Importance of having derailer cables on TT

[runtimmyc]

So, I'm in the middle of project bike and I am a little confused. This frame is made so that the derailleur cables are routed near the bottom bracket and I have heard that it would be better if they went along the top tube. I have the frame sanded down to the bare steel, so if I were to put guides on the top tube, now would be the best time.

Should I get some welded on there? How about gluing some on there for simplicities sake? Does any body sell guides or should I look for something similar in a hardware store?

[dirtyphotons]

i've heard jb weld works pretty well for the job.

[runtimmyc]

i've heard jb weld works pretty well for the job.

That's what I was thinking too.

[dirtyphotons]

oh yeah, one other consideration is your front derailleur.

top tube cable routing means top pull front derailleur usually.

[flargle]

Is it worth the trouble? Kona, Felt, Trek, Cannondale . . . all seem to route them under the BB.

[Ronsonic]

Unless you have a frame shop braze them on, I wouldn't try anything semipermanent. There always used to be clamp on cable guides for the top tube.

Unless you're riding in serious mud there isn't that much advantage to the top tube run.

[vanwaCX]

Many production cross bikes route the front dérailleur cable along the down tube. This removes the necessity of either a top pull front mech or a pulley affixed to the seat tube to redirect the cable. These very same bikes will route the rear mech cable along the top tube.

The idea of routing cable along the top tube is meant to get the cables out of your way when shouldering. I've got two bikes; one routes the front mech via the down tube and the other routes is via the top tube and uses a pulley. I don't have problems shouldering either.

There doesn't seem to be any debate about routing the rear mech cable along the top tube. However, this routing means that the rear dérailleur noodle (last loop of cable housing) comes down from the seat stay. It seems that this configuration allows more mud and grime to slither down the cable and into the housing. This reduces shifting performance perceptibly. If the noodle comes off the chain stay when it's routed via the down tube, gravity doesn't assist the mud and grime to enter the housing and the shifting stays better longer.

So if you can live with shouldering the bike with cables running down the down tube, I'd recommend leaving well enough alone.

[runtimmyc]

Well said, you guys convinced me not to do any extra work. Thanks!

[flargle]

The idea of routing cable along the top tube is meant to get the cables out of your way when shouldering.I guess that's one reason, but you're still grabbing cable when you suitcase it.

I would not want to shoulder a bike with a cable running under the TT, though.

FWIW the Blue CX6.5 routes everything on top.

[vanwaCX]

but you're still grabbing cable when you suitcase it.

You would still be stuck with a brake cable along the top tube so the reasoning is, what's a couple more? There are more than a couple production bikes with all three cables routed along the top of the top tube. It just seems like the most popular have the front mech down the down tube.