Using a fixie crank on a MTB

Hi all.

Apologies if this has been asked but I can't seem to find the actual answer.

I have a Giant Boulder bike converted to ebike and I want to move on from the 3 speed crank to a fixie style crank.

Other than chain line, will the crank actually work. I mean, the chains are the same, are they not? I just don't see why it won't work but I can't find any evidence either way.

Thanks

Hunt

Some fixies use an "ever so slightly" wider 1/8th inch chain and sprockets (4/32?). The majority of chain and chainrings for bicycles with a 7-speed freewheel on the rear wheel use the common 3/32-inch.

I'm told the 11-speed stuff is narrower on its outer width because they use flush-head rivets (in order to squeeze-in extra sprockets into the same width of space as before), but the 11-speed chains' inner "tooth pocket" dimension can still run on common 3/32 sprockets. A 3/32 chain would run on a single 11-speed sprocket, but...if there are two or more in the cassette freehub in their usual spacing, the sprockets in the 11-speed cluster are too close together, due to the protruding "common style" rivet head on 3/32-style chain links (unless you remove a few sprockets and add spacers to the remaining sprockets).

spinningmagnets said:

Some fixies use an "ever so slightly" wider 1/8th inch chain and sprockets (4/32?). The majority of chain and chainrings for bicycles with a 7-speed freewheel on the rear wheel use the common 3/32-inch.

I'm told the 11-speed stuff is narrower on its outer width because they use flush-head rivets, but the 11-speed chains' inner "tooth pocket" dimension can still run on common 3/32 sprockets

Click to expand...

Oh yes. Ah ok thank you for that. So the fixie chainrings I've been looking at are thicker apparently. The chain I'm currently using is the smaller size.

Thank you for clarifying!
Now to find a 48tooth fixie crank set that can take the smaller size chain!

Or just get a wider chain. I use a BMX-style chain on my trike because several of the sprockets in the chainline are from single-speed systems, and are too wide for multispeed chain to fully fit down over them.

You don't need a different crank; you need a chainring that can accept multi-speed chain (3/32"). Somewhere in the 11-12 speed range, maybe the chain becomes too narrow to behave appropriately on some 3/32" rings, but in my experience even 10-speed chain works fine on generic 3/32" BMX chainrings.

Thank you all for your responses.

I have a 7spd cassette on the way (it's the only size that will fit my frame and has an 11T small cog). I've got a 7speed now but smallest cog now is a 14 which means I'm maxing out at about 50kmph without peddling like a mad man haha. Being a 7speed cassette I imagine a wider chain will be ok compared to if it was a 10 or 11 speed where the gears are closer together.

I'll ask the local bike shop if they have a chain that will work with a single fixie style chainring and any 7speed cassette.

Cheers again!
Hunt

My experiences are that the problem with using a multiple speed chain as a single speed is that there is a lot of slack in the chain. I ran into this with my Cyclone 4kw on my Townie 21D (3x7)
When I purchased a single speed chain SRAM (PC-1) there was very little slack in the chain.

It was like that 10 years ago as well when I had a Hybrid road/mtb bicycle with a rear derailleur that broke off and I tried to use a multiple speed chain as a single gear.

redbeardbeer said:

I'll ask the local bike shop if they have a chain that will work with a single fixie style chainring and any 7speed cassette.

Click to expand...

Why exactly do you want to use a fixie chainring/crank?

If it is just to have only one gear up front, just unbolt the derailer off of the frame and take the shifter off, and put the chain on the big ring. If you really only want one ring, take the other two off.

If there's some other reason, let us know so we can help you find a solution that will work.

What he said.

In addition, the better MTB cranks have removable chain rings. This allows you to build a single speed crank out of it, using whichever ring you like best.

Or what I have liked doing, build a custom two or three ring front gear, and remove the front derailleur. On my bike that burned, I had a 56 tooth big ring, and a 48 tooth small one. Mostly I used the 56, but if I wanted to ride less than 15 mph, it was good to drop to the 48 tooth.

Lastly, an option you might like is simply a crank off a 7 speed bike. That can be nice because the chain ring includes a guide on both sides of the gear, that keeps the chain on the ring despite shifting in the rear, and acts a bit like a chain guard keeping your pants cleaner.