Front Derailleur slow to shift



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Casimir Mazik

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I have a Marin San Anselmo Hybrid (24 spd) that I bought used two months ago. The front derailleur
has no identifying markings, but according to the Marin Website this bike should have a Shimano
Nexave T-400. The rear derailleur is marked Shimano 8515, but according to the website it should be
a Deore. I have checked the adjustments according to the Park tool website and everything is set
correctly. When I have the bike upsidedown (I don't have a workstand) and pedal and shift, it
shifts just fine. When I ride it, shifting from the middle sprocket to the smallest sprocket takes
about 4 cranks of the pedal. All other shifts are normal. The bottom bracket does not wobble, but I
do get the chain rubbing the derailleur cage sometimes when the rear derailleur is set to the
smaller outer sprocket when riding, not with the bike upsidedown. When I got the bike it had only
200 miles on the odometer. I have added 70 miles (average 15 mph) and this shifting problem has
been recent. My previous bike was a department store 10 spd which I remember had to have the front
derailleur cage spread open to prevent the chain rubbing. I hope I don't have to that with this
one. What should I try next?
 
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David Kunz

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Casimir Mazik wrote:
> I have done some further research on this problem. The rear derailleur is not a Deore but a
> Shimano Alivio and although the front derailleur and the shifters are not marked, close comparison
> to online pictures makes me think they are Alivio as well. These are all OEM, so would upgrading
> to at least an XT front derailleur possibly help?
>
>

No. Alivio is a fine group set. And, the front DR is probably the least demanding part.

Your problem is probably that the shifting cage is not moving far enough in on the shift. Loosen the
cable in 1/4 turn increments until you get the performance that you want. But, understand that you
may start degrading your up-shift at some point or you may introduce cable rub when the rear DR is
in the smallest cog.

If the above happens (you can't hit the right compromise on cable adjustment), check the positioning
of the DR. It should be 1-3 mm above the big ring, and when in the outer gear front and back
(biggest CR/ smallest cassette), the portion of the chain that overlaps the outer part of the DR
cage should be parallel to it (loosen and turn the DR to adjust this -- I usually loosen it a little
and tap it gently). For more info, see Barnett's manual (http://rideitbent.net, 3/4 of the way down)
chapter 33, or check out Sheldon Brown's web site (http://sheldonbrown.com).

David
 
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Peter Cole

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"Casimir Mazik" <[email protected]> wrote in message
news:[email protected]...
> I have a Marin San Anselmo Hybrid (24 spd) that I bought used two months ago.
>. When I ride it, shifting from the middle sprocket to the smallest sprocket takes about 4 cranks
> of the pedal. All other shifts are normal.

Front derailer adjustment can be a bit fiddly. Shimano usually ships FD's with a plastic block
holding the mechanism open, and a transparent plastic overlay showing ideal gap from the derailer
edge to the teeth on the largest ring. The gap should be very small (~1 mm if I recall), you can use
anything to hold the mechanism open (I use a marker pen). It sounds like your FD isn't moving far
enough inward when you shift down to the smallest chainring. This could be because: the edge of the
derailer isn't parallel with the chainring, the derailer is a bit too high, the limit screw is
limiting inward travel too much, the BB axle is a little too long for your tubing size, etc. If the
derailer is aligned properly, and the limit screw is set properly, I've found that rotating the FD
slightly, so that the rearmost part of the cage angles in toward the frame a small amount, will give
the slight nudge needed to downshift into the smallest ring. You'll get a little more rub in cross
gears, but that's usually an OK tradeoff.
 
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Mikeyankee

Guest
Here are three things to try:

(1) Check that cable is free to move, cable housing lubricated, no burrs or kinks in cable, etc.

(2) Loosen the FD's inner stop in 1/4-turn increments so that the cage moves closer to the seat
tube. See if this helps.

(3) Height adjustment of Shimano front derailleurs seems to me to be trickier than Campy, though I
base this on experience with road doubles only. Anyhow, I find the Shimano FD's work better a
wee bit higher above the chain. I use a popsicle stick as a gauge. Put the FD on the middle ring
(I use the inner ring on a double), lay the popsicle stick along the chain rollers, lengthwhise,
and set the FD cage height for a tight, almost gripping fit. That may help, though from your
description I do not think there's anything wrong with the FD height.

Mike Yankee

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Mikeyankee

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Clarification:

To use the popsicle stick as a gauge, place it lengthwise along the chain rollers and SIDEWAYS (not
flat) so that you are measuring ~9 mm from the chain rollers to the to bar of the FD cage. This
gives a couple of millimeters more clearance than Shimano specifies, and it works better for me.

Mike Yankee

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Mikeyankee

Guest
FURTHER CLARIFICATION:

Put chain on BIG RING; rear on second largest cog. Apologies to all for today's brain farts! The
correctly edited procedure is below:

>Height adjustment of Shimano front derailleurs seems to me to be trickier
than Campy, though I base this on experience with road doubles only. Anyhow, I find the Shimano FD's
work better a wee bit higher above the chain. I use a popsicle stick as a gauge. Put the FD on the
BIG RING and the RD on the second-largest cog. Lay the popsicle stick along the chain rollers, using
its 9 mm width to set the FD clearance above the chain rollers (not the side plates, which are
higher). Aim for a tight, almost gripping fit.

Mike Yankee

(Address is munged to thwart spammers. To reply, delete everything after "com".)
 
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Matt O'Toole

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"MikeYankee" <[email protected]> wrote in message
news:[email protected]...

> FURTHER CLARIFICATION:
>
> Put chain on BIG RING; rear on second largest cog. Apologies to all for today's brain farts! The
> correctly edited procedure is below:
>
> >Height adjustment of Shimano front derailleurs seems to me to be trickier
> than Campy, though I base this on experience with road doubles only. Anyhow,
I
> find the Shimano FD's work better a wee bit higher above the chain. I use a popsicle stick as a
> gauge. Put the FD on the BIG RING and the RD on the second-largest cog. Lay the popsicle stick
> along the chain rollers, using its 9 mm width to set the FD clearance above the chain rollers (not
> the side plates, which are higher). Aim for a tight, almost gripping fit.

I haven't tried this. I've always found that with my XT derailer, getting it as close to the
chainring as possible improves shifting. I get the best results when I lower it until it rubs, then
back off just enough. But maybe I'm going too far. I'll give your technique a try.

I have problems shifting both ways, on and off the big chainring. If the derailer isn't really low,
it won't shift up. But it has trouble pulling the chain down to the middle ring unless there's
virtually no tension on it. This sucks for last minute shifts on hills, one of the great benefits of
modern drivetrains. OTOH, the chain won't stay on the big ring if I'm more than 4 cogs over at the
rear. I attribute all this nonsense to my oversized seat tube, and long BB axle needed because of
it. Also, these front derailers are sloppy to begin with, and they wear out. I'm on my third one.
Not like the ones from 10 years ago...

Anyway, thanks for the pointer. I'll give it a try. Corrections and suggestions are welcome.

Matt O.
 
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Casimir Mazik

Guest
Thanks to all. The FD height was very close and did not need adjustment. The rotation also was
correct. I did play with the L limit, but that did not make a difference. The cable barrel
adjustment did correct the shifting a lot even though I moved it very little. I see what you mean
that adjusting the FD is finicky. All the shifts are now immediate, except the middle to innermost
sprocket which takes a quarter crank of the pedal. That is very acceptable compared to what it was.
 
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