BMX brakes
 

Hi all,

This question may be better for the BMX section of this forum, but I thought I'd start with mechanics. I am not a mechanic, but can usually do simple repairs.

A few days ago, a friend of my son's left his BMX bike in our garage. Then he left town for a few weeks. I knew that its rear brakes did not work so I took a look. The cables were not even connected. There was little wear, and enough extra cable so that I could attach it fairly easily, so I did.

But as I looked closer, I realized these brakes are unlike any I've seen before -- the rear brakes only. (The front are rather ordinary side pulls). I should add that this appears to be a low-end bike, so that has to be factored in.

There are two brake cables coming out of the right hand grip/brake lever. They attach to either side of a mechanism on the headset area. An entirely different set of cables is attached to a lower part of this mechanism; they continue along the top tube and connect to a straddle cable that connect to the brakes.

So...by activating the rear (right) brake lever, part of the disk mechanism in the headset area is raised. This in turn pulls the second set of cables, which pull on the straddle cable, etc etc.

It seems totally weird to me -- reinventing the wheel, or in this case the brakes. It seems like more parts means more possibility for parts failure. What is this style of brakes called? Are they common to BMX bikes? Or are they cheapo brakes on my son's friend's cheapo bike?

Attached is a photo showing the mechanism in the headset area.

That is a very cheap version of a rotator that allows in-air tricks that include twirling the front wheel and bars around. As you might imagine it does not do much for the efficiency of the rear brake.

It's a gyro system, meaning that the rider can do "Bar Spins" without getting the rear brake cable tangled. They are standard on many BMX bikes, can be a little fiddly to set up particularly on lower end models. Many riders these days either ride brakeless or with only a rear brake but with a very long direct cable so that bar spins can still be performed.
http://en.wikipedia.org/wiki/Detangler

Thanks for the replies and for the info. It all makes sense, now that I understand the "bar spin" aspect.

And thanks for the link, too. Further enlightenment.

"Never been frightened of being enlightened."

Now back to my road bike.

Cool!

Front brake cable goes through a hollow stem bolt - right? My very favorite ones to work on have a below the chain stay U-brake. Setting those up requires the use of words that only bike mechanics are allowed to say.