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Bouncy back end? Handling all gone to bollocks? You need a new
rear shock ...
Original manufacturers' shocks on all but the most expensive bikes
are necessarily built down to a price. After a few years and thousands
of miles they lose damping and most are not rebuildable. Many do
not offer enough compression damping, causing the bike to sit down
when exiting corners. This makes the front feel light and twitchy
on bumpy roads. So a good quality replacement shock can offer real
advantages to the bike's handling, particularly if your present
OE shock is shot!
The aftermarket shock range is dominated by Ohlins, White Power
(WP nowadays), Maxton and, increasingly, Penske. Prices range from
£450 or so for the more basic typres to £800 plus for
the full house multi adjustable stuff with ride height adjustment
and hydraulic preload.
Any shock you fit should be sprung for your body weight, and the
basic adjustment needed is compression, rebound and spring preload.
This is enough to enable you to set up the shock for your riding.
More expensive models offer variable rate adjustment where the high
speed and low speed compression damping can be adjusted separately.
High speed damping is controlled by the bypass valve or blow-off
rate of the shims, and low speed damping by the shim stacks.
Spend more money and you get variable length, so you can adjust
the ride height, and hydraulic preload. Ride height adjustment is
useful, but hydraulic preload is unnecessary - although it does
look trick! Some argue that it's useful if you regularly carry a
pillion, but as the spring rate is then all wrong it's not really
a viable argument.
WP do two basic configurations, a road shock and a more
adjustable race shock.
3612 / 4681 SA shock
Rebound damping adjustable in 11 positions
Compression damping adjustable in 7 positions.
Spring pre-load continuously adjustable (hydraulic adjuster optional)
Shock absorber body contains an oil/nitrogen mixture - nitrogen
reservoir to separate oil from the nitrogen
WP 4618 high performance shock
Available for supersports bikes such as the R1, Blade etc., this
shock has both high and low speed compression damping and ride height
adjustment.
Rebound damping adjustment in 35 positions
Compression damping low speed in 24 positions, high speed continuously
adjustable
Spring pre-load continuously adjustable (hydraulic adjuster optional)
Axial spring bearing
Standard with adjustable length.
 Ohlins
offer a wide range of shocks depending on the type of bike and the
intended use. The types offered are:
Type E:
An emulsion shock absorber where oil and gas are mixed in the main
body. Used on small, light bikes and where space is too limited
for a type P. Performance degrades rapidly with heat.
Type D:
A De Carbon based shock with internal reservoir and dividing piston
built into the main body. The damping oil is placed under pressure
by gas and separated from the gas by a floating piston. Improved
cooling gives more consistant damping and longer damper life.
Type P:
De carbon with external piggyback reservoir and dividing piston.
The reservoir is an extension of the shock absorber. More oil and
larger cooling areas improve performance and durability.
Type H:
De Carbon shock with hose mounted reservoir and dividing piston.
The remote reservoir stays much cooler to give improved performance
and durability under more extreme conditions.
Features, depending on model (and price!) include:
Adjustable compression damping - adjuster wheel on reservoir
Adjustable rebound damping - on piston shaft above end eye
Hose mounted hydraulic spring preload adjuster
Integrated hydraulic spring preload adjuster on shock body
Adjustable length
Separate adjusters for high and low speed compression damping.
Penske 8900 Series
The 8900 series shock is completely owner rebuildable and revalvable
if required. Integral reservoir contains increased nitrogen volume
for more consistent damping over a long duration.
Fully CNC machined 7076 - T6 aluminium, no castings.
Hard anodised finish, making the unit both lightweight and strong.
Completely hand built and dyno tested.
Heavy duty 5/8" diamter chrome plated stainless steel shaft.
The best spring available matched to your weight.
Adjustable spring preload.
Low friction/stiction shaft bearing and high quality seals and wiper.
Adjustable length eyelet, tune for the set up you need.
25 click rebound adjuster for extra fine rebound settings.
Three Choices For Compression Adjustment
8981 - 6 click compression range. Proven performance.
8986 - 10 click compression range. Step-up to a smoother ride.
8987 - Independent high and low speed compression damping.
Maxton
Maxton have been building road and race shocks for donkeys' years.
They are based on Koni units but modded to suit customers' requirements.
Their units are fully adjustable via a shim stack system and has
a spring to suit rider weight. They basically do two types. Both
are full adjustable for compression, rebound and preload but the
more expensive (£560) type has a second compression damping
adjuster to give variable high and low speed damping.
A big advantage buying Maxton is the fact that they are built locally
in the UK, so any rebuilds or modifications should be easy to obtain.
Having said that, there are many good suppliers who undertake full
servicing and setting up of their supplied shocks so it should never
be a real problem.
 All
shocks should come with a spring suited to your weight and with
basic settings. After that you can tweak away to your own requirements.
Life is easier if the adjusters have decent knobs rather than fiddly
screws.
 This
WP unit for the R1 has concentric knobs, one each for high and low
speed compression damping. At the base is a chunky adjuster for
rebound - easy for quick adjustment on the road without having to
rummage about in the toolkit for a screwdriver.
Which one to buy? It's your choice. Talk to the suppliers and check
with anyone you know who already runs a replacement shock. Remember,
set-up advice is important so choose a supplier who can offer you
good backup and knows what he's talking about. If you go to club
races talk to racers in the paddock - they can give invaluable advice.
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Treated
the R1 to a new shock - the old OEM one has done nearly 30,000 miles
and has lost any semblance of meaningful damping.