Hello, I'm building a touring bike with an MTB crank (22-32-44). I naively thought that an MTB FD would be better than a road one due to cage shape. But most MTB FDs are designed for a 66-69 degree chainstay angle, while my bike should need a 63-66. What effect does a wrong chainstay angle have?
Which one would be better for my bike: a road FD (wrong teeth) or an MTB one (wrong angle)?
Further info: my bike is 8 speed and I use pre-2007 Campagnolo brifters.
> Hello, > I'm building a touring bike with an MTB crank (22-32-44). I naively > thought that an MTB FD would be better than a road one due to cage > shape. > But most MTB FDs are designed for a 66-69 degree chainstay angle, > while my bike should need a 63-66. What effect does a wrong chainstay > angle have?
> Which one would be better for my bike: a road FD (wrong teeth) or an > MTB one (wrong angle)?
> Further info: my bike is 8 speed and I use pre-2007 Campagnolo > brifters.
> Thanks, > Federico
Front derailleurs are pretty brutal devices even in this day and age, so i doubt they care that much about the angle of the seat tube (and the angle of the chain varies by way more than 3 degrees, anyway.) A bigger problem might be that MTB vs. road derailleurs may be designed for differing amounts of cable pull (Shimano's certainly are, with the MTB models pulling more cable per shift; I dunno about other brands).
> Hello, > I'm building a touring bike with an MTB crank (22-32-44). I naively > thought that an MTB FD would be better than a road one due to cage > shape. > But most MTB FDs are designed for a 66-69 degree chainstay angle, > while my bike should need a 63-66. What effect does a wrong chainstay > angle have?
> Which one would be better for my bike: a road FD (wrong teeth) or an > MTB one (wrong angle)?
> Further info: my bike is 8 speed and I use pre-2007 Campagnolo > brifters.
> Thanks, > Federico
I think you mean seat tube angle, not chainstay angle and use the FD that most follows the chainring arc. Probably a MTB fd, since with ERGO, any FD will work with the LH shifter.
> On Jul 19, 2:13 pm, "f.co...@gmail.com" <f.co...@gmail.com> wrote: >> Hello, >> I'm building a touring bike with an MTB crank (22-32-44). I naively >> thought that an MTB FD would be better than a road one due to cage >> shape. >> But most MTB FDs are designed for a 66-69 degree chainstay angle, >> while my bike should need a 63-66. What effect does a wrong chainstay >> angle have?
>> Which one would be better for my bike: a road FD (wrong teeth) or an >> MTB one (wrong angle)?
>> Further info: my bike is 8 speed and I use pre-2007 Campagnolo >> brifters.
>> Thanks, >> Federico
> I think you mean seat tube angle, not chainstay angle and use the FD > that most follows the chainring arc. Probably a MTB fd, since with > ERGO, any FD will work with the LH shifter.
No, he doesn't. Some models of MTB fd are available with a repositioned cage to compensate for the change of angle you get when using bigger (700c, 29?") wheels. Problems you can run into are chainrub and the cage fouling the chainstay
Huh?? put a 700c on front and back and no angle changes... The relationship between the chainrings, chain, and FD is determined largely by the seat tube angle and very slightly by the bb drop. Maybe there are chainstay clearance issues, but those wouldn't be changed by wheels either.
> Huh?? put a 700c on front and back and no angle changes... The > relationship between the chainrings, chain, and FD is determined > largely by the seat tube angle and very slightly by the bb drop.
I'm not a framebuilder, but seat tube angle varies (roughly) from 70 to 75 degrees, so 5 degrees at most. On the other hand, a difference in BB drop between 0 and 8cm gives a difference of 10 degrees (on a 43 cm chainstay). So BB drop looks more important than seat tube angle!
On Jul 19, 1:13 pm, "f.co...@gmail.com" <f.co...@gmail.com> wrote:
> Hello, > I'm building a touring bike with an MTB crank (22-32-44). I naively > thought that an MTB FD would be better than a road one due to cage > shape. > But most MTB FDs are designed for a 66-69 degree chainstay angle, > while my bike should need a 63-66. What effect does a wrong chainstay > angle have?
> Which one would be better for my bike: a road FD (wrong teeth) or an > MTB one (wrong angle)?
> Further info: my bike is 8 speed and I use pre-2007 Campagnolo > brifters.
If the chainstay angle is too narrow, the chain might hit the top of the derailleur cage in some gear combinations, especially if you go over the rated capacity of the derailleur. Since you are matching FD to crank, you shouldn't have a capacity problem and it will likely work.
A current road FD likely won't work as the Shimano ones at least are optimised for something like 53-39-30 rings (23 capacity) and don't like anything different. Older Ultegra 9-speed triple derailleurs would handle a 52-42-26 (which requires a 26 capacity) while a Campy Racing-T couldn't handle it (chain rub on the bottom of the cage in this case).
> Front derailleurs are pretty brutal devices even in this day and age,
Amen. They are just about as delicate and sophisticated as using salad tongs to jerk your chain between different rings. I hope I live to see them lying in a grave alongside semi-pneumatic tires, cottered cranks, and stem shifters.
Chalo Colina wrote: > pm wrote: >> Front derailleurs are pretty brutal devices even in this day and age,
> Amen. They are just about as delicate and sophisticated as using > salad tongs to jerk your chain between different rings. I hope I live > to see them lying in a grave alongside semi-pneumatic tires, cottered > cranks, and stem shifters.
OK, if you were redesigning the bicycle from scratch, what would you use to obtain wide range gearing?
-- Tom Sherman - Holstein-Friesland Bovinia "People who had no mercy will find none." - Anon.
> >> Front derailleurs are pretty brutal devices even in this day and age,
> > Amen. They are just about as delicate and sophisticated as using > > salad tongs to jerk your chain between different rings. I hope I live > > to see them lying in a grave alongside semi-pneumatic tires, cottered > > cranks, and stem shifters.
> OK, if you were redesigning the bicycle from scratch, what would you use > to obtain wide range gearing?
Epicyclic gears sure seem to do the same basic job a whole lot better-- they're cleaner, much longer-lasting, and less damage-prone. Cars use epicyclics, but they would never use derailleurs.
If I had to do bike design over without existing parts standards, I'd probably skip the chain altogether and use a toothed belt instead.
