How to convert a multi-speed bike to single-speed with coaster brake?

Question

Now I don't want to take all the credit for this bike, but I'm pretty sure Trek must've lovingly had me in mind when they made this. I mean come on. This bike is awesome. Buying their beach cruiser was one of the best decisions I've ever made. Now I've got my eye on this puppy.

So speaking of the beach cruiser, I really liked that it braked when you pedaled backward. I also liked the single gear splendor. I'd rather be climbing in a single gear at 3mph than zooming past all the ladies in top gear. More time to ask them whether you're supposed to floss before or after you brush. Just kidding. But seriously. The answer is after.

Back on point, can you modify a bike to be single gear and do that backward pedal brake thing? Think Trek would do this for me if I requested it with my order? How hard is it going to be to custom mod my rig with tools and stuff?

Answer 1

The desired conversion is possible, but maybe Trek won't do it as a "default" service. You could consider going to the local bike shop and trade some of the bike parts (specially the gearing system) for a coaster brake wheel.

If your bike is like the one in the photo, you need to replace the rear hub, and get rid of the cogset, the derailer and the twist-shifter. You can do this at home if you have some mechanical skils, but replacing the hub and relacing the spokes is not very simple.

And if you're so chatty with the lovely ladies as you are when asking questions on the internet, they sure get a lot of talk! ;o)

EDIT: As Freiheit has correctly pointed, when you put a single cog and get rid of the derailer, something must be added to compensate for the almost inevitable chain slack. I suggest a tensioner like this, of DMR brand (with a bolt, to be placed in a fixed position, not a spring):

MORE EDIT!!!! As people correctly pointed out, you CANNOT use a chain tensioner if you use a coaster brake. So the solutions are:

• Use a chain tensioner but not a coaster brake;
• Choose a magic combination of chainring and cog size (very difficult, might not give you a good gear ratio, cannot compensate for chain slack;
• Use an adaptor (usually not the most robust solution, but ok for a cruiser if you really want the coaster brake):

Answer 2

I used a carbon fiber frame to make a single speed with a coaster brake. I had to reinforce the part of the frame where the lever of the coaster brake is attached. I used spacers and no spring chain tensioner. It works great to go around town to get coffee in a terrace.

In my opinion all depends on what is the purpose of the bike.

Answer 3

Its hard to do with a vertical dropout but you can usually "cheat" it using a 1/2 link in the chain. It will allow for some wiggle room with getting the chain tension right, note that this is not a perfect fix (sometimes it works, sometimes it doesn't) even if it works your chain will probably still be a little too slack (or too tight). List of parts you will need for the conversion: Coaster brake rear wheel of appropriate diameter and axle spacing, 1/2 link for chain and or possibly replace the chain with an 1/8" width chain and 1/2 link. That's it... Best solution: Find a similar bike from a different manufacture that comes specked with a coaster, there are a LOT of bikes out there nowadays I'm sure your unicorn is lurking out there some where. Buena suerte!

Answer 4

Chain tension is not the problem. A multispeed chain does not work, at least not well on a single speed bike. You would need to install a single speed chain (correct width) that is cut to the correct length. It can get complicated. Good Luck.