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Wong Way
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Discussion Starter · #1 ·
hello, I'm setting up my new Jamis Dakar XC frame with some avid bb7 brakes and i cannot for the life of me figure out how to keep the cable from slacking. Everytime I tighten the cable and test out the brakes it slacks on the top tube. Anyone got some ideas of how to run the cable on a full suspension?:madman:
 

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Derailleurless
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9,122 Posts
I'm unclear on the question. It's no different than running the cable to the rear derailleur. If you only have hydro hose guides and not proper cable stops, you'll either need to run full-length housing.

In fact, even with traditional cable stops, for the most reliable, trouble-free installation, consider a full-length housing run.
 

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Ride Responsibly
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Try pulling the cable tight enough (at the caliper clamp) to activate the brake and locking it there (push the actuator lever to engage brakes while pulling cable tight).
With everything all tightened up you may be able to see what the problem is a bit easier. Look for housing movement when you apply the brake. Just a thought.
 

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Live 2 Ride
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I would just make sure the housing is just as long as the rear derailleur's housing and add a few more inches.
 

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Old man on a bike
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Kona0197 said:
I would just make sure the housing is just as long as the rear derailleur's housing and add a few more inches.
Huh? That may work for your bike but how do you know that might work for the OP's bike? You familiar with his routing for both brake and derailleur (and which derailleur)?
 

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Live 2 Ride
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I would assume since both cables end up near the end of the dropouts on both sides that if he uses full length housing and ads a few more inches than the rear derailleur side he would be fine.
 

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I've seen this problem before....

make sure that when the bike is in the stand or the suspension is unloaded and fully extended (i.e. no weight on the bike) that your cable housing is fully seated in the stops. A slightly short run of housing will cause this problem. I'd be almost willing to bet that the last run of housing from the frame down the seat stay to the brake is a bit short and doesn't bottom out in the stop on the frame or the stop on the brake caliper. Then when the suspension is weighted and sags the housing bottoms in the stop and allows the cable to go slack. It doesn't take much just a couple of mm's short will cause problems.

So check the housing runs, particularly the rear/last run from the frame to the caliper.

Good Dirt
 

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Old man on a bike
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Kona0197 said:
I would assume since both cables end up near the end of the dropouts on both sides that if he uses full length housing and ads a few more inches than the rear derailleur side he would be fine.
Big assumption, grasshopper.
 

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Official ***** Idiot
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I had the Expert frame, basically the same thing as the XC. Longer travel, I think. Run full cable housing, and yes, you do have to have the length pretty close. There's some wiggle room. Even with dang near perfect cable runs, it's going to slacken on you as the suspension compresses. Let me think about that one, that was ten years ago on the original XC Avids. There was a little tweak I did to keep the housing from going weird when the lever was squeezed. Did you check the disk brake primer on the home page here? I'm planning on looking at it in the next few days, I wrote the mechanical part a looooooong time ago. Probably needs updating.
 

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I'm going to replace some Hayes HFX 9 brakes with BB7s on my FS next week. I'm not sure I understand the problem here.

I don't have cable stops on my frame, just hose guides. Zip ties keep it all tight. I had planned on a full run of housing from prior experience on my hard tail.

Is this the proper sum up? If everything is zipped up tight from the bar to the seat stay, then the same down the stay to the brake, then I just have to get the slack around the seat post right to avoid kinking (too short) or slackening (too long). Is this the long and short of it? I reckon this is one of those trial and error gigs, huh? How do you reliably measure that?
 

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Bicyclochondriac.
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Bikinfoolferlife said:
Big assumption, grasshopper.
Agreed.

Besides, is it not easier to just cut the housing to length in place?:confused:
 

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GrantB said:
I'm not sure I understand the problem here.

I don't have cable stops on my frame, just hose guides. Zip ties keep it all tight. I had planned on a full run of housing from prior experience on my hard tail.

Is this the proper sum up? If everything is zipped up tight from the bar to the seat stay, then the same down the stay to the brake, then I just have to get the slack around the seat post right to avoid kinking (too short) or slackening (too long). Is this the long and short of it?
In a nutshell, you've got it right.

The only "problem" I've had is when using stiff housing like Ripcord. The compressing suspension would try to "push" the housing forward through the tie-down on the frame. Extra zip ties were needed to create enough pressure and friction. But using soft, supple standard brake housing, the problem doesn't exist.
 

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Old man on a bike
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GrantB said:
I'm going to replace some Hayes HFX 9 brakes with BB7s on my FS next week. I'm not sure I understand the problem here.

I don't have cable stops on my frame, just hose guides. Zip ties keep it all tight. I had planned on a full run of housing from prior experience on my hard tail.

Is this the proper sum up? If everything is zipped up tight from the bar to the seat stay, then the same down the stay to the brake, then I just have to get the slack around the seat post right to avoid kinking (too short) or slackening (too long). Is this the long and short of it? I reckon this is one of those trial and error gigs, huh? How do you reliably measure that?
I find that firmly securing the housing to the swingarm, but leaving it a bit loose on the guides on the front of the bike to allow for suspension movement works best for me. YMMV.

I haven't purchased pre-cut housing in quite a while, having full runs on a few bikes and having a few bikes, trying to buy pre-cut housing is just a pain (you're still going to end up customizing lengths even if you have stops). Much cheaper and easier to buy in bulk and use as needed; makes for quick service anytime you need new housing, too.
 

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Good idea on some slack up front but nice and tight on the stay. Also, I'm with you on buying the housing in some bulk.
 

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Sooooo. I skimmed through all this pretty quick so I'm sorry if it has been covered.

I'm assuming that you've got proper cable stops for your housing. If you do I've got two questions/suggestions

A. Have you tried pre-tensioning your brake caliper (ie. put some tension on your brake caliper when you're bolting down your cable, dial out outboard pad accordingly)?
B. Have you tried running with a higher spring tension on your caliper?

Slack cables are typically issues of low spring tension or some sort of obstruction/friction (cable housing kink, dirty cable, zip tie being too tight).
 

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Never trust a fart
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I've been running BB7's on my Kona Kikapu Deluxe FS bike. Zero issues. Key is, as stated above, is proper cable length and making sure to use full length housing.
 

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Wong Way
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70 Posts
Discussion Starter · #18 ·
ok so i ran full cable housing through the frame and it seems to have help quite a bit, my only other concern now is my rear shock, i bout this frame brand new and its from 2004 and i do not know how the seals are. I fill it to roughly 180psi and it seems to slowly drain while sitting in my basement on the stand. any opinions???
 

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Old man on a bike
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godbout.t said:
ok so i ran full cable housing through the frame and it seems to have help quite a bit, my only other concern now is my rear shock, i bout this frame brand new and its from 2004 and i do not know how the seals are. I fill it to roughly 180psi and it seems to slowly drain while sitting in my basement on the stand. any opinions???
It's new but from 2004? You've been aging it? May as well service it if it's leaking, but are you sure it's leaking when you say "seems"?
 

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Wong Way
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70 Posts
Discussion Starter · #20 ·
well i bought it from a guy i know and it was just sitting around, never built. And the shock is a Fox Float r. and i believe it's leaking, i put air in and its fine then about 2 days later its lost about 1/4 air or more.
 
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