Fitting A Coaster Brake (back Pedal Brake) To A Mountain Bike?

is it possible to fit a 'coaster brake' (ie. one of those type brakes that are built into the bottom bracket that allow you to brake by 'back pedalling' ) to an adult size mountain bike?
i've only seen them really on bmx style bikes and never on a mountain bike. anyone know if this is possible to do and if so where i could get one of these type brakes?
thanks

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6 Comments »

kaz said:

sorry this is not possible on a mountain bike. The gears do not work properly if it is back peddled so it would be contraindicated. But sounds like it would have been a great idea otherwise.

# 24 January 2010 at 11:03 pm

bogeesem… said:

There is no reason this couldn’t be done with time, determination and perseverence.
First of all, your bike will have to be a single speed. There is no way I am aware of to build a geared bike with a coaster brake.
Secondly, you will have to find a coaster hub with a long axle. Most coaster hubs are 100 or110mm in width. A mountain bike is usually built for a 135mm width hub. You may be able to retrofit a long axle into a regular hub. In any case, you’ll have to add a bunch of washer on either side of the hub to make up the differential in spacing. Personally, I wouldn’t trust that long, unsupported axle to be particularly strong. You’ll also have to figure a way to attach the coaster brake’s reaction arm to the chainstay of the bike.
Thirdly, most mountain bikes have vertical dropouts. Without a derailleur taking up slack chain, vertical dropouts make it difficult to get the chain the right length . You may need to get a chain tensioner to deal this. Keep in mind, if your chain pops off, your coaster brake become useless.
Beyond the strength of the axle and chain tension issues, I would also be very concerned about the operation of a coaster brake on a mountain bike. For one thing, it is often necessary to back pedal to clear an obstacle like a low stump or rock. Perhaps even worse, would be hitting an obstacle with a pedal and getting an inadvertant application of the brake. Finally, I hope you don’t intend to remove your front brake. I’d hate to be flying down a hill and only have a rear brake to stop with.
Hope this helps.

# 25 January 2010 at 4:14 am

sfr1224 said:

Coaster brakes are available in the rear hubs some manufacturers make. SRAM do a coaster-braked gear hub called the Spectoro & i-Motion. These are not suitable for an MTB application.
AFAIK, there are no bottom bracket brake sytems, but I’m no BMX expert…

# 25 January 2010 at 5:23 am

haardvar said:

I have never seen a coaster brake that wasn’t built into the hub of a single speed bike.
Since modern Mountain Bicycles have 8-9 speed cassettes on freewheel hubs, you can’t add a coaster brake.

# 25 January 2010 at 10:25 am

Anonymous said:

You would have to make a custom rear wheel with a coaster brake hub. You would have to do some research to see if you can find a coaster hub with 135mm spacing (to fit between the dropouts). I don’t know of any right off hand.
To my knowledge most coaster hubs are for 110mm dropouts (like a kids big box store bmx bike), but with longer axles you can add spacers on either side of the hub before fitting it to the bike. The axles/wheel bolt on a coaster hub is normally long enough to fit past the 135mm dropouts and still thread the nuts on.
I did a quick search on bikeforums and there is a thread discussing exactly this. The common answer was to pick up an old coaster hub and lace it to a MTB rim. Not really intended for mountain use, but would work fine for city/commuter use. Like a fixed gear but with the ability to coast.

# 25 January 2010 at 3:45 pm

DH1 said:

Welp, there is ONE answer that is correct up there. Rohloff and SRAM/iMotion make what you are looking for although they are a little fancier than just a coaster brake.
They offer multi speed internal hubs (3, 5, 7, or 9 speed) with coaster brakes to which you can affix a 7 or 8 speed cassette. This means that when combined with a triple chainring you can have a theoretical 216 gears!
If what you are asking is if you can retrofit your current hub with a coaster brake, the answer is no, but you could build up a hell of a new rear wheel!
By the way, all of the iMotion and Rohloff stuff is MTB capable.

# 25 January 2010 at 7:44 pm