Cyclocross Cable Routing
What is the effect and affect of types of cable routing in Cyclcross?
I've noticed that some frames route the cables similar to MTB bicycles, while others use the road bicycle cable route.
Really a subtle difference - chances are you won't notice during practical riding in most circumstances. Road cables generally have the shifting routed along the underside of the downtube. Mountain and some cyclocross bikes have all the cables (rear brake, front and rear derailleurs) mounted along the topside of the top tube. In theory, this prevents your cables from getting snagged on tree limbs and rocks from below. The caveat is that road derailleurs are "bottom-pull" and are meant to be matched to standard road cable routing along the bottom of the down tube, while mountain bike derailleurs are generally "top-pull". So if the front derailleur cable is mounted along the top tube and you want to use a road bike derailleur, you have to use a pulley adapter mounted on the seat tube just above the bottom bracket. This does work just fine. Some production bikes come with this setup already, such as the Bianchi Axis. You can also retro-fit an existing road frame with a clamp-on pulley adapter and clamp-on top-tube cable stops.
I first noticed the rear derailleur cable route and the cable route going on underside of the downtube; but didn't consider the front derailleur cable pull setup. I've purchased a Kona JTS. Seems there is no standards in the bicycle world as I just purchased a Giant XTC with a Rapid Rise derailleur; which I wasn't aware of until I began riding it. It's different but OK. . .
Originally Posted by SAB
I am also curious about any actual shifting performance effects from cable routing during a muddy race.
I assume you will be racing mostly in MABRA (mid-atlantic) events. The mud we get here on the East Coast, in general, is not quite what you see in the Northwest (check out pics of nationals in OR...) or the big cyclocross countries of Europe. You still see plenty of mud, just not swimmin in it- in fact the early season is generally fairly dry here. The point being that the main advantage of a top-pull front derailleur is to keep the cable high away from the bottom bracket in soupy mud. Top- pull front derailleurs designed for double cranks with larger rings are rare (I'm not sure if they exist at all, I've never seen one). Top pull derailleurs were designed for MTB cranks, not cyclocross bikes. They have some advantage in nasty mud or freezing slush, but in moderate or dry conditions they just don't shift as nicely as a nice familiar bottom pull road derailleur that was designed for ring sizes like 38-48t. I have 2 bikes, one with each kind. 90% of the time, I'd rather have a regular bottom pull derailleur for a double ring cross setup. And that other 10%, well, ain't nothing working then. Your problem is always at the back end with the cassette and at the brakes in that kind of mess. Which is why its nice to have the luxury of 2 bikes to switch out. Anyway, for East Coast racing, I'd go for a bottom pull derailleur setup, or even better, to cover all your bases forget it and just use a single ring (like a 42-44). I see lots of dropped chains in the C races from people bouncing their bikes on the remount. A single ring will keep the chain in place and you only give up 1 top end and 1 low end gear. Keep it simple-
Lots of practical and knowledgeable advice.
Actually there is a big difference. The reason they are mounted on top is for a couple of reasons. You dont get crap caught up in the cables and when you have to carry your bike, i.e. your arm & shoulder going thru the triangle, you wont get snagged in your cables (if they were mounted on the bottom of the tube).