Revoshift gear changes

in message <[email hidden]>, Zill

(') said:

My last bike, several decades ago, had Sturmey Archer 3-speed hub gears!

I have now bought a new 18-speed bike with Shimano gears and Revoshift
grip-shifters. The right-hand shifter has six numbers corresponding to
the six back gears but the left-hand shifter has 12 marks and indents
from L to H. As the crank chainring has three gears, I expected the
shifter to have three positions.

Can anyone confirm that it is "normal" for these shifters to have more
positions than there are gears.

It's not 'normal' for Shimano shifters to have more positions than there
are gears, and consequently most Shimano derailleur gear systems
continually rub on the front changer when using the largest or smallest
sprockets on the cassette. It's good to see that Shimano are learning.

The 'extra' positions, which SRAM and Campagnolo systems have always had,
allow the front changer to be 'trimmed', avoiding this rubbing problem.

Quoted message said:

It seems to be quite difficult to change
to the middle crank chainring without any clear indication on the
shifter. I also find that I have to move the shifter one way or the other
to minimise noise from the chain rubbing the chain guide, depending on
the
rear gear in use. Is this the reason for not giving three clearly
defined positions?

Precisely.

Quoted message said:

Any info to this newbie gratefully received, including the best way to
change up and down the gears - I realise I shouldn't use the "extreme"
gears but what is the best sequence up and down?

Depends largely on ratios. Best general advice, at least until you've got
comfortable with the system, is stay in the middle ring at the front
whenever possible, changing up to the larger or down to the smaller only
when you run out of ratios on the middle.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; I can't work yanks out......
;; Why do they frown upon sex yet relish violence?
;; Deep Fried Lettuce

In article <[email hidden]>
Zill <[email hidden]> wrote:
<snip>

Quoted message said:

Can anyone confirm that it is "normal" for these shifters to have more
positions than there are gears. It seems to be quite difficult to change
to the middle crank chainring without any clear indication on the shifter.

You just have to get used to the feel of it - back in the good old days
we didn't have indexed shifting but we managed just fine "by ear".

Quoted message said:

I also find that I have to move the shifter one way or the other to
minimise noise from the chain rubbing the chain guide, depending on the
rear gear in use. Is this the reason for not giving three clearly defined
positions?

Yes.

Quoted message said:

Any info to this newbie gratefully received, including the best way to
change up and down the gears - I realise I shouldn't use the "extreme"
gears

Quite right - the big front ring shouldn't be used with the biggest rear
sprocket (or two), and the small front ring shouldn't be used with the
smallest rear sprocket (or two), the middle front ring should be OK with
all the rear sprockets although it may be better to avoid using the
largest and smallest rear sprockets. The straighter the chainline (i.e.
the more nearly it is parallel to the longitudinal axis of the bike) the
less lateral stress there is on the chain, using the smaller front
chainrings puts more longitudinal stress on the chain. Keep the chain
clean and well lubricated and it will last longer, replace it before
it's badly worn and the rest of the gear system will last longer.

Quoted message said:

but what is the best sequence up and down?

There isn't really a sequence, as there's considerable overlap in the
range provided by each of the front chainrings. Depending on the sort
of riding you do you can probably spend most of your time on the middle
chainring and fine-tune with the rear shifter. If you want to go faster
downhill shift to the big front ring, if you want to go easily uphill
shift to the small front ring - just use whatever combination is
comfortable, subject to the chain wear 'rules' above.

When approaching a hill or stopping it's best to get into a lower gear
sooner rather than later, to avoid crunchy gearshifts or being stuck in
too high a gear. Don't back-pedal more than you need to e.g. to align
the pedals when starting - derailleur systems can object to this by
throwing the chain onto a different sprocket.

On Sun, 01 Oct 2006 16:27:47 +0100, Rob Morley wrote:

<snip>

Quoted message said:

There isn't really a sequence, as there's considerable overlap in the
range provided by each of the front chainrings. Depending on the sort
of riding you do you can probably spend most of your time on the middle
chainring and fine-tune with the rear shifter. If you want to go faster
downhill shift to the big front ring, if you want to go easily uphill
shift to the small front ring - just use whatever combination is
comfortable, subject to the chain wear 'rules' above.

When approaching a hill or stopping it's best to get into a lower gear
sooner rather than later, to avoid crunchy gearshifts or being stuck in
too high a gear. Don't back-pedal more than you need to e.g. to align
the pedals when starting - derailleur systems can object to this by
throwing the chain onto a different sprocket.

Many thanks for the practical advice Rob. I thought I had figured out the
general principles but it is great to have confirmation from an expert :-)

One other query is that I seem to be able to change the front chainring
from the smallest to the largest but cannot go direct to the middle ring -
I have to go to the largest then back again. Is this normal or just my
finger trouble?

Zill said:

One other query is that I seem to be able to change the front
chainring from the smallest to the largest but cannot go direct to
the middle ring - I have to go to the largest then back again. Is
this normal or just my finger trouble?

Finger trouble. You'll find that you need to fractionally over-shoot the
position to get the chain to lift, then relax back a tad once the chain has
been picked up by the teeth. Easing the pedal pressure (so bike is almost
freewheeling), but still keeping the pedals going round, may help with
smooth gear shifts.

Its more difficult for the chain to be picked up from the smaller rings to
the larger. Hence the problem in one direction. Its relatively easy to knock
the chain off a larger ring and have it land on a smaller one.

Some gear shifters (eg. those with push levers) include a slight over-shoot
on the left (front) changer to help with this problem. Another trick some
makers include are various ramps, pins, and notches in the gear rings to
help with the gear change.

- Nigel

--
Nigel Cliffe,
Webmaster at http://www.2mm.org.uk/

In message <[email hidden]>

Zill said:

One other query is that I seem to be able to change the front chainring
from the smallest to the largest but cannot go direct to the middle ring -
I have to go to the largest then back again. Is this normal or just my
finger trouble?

Definitely NOT normal. Try fine tuning the angle and height of the
derallier mech or as it is new take it back to the shop and let them get it
right.

--
CTC Right to Ride Representative for Richmond upon Thames

In article <[email hidden]>
Zill <[email hidden]> wrote:
<snip>

Quoted message said:

One other query is that I seem to be able to change the front chainring
from the smallest to the largest but cannot go direct to the middle ring -
I have to go to the largest then back again. Is this normal or just my
finger trouble?

It could be that you haven't got used to the 'feel' of shifting - you
need to push the chain enough to make it climb, but not so much that it
climbs too far. If you're pedalling too hard when shifting up, the
chain can tend to slip and jump back down rather than climbing cleanly,
so make sure that you're pedalling fairly fast and smoothly but without
much pressure to avoid this. It's probably best to shift down a couple
of clicks with the rear derailleur before shifting up with the front
derailleur. Of course it's possible that the front derailleur isn't
correctly adjusted, but it's quite likely a question of technique.

On Sun, 01 Oct 2006 15:59:05 +0100, Zill wrote:

<snip>

Quoted message said:

Any info to this newbie gratefully received, including the best way to
change up and down the gears - I realise I shouldn't use the "extreme"
gears but what is the best sequence up and down?

Many thanks for all the informative replies gents. I now understand my
new bike a lot better!
All I have to do now is to learn how to apply all this knowledge to making
smooth and quiet gear changes :-)