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Old 04-21-10, 01:27 PM   #1
rustmyrtle
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double cable rear brake?

Hi there.

The son of one of my neighbors rides a mongoose BMX bike. He never gets off of it, so I was not surprised when his mom asked me to take a look at his brakes because he was complaining they didn't work.

First problem, there was only 1 brake pad per caliper.

Second problem, the cables and housing had rusted together.

I replaced the cable and housing on the front brake, but the back brake has me mystified. I'm going to give a description below--please pardon my stupidity, as I have never worked on BMX bikes really.

There seem to be two cables in the lever, which travel to different sides of a metal disc around the stem. When the lever is squeezed, this disc is raised. The disc also connects to two other cables, which travel one to each brake arm of a brake shaped like an X with a single pivot.

Where do I find the cables to replace these? how do I service that disc thing?

Thanks!
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Old 04-21-10, 06:50 PM   #2
Greyryder
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The "disk thing" is a detangler, usually called a Gyro. It allows for bar spin type tricks, without wrapping the cable around the front of the bike. Dan's Comp should have the cables you need.

I've heard it can be a pain to get the cables and barrel adjusters all set up just right on gyros. I've always run race bikes, so I don't have any first hand experience with freestyle bike brake systems.
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Old 04-21-10, 07:27 PM   #3
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Quick warning on the detangler: Don't just cut the cables attached to it thinking that you can easily run new ones using standard brake cable and housing. Been there. Done that. Felt stupid afterwards.

If the kid does not spin the bars when doing tricks, I suggest offering to recable the brakes without the detangler. The kid will have a simpler, more reliable brake without it.

I too have a neighbor kid...
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Old 04-23-10, 07:58 AM   #4
rustmyrtle
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Thanks guys!

Unfortunately, this kid is all about the tricks. He's something of a bike genius actually. I'm not sure he was at all hindered by having no brakes. I can't wait until he's older and I can build him a fixed gear.

If I get the right gyro cable, should I be able to put it in and fix it like a "normal" brake? There seem to be different sizes of these--how do I know what I measure?

Thanks,
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Old 04-23-10, 08:10 AM   #5
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Rust, can you measure the existing cable? I see that the catalog listing at Dans Comp shows the cable lengths for small versus medium versus large.

Link to listing: http://www.danscomp.com/511003.php#

Last time I replaced a gyro, I just took it to a nearby shop that does a good business in BMX bikes and had them hand me a replacement. That way, I knew I had the right thing.

Here's a link to a page with a link to some PDF instructions that helped me:

http://www.danscomp.com/serve.php?se...=gyro_faqs.htm

Don't be intimidated by the gyro. It's "different" from what you're used to, but at the end of the day, you've still just got a cable pulling on a brake.

As I recall, that interface around the head-tube can be a source of slack in the brake cable. But if you've worked on bikes, you shouldn't have any trouble in reeling in any slack. There are adjusters to use in doing that.
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