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New Cable Stretch

Old 05-24-19, 12:41 AM
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CaptMike
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New Cable Stretch

Noob cable install question. I am changing both brake and shifter cables and housings on my older MTB. I have the Park 4th hand tool, and have seen how it works. My question is, how much do you stretch the new cable? Finger stretch it, then do a hand full of the cable tool, for the brake cables? I have the barrel adjusters all the way in, then a partial turn out. Any rule of thumb? And is it the same for the derailleur cable? Or just finger stretch that one, lock it in, then see what you have. Thank you.
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Old 05-24-19, 02:09 AM
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Originally Posted by CaptMike View Post
Noob cable install question. I am changing both brake and shifter cables and housings on my older MTB. I have the Park 4th hand tool, and have seen how it works. My question is, how much do you stretch the new cable? Finger stretch it, then do a hand full of the cable tool, for the brake cables? I have the barrel adjusters all the way in, then a partial turn out. Any rule of thumb? And is it the same for the derailleur cable? Or just finger stretch that one, lock it in, then see what you have. Thank you.
For brakes, All adjusters to their minimum, I get it taught by hand, making sure all the housing ferrules are properly seated.

For derailleurs, control adjusters all the way in, rear derailleur adjust one turn out, make sure both chains are on the smallest cog and control to minimum number, stretch by hand.

Once set and checked out, trim excess from cables and crimp on a cable end.

I only use the 4th hand tool when I am adjusting a (already installed) short cable or when my fat fingers aren't working right.

I sometimes use a trigger clamp to hold brake pads in towards rim like this
https://www.homedepot.com/p/DEWALT-6...196D/205418759
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Old 05-24-19, 08:24 AM
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the housing and the ferrules on its ends settling in is a bigger factor in what is called 'cable stretch'..
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Old 05-24-19, 09:40 AM
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I've found that pulling a rear shifter cable too taught doesn't allow the RD's spring to pull chain down to higher gears. After tightening the cable nut with the RD in its high gear position, I give the cable a sideways pull with my hand to get out any slack (if it's not all routed through the downtube like on newer bikes). I then loosen the nut and gently pull the cable end with pliers or just my hand to set it "just" taught then tighten the nut. Anything after that can be taken up with the adjusters. The goal is loose enough to allow RD to pull chain down to higher gears, taught enough for crisp shifts upwards to lower gears.
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Old 05-26-19, 09:20 AM
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What kind of brakes?

For derailleurs I just pull the cable snug with my fingers or a needle nose plier. Honestly, I suspect it's more important to get the cable housings snugly seated in the frame stops than to worry about cable stretch.

For brakes it depends a lot on what kind of brakes you have. Calipers and V-style brakes I just use my fingers. Newer style canty's too. Older style canty's can be interesting.
The most challenging are freestyle BMX bikes with under the chain stay brakes. Those sometimes require my 3rd hand tool, my 4th hand tool, and the use of words that are not permitted to be uttered on US Navy ships.

My 4th hand I mostly just use for pulling cable ties.
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Old 05-26-19, 01:29 PM
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Thank you guys for the replies. The bike I am working on now is my old Fuji Suncrest MTB. It has cantilever brakes with straddle cable. I just got back into town for a day, and am going to take a look at them. When I took them apart, I lost the clamp screw on the NDS brake, to tighten the straddle cable. So I have to see what I have to rig up to replace that. It doesn't look like there is much use for the 4th hand tool. I may try Joe's clamp idea. I appreciate the replies.
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