Putting a disk brake outside the frame?

[pengyou]

I wasn't sure where to put this question but it is frame related.

I have a single speed beach bike that I love to ride very much. What I especially like is the upright riding position - no arched back at all. I am sure this is not good for wind resistance but it lets me ride the bike a long time.

There is one aspect of the bike I am not impressed with and that is the braking. I have seen some pretty hefty drum type brakes on ebike sold locally but they are pretty thick - more than 3/4" - and I don't think there is any room between the wheel and the frame to install one. Is it possible to install this kind of thing outside of the frame? I have seen some bikes modified for motors that have gears outside of the frame, rather than inside the frame as most are.

If not...is it feasible to modify the rear part of the fork - actually have someone cut it off behind the seat post and add another per my specs?

[Peterpan1]

Just for starters you can upgrade just about any rim brake, assuming aluminum rims, to do a great job. Just start upgrading component parts to better quality, that would be caliper, pads, cables housing, and levers. Usually all you need is to upgrade the front brake, though cheaper quality sets are sometimes paired. For instance Nashbar sells a reasonable canti for about 15 bucks a pair.

You probably can mount a disc on a bike without using the fork to hold the caliper. It is done on motorcycles often enough. It would require some fabrication but not welding.

[pengyou]

Thanks! I have steel rims. Do aluminum rims hold up under heavy applications? I am going to convert this bike to an ebike and will frequently have a person on the back - total weight about 450 pounds. I am also hoping to get away from the rim brake because I have heard that they do not perform very well in wet weather or freezing weather.

[Peterpan1]

Al rims are the top rim for all cycling applications, pretty much. They stop much better in wet weather than steel rims. Discs can still have an advantage both generally and in wet or muddy weather. However, unless you are contemplating something quite out of the norm as far as bikes are concerned you should be able to get acceptable performance with rim caliper brakes. Disc brakes can do weird things on bike like pop the front wheel out or collapse the spokes. Of course they are also very popular, it's just a mater of getting the details right.

Most tandems use al rims and caliper brakes.

Check this out:

http://tandem-fahren.de/Mitglieder/Christoph_Timm/Disk_or_drum.html

[pengyou]

Thanks. Is it possible to use 2 brakes on the rear wheel? one drum and one rim brake?

[Peterpan1]

Should be possible. the rear wheel is much less efficient at stopping. I like two brakes on the front wheel as a concept. Some tandems have a drag break on the back which is designed to cut some of the heat out of the system on long decents while you modulate with the other brakes. There is a version of the 287 lever that operates three brakes off of two levers. These tamdem hubs probably use the 145 or 165 hub spacing so they may not be stock for a single frame, with a few custom exceptions.

My concern about 2 brakes up front is more redundency and variable stopping. Since the front is so important, I want to be sure there is always something that works up there. And I also want to be sure that the brakes work in different wet or mud conditions. There can be wheel true issues with some systems, fiddly tuning, etc... It's overkill for sure, but as long as one doesn't belt and suspenders the whole bike it shouldn't hurt anything.