CAAD12 Rear Brake Sticking

G1032

Hi folks
CAAD12. New enough. Less than 3500km on it. 105 R7000.

Seems to be a lot of friction on the rear brake cable, to the point that the caliper doesn't always retract fully after being released and if it does fully retract it is slow to do so.

The caplier moves smoothly when no cable attached. No issue with spring. Behaves the exact same as front when moving by hand.
The lever is smooth as long as it doesn't have to pull the cable. 100% no issue with caplier or lever..

So the issue is friction on the cable. I can 'hear' friction from the top tube when the lever is pulled.
I replaced the inner and outer cables with 'Alligator' housing and cables from the local shop. It was perfect for a couple of days. Then started 'sticking' again. So then I bought Shimano brake cable set and replaced all again. Same result. Perfect for a couple of spins and then 'sticking' again.

Ferrules / housing ends are correctly installed.

It's as if the inner cable is rubbing off something inside the frame. Is that even possible? Certainly sounds like it, but what could it be rubbing off inside the frame??

Any ideas here on how to get proper performance from the rear brake?
Thanks

Cee-Jay-Cee

Is the brake cable that’s inside the top tube bare or have you a sleeve or anything over it?

Are there are severe bends at the front or rear?

G1032

Cee-Jay-Cee wrote: »

Is the brake cable that’s inside the top tube bare or have you a sleeve or anything over it?

Are there are severe bends at the front or rear?

The cable inside the top tube is bare. Should there be a sleeve over it?

Doesn't seem to have any severe bends. I've cut housing to the same length as original housing (assumption being that that should have been OK !!. It does seem OK anyway)

CramCycle

Could be friction inside the housing. change the cable and the outside housing and that should sort it out. Happened to mine where it rusted a bit. If your really lazy you could blast some PTFE spray down the housing and see does that help but I would recommend replacing the cables and housing at the same time in this case and blast it with some PTFE spray every now and again.

G1032

CramCycle wrote: »

Could be friction inside the housing. change the cable and the outside housing and that should sort it out. Happened to mine where it rusted a bit. If your really lazy you could blast some PTFE spray down the housing and see does that help but I would recommend replacing the cables and housing at the same time in this case and blast it with some PTFE spray every now and again.

Cheers
I've already done that (changed the housing and inner) twice :-(
Second time was with Shimano kit

G1032

Cee-Jay-Cee wrote: »

Is the brake cable that’s inside the top tube bare or have you a sleeve or anything over it?

Are there are severe bends at the front or rear?

Cee-Jay-Cee..... Does that cable need a sleeve over it? If it needs one what do I get? Are we talking something like what you'd find inside gear cable housing? Or is there specific sleeve for brake cable?

CramCycle

G1032 wrote: »

Cheers
I've already done that (changed the housing and inner) twice :-(
Second time was with Shimano kit

Would the cable not be sitting into the shifter/brake lever correctly. I would unhook it from the brake, put a bit of light tension on the cable and pull the brake lever, is it releasing easily? Are you sure the callipers are releasing easily?

G1032 wrote: »

Cee-Jay-Cee..... Does that cable need a sleeve over it? If it needs one what do I get? Are we talking something like what you'd find inside gear cable housing? Or is there specific sleeve for brake cable?

No need for a sleeve inside the frame, just a sleeve from the hoods to the point it enters the frame, and from the brake calliper to where the cable comes out of the frame. Inside the frame it doesn't.

The way the callipers work, they are always putting tension on the cable, you pulling the cable overcomes that tension, and the callipers close (they want to be open). If the callipers are opening, but slowly, they will be the issue. Unhook the cable, pinch the callipers closed by hand and release, it should spring open instantly, not slowly.

sin_26

You probably need this

https://www.allspeed.com/product/jagwire-lined-end-caps-188074-1.htm

If you listen carefully lots of metal friction is where cable enters and ends top tube

G1032

CramCycle wrote: »

Would the cable not be sitting into the shifter/brake lever correctly. I would unhook it from the brake, put a bit of light tension on the cable and pull the brake lever, is it releasing easily? Are you sure the callipers are releasing easily?

Definitely sitting in the shifter/brake correctly. First thing I checked. Expected to see it loose in there but no, sitting correctly.

CramCycle wrote: »

No need for a sleeve inside the frame, just a sleeve from the hoods to the point it enters the frame, and from the brake calliper to where the cable comes out of the frame. Inside the frame it doesn't.

This is what I thought alright.

CramCycle wrote: »

The way the callipers work, they are always putting tension on the cable, you pulling the cable overcomes that tension, and the callipers close (they want to be open). If the callipers are opening, but slowly, they will be the issue. Unhook the cable, pinch the callipers closed by hand and release, it should spring open instantly, not slowly.

Ya, when cable is disconnected there is spring in the calipers. They open instantly. No friction whatsoever. Spring is perfect. Like, it's a strong spring back and works perfectly initially when new cables fitted but that doesn't last long.

Anyone know what this is for?
https://www.evanscycles.com/nokon-teflon-liner-2m-x-1-7mm-EV190699

Looks like some kind of sleeve to cover inner cable? Not sure how that would stay in place?? But we seem to be in agreement anyway that that shouldn't be needed....

G1032

sin_26 wrote: »

You probably need this

https://www.allspeed.com/product/jagwire-lined-end-caps-188074-1.htm

If you listen carefully lots of metal friction is where cable enters and ends top tube

Cheers
Makes sense, but look at the price :eek:

Bottle of 50. I just want two!! But I'll google for similar. Thanks

sin_26

G1032 wrote: »

sin_26 wrote: »

You probably need this

https://www.allspeed.com/product/jagwire-lined-end-caps-188074-1.htm

If you listen carefully lots of metal friction is where cable enters and ends top tube

Cheers
Makes sense, but look at the price :eek:

Bottle of 50. I just want two!! But I'll google for similar. Thanks

Ah a haha didn't spot that. Just added random link with picture to give you an idea.
Best bet is to go to LBS and have a chat with mechanic. If he is nice fella he should give you couple for free

Cee-Jay-Cee

G1032 wrote: »

The cable inside the top tube is bare. Should there be a sleeve over it?

Doesn't seem to have any severe bends. I've cut housing to the same length as original housing (assumption being that that should have been OK !!. It does seem OK anyway)

No I was asking in case you were using a rubber sleeve on it to prevent rattling which may have become snagged.

Borderfox

I'm getting the left lever (rear brake) replaced under warranty due to problems shifting but the action on the rear brake is not great so will let you know how it is after replacement

Plastik

What's the cable run like where it enters the headtube, any picture?

Because everything is working perfectly for a few spins after fitting new hardware - I'm going to guess that the outer and/or inner cable where it enters the headtube is getting kinked/squashed. Do you travel with your bike in a boot with the handlebars turned 90 deg?

G1032

Plastik wrote: »

What's the cable run like where it enters the headtube, any picture?

Because everything is working perfectly for a few spins after fitting new hardware - I'm going to guess that the outer and/or inner cable where it enters the headtube is getting kinked/squashed. Do you travel with your bike in a boot with the handlebars turned 90 deg?

Hmmmm. Cable enters the top tube and I think that's where the problem lies
Yes, I do travel with the bike in the boot and the handlebars turned 90 degrees.
Possibly need to lengthen the housing coming from the shifter to the top tube!
Cheers

In any case it's something else to investigate. I'll have a look this evening and see if there is any strain on the housing when I turn the bars 90 degrees

Borderfox

There is loads of slack on mine going into the top tube, far more than I would allow but it's factory fit so left it. As nice as internal cables look they are a pain in the ass to sort out

Borderfox

Got the bike back on Tuesday and the action On the rear brake is back to normal

G1032

Borderfox wrote: »

Got the bike back on Tuesday and the action On the rear brake is back to normal

I dropped mine into shop yesterday. Had enough of it and had no more time for investigating possible fixes.

G1032

CramCycle wrote: »

The way the callipers work, they are always putting tension on the cable, you pulling the cable overcomes that tension, and the callipers close (they want to be open). If the callipers are opening, but slowly, they will be the issue. Unhook the cable, pinch the callipers closed by hand and release, it should spring open instantly, not slowly.

sin_26 wrote: »

You probably need this

https://www.allspeed.com/product/jagwire-lined-end-caps-188074-1.htm

If you listen carefully lots of metal friction is where cable enters and ends top tube

Dropped it in to bike shop yesterday and got it back today. Working perfectly again.
He replaced inner cable (only because he snipped the old :-) )
He removed the caliper and cleaned it (although did say it wasn't bad at all)
He replaced the ferrule that goes into the top tube with a jagwire one like sin_26 posted here.

The ferrule was the single biggest reason for the friction causing the poor return.

Thanks for the suggestions/replies folks