Installing a bottom pull front derailleur on a top pull cyclocross bike.
So I inherited a Trek 7500fx from my dad, and it has some Sora STI brifters on a drop bar. Now I wanted to adjust the front derailleur because you had to hold the lever to get it into the biggest cog, turns out it's a Nexave mtn derailleur, and now it won't go between more than two cogs. I check this forum and it turns out Shimano road and mtn components don't mix (except rear derailleurs from what I understand), so I go and grab a Ultegra road derailleur at the local used store. As I walk out I realise it's a a bottom pull derailleur (duh!), and the store doesn't accept returns. So how do I go about solving this problem? I have only found clamp on pulleys for smaller diameter tubes (mine's a 34.9mm). Suggestions?
Hmmm. What about a Sturmey-Archer shift cable pulley? Clamp it down by the bottom bracket, run the cable around it, it'll reverse the direction of the cable so it'll be coming up from below the derailer. Will it work? I dunno, but it might be worth a shot.
Oh, wait. Upon closer reading, I see that you have considered this and couldn't find anything that would clamp your tubes. Well, you might be able to find away to come up with a way of clamping it. I can't really think of any other way to solve the problem.
Rans Enduro Sport, Hase Kettweisel Tandem, Merin Bear Valley beater bike
How big is your down tube?
Problem Solvers makes cnc clamp on cable stops in sizes up to 1 1/2". If that'll fit your down tube you can run your shift cable under the bottom bracket in the conventional manner. If you decide to order one through your LBS the QBP part number is BR5461. Unfortunately, they ain't cheap.
Ok, so the Sturmey-Archer clamp pulley was a good idea, but it only comes in 1 1/8" diameter, i need 1 3/8" (34.9mm). As for the downtube, it's one of them oval suckers so a traditional road bike cable routing won't work with clamp ons. I was actually thinking about using two clamp on cable stops and routing the cable so as to have it come around if that makes sense. More or less a pulley using cable stops and a piece of cable housing. Think this'll work? Thanks, for the help thus far.
Sure looks like 2 to me but I really don't know. Do you think you will have enough room beneath your derailleur for a big enough cable housing loop? You might want to check out your rear derailleur for a comparison.
What are you using for front chainrings? A Shimano Deore LX M571 downpull derailleur is rated for 48 tooth chainrings. The QBP part number in 31.8mm clamp size is FD5676. It's a big step up in quality from your old Nexave derailleur.