Raise the forks through the yokes to drop the front end

Now suspension consists of those long bouncy things at the front which hold the wheel on and the little springy thing squeezed between the the engine and the swingarm which gets covered in crap from the back tyre.

On any half decent sports bike you've got 8 forms of adjustment in total - ride height, spring pre-load, rebound damping and compression damping front and rear. 'Course, that's 12 if you count both forks. So twiddling with any of this stuff is a trip into mystery and adventure ..

Use a suitable spacer to increase rear ride height

Ride height does what it says, changes the height the bike rides at ... which is kind of self evident but we have to make the point just to keep you awake. The most common mod is to speed up the steering by raising the front forks through the yokes, so lowering the front end, and jacking up the back end either by using a spacer between the shock top and mount or, if you've got a really posh bike, winding up the inbuilt ride-height adjuster. Normally the most you can reasonably go to is 10mm each end. Raising the rear will also help ground clearance. It won't turn an old R1 into a K5 but it will help the steering turn-in a little bit better.

Alloy collar above spring screws down to increase preload

Spring pre-load determines the amount of static sag and the shock will either have a screw collar for adjustment or a posh remote hydraulic twiddler. An easy way to check this is to park the bike on its sidestand, then simply rock the bike and watch what happens to the suspension. If it compresses noticeably as it comes upright then time for a proper check.

Get someone to hold the bike upright and measure the distance from the axles to a mark somewhere above on the chassis. Then lift each end in turn and measure between the same points. Now sit on the bike and do it again. If you're a quick rider you want only minimal sag, perhaps 10 mm at the rear and no more than 25 mm at the front. Too much and the bike will get very unsettled over uneven roads at high speeds.

The little screw does the rebound and the silver nut does spring preload

Rebound damping, adjusted by the little screws at the top of the forks and the screw or knob on the bottom of the rear shock. Start by backing all the screws out and then do a static test, bouncing the bike up and down and increasing rebound until you can feel some resistance as the springs unload. Now go for a ride. If the front bobbles as you come off the brakes or weaves about as you bounce out of small dips you need to increase rebound at the front until this goes. If the back end weaves about as you power through bends then increase rear rebound. Keep fiddling until the bikes feels stable. Go too far and the tyres will have to help the suspension too much as it fails to recover quickly enough from the last bump and pumps down - then you'll start to lose grip.

Knurled knob at top adjusts compression on rear shock

Compression damping - probably the hardest one to get a feel for. Adjustment is by the little screws at the bottom of each fork leg and either a screw on the shock top or the knob on the remote gas reservoir. Too much fork dive under braking and a loose feel when suddenly tipping into a corner indicates insufficient from compression damping. A slappy front end when accelerating hard means the rear shock is compressing too much, so unloading the front - increase rear compression. A loose feeling from the back when powering though bends also indicates insufficient rear compression damping. The end result is a very personal thing, as it's a compromise between bone-jarring accuracy of line and luxomatic plushness with 'orrible vague handling.

Projecting screw on the bottom of the fork leg adjusts compression

Don't be afraid to experiment hugely with the suspension settings. If you're a scaredy-cat note down your original settings on a piece of paper and stick it on your fridge. If you've never fiddled properly with all those little screws and spring collars you'll be amazed how much you can change the feel of your bike. And you can create some proper set-ups for track use - rather than wallowing about in the slow group you will be Mr. Getoutamyway in the fast lot! At the end of the day you can simply return your suspension to pot-holed crap British roads settings and wallow homeward in perfect comfort, but this time with nicely re-profiled footpegs and end can and thoughts of rearsets for more ground clearance ....

Regular twiddling will also keep your bike handling as best it can. All of us are guilty of getting good settings and then forgetting them for ages. Then we ride a new bike and think "Blimey, this is sharp". So immediately we start adjusting our own bike and bingo ... mega sharp handling again, as we compensate for wear and tear on springs, damping oil, etc. If your bike's a few years old it's worth changing the fork oil and seals. If the rear shock is showing its age it's probably best replacing with Ohlins, WP, Penske or whatever takes your fancy rather than going for a rebuild - many factory shocks aren't rebuildable anyway. Trouble is, the front end will then be letting you down as standard production forks are often built way down to a price, and valving can be suspect. You don't necessarily need to buy new forks, but replacing the internals with K-Tech kit can improve control and the cost of the bits you need should not be much more than £200 plus fitting.

A word on high and low speed damping. Bang though a bloody great pothole in the road and wham!, the suspension has to blow oil fast to allow a sudden large amount of spring movement to absorb the shock. Basically the shim stacks lift and allow the oil to flow through bypass holes - this is high speed damping, which often happens when you're travelling slowly.... Now you're belting along a good road with some cracking dips and rises, compressing the suspension by fine degrees, the oil flow controlled by the shims. This is low speed damping in action, even though you're going quickly the suspension is moving relatively slowly to absorb the rise and fall of the bike as the loading changes.

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 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.

I treated my old 2000 R1 to a new shock - the old OEM one has done nearly 30,000 miles and has lost any semblance of meaningful damping.

On the advice of Darren Wnukoski of Motorcycle Technics I bought a WP 4618 - he reckons this is tops for the R1. The main benefit from my viewpoint was no dangly bits to find a home for, the reservoir being mounted on the shock body, and adjustable high speed compression damping - useful on bumpy back roads.

The WP has made a huge difference to the stability of the bike. It no longer bucks and weaves its way out of bends but tracks like a thing that tracks very well. The WP unit is good at soaking up the bumps as well as transforming the bike's handling. If in doubt, listen to Darren - he knows what he's talking about.

Tet had a quick go on the R1 and was so impressed he has fitted a WP to his Blade ...

Upside down forks are very sensitive to variations in oil level. The level does not have much affect in the early stage of fork travel but increases as the forks compress. When the oil level is lowered the 'air spring' in the latter half of travel is lessened, thus the forks are softer. Manufacturers normally quote their recommended air gap, the distance between the top of the fork stanchion and the oil surface. Usually this is in the range 80mm to 110mm with the spring removed and the fork fully compressed, although Ohlins forks are measured with the spring in place.

The above diagram shows the relationship between the fork offset, trail and castor, the latter two often quoted in bike road tests in magazines. These determine the level of resistance to turning the forks from the straight ahead position and the stability of the steering in its steady state. With telescopic forks, everything changes when you hit the brakes, as the steering head dives down, shortening the forks and reducing the castor and trail and also the wheelbase of the bike. This effectively quickens up the steering, helping the bike to turn, but unsettling the front when the suspension unloads on release of the brakes. For fast road and track riding, fork dive is minimised by stronger springs and increased compression damping, while increased rebound damping helps control the change in attitude when the brakes are released.

If you really get into suspension tweaking you will meet such fascinating mysteries as air gaps, linear versus progressive springs, oil viscosity, shim stacks, etc. etc. Learn enough about all this stuff and you can phone up Ron Williams and tell him why he set your forks up all wrong! Yup, you too can fine tune your compression damping by decreasing your air gap by 2mm ...

If your bike looks like this then sell it and get something with adjustable suspension!

It's becoming increasingly popular to re-valve and respring standard production forks. In view of the slight vagueness of the Yamaha R1 forks we thought we'd try modding them to see what the effect was.

First stage it to buy the Ohlins kit - valves, springs and oil. Then get your hands on a spring compressor and holding plate, otherwise you'll damage the forks trying to get them apart and you'll never get 'em together again.

The basic fork components - damper cartridge is still in the stanchion.
Strange tools at the top are the spring compressor and holding plate.

Before you take the forks off the bike, back off the spring preload and loosen the cap nuts - they can be bloody tight and the yokes are a safer way of gripping than having to trap the fork tube in the jaws of a vice.

Holding plate doing its thing

Undo the fork cap and drain the oil. Using a strongish friend and the spring compressor mounted on the spacer tube, compress the spring to reveal the locknut and then slide the holding plate under the nut. Now you can remove the fork cap, spacer and spring.

Pull the main fork tube off the stanchion, taking care not to damage the dust and oil seals. It's worthwhile replacing the fork seals while the forks are stripped.

Now a slightly tricky bit. At the base of the fork leg is a recessed allen bolt which secures the cartridge. This is often a bugger to remove as the cartridge turns around with the bolt - use a hammer air drill to spin it off.

Once the bolt is off, gently withdraw the damper, covering yourself with a generous amount of fork oil in the process. Be a bit careful here, 'coz what you've now got in your hands is a very expensive bicycle pump full of oil, so start waving it about and pumping the tube in and out and you'll cover your bike, garage and helpful friend with jets of 'orrible fork oil. So point it into a drip tray and pump the oil out in a more considerate fashion.

Prize off the spring seat ring to expose the castellations so you can use a C spanner to unscrew the damper tube, holding the outer tube with the compressor gizmo, as shown in the photo on the right. Be careful to support the tube and don't bend it! There's a lot of fairly feeble light alloy here, so it's easy to damage things.

With the gizmo still in place, unscrew the compression
damping assembly from the bottom of the cartridge tube.

Withdraw the cartridge tube and you should have something which looks like the photo on the left. The rebound damping control assembly is screwed onto the end of the tube. Use the fork cap and locking nut at the other end, lock 'em up tight and then hold them while you unscrew the rebound assembly. Once it's off, the needle and spring are inserted into the tube and the new valve assembly screwed on.

On the R1 we found that the damper rod was now too long, as the needle projects much further into the tube than the original setup, so we had to trim 20mm off the rod. If you do have to shorten the rod make sure you are completely sober and measure everything at least six times before cutting.

Unscrew the retaining nut from the compression damper assembly and remove the shims and valve. Our new stuff came on a tie wrap - the components are in order and it's important to keep them in the same sequence as supplied, so make sure you don't cut the tie and then drop 'em all over the floor! Put the various shims and the valve on in the required order and secure them with the supplied locknut.

Now put everything back together and fill up with oil. We used a 110mm air gap with the spring out, but you'll have to check the best setting for your bike. Springs are 9½ pounders, but may need varying if you're a fat bugger.

Initial impressions? Damping is more progressive and the range goes right from super-plush to hard as nails, with good control of the front even on the softer settings. A blast over to Nurburg via the Ardennes and a couple of dozen laps of the 'Ring showed that the forks work well. Mind you, Scott Ingram on a bog stock '99 R1 was still quicker ... so fancy forks can't make up for crap riding!

The rebound valve on left comes assembled - the needle sits in the
cartridge tube and regulates the rebound damping. The compression
bits are in order on the tie wrap - don't get the shims out of order!

Front wheel chatters entering a corner, the problem disappearing as soon as you let the brakes off or when power is applied.
The fork is working too low in its travel.
Solution:
Apply more preload
Change to a harder spring
Reduce oil level if a tie wrap on the fork tube indicates a lot of stroke is unused
Check fork friction (stiction)
Rear ride height is too high - possibly too much spring preload. Reduce ride height.

Front wheel skips during heavy braking
Forks are bottoming out
Solution:
Increase spring stiffness
Lower oil level if a lot of stroke remains

Front end feels vague mid corner
Poor damping control
Solution:
Insufficient rebound damping - increase
If suspension feels harsh it may be too much rebound or compression damping - reduce

Front end loses grip exiting corners
Insufficent spring compliance or damping control
Solution:
Increase front rebound damping
Reduce front spring preload
Increase rear compression damping or spring rate

Unfortunately the rear shock set-up affects the behaviour of the front end in some circumstances, so there is often no easy answer to a particular handling problem. The most important thing to remember is never change more than one thing at a time .... Always test the bike after any change in the setup to see what affect it has. And make sure you note down your original settings, so if it all goes haywire you can start again from scratch.

Preload:
Preload controls ride height. It does not make the suspension harder or softer. What it does do though is alter the angle of the steering, which affects turning speed, and it also changes the weight distribution, which can affect front/rear grip.
Front Preload:
Increase it to put more weight on rear to get better rear traction, or stop the bike diving on the brakes. Too much will cause slow turning and possible front lock ups on braking.
Decrease it to get more feel from front tyre in corner. Puts more weight on front which increases front traction. Too little will cause dive bombing.
Rear Preload:
Increase it to quicken the steering. Too much will cause loss of traction as bike skips over dips in road, and can make the bike generally unstable.
Decrease it to improve stability. Too little and the bike will be slower turning and it will squat when you accelerate, leading to tank slappers.
Compression damping:
This affects the speed at which the shock can compress, under accelerating (rear) or braking (front), and also when riding over bumps. High speed damping usually operated by blowing the shim stack, allowing quick release of oil to compensate for a sudden shock like a pot-hole. Low speed damping controlled by the shims, allowing very subtle oil flow according to suspension loads.
Front Compression:
Increasing will remove some of the dive under heavy braking. Also it will increase the feedback and soak up small bumps better. Too much will cause instability, a rough ride, and it will reduce the grip available at the front.
Decreasing will smooth the ride. Too little will cause excessive front tyre loading and can have the bike standing up on the brakes mid corner.
Rear Compression:
Increase to make the bike run true and hold a line around a corner. Too much and the bike could launch you into space after a bump, and the rear tyre will lose traction on undulations.
Decrease compression to smoothen the ride. Too little will allow the bike to squat under power and run wide in corners.
Rebound damping:
This affects the speed at which a shock rebounds, which allows the wheel to return to the ground after hitting a bump.
Front Rebound:
Increase the damping to help the bike hold a line, and help front stability. Too much will gradually jack the front down as each bump compresses the front further and further. Also it will cause loss of feel and a tendency for the front to wash-out.
Decrease to help the front react to bumps, and to keep it in contact with the tarmac. Too little will decrease front stability.
Rear Rebound:
Increasing will help to stop the rear bouncing around, and the front "pushing" in corners. To much will cause front end shake and overwork the rear tyre.
Decreasing will smoothen the ride on a bumpy road, and decrease the rears tendency to step out on a bumpy corner. Too little rebound will cause running wide on corners.