Forks - How are they adjustable

I am sure I am not alone in being confused about the setup and
adjustment of front forks. I Have some Rockshox SID XC front forks
which I can pump up to-taste with my little high pressure pump.

My question is, I see that other forks have a red switch on the top
which allow "lock-out" which I presume stops them being effective. Is
this an On/Off thing or do forks exist with variable lock-out ?

Some guy in the shop mentioned forks with a variable rebound
adjustment too. I'm not sure whether this is desirable or just OTT ?

Any help appreciated,
Dave

"David" wrote in message
om...

My question is, I see that other forks have a red switch on the top
which allow "lock-out" which I presume stops them being effective. Is
this an On/Off thing or do forks exist with variable lock-out ?

Some forks may have a complete lock-out that does exactly that. Others,
Marzocchi f'rinstance, have a sort of semi lock-out that once engaged allows
about 30mm of travel, IIRC, but at a lower ride height, a good thing IMO.
My Duke U-Turns have adjustatble travel, 63-105mm great for lowering the
front end for climbing and of course being able to increase the travel for
descents not only increases bump absorbsion but also raises the front end
for a more confidence inspiring position.

Some guy in the shop mentioned forks with a variable rebound
adjustment too. I'm not sure whether this is desirable or just OTT ?

Pretty common, if the fork has no rebound damping it will pogo, too much and
it will stack up and cease working, having adjustment allows you to tune it
for your weight, riding style and the terrain.

Pete

in message , David
') wrote:

I am sure I am not alone in being confused about the setup and
adjustment of front forks. I Have some Rockshox SID XC front forks
which I can pump up to-taste with my little high pressure pump.

My question is, I see that other forks have a red switch on the top
which allow "lock-out" which I presume stops them being effective. Is
this an On/Off thing or do forks exist with variable lock-out ?

Some guy in the shop mentioned forks with a variable rebound
adjustment too. I'm not sure whether this is desirable or just OTT ?

Different suspension units (this includes suspension forks, but also
rear shocks) have different adjustments and on the whole more is better
provided the mechanics are adequately sorted. Essentially the problem
is that the rider makes up a very significant proportion of the total
weight (unlike motor vehicles where the passengers are usually at most
a third of the total weight). Consequently, one suspension setting will
not suit all riders, irrespective of what conditions they ride, and
different riding conditions may merit different tuning as well.

As you've noted you can alter the spring rate of air suspension just by
pumping it up. So you can make it more or less plush without bottoming
out under your weight. If you have spring forks instead of air ones,
it's sometimes possible to change the preload on the spring and to
adjust the spring travel, but to change the spring rate you have to
actually take the whole spring out and replace it with one of a
different rate. With oil damped forks you can adjust the damping either
by opening or closing the apertures in the damper through which the oil
is forced (the usual way on adjustable forks) or by changing the
viscosity of the oil. Some sophisticated suspension units have a
pressurised air chamber on each side of the piston, and this is where
the adjustable rebound comes in. And there are variants on stable
platform valves, which are damping valves which open differently for
different speeds of suspension movement, and (if fitted) these are
usually tunable too. Finally as you note there's lockout, which is
useful if you're riding on tarmac as on good surfaces long-travel
suspension tends to bob a bit and actually hold you back.

General advice is to pressurise the system so that with you just sitting
on the bike, not moving, the suspension compresses about a quarter of
its total travel (this is called 'sag'). To adjust damping/rebound,
find a smooth road with a sleeping policeman (ideal) or kerb (OK
provided your tyres are hard enough). Pedal up to your normal riding
speed and then go over the obstruction not pedalling and sitting as
still as possible. If the suspension smoothly returns to its normal
'sag' position after the obstruction that's ideal. If it overshoots and
bounces around its sag position for a few bounces before settling down
you need more damping. If it doesn't make it back to its sag position
then you need less damping, or else you need to service your seals and
bushes.

I should say that having serviced some cheaper forks with lots of
adjustments I'm pretty unimpressed with the mechanical construction.
While I said above more adjustment is better because you can tune the
forks to your weight and riding style, it's not better if it isn't
robust enough to do the job. Good forks are expensive to make and
involve a lot of precision engineering, so don't buy a cheap fork with
lots of knobs to twiddle.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/

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In article , says...
Seems to make sense to me, though I'm amazed to discover that there's
such a thing as remote lockout. Does anyone know is this a mechanical
thing or is it electronic? Bet it's a pricey bit of kit either way.

Amusingly, a fork with exactly this ability was mentioned in another
thread recently. It's the Manitou Nixon and has a lockout switch on the
handlebars. I don't know the price but if you Google for it, you'll find
more information.

Jon

David wrote:
My question is, I see that other forks have a red switch on the top
which allow "lock-out" which I presume stops them being effective. Is
this an On/Off thing or do forks exist with variable lock-out ?

Funnily enough, they brought this up in the commentary in the men's
olympic cross country this morning. Apparently, the French rider they
were talking about, Absalon, has a switch on the end of his bars that
operates the fork lockout - the idea is that for the parts of the course
where bouncy suspension would be a hindrance, he locks the forks and
rides rigid.

Seems to make sense to me, though I'm amazed to discover that there's
such a thing as remote lockout. Does anyone know is this a mechanical
thing or is it electronic? Bet it's a pricey bit of kit either way.

d.

"davek" wrote in message
...

Seems to make sense to me, though I'm amazed to discover that there's
such a thing as remote lockout. Does anyone know is this a mechanical
thing or is it electronic? Bet it's a pricey bit of kit either way.

Usually a small lever, similar to a thumb shifter, that pulls a boden cable.
The cable can be made to replicate what you'd do manually by pulling a lever
or rotating a pulley.

Pete

Peter B wrote:
Usually a small lever, similar to a thumb shifter, that pulls a boden cable.
The cable can be made to replicate what you'd do manually by pulling a lever
or rotating a pulley.

Makes sense. And shows how little I know about how sus forks work.

d.

Thanks for your comprehensive answer. I have vague recollection of
physics damping rate, oscillation frequency and stuff, but I'd rather
not remember to be honest :-)

I remember when climbing up a steep hill, even with the front shock
set pretty hard it did limit my power significantly. I'm not racing so
a handlebar lockout may not be necessary, but a lockout of some sort
would be useful.

Dave

in message , davek ')
wrote:

David wrote:
My question is, I see that other forks have a red switch on the top
which allow "lock-out" which I presume stops them being effective. Is
this an On/Off thing or do forks exist with variable lock-out ?

Funnily enough, they brought this up in the commentary in the men's
olympic cross country this morning. Apparently, the French rider they
were talking about, Absalon, has a switch on the end of his bars that
operates the fork lockout - the idea is that for the parts of the
course where bouncy suspension would be a hindrance, he locks the
forks and rides rigid.

Seems to make sense to me, though I'm amazed to discover that there's
such a thing as remote lockout. Does anyone know is this a mechanical
thing or is it electronic? Bet it's a pricey bit of kit either way.

The better Cannondale Lefties have electronic remote lockout; so do some
Pace forks. Other units have cable operated remote lockout. My Jekyll
had cable operated remote lockout on the rear shock when I got it, but
seeing that it took up valuable space on the bars and when you need
lockout it's because you're on a smooth track where it's easy to reach
down to the actual lockout lever on the shock body I've taken it off.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/
.::;===r==\
/ /___||___\____
//==\- ||- | /__\( MS Windows IS an operating environment.
//____\__||___|_// \|: C++ IS an object oriented programming language.
\__/ ~~~~~~~~~ \__/ Citroen 2cv6 IS a four door family saloon.

in message , David
') wrote:

Thanks for your comprehensive answer. I have vague recollection of
physics damping rate, oscillation frequency and stuff, but I'd rather
not remember to be honest :-)

I remember when climbing up a steep hill, even with the front shock
set pretty hard it did limit my power significantly.

That's a technique problem. I know, because it's a technique problem I
used to have myself. You're climbing in too high a gear and not
spinning fast enough. Try dropping down at least two gears below where
you think you want to be and really spinning your legs. You'll find
that not only does your suspension not bob, you'll have better traction
and will get up the slope faster.

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/
Windows 95:
You, you, you! You make a grown man cry...
M. Jagger/K. Richards