Some Gearing/Front Mech Questions

Callaghan said:

If I ran 40/30 or similar (double) chainrings on my road bike -- what
should I look out for when purchasing a double front mech? Is this range a
special circumstance when choosing? Can I have reasonable shifting
performance in a setup like this?

Need a front mech that
-matches or is close to the arc of the big chainring and
-is compatible with the left/front shifter.

Remember that triple road FDs move the chain from a 30/39(shimano), a
7800, 6600 or 10s 105 would probably work fine.

Quoted message said:

At present I have Suntour X-1 front mech, Sugino Fuse 500 chainset with
46/36/26 and Shimano barcons. I never use the 46 and hardly ever use the
26. I don't pedal down hills very often but I don't mind getting out of
the saddle to pedal up them.

The cassette is 11-30 but I'd /prefer/ closer ratios with a block in the
range of 14 - 26 or the like. I'm usually cruising in 36 x 16 with a
cadence of about 80rpm.

Also, can I convert my Sugino triple to accommodate?

I've never done this type of adjustment so any advice will be gratefully
received. Perhaps you're running a similar setup?
--
Callaghan

Callaghan said:

If I ran 40/30 or similar (double) chainrings on my road bike -- what
should I look out for when purchasing a double front mech? Is this range a
special circumstance when choosing? Can I have reasonable shifting
performance in a setup like this?

At present I have Suntour X-1 front mech, Sugino Fuse 500 chainset with
46/36/26 and Shimano barcons. I never use the 46 and hardly ever use the
26. I don't pedal down hills very often but I don't mind getting out of
the saddle to pedal up them.

The cassette is 11-30 but I'd /prefer/ closer ratios with a block in the
range of 14 - 26 or the like. I'm usually cruising in 36 x 16 with a
cadence of about 80rpm.

Also, can I convert my Sugino triple to accommodate?

I've never done this type of adjustment so any advice will be gratefully
received. Perhaps you're running a similar setup?
--
Callaghan

One thing to watch out for is the tail of the front mech cage hitting
the frame. For example, I installed a mountain bike triple (42T big
ring) on my cyclocross bike, and the Shimano 105 front derailleur hit
the frame's chain stay before the cage was low enough to be within 3 mm
of the teeth.

dianne_1234 said:

Callaghan said:

If I ran 40/30 or similar (double) chainrings on my road bike -- what
should I look out for when purchasing a double front mech? Is this range a
special circumstance when choosing? Can I have reasonable shifting
performance in a setup like this?

I currently use 46/30 front rings, and a (about) 1985 Campy front
derailleur. It works fine. You do have to be careful to adjust the front
derailleur carefully (keep the top within a couple millimeters of the
big ring; enough to clear the ring in all positions, but the tighter it
is the better the shifting will be. I have no idea how this will work
with Shimano (indexed) front shifting, but with Campy, which is (was?) not
indexed in the front, it works well.

Quoted message said:

Quoted message said:

The cassette is 11-30 but I'd /prefer/ closer ratios with a block in
the range of 14 - 26 or the like. I'm usually cruising in 36 x 16 with
a cadence of about 80rpm.

You might as well go a bit larger on the large ring, since the difference
between a 40/30 front and your 14-26 rear, versus a, say, 46/30 front
with that same cassette, --- the difference will only be that you have
more repeated gears with the 40/30, plus of course having a lower top
gear. You basically gain nothing.

Quoted message said:

Quoted message said:

Also, can I convert my Sugino triple to accommodate?

I have a Sugino 94/58 "compact" mountain bike crankset. I suppose yours
is a 110/74 since they are more common on road bikes. This can be turned
into a 40/30 (or 46/30) double, using the middle and granny positions.
Finding a 30-tooth inner ring will take some searching, but the 40 outer
ring should be no problem.

--

David L. Johnson

__o | Let's not escape into mathematics. Let's stay with reality. --
_`\(,_ | Michael Crichton
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