Possible problem with carbon frame, cable rubbing.

wayne0308

Hi there,

I have a cable rubbing against a part of my frame and I wanted your opinion on it, please bear with me while I explain it.

I had a bike built for me earlier this year. I only noticed a while ago when I went to tune up the front derailleur that I have a cable rubbing against the underside of the bottom bracket.

My front derailleur is a pull down derailleur, and the cable for this routes under the bottom bracket and then up to the handle bars to the shifter. There is a cable guide under the bottom bracket but the guide for this cable is not long enough to reach around the corner and the cable has been rubbing against the frame here. It's cut itself a very small notch but I can see this getting worse so I've bodged a temporary solution with a bit of rubber but it makes shifting a little harder.

Is this normal enough to just leave as it was? Should that cable be touching the frame at all?

I'm a bit worried because I'm not sure how deep it will cut into that section of the frame if I leave it.

Paul Kiernan

A photo would help if you have a camera.

The cable certainly shouldn't be touching the frame. The cable guides for the BB come in different sizes and you obviously need a bigger one.

bcmf

Some frames that have a big BB area have a small hole that the cable goes thru from the cable guide and up thru the frame to the FD. Certainly the cable should not be making contact withe the frame there.

wayne0308

Paul Kiernan wrote: »

A photo would help if you have a camera.

The cable certainly shouldn't be touching the frame. The cable guides for the BB come in different sizes and you obviously need a bigger one.

I'll try upload one when I get home. The cable guide that's on it, I would say it's approx an inch too short.

I've been looking around and the ones I can find are about the same size as the one I have unfortunately...

wayne0308

bcmf wrote: »

Some frames that have a big BB area have a small hole that the cable goes thru from the cable guide and up thru the frame to the FD. Certainly the cable should not be making contact withe the frame there.

This does make sense. I've seen holes there that I thought were strangely placed, funny but I thought they were for leaving any water that might find it's way in out.

I'll check for a corresponding hole on the seat tube near the bottom bracket area. The hole that is on the underside of the bottom bracket area is still about 5 or 6 mm away from the guide I'd say. I reckon I will find one. At that point I suppose it's just a case of finding a cable guide that can reach to the hole right and rerouting the cable.

Paul Kiernan

This is my carbon Planet-X guide which routes the cable into the hole in the frame.

and this is the cable guide on my other alu frame bike....


I'm not sure but I imagine the correct cable guide should be supplied with the frame(?).

Would you believe I washed both those bikes since I last used them. Looks like I missed a bit:o.

wayne0308

Paul Kiernan wrote: »

This is my carbon Planet-X guide which routes the cable into the hole in the frame.

<image>

and this is the cable guide on my other alu frame bike....

<image>


I'm not sure but I imagine the correct cable guide should be supplied with the frame(?).

Would you believe I washed both those bikes since I last used them. Looks like I missed a bit:o.

I suppose it should have been. Thing is the frame would have been hanging up in the shop for the last few years I'd say and it wouldn't surprise me if they took it off for another build may be.

The frame is oldish (Merlin C110).

Just thinking about it, the cable is pretty badly crimped at the derailleur clamp so I might need a new cable as it may not fit through the hole in the frame. If I do need a new cable I may just drop it up to a bike shop and get it done there as I don't fancy going near those shifters

Lemag

wayne0308 wrote: »

If I do need a new cable I may just drop it up to a bike shop and get it done there as I don't fancy going near those shifters

Threading a new cable should be very easy. Just shift into the highest or lowest position (it's one of these but I can never remember until I have to do it) and the cable should feed through nicely. I've used these. You'd need to get some cable cutters but the cable housing might still fit fine.

wayne0308

Lemag wrote: »

Threading a new cable should be very easy. Just shift into the highest or lowest position (it's one of these but I can never remember until I have to do it) and the cable should feed through nicely. I've used these. You'd need to get some cable cutters but the cable housing might still fit fine.

Excellent, thanks for that. I actually have a decent cable cutter that I got on sale so I could give it a go myself I suppose.