Damping Adjustment affecting Gear Shifting ?

David said:

I have a full-sus bike fitted with a Rockshox SID Rear damping
adjustment. I havent touch any of the setting on this shock until a
couple of weeks ago when I put some more air in both the pos and neg
chambers. Unfortunately since "about that time" the bike seems to jump
between small rear cogs: about 6-7 of 9 when the large front cog is
engaged.

Sounds like the indexing is slightly out -- could be that the cable has
stretched a bit. How long have you had the bike and have you ever had the
gear cable re-tightened? Just coincidence that it became apparent at the
same time as your sus adjustment.

David said:

I have a full-sus bike fitted with a Rockshox SID Rear damping
adjustment. I havent touch any of the setting on this shock until a
couple of weeks ago when I put some more air in both the pos and neg
chambers. Unfortunately since "about that time" the bike seems to jump
between small rear cogs: about 6-7 of 9 when the large front cog is
engaged.

There is a red knob for damping adjustment which I dont recall
touching but it appears to be set to minimal damping.

Another behaviour I have noticed is the loss of power and more "slack"
in the pedals when I am riding.

I try adjusting the damping when I next go out, I am curious: are the
two problems likely to be related to the suspension setup ?

Any help appreciated.
Dave

Check the length of the cable housings between the main frame and rear
triangle. I have come across situations where they are marginally too
short for full travel which results in ghost shifts when it approaches
and leaves full travel. Its just possible that your damping adjustment
has extended the travel range and exposed the problem. OTOH it could be
coincidence.

Tony

in message <[email hidden]>, David

(') said:

I have a full-sus bike fitted with a Rockshox SID Rear damping
adjustment. I havent touch any of the setting on this shock until a
couple of weeks ago when I put some more air in both the pos and neg
chambers. Unfortunately since "about that time" the bike seems to jump
between small rear cogs: about 6-7 of 9 when the large front cog is
engaged.

There is a red knob for damping adjustment which I dont recall
touching but it appears to be set to minimal damping.

Another behaviour I have noticed is the loss of power and more "slack"
in the pedals when I am riding.

I try adjusting the damping when I next go out, I am curious: are the
two problems likely to be related to the suspension setup ?

The gear problem is unlikely to be related, except if the cable outer of
your gear cable is too short and is pulling tight at some point in the
suspension travel. Loss of power is highly likely to be related. An
underdamped rear shock will tend to bob badly when you're pedalling,
and that will result in loss of power - essentially your pedalling
effort is going into compressing the suspension.

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

;; Woz: 'All the best people in life seem to like LINUX.'
;; <URL:http://www.woz.org/woz/cresponses/response03.html>

Simon Brooke said:

The gear problem is unlikely to be related, except if the cable outer of
your gear cable is too short and is pulling tight at some point in the
suspension travel. Loss of power is highly likely to be related. An
underdamped rear shock will tend to bob badly when you're pedalling,
and that will result in loss of power - essentially your pedalling
effort is going into compressing the suspension.

....which will be returned on the suspension rebound. If not you would
expect you shock to get rather warm disippating all that lost pedalling
energy.

Tony

Tony Raven said:

Simon Brooke said:

The gear problem is unlikely to be related, except if the cable outer of
your gear cable is too short and is pulling tight at some point in the
suspension travel. Loss of power is highly likely to be related. An
underdamped rear shock will tend to bob badly when you're pedalling,
and that will result in loss of power - essentially your pedalling
effort is going into compressing the suspension.

...which will be returned on the suspension rebound. If not you would
expect you shock to get rather warm disippating all that lost pedalling
energy.

Tony

Dear Tony,

If some power is going into bouncing the bicycle and rider
up and down, doesn't that subtract from the power available
for moving it forward?

And don't shock absorbers warm up with constant action? The
damping units are usually good at radiating the heat, but if
a shock could somehow be insulated, wouldn't the temperature
rise as damping fluid was forced back and forth rapidly
under pressure?

That is, even if power is returned when a spring is
compressed and then released, doesn't the spring heat up?

Carl Fogel

Quoted message said:

Tony Raven said:

Simon Brooke said:

The gear problem is unlikely to be related, except if the cable outer of
your gear cable is too short and is pulling tight at some point in the
suspension travel. Loss of power is highly likely to be related. An
underdamped rear shock will tend to bob badly when you're pedalling,
and that will result in loss of power - essentially your pedalling
effort is going into compressing the suspension.

...which will be returned on the suspension rebound. If not you would
expect you shock to get rather warm disippating all that lost pedalling
energy.

Tony

Dear Tony,

If some power is going into bouncing the bicycle and rider
up and down, doesn't that subtract from the power available
for moving it forward?

But the rider and bike bounce up and down less on bumps than they
would without suspension, so the real question is whether the path is
bumpy enough that the efficiency of nonmotion of the rider is greater
than the losses due to bobbing/damping, etc.

Quoted message said:

And don't shock absorbers warm up with constant action?

Ride and see. Mine doesn't get warm enough to notice.

Quoted message said:

The
damping units are usually good at radiating the heat, but if
a shock could somehow be insulated, wouldn't the temperature
rise as damping fluid was forced back and forth rapidly
under pressure?

In theory, yes, but this isn't a theoretical world.

Quoted message said:

That is, even if power is returned when a spring is
compressed and then released, doesn't the spring heat up?

Not enough that you could measure it. Most springs are *very*
efficient.

The laws of thermodynamics do not state that their application always
produces a significant result.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Quoted message said:

The gear problem is unlikely to be related, except if the cable outer of
your gear cable is too short and is pulling tight at some point in the
suspension travel. Loss of power is highly likely to be related. An
underdamped rear shock will tend to bob badly when you're pedalling,
and that will result in loss of power - essentially your pedalling
effort is going into compressing the suspension.

Thanks for the help, with the damping now set correctly the loss of
power problem seems reduced, and the gear skipping still happens,
although less frequently.
Dave