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PostPosted: Fri Mar 16, 2018 10:19 am 
Dirt Disciple

Joined: Wed Mar 14, 2018 3:56 pm
Posts: 20
I got back into cycling about 6 years ago after a looooong break of about 15 years. My old mountain bikes (yes, I still have them), all have one thing in common, top tube-routed cables. Since my return to cycling I've become a cycle commuter, it's only a 7 mile ride each way, but I do it all year round and in all weathers. I soon remembered why I'd chosen my previous bikes based, among other things, on their top tube cable routing. Bikes designed with cables routed along the down tube need a cable-slider, usually plastic/nylon, fitted under the bottom bracket. This is right in the firing line of all the crud flung off the front tyre (even when mudguards are fitted). The rear derailleur cable is also subjected to further abuse on its path along the right-hand chain stay. Compare that with a top-tube cable routing design. The cables are kept up high, out of the way of road filth and the final loop before the cable attaches to the rear derailleur can be made tighter because the "angle of approach" is less acute. For me, it's a "no-brainer" and apart from a very minor drawback of having to take extra care when clamping the bike in a workstand, I really can't see any disadvantages to top-tube cable routing. Let me know your thoughts.


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PostPosted: Fri Mar 16, 2018 11:43 am 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
Posts: 9109
Location: New Forest, UK
The big disadvantage in my mind is that the rear mech's last section of outer faces upwards and therefore water runs down it and inside. This gums up relatively fast compared to a cable routing along the chainstay where at least the moisture runs uphill. There is that little rubber hat you can get to sit just above the cable entry which breaks water flow.

The other disadvantage (slight) is the cables do tend to get rubbed and scratch the top tube.

The answer to both problems is to use a sealed cable system, with the outer pipes and cable ends.


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PostPosted: Fri Mar 16, 2018 12:10 pm 
Dirt Disciple

Joined: Wed Mar 14, 2018 3:56 pm
Posts: 20
Found these: https://www.ebay.co.uk/itm/5-x-Shimano- ... 1755402374


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PostPosted: Fri Mar 16, 2018 2:18 pm 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
Posts: 9109
Location: New Forest, UK
90sCro-MoFan wrote:


They don't work! Water and muck gets in. However with different end caps and a plastic pipe over all exposed inner, it's fine.
https://www.raceviewcycles.com/transfil ... rrency=GBP


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 Post subject: Re:
PostPosted: Fri Mar 16, 2018 2:31 pm 
Dirt Disciple

Joined: Wed Mar 14, 2018 3:56 pm
Posts: 20
Aha, gotcha! I'll consider giving that a try when I strip my commuter bike down later in the spring. Thanks for the info!


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PostPosted: Sat Mar 17, 2018 3:41 am 
Retro Guru
User avatar

Joined: Fri Jan 13, 2012 2:28 am
Posts: 1217
Location: Near Gatwick
hamster wrote:
90sCro-MoFan wrote:


They don't work! Water and muck gets in. However with different end caps and a plastic pipe over all exposed inner, it's fine.
https://www.raceviewcycles.com/transfil ... rrency=GBP


The only one that seem to suffer on mine is the last outer on the rear mech.
The cables running over the plastic on the bottom bracket have never been an issue, they can't run better
in mud[can they].
I do dislike rear brake cable stops on the left of the top tube, the cable is better routed and[probably in my head] runs smoother if it is on the oppositie side to the lever.


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 Post subject: Re:
PostPosted: Sun Mar 18, 2018 11:08 am 
Dirt Disciple

Joined: Wed Mar 14, 2018 3:56 pm
Posts: 20
I'm probably a lazy bugger and don't keep my commuter bike as clean as I should, but I've had both front and rear derailleur cables fray badly on my old Raleigh. It's not an issue if you keep the bike clean, of course, but it's finding time, that's the problem with me.
I even lost the slider off that bike too, it just fell off at some point. It wasn't screwed in, like most, it had a stupid plastic plug affair holding it in which was secured from inside the bottom bracket shell with another, cone-shaped piece of plastic that wedged in. I reckon when I changed the bottom bracket for a cartridge type, it probably buggered up that silly plastic arrangement as I was threading it in. Which, to me, highlights another drawback to the bottom-routed cable design - extra parts to worry about.
I use 4 donuts on each cable along the top tube, that's usually more than enough to keep them from contacting the paintwork.
Will definitely try Hamster's tips on water-proofing the rear derailleur cable through, maybe all three (I don't have a front mech), 'cos my grip-shifter feels stiff as f*ck at the moment.


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