solution. Besides, I’ve been wanting to build a wheel myself, and this is a good excuse to try it.

[dkel]

@Harry Meatmotor 113200 wrote:

Your best bet will be to remove the rear derailleur entirely, tho it might be worth it to check if there’s enough clearance when the RD is shifted into the position of the smallest cog on the cassette, just to get it out of the way.

As far as the front derailleur is concerned, you’ll likely be able to adjust the limit screws to lock the front derailleur in position. But then you’ll need to figure out what to do about the derailleur cable (probably best to just remove it, too).

Trying to run fixed without changing anything but the wheel and chain, so I can switch back and forth easily. Like I said, maybe a dumb idea…but possible?

[Harry Meatmotor]

@dkel 113213 wrote:

Trying to run fixed without changing anything but the wheel and chain, so I can switch back and forth easily. Like I said, maybe a dumb idea…but possible?

So the more I’ve thought about this one, I think it won’t be possible to do it that simply. I do think keeping the RD on the bike will be a little dangerous, but it’s hard to say without putting eyes on a mocked-up setup. If you were running a 1x setup up front, it might be feasible, tho. What I’d personally think through is running the RD cable through full length housing and swapping out the RR STI lever, RD cable and RD all at once by removing brake lever from the clamp, and replacing it with a dummy lever. You’d still need to remove and replace the rear brake inner cable, since that cable runs under the bar tape. Also, if you were to go 1x up front, you’d be best served running a narrow-wide chainring, which would limit you to running 3/32″ chains, not fixed/singlespeed 1/8″ chains.

[dkel]

@Harry Meatmotor 113220 wrote:

So the more I’ve thought about this one, I think it won’t be possible to do it that simply. I do think keeping the RD on the bike will be a little dangerous, but it’s hard to say without putting eyes on a mocked-up setup. If you were running a 1x setup up front, it might be feasible, tho. What I’d personally think through is running the RD cable through full length housing and swapping out the RR STI lever, RD cable and RD all at once by removing brake lever from the clamp, and replacing it with a dummy lever. You’d still need to remove and replace the rear brake inner cable, since that cable runs under the bar tape. Also, if you were to go 1x up front, you’d be best served running a narrow-wide chainring, which would limit you to running 3/32″ chains, not fixed/singlespeed 1/8″ chains.

Why would you need to change any of the other components? Leave the RD on, but shifted out of the way; or does it collapse into a position that it is in the way without a chain running through it?

[DismalScientist]

I would think that the rear derailleur would not get in the way if is just left hanging there. If it is in the way, you can potentially mess with its limit screws to get it out of the way. I s’pose that the choice to remove it depends on how frequently you want to switch between gear and fixed riding.

When riding fixed with a double chainring, it’s probably best to stick with a 3/32″ chain, just the way Sheldon likes it.

[DismalScientist]

@dkel 113225 wrote:

Why would you need to change any of the other components? Leave the RD on, but shifted out of the way; or does it collapse into a position that it is in the way without a chain running through it?

Horizontally the rear derailleur moves to the smallest cog the limit screw allows. The arm springs back when not under chain tension, so the arm should be out of the way. (If you people used levers for shifting, this would be obvious.:rolleyes: You pull to shift to bigger cogs.) My problem is trying to figure out where the fixed cog is in relation to the various cogs on the cassette. It could very well be that the RD is outside of the chainline after putting on the wheel with the fixed cog.

[dkel]

@DismalScientist 113194 wrote:

Shifting the front derailleur which riding fixed would hardly be disastrous, just embarrassing for you and hilarious for spectators. Why don’t you adjust the limit screws so that the front derailleur can’t be moved.

A zip tie around the FD lever would allow it to shift onto the big ring, but not off. No fussy limit screw adjustments!

[GB]

@dkel 113234 wrote:

A zip tie around the FD lever

Sounds like this bike is destined to be hilarious for those around you.

[dkel]

@GB 113236 wrote:

Sounds like this bike is destined to be hilarious for those around you.

If you think zip ties are “hilarious,” you probably ought to get out more. :rolleyes:

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