FD and chainstay angle: 63-66 vs 66-69
f.c...@gmail.com
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
pm
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).
-pm
Qui si parla Campagnolo
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.
M-gineering
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
--
/Marten
info(apestaartje)m-gineering(punt)nl
JG
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.
JG
M-gineering
> Huh?? put a 700c on front and back and no angle changes.
sounds like you are a consumer faffing about and not a framebuilder ;)
--
/Marten
info(apestaartje)m-gineering(punt)nl
JG
Sounds like you are an engineer that thinks "using bigger wheels"
means "desiging a frame which uses bigger wheels";-)
JG
f.c...@gmail.com
> 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!
Bye,
Federico
Orin
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).
Orin.
Chalo
>
> 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
Tom Sherman
to obtain wide range gearing?
--
Tom Sherman - Holstein-Friesland Bovinia
"People who had no mercy will find none." - Anon.
Chalo
>
> 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?
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.
Chalo
carl...@comcast.net
Dear Chalo,
Not arguing, just curious.
Do you know of any toothed-belt production bikes, outside the Japanese
subway models?
Cheers,
Carl Fogel
Chalo
>
> Chalo wrote:
> >
> >Tom Sherman wrote:
> >>
> >>ChaloColina 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?
> >
> >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.
>
>
> Do you know of any toothed-belt production bikes, outside the Japanese
> subway models?
Thun of Germany makes a system that has been used on the Mercedes bike
and other German and Dutch models.
Ellsworth's "The Ride" cruiser has toothed-belt drive. I don't know
who makes the belt or sporockets.
Spot Bikes and Jericho have both made toothed-belt bikes for at least
limited sale. Spot produces a belt-compatible dropout that can be
retrofitted to other steel frames.
The main problem preventing toothed-belt retrofits of other bicycles
is the need for an elevated chainstay or a rear triangle that can be
opened to insert the belt.
Chalo
M-gineering
another -nasty- example is the Strida folder
GAtes is currently pushing the Carbon Drive belt system
--
/Marten
info(apestaartje)m-gineering(punt)nl
carl...@comcast.net
Dear Chalo,
Thanks for those leads.
Ellsworth The Ride:
http://www.rei.com/product/760062
Yikes! Weird frame, $4,000, CV hub, ISIS BB, 26x3.0 tires!
The page says that "The Ride" uses a belt drive:
"Smooth and quiet belt drivetrain eliminates noise while offering
non-slip power transfer and reliable service in all types of
conditions."
http://www.rei.com/product/760062
But the hub picture (5th in the "available images") shows a chain:
http://media.rei.com/media/c/1183978.jpg
***
Spot Bikes drive:
http://reviews.mtbr.com/interbike/spot-bikes-belt-drive-carbon-drive-system-bikes/
Interesting details and photos with stuff about weight, efficiency,
durability, and so on.
***
Jericho seems to be gone, possibly because the owner omitted the
crucial leading "F" in his name:
"Josh Ogle . . . has had a turn of bad luck regarding his business. He
is disillusioned about business and does still produce some small
quantity of bikes in conjunction with Jason Grove of El Camino Fab
(http://www.elcaminofab.com/)."
http://forums.mtbr.com/archive/index.php/t-176087.html
Jericho belt drive on an Orange bike:
http://www.singletrackworld.com/article.php?sid=2426
Yikes! One hundred pounds of tension needed to work right!
Thanks again for those leads.
Cheers,
Carl Fogel
carl...@comcast.net
Dear Marten,
Er . . .
http://www.foldsoc.co.uk/Mike/strida3.html
That's . . . a very interesting bicycle.
:-)
Cheers,
Carl Fogel
M-gineering
>
> Dear Marten,
>
> Er . . .
> http://www.foldsoc.co.uk/Mike/strida3.html
>
> That's . . . a very interesting bicycle.
>
> :-)
>
> Cheers,
>
> Carl Fogel
I think were currently running Mk5 Strida's. Still not as fast as a pair
of running shoes, and folded bigger than ready to ride (for want of a
better word)
But that's only my opinion ;)
--
/Marten
info(apestaartje)m-gineering(punt)nl