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Discussion Starter · #1 ·
I'm seeking advice about optimal rear brake cable routing on my new frame.

I'm running Avid BB7 mechs on a four-bar/horst FS (and new to the FS game) with full housing, and what I for a while assumed was me being tired and weak during long rides turned out to me being tired and weak AND having my rear brake dragging.

It appears that periodically the activation of the suspension shifts the position of the rear cable housing, after which the guide clips stop/catch the housing in the new position in a way that slightly actuates the caliper lever arm, producing drag at the rear brake.

I've tried running the housing fairly straight from underside of the toptube across the span of the linkage/swingarm, then down the "seatstay".
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I've also tried a very similar routing except with a bit of swoop arching up over the linkage/swingarm gap (that is, with housing looping up right at the toptube/seattube junction). This seemed more sensible, obviously, but in both cases I see evidence of cable housing movement from suspension activation. In fact, the loop seems to work itself flatter and flatter with the movement of the suspension.
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I assume that ditching the little housing guide clips and replacing them with tightly cinched zipties may hold the housing in place better. But I'm wondering, while I'm at it, if there is an optimal routing for the cable, based on others' experiences. That is, how much loop do I want in the cable housing here? An additional concern is that if I do try to hold the housing in place more firmly with zipties, if it does then move/shift from suspension movement, it will be even less likely to move back to the appropriate position again.
Has anyone else had problems of this kind? Any advice?
 

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My wife has the xc004 (same frame as yours) and the loop for the rear brake is about the same as your (they're hydros though) 2nd pic. They are also held in with zip ties instead of the clips. They don't move when the suspension is moved up/down.

Are you sure the brake is activated when the suspension moves? Make sure they are activating before you pursue any "fixes".

Also, when I ride my wife's bike, it feels like I'm pulling a trailer with 50 lbs behind me vs riding my own bike (BMC Fourstroke).
 

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Discussion Starter · #3 ·
Thanks.
I am indeed sure that the housing moves in a way that activates the brake. First, I see lots of signs of rubbing on the frame and the housing in the relevant area. More importantly, I've also discovered the brake actually hung up many times, with the fix being either a hefty jerk on the rear brake lever (while riding), or a dismount and manual adjustment to the housing.
Aside from the brake dragging periodically, I've found my ride nimble, fast, and dynamic. It's not a true XC004, after all (it's spec'd better than the XC604 even, using the same frame with different paint). I simply got a good deal on a replacement frame (after damaging my previous), swapped all parts including headset, suspension components, etc.
If only I could get the damn brake to behave I'd go faster (and get less workout). It's particularly annoying because, when riding terrain with lots of steep relief and transitions, dramatic suspension activity on a downhill leads to a hanging rear brake as I transition quickly to an uphill. Pant. Pant.
 

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I had a Kona Bear with BBDB (predecessor to BB7) brakes that would do something similar. It wouldn't be enough to actuate the brake, but you could feel the suspension cycling in the brake lever. I don't have a solution, unfortunately. Can you dial out the brake pads a little more so it doesn't rub? And are you running continuous housing?
 

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Discussion Starter · #5 ·
Yep. The housing is continuous. This is my preference, and I can't switch to segmented housing anyway. I'd like to avoid dialing out the pads, and I'd like to avoid having to switch to hydros if I can help it (really prefer the BB7s).
I have thought of using Nokon housing since the zip ties would likely catch on the segments in a way that held the housing in place. However, I'm trying to avoid an excuse to buy an expensive upgrade for something like cable housing.
 

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OT: Is your bike an upgraded XC004 frame or an XC604? I thought only the XC004 came in green. Either way, they're both the same frame. You got a bigger picture (full bike)? I like looking at pictures. :)

Another thought is use zip ties and then put a couple drops of super glue on it. That way the glue holds the cable from slipping.
 

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Pic 2 is correct except for the zip tie. The zip tie should bee loose on the front der/brake housing as a trainer so the housing routes close to the frame. You can remove the shock and lift the swing arm up and down to get an idea on the cable movement or use your imagination. The clips are designed to hold the housing even when running straight housing. At pivot points the housing should fallow the arc so their is no added tension either pushing or pulling. :thumbsup:
 

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Sometimes it makes sense to route the cable down by the lower link because there's significantly less suspension movement at that point. I can't see enough of your bike to know whether or not it's a good idea in this situation.
 

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Discussion Starter · #9 ·
the-one1 said:
OT: Is your bike an upgraded XC004 frame or an XC604? I thought only the XC004 came in green. Either way, they're both the same frame. You got a bigger picture (full bike)? I like looking at pictures. :)

It's an upgraded 004. Sorry about my ambiguous description above. Yeah, I got the 004 frame because it's the same as the 604 (in green). If you really want another picture, I can post in the AM.
 

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Discussion Starter · #10 ·
dogonfr said:
Pic 2 is correct except for the zip tie. The zip tie should bee loose on the front der/brake housing as a trainer so the housing routes close to the frame. You can remove the shock and lift the swing arm up and down to get an idea on the cable movement or use your imagination. The clips are designed to hold the housing even when running straight housing. At pivot points the housing should fallow the arc so their is no added tension either pushing or pulling. :thumbsup:
Thanks, dogonfr. Do you mean to say that there should be a ziptie there, only looser, to keep the cable from bowing out?

Can you recommend something to keep the housing from sliding? My problem is that even despite the ziptie you see in the pic, the housing wants to slide significantly, which is what gives me the brake hangup.

What about theOne-1's suggestion about a well-cinched ziptie with superglue to replace the clips?
 

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Pithecoid said:
Good thought. In my case, that routing won't work. I wish it did...
What if you run the brake hose between the TT and front derailleur housing. Is their room for the rocker to clear the housing still? You can put a zip tie around the hose behind the guide to prevent the hose from being pushed through. This is like a training session for the cables and hoses as time goes by they will have permanent shape and no problems. :cornut:
 

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Discussion Starter · #13 ·
dogonfr said:
What if you run the brake hose between the TT and front derailleur housing. Is their room for the rocker to clear the housing still? You can put a zip tie around the hose behind the guide to prevent the hose from being pushed through. This is like a training session for the cables and hoses as time goes by they will have permanent shape and no problems. :cornut:
Yeah. That seems like it would work.
Thanks.
 

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I would have routed the brake inside the fork on that bike. Less chance it getting caught on something on the trail.
 

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Discussion Starter · #17 ·
Kona0197 said:
I would have routed the brake inside the fork on that bike. Less chance it getting caught on something on the trail.
What do you mean, exactly? Do you mean that you'd run the cable inside and back through the arch, or just that you'd route it back on the inside of the slider below the arch?

The housing guide built into the fork has a shape and orientation make the routing you see the only natural route. When you say "on that bike", is that to say that there's something unique about my setup that warrants an alternative routing, or do you think some kind of inside routing is preferable in general. Any tips appreciated.
 

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Discussion Starter · #18 ·
the-one1 said:
Ooooooooo :)
Not exactly the "XC004", huh.
Just don't confuse me for one of those guys into blingyness. :)
My GF decided to surprise/cheer me up by contributing to the build with the crazyass wheelset. They sure do call attention to themselves, which isn't quite my style (the KHS frame, e.g.). I have gotten used to them, mostly because I love their engineering and performance.
 

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Discussion Starter · #20 ·
Yeah, your marz fork is set up nicely that way. I'll have to play with mine and weigh tradeoffs in terms of secure placement in the housing guide vs routing inside the slider leg. I can't do both efficiently.
Thanks.
 
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