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Front Der. choice for CX bike with top pull cable(13 posts)

Front Der. choice for CX bike with top pull cableclimbo
Aug 16, 2001 4:16 PM
What types of der. can you run for a CX bike with top tube cable routings? I'm guessing that you have to go to a mountain front as no road models seem to accomodate top pull cable routing.
Seat tube cable pulleyBipedZed
Aug 16, 2001 7:32 PM
IF and Steelman bikes have a cable pulley on the seat tube just above the BB shell to allow for a down-pull road front der. with top tube cable routing.

On my Bianchi Axis with TT routing I wasn't getting satisfactory results with a mountain front der due to the cage shape with my 48 large ring. I got a Sturmey Archer (old English 3-speeds) clamp-on cable pulley that you mount in the same location. These clamps are only available in 1" and 1 1/8" clamp sizes so if you have a larger seat tube you'll have to go to the hardware store and get a longer clamp screw and kind of bend the mount to fit. It takes some work but it's worth it to be able to run a road front derailleur. If you do run mountain cranks (like a RaceFace 48/36) you will have to get a 103mm BB so the road front will have enough throw to the big ring.

You can get the cable pulley from Harris Cyclery (Part#HSJ52O/1):
http://www.sheldonbrown.com/harris/sturmey.html
cool, I'm impressedlonefrontranger
Aug 16, 2001 8:00 PM
dude, you have much knowledge. Care to be my consultant when I lobotomize the Redline?

See you at the Coal Miner's!
103mm BB??Jan Gerrit Klok = "TUFO-man"
Aug 16, 2001 9:36 PM
I am INDEED using a Race Face crankset, but with a single 42 outer ring. The present old-XTR 107mm BB is not ideal, for the crankarms still have a lot of clearance from the chainstays, and my chainline could be much better. Switching to the 42 to the middle position is very complicated to do in a safe manner.
Now I hear you talk of a 103mm BB. Who makes these?? Are they any good?

Thanks in advance,

Jan Gerrit
Shimano BB-7410BipedZed
Aug 16, 2001 10:15 PM
The Shimano Dura Ace 8 speed BB with sealed cartridge bearings and tapered spindle. Comes in a 68-103mm. They are still available in the US at Excel Sports and Branford Bike - not sure about availability in Europe. It doesn't seem like 4mm would make a huge difference, but I switched from a UN72 107 to the 103 and my chainline problems were completely solved.

http://www.excelsports.com/item.asp?major=1&minor=6&description=Dura%2DAce+Bottom+Bracket+8+Speed&vendorCode=SHIM
http://www.branfordbike.com/bottombr/bb5.html#item3
One more thingBipedZed
Aug 16, 2001 10:25 PM
The current Campagnolo BBs have 102mm spindles, but I don't recommend using Campy BBs with RaceFace cranks because the Campy taper flats aren't ISO compliant which is what non-splined Shimano and RaceFace cranks are designed for.
ThanksBipedZed
Aug 16, 2001 10:18 PM
I racked my brain for the first part of last season trying to solve my front shifting woes. I guess all those old 3 speeds I had to work on at my first bike shop job paid off.

I love setting up cyclo-cross bikes as it actually allows you to be very creative. Let me know when you want to start working on the Redline, hell, I'll even help you do the wrenching if you want.

Time for bed.
Thanks from me too!Jan Gerrit Klok = "TUFO-man"
Aug 17, 2001 6:11 AM
I´m going to try and find a BB here in Europe, or I´ll get one from overseas. I totally believe 2 mm on each side can make big differences for the chainline.
Hey, maybe my Rohloff chainguide (Did anyone give that a try before me?) will be easier to set up then. After all, it was never designed for a shifting chain, let alone with an imperfect chainline.
it will be a unique challengelonefrontranger
Aug 17, 2001 8:00 AM
I'm planning to go Daytona or Chorus, so if Campy thoroughly aggravates you, feel free to say no on the consulting gig. I will be happy to bribe you with your choice of beer, food, homemade cookies etc...

Something the guys at Vecchio's recommended was to run a Campy Racing triple, leave the outer ring off and install a chainguard. Anything will be lighter than the current group, so I'll not sweat the few extra grams from the crank / BB.

If I'm stuck with STI because of compatibility issues with the smaller gearing, I won't fight it. I do really prefer the way Ergo works, and I'd also like to have the option of swapping wheels within the stable.
Racing TripleBipedZed
Aug 17, 2001 8:20 AM
I'm not as familiar with Campy stuff, but I have nothing against Campy equipment. In fact Campy presents challenges that I like trying to solve.

The Campy Racing triple seems interesting, but a 30 inner ring seems really low, unless you can get something larger with that BCD. Otherwise 30-40/42 means you'll probably want almost a straight block in the rear. What is the alternate chainring availability with the Racing Triple BCD?

Speaking of which, if you go with 10 speed and want wheel swapping options, you'll have to get a Wheels Mfr cassette for your Shimano wheels. If you go 9-speed Ergo then I've seen guys run Shimano 9 speed cassettes with no problems at all.

Just some initial thoughts...
Racing Triplelonefrontranger
Aug 17, 2001 9:31 AM
The guys at Vecchio's recommended a 34/44 with this setup, but I'm not sure of the BCD, sounds like I need to do some more research.

Since I never had issues with racing the 'cross bike geared like it was (50/38 - 13/26) in road races, I probably won't take much of a penalty from small gearing. Not only do I prefer to spin, but I don't think (especially as a Cat IV woman) that I am able to produce the horsepower you guys do.

The old gearing I had on the 'cross bike worked well for Midwestern 'cross races, which are primarily speed courses set up like a flat grass crit with hurdles. I'm told that the Front Range courses have a lot more deep sand, runups, grinder climbs and other obstacles which will make the 50/38 gearing I currently have too tall. Frankly it was too tall on some of the grinder climbs we had in the Midwest, but those were rare.

Thanks again for all your good advice!
Racing TripleCliff Oates
Aug 17, 2001 10:01 AM
FWIW, the biggest ring I see for a 74mm BCD from any manufacturer is 32. Campy does have a 44t 135 BCD ring from their triathlon parts line (Crono), otherwise 40 and 42t rings are the norm. You might also ask the guys at Vecchios about running a 110mm BCD crankset like the Sugino XD 500 or TA Zephyr. Campy front ders don't much care whose cranks you use.
Seat tube cable pulleyThe Walrus
Sep 3, 2001 3:15 PM
I had much the same issue with my Axis, but I was trying to run a triple crank and found the STI levers (8-sp 105) wouldn't pull enough cable for a MTB derailleur. Had to go with a 105 triple, and was faced with the cable-routing dilemma. Eventually discovered a part in the QBP called an E-clamp (look for it in the front derailleur area; it's for the Shimano bottom-bracket mount derailleurs). It has a boss with a 5mm thread, which allowed me to mount the pulley, bushings and machine screw from a Travel Agent V-brake adapter, and then clamp the whole thing on the seat tube between the bottom bracket shell and the derailleur clamp. It works very smoothly, especially if it's positioned so that the cable run between the pulley and derailleur is close to what it would be if you had a bottom-routed cable. The E-clamp is available in a variety of diameters. Gawd, am I glad I finally figured this out!