Cable Rub on Stumpy
I have a 2006 stumpy comp and the rear derailleur cable is fed under the bottom bracket to the right chain stay and then it loops around into the derailleur. I've put about 4000 miles on this bike, and was looking the frame over and found that where the cable housing contacts the BB area of the frame there is a good 2-3mm groove of rubbed raw aluminum. How concerned about this should I be? Is it something that I should remedy with a patch? Should I fill in the groove with some type of special compound?
I'll try and post picks if I can.
check rear brake cable
right where it passes next to the shock, thats where I got my dig. No damage under the BB for me.
I hate it when that happens.
I started using automotive chip guard by 3M. It's a transparent film (sticker) you can buy and cut to the size you need. You can barely see it when it's on the frame and the stuff is tough.
2015 Kona JTS
2014 Scott Scale 710
2014 Giant Anthem 27.5
2013 DeVinci Leo SL
Ummm...there shouldn't be any contact....
between the bottom of the BB housing and the cable housing that runs under it even at full compression of the rear suspension (I'm assuming that this is a Stumpy FSR?). Somebody set up that length of housing too short! To correct this problem you'll need to replace the cable and housing. For that section that runs under the BB you'll need to put one end of the uncut housing in the forward cable stop on the down tube. Let the air out of the rear shock and fully compress the suspension and hold it in place with a strap or have somebody hold it. Then holding the cable in the forward stop and run it to the chain stay stop. With the housing held between your fingers at the chain stay stop, adjust until you have 1 to 2mm of space between the bb and the cable housing at the closest point. Compensate slightly for the length that the housing will be inserted into the stop and hold. That's where you need to cut your housing. Install the end caps on the housing, insert into the stops and install your cable and your golden. The housing will bow down a little with the suspension at full extension, but that is as it should be.
I'm surprised that you aren't experiencing ghost shifting in the rear with the housing making that much contact with the bb housing. That's usually the first indicator that that run of housing is too short. As the suspension compresses the housing hits the bb and pulls on the cable causing the rear derailleur to move slightly and start to shift to the next lower gear.
Anyway, you shouldn't have to use a filler of any kind. But it wouldn't hurt to find some touch up paint and paint it over. While aluminum doesn't rust, it does corrode over time. But it shouldn't hurt anything to leave it as is. Just adjust that housing length so you're not doing anymore damage in the future.
"I do whatever my Rice Cripsies tell me to!"
Well I've not had any issue with the rear derailleur ghost shifting that wasn't related to me smashing it on a rock.
I have, however, always had issues with new chains disengaging with the front rings, even with an entirely new drive train, when the suspension is compressed and I am pedaling. I assumed that this was due to the chain stretching to fit my drive train, as it usually goes away after 100 miles of good climbing or so.