Stretched brake cable with child seat - what needs replacing?

[jimster99]

Hi all,

Random question time!

I have a child bike seat on my bike. The metal arms connecting the child seat to the frame pass close to the rear brake cable and I have (on 2 bikes...!) put the arms repeatedly on the wrong side of the bike cable (when removing and reinstallig the seat), and then used the brake. When I do this, the brake still works but the cable is stretched over the metal arms, and after doing it a few times the brake lever gets permanently much stiffer. Don't judge me (the child seat has quite a few bits that have to align properly and in a hurry its easy to get it wrong!)

I assume what is happening here is that the brake cable is stretching inside the cable housing when the brake is used, and the damage increases the friction inside the housing. To repair it, am I likely to need to replace both the cable and the housing? Or is there aother easier to fix solution that I am missing?

Thanks!!!:D

[PT1029]

Does the cable/lever go stiff without the child seat fitted?
If it is only stiff with the child seat fitted/incorrect arm/cable routing, then the issue is with the tight/incorrect cable routing when the child seat is fitted.
If the correct seat fitting is with the cable between the seat arm and bike frame, tie the cable closer in to the bike frame (but don't tie it so it can't move a bit.
If the cable needs to be on the outside, would having a longer loop in the cable help? This could be a new/longer cable, or if a full length cable, you might be able to slip it through the cable guides a cm or 2.

A photo would help with/without the child seat fitted.

When fitting rear brake cables at work when child seats are fitted, the key is in weather the cable is best inside or outside the seat support arm, how high (or not) the seat bracket is mounted on the bike (sometimes little latitude here), and whether to use a 90 deg/135deg/flexible noodle (assuming you have V brakes that is).

[jimster99]

Does the cable/lever go stiff without the child seat fitted?
If it is only stiff with the child seat fitted/incorrect arm/cable routing, then the issue is with the tight/incorrect cable routing when the child seat is fitted.
If the correct seat fitting is with the cable between the seat arm and bike frame, tie the cable closer in to the bike frame (but don't tie it so it can't move a bit.
If the cable needs to be on the outside, would having a longer loop in the cable help? This could be a new/longer cable, or if a full length cable, you might be able to slip it through the cable guides a cm or 2.

A photo would help with/without the child seat fitted.

When fitting rear brake cables at work when child seats are fitted, the key is in weather the cable is best inside or outside the seat support arm, how high (or not) the seat bracket is mounted on the bike (sometimes little latitude here), and whether to use a 90 deg/135deg/flexible noodle (assuming you have V brakes that is).

Thanks! The brake lever gets gradually but permanently more stiff (both harder to pull the lever in and slower to return when released). This persists whether or not the child seat is fitted. To clarify, I know the solution to not make the problem worse (fit the bike seat correctly) but I am really asking for advice in what exactly has happened to the brake cable and how do I fix it?

A picture tells the story better than a thousand words so here you go:

WHEN I ACCIDENTALLY PUT THE CHILD SEAT ON INCORRECTLY

WHEN I FIT THE CHILD SEAT CORRECTLY

[PT1029]

Looking at the 2 photos, I would say if 1 photo has no brake rub the other probably will have brake rub.
If the stiffness happens with/without the childseat, then the child is innocent (on this occasion at least).
Your problem is either the cable corroding/going stiff, or the brake arm pivots corroding/going stiff.
Corroding cable, could be red rust, or white powered (galvanized zinc coating oxidizing). Sometimes a wipe clean and oil does the job (I refer to the sections in the outer cable un hook the noodle and the outer cable from the cable stops and slide things along/up and down to see what is happening inside the outed cable), sometimes it needs a new cable.
If you have a new cable, it is probably worth checking and or refitting the pads so the fatter brake pad spacers are on the rim side of the brake arm, and the thinner spacers on the outside, then check if the cable/noodle clears the child seat arm when teh brake is on.. Occasionally space available means the spacers have to be the other way round (thinners spacers on the rim side)

Brake pivots. Remove the child seat, unhook the cable noodle from its slot. Push each brake arm against the rim, release and see if they spring back freely. If one/both does not spring back freely, then the arm needs removing, the pivot cleaning.greasing and refitting.
Occasionally brake arms spring back poorly/weakly due to poor spring tension.

[peetee]

I think you will always have an issue with either the brake rubbing or no actuating properly. The curved metal pipe (noodle) should move away from the centre as the brake is released but it is too confined and is forced to swing at an angle rather than move back. That causes the the cable to be drawn down which effectively drags the caliper with it and the brake remains on.
My solution would to be to remove the reflector, replace the 90 degree noodle with a (front brake specific) 120 degree noodle and route the cable around the other side of the seat tube.

[531colin]

I would try to move the cable so that it works with the cable "between the legs" (so to speak!) of the child seat.....but ideally not touching the leg of the seat.
Then the seat is easy to put on and off, and it works the same with or without the seat.
to do this I would try.....
Swap the front mech. cable and brake cables over at the cable stops on the top tube. (to give the brake cable a smoother route in its "new place")
Route both of those cables to the chainside of the seatpost.
Fit a flexible noodle https://spacycles.co.uk/m7b0s101p3530/S ... h-Adjuster in place of the rigid noodle.
If anybody can remember what it was called or who sold it.....you used to be able to buy "outer" which was made of stuff like a string of beads with a lining tube, that might help.
You could probably use 2 flexible noodles if it helped.

[jimster99]

Thanks all - to clarify, the issue is definitely in the cable or housing (the lever and the brakes themselves move freely when disconnected from the cable), so I suspect that the cable having been bent round the child seat post has frayed something inside the cable at the contact point, so will consider replacing (or leaving it for now, as it still works, just a bit less smoothly than before).

I'm also looking at getting a brake cable/housing kit. Decathlon sells one but the photos leave me confused - could someone explain what the two arrowed items in this picture are for? PS I have watched the park tool video on brake cable housing replacement...still none the wiser as to the two mystery items!

[Jdsk]

I'm also looking at getting a brake cable/housing kit. Decathlon sells one but the photos leave me confused - could someone explain what the two arrowed items in this picture are for? PS I have watched the park tool video on brake cable housing replacement...still none the wiser as to the two mystery items!

I think that the bigger one might fit in where the cable exits the lever and act to guide the housing.

And the smaller might be rubber rings to keep the bare cable off the frame.

Jonathan

[peetee]

I'm also looking at getting a brake cable/housing kit. Decathlon sells one but the photos leave me confused - could someone explain what the two arrowed items in this picture are for? PS I have watched the park tool video on brake cable housing replacement...still none the wiser as to the two mystery items!

I think that the bigger one might fit in where the cable exits the lever and act to guide the housing.

And the smaller might be rubber rings to keep the bare cable off the frame.

Jonathan

The bigger is an optional part for brake levers with a bare interface (ie no adjuster) where the cable enters. The smaller, is indeed, as stated.

[jimster99]

thanks Jonathan - that makes sense to me!

[jimster99]

Just to complete this thread, I've read the sheldown brown article on cables and now understand what has happened.

When the arm of the child seat is on the wrong side of the brake cable so that the cable is bent around the arm, when i pull the brake lever, the helical cable housing crushes against the child seat arm and is permanently bent out of place, increasing the cable friction, causing the symptoms I described.