Cabling Question
 

I noticed that some cross bikes have the cables run down the down tube like a road bike and some have the cables run along the top tube. Does this make a difference?

No.

For a CX bike, exposed cables down in path of the tire mud-spray will foul easier than exposed cables on the TT. No consequence if the cables are run inside housing.

That's the intention, but in practice it makes no difference. Look at pro podiums- you'd be hard pressed to find one with all three running the same routing.

+1

The cables running down the downtube are the simplest and best routing. The pulley needed on the toptube routing is problematic, IMO.

Thank you

Yup. Even though I love my crossbike, I wish it didn't have top tube routing.

I use a Speen Umlenker instead of a pulley, and find that it works quite well.

I ran my 'cross bike all winter. Put it on the stand a couple of months ago for a "complete overhaul", and just got around to the pulley this weekend. Holy ****, I couldn't believe the crud it accumulated!

On Monday, I ordered fenders (I don't race 'cross, I use the bike on the road when the weather is ****). An incredible amount of crud elsewhere too, not to mention the "skunk stripe" on my back, both of which will be greatly reduced with the fenders.

On my CX bike, I use an old MTB Deore XT FD that is configured for top-pull cable, shift great. The new shimano cross-specific grouppo also has a more road-looking top pull FD option now.

there are plastic covers for those rollers.. for crud shedding..
when Keith Bontrager was still a guy building bike frames ,
he just located the cable run & pulley on the right side of the seat tube.

I had a Nishiki Alien, they preceded top pull FD,
so they used the housing to push from the top.
and anchored the cable to the BB shell ..

The reason for cabling above the top tube is to keep the cabling from getting smothered with mud. If it were not this way, we would be changing cables much more often especially at the rear derailleur housing loop!

You'd think so, but in my experience downtube routing of exposed cables works fine. With top tube routing, the rear der housing becomes a water catcher (see photo below), unless you run housing all the way down the seatstays. (Which is what I do.)

Then you have to deal with the top-pull for front der, so in theory it seems like a good idea but I prefer downtube routing.

http://static.ddmcdn.com/gif/mountai...derailleur.jpg

I recently bought a new cross frame that has top tube cable routing. I had a LBS transfer parts from my old frame onto the new one, but it needed a new front derailleur (different seat tube diameter than the old one). The LBS picked out a Shimano Alivio top pull FD, which has most of the mechanical stuff between the seat tube and rear tire. That left me with about 4 mm clearance between the two, meaning that if I wanted to put fenders on it or even a fatter tire, I would be out of luck. I immediately pointed it out to the mechanic, who ordered a Deore FD. That gave me an extra mm or two. On the third try, he found a SRAM FD that has the mechanical stuff laterally to the seat tube. Much better.

During this episode, I suggested a couple times that he put on a road bottom-pull FD and a pulley, but he didn't want to do it that way for reasons he didn't make clear.

So the moral of the story is, some top-pull FDs will eat up the clearance between the seat tube and rear tire. If you care about that, make sure to select your FD with care....

I would be interested to know what Sram FD and what make brifters you are using. Do you have Sram Brifters?

I have a SRAM X9 mountain FD and 3-speed/9-speed Tiagra brifters. It shifts ok, but the LBS spent a lot of time dialing it in. I'm keeping my fingers crossed that it will continue to work ok. The LBS strongly encouraged me to bring it back in a few weeks after cable stretch or whatever else might degrade shifting performance.