Suspension Set-up Guide

Suspension setupCorrect suspension setup is the key to fast consistent laps. Setting your bike up specifically for the track is necessary if you want to go get the best out of yourself and your bike.

To what extent you change your suspension settings will depend on whether your bike will also have to cope with riding on the road. Tracks are generally smooth and grippy, roads aren’t. If you are only going to use the bike on the track you have the luxury of fitting harder springs and modifying internals. If you ride on the road as well as the track you will probably want to keep a certain comfort level and concentrate on just optimising the current equipment

With incorrect suspension setup, tyre wear is increased and handling suffers, which in turn can result in rider fatigue. Lap times can be dramatically slower and in extreme case safety can be compromised.  Hopefully the following guide will help you dial in your suspension for faster and safer riding both on and off the track.

Firstly you will need to check the Fork and Shock sag: this is the amount the forks and rear shock settle under load. To measure it do the following: push down on the forks to settle them, then mark the stanchion with a felt pen or put a cable tie where the dust seal is sitting. Next ask some for help to lift on the bars so the front wheel is just off the ground and measure the amount the forks have traveled down. This is the static sag (or unladen sag), changed by adjusting the spring preload (more preload = less sag). Repeat the same process for the rear, this time measuring the distance from the wheel spindle to a fixed point on the tail. Now you are ready to begin setting up your suspension. The key is to do it a little at a time and make notes as you go.

Basic Setup: Check the following

*

Forks sag 18-22 mm for dry track, 23-27mm for rain.
*

Shock sag 8-10mm for dry track, 10-14mm for rain.
*

Check chain alignment. If not correct, bike will crab walk and sprocket wear will be increased.
*

Proper tyre balance and pressure, starting with 30psi front and 32psi rear (either dry and wet).
*

Steering head bearings and torque specifications – if too loose, there will be head shake at high speeds.
*

Front-end alignment. Check wheel alignment with triple clamps. If out of alignment, fork geometry will be incorrect and steering will suffer.
*

Crash damage, check for proper frame geometry.

Stock Tuning Limitations

Manufacturers plan on designing a bike that works moderately well for a large section of riders and usages. To accomplish this as economically as possible, they use valving with very small venturis. These are then matched to a very basic shim stack which creates a damping curve for the given suspension component. At slower speeds this design can work moderately well, but at higher speeds, when the suspension must react more quickly, the suspension will not flow enough oil, and will experience hydraulic lock. With hydraulic lock, the fork and/or shock cannot dampen correctly and handling suffers. The solution is to re-valve the active components to gain a proper damping curve. It does not matter what components you have, (Ohlins, Fox, Kayaba, Showa), matching them to your intended use and weight will vastly improve their action. Furthermore, if you can achieve the damping curve that is needed, it does not matter what brand name is on the component. Often with stock components, when you turn the adjusters full in or out, you do not notice a difference. In part, this is due to the fact that the manufacturer has put the damping curve in an area outside of your ideal range. Also, because the valves have such small venturis, the adjuster change makes very little difference. After re-valving, the adjusters will be brought into play, and when you make an adjustment, you will be able to notice that it affects the way the way the fork or shock performs.

Another problem with stock suspension is the springs that are used. Often they are progressive, increasing the spring rate with increased compression distance. This means that the valving is correct for only one part of the spring’s travel, all other is compromise. If the factory does install a straight-rate spring, it is rarely the correct rate for the weight of the rider with gear. The solution is to install a straight-rate spring that matches the valving for the combined weight of the bike, rider and gear to the type of riding intended.

Remember!

* Always make small adjustments, more is not always better.
* Always keep notes of what you have done.
* Suspension tuning is an art – be patient

Bike Preparation Guide

race bike preparationThe following article aims at describing how to prepare a bike for use on a track. In the first part we’ll deal with preparation of a road-legal bike for a track day, and in the second part the modifications for racing.

Track day preparation

Most organisations in the UK don’t have any special requirement in terms of bike preparation, so you can get away with minimal changes. In general they are all aimed at reducing the risk of damaging other riders so all plastic/glass parts that can splinter have to be removed or covered in gaffa tape. This include:

* mirrors
* indicators
* headlight/rearlight
* number plate

This will also reduce the cost of repair in case of a minor spill. Likewise, it may be a good idea to consider removing the side panels of the fairings (if applicable) before venturing on the track.

Everything else is common sense , so check the chain is properly tensioned and lubed, brakes are working and tyres have plenty of tread left: nobody will compliment you on your crashing skills in the wet when their session is delayed or canceled because of you. Talking of brakes, it is strongly recommended to fit braided hoses at the front: although they might remove a certain degree of feel, they will greatly reduce brake fading which would spoil your enjoyment after two laps.

One final recommendation: There is now a growing trend that some circuits are subject to noise regulations. This means that race cans are out of the question, as well as standard ones if they have been tampered with: the homologation print on the exhaust is not a guarantee you’ll be allowed on the track as controls are carried via phonometers and they could check the total noise of the bike, including the clutch (heard this, Ducati boys?).

 

Race preparation – Compulsory

It is important to remember that all this info is available via the ACU and as such they are subject to change every year. The basic concepts however are always applicable.

Lockwiring – No bike is allowed on the race track without lockwiring in three key areas: sump plug, sump filler cap and oil filter. This of course only applies to 4T bikes, not 2T such as Suzuki RGV250, Yamaha TZR250 or Suzuki RG500. A lockwiring kit can be bought from a variety of sources and shouldn’t cost much more than £15.

Lockwiring the sump plug will be best achieved by emptying the sump (take it as an opportunity to replace the oil with a good fully synthetic one like Motul 3100V or Castrol R4) and lockwiring the bolt to a fixed part of the engine. You will need to drill the bolt, which might be difficult without proper tools: the local engineering shop should be able to help.

The next step, the oil filter, is a much easier job: just put a large hose clip around the filter itself and lockwire it onto a fixed part of the engine.

After refilling the engine with fresh oil, you can drill a small hole in the filler cap and tie it to something on the engine or the frame. A good idea is to use one of the tabbed washers that sometimes come with the lockwiring kit and put it under one of the engine bolts.

That’s it! You can be smart and lockwire other critical parts of the bike such as brake calipers or wheel spindles, which although not required is always a good idea.

Other changes – It is compulsory to replace the coolant (when applicable) with plain water (use distilled water to reduce the risk of scale clogging the passages). As per the lockwiring description above, its aim is to avoid spillage on the track. And plain water is a better coolant anyway.

Another requirement is for fitting a catch tank under the engine. This is usually achieved by fitting a racing bellypan which features a dam at the back. The catch tray needs to be drilled with at least a hole in the lower part, and close it with a rubber/plastic plug. The idea is that in case of wet racing the plug can be removed to let the water out. In some cases it might be necessary to fit a catch bottle as well for overflow and breather pipes, but if they fit in it, you can use the bellypan for this purpose as well.

You will need to remove both the centre and the side stand. Most clubs allow lockwiring of the side stand, thus avoiding removing the cut-off switch fitted to most bikes.

Recommended Changes

Two modifications which are not compulsory but very popular are fitting braided hoses at the front end and replace the original fairing with a race one (where applicable). Both changes are not always compulsory, although most clubs require braided hoses. For bikes with two front discs, the hoses have to be two separate lines as this allows to slow down the bike in case one of the hoses fail. Replacing the faring with a race one is just common sense: the OEM ones are far more expensive and heavier. Costs vary, but you can expect to pay up to £50 for the braided hoses and approx. £2-300 for a complete fairing. The seat unit is an additional £100 max.

Another one of the changes that some racers go for is replacing the clocks. There is not much weight saving, in particular for bikes from the second half of the ’90s; however race clocks are usually more robust and precise, can be better positioned with race brackets and can be adjusted for a tuned engine (rev range, shift lights, etc.). That comes at a price though, and you can expect to pay up to £300 for a high quality set like Spa Design, made up of rev counter, oil and water temperature.

You will definitely benefit from a selection of gears, but to start with a smaller front sproket and a couple of rear ones should be enough. You can start with one tooth less at the front and 2 x two teeth more at the back (eg. reduce from 15 to 14 at the front and increase from 41 to 43 and 45 at the back). Remember to avoid making the rear a multiple of the front (or the other way round), like 15 at the front and 45 at the back, as this will increase chain wear. A race conversion (usually 530 to 520 pitch) give a sensible weight difference which affects handling and reduces power losses from crank to wheel.

We will not dwelve into suspension modifications as this varies from bike to bike: if you are just starting to race, many last generation bikes like CBR600 or R6 already have a good set-up to start with, and there’s a large selection of aftermarket products to choose from, like Öhlins or White Power (WP).

Finally a word of advice: if you tune your bike avoid adding just a race can as the difference in power is minimal in comparison to a full race system. An Akrapovic race can increased power by 2-3bhp on our GSX-R 600, while the full system was pushing out up to 7bhp more (with properly set Dynojet carb kit and filter, of course), making a huge difference across the whole range.

 

[nms:race bike,5,1,500,tbks]

Rear Shock Adjustment

Rear Shock Adjustment

Adjustment Locations on Shocks

Rebound adjustment (if applicable) is located at the bottom of the shock. Compression adjustment (if applicable) is located on the reservoir. Spring prelude is located at the top of the shock.

Shock: Lack of Rebound

Symptoms:

*

The ride will feel soft or vague and as speed increases, the rear end will want to wallow and/or weave over bumpy surfaces and traction suffers.
*

Loss of traction will cause rear end to pogo or chatter due to shock returning too fast on exiting a corner.

Solution: Insufficient rebound – Increase rebound until wallowing and weaving disappears and control and traction are optimized.

Shock: Too Much Rebound

Symptoms:

*

Ride is harsh, suspension control is limited and traction is lost.
*

Rear end will pack in, forcing the bike wide in corners, due to rear squat. It will slow steering because front end is riding high.
*

When rear end packs in, tires generally will overheat and will skip over bumps.
*

When chopping throttle, rear end will tend to skip or hop on entries.

Solution: Too much rebound. Decrease rebound “gradually” until harsh ride is gone and traction is regained. Decrease rebound to keep rear end from packing.

Shock: Lack of Compression

Symptoms:

*

The bike will not turn in entering a turn.
*

With bottoming, control and traction are lost.
*

With excessive rear end squat, when accelerating out of corners, the bike will tend to steer wide.

Solution: Insufficient compression. Increase compression “gradually until traction and control is optimized and/or excessive rear end squat is gone.

Shock: Too Much Compression

Symptoms:

*

Ride is harsh, but not as bad as too much rebound. As speed increases, so does harshness.
*

There is very little rear end squat. This will cause loss of traction/sliding. Tire will overheat.
*

Rear end will want to kick when going over medium to large bumps.

Solution: Decrease compression until harshness is gone. Decrease compression until sliding stops and traction is regained.

[nms:rear shock,6,1,50,tbk]

Front Forks Setup

Adjustment Locations on Forks

Rebound adjustment (if applicable) is located near the top of the fork. Compression adjustment (if applicable) is located near the bottom of the fork. Spring preload adjustment (if applicable) is generally hex style and located at the top of the fork.

TroubleShooting

Lack of Rebound

Symptoms:

* Forks are plush, but increasing speed causes loss of control and traction
*

The motorcycle wallows and tends to run wide exiting the turn causing fading traction and loss of control.
*

When taking a corner a speed, you experience front-end chatter, loss of traction and control.
*

Aggressive input at speed lessons control and chassis attitude suffers.
*

Front end fails to recover after aggressive input over bumpy surfaces.

Solution: Insufficient rebound. Increase rebound “gradually” until control and traction are optimized and chatter is gone.

Too Much Rebound

Symptoms:

*

Front end feels locked up resulting in harsh ride.
*

Suspension packs in and fails to return, giving a harsh ride. Typically after the first bump, the bike will skip over subsequent bumps and want to tuck the front.
*

With acceleration, the front end will tank slap or shake violently due to lack of front wheel tire contact.

Solution: Too much rebound. Decrease rebound “gradually” until control and traction are optimized.

Lack of Compression

Symptoms:

*

Front-end dives severely, sometimes bottoming out over heavy bumps or during aggressive breaking.
*

Front feels soft or vague similar to lack of rebound.
*

When bottoming, a clunk is heard. This is due to reaching the bottom of fork travel.

Solution: Insufficient compression. Increase “gradually” until control and traction are optimized.

Too Much Compression

Symptom:

*

Front end rides high through the corners, causing the bike to steer wide. It should maintain the pre-determined sag, which will allow the steering geometry to remain constant.

Solution: Decrease compression “gradually” until bike neither bottoms or rides high.

Symptom:

*

Front end chatters or shakes entering turns. This is due to incorrect oil height and/or too much low speed compression damping.

Solution: First, verify that oil height is correct. If correct, then decrease compression “gradually” until chattering and shaking ceases.

Symptom:

*

Bumps and ripples are felt directly in the triple clamps and through the chassis. This causes the front wheel to bounce over bumps.

Solution: Decrease compression “gradually” until control is regained.

Symptom:

*

Ride is generally hard, and gets even harder when braking or entering turns.

Solution: Decrease compression “gradually” until control is regained.

 

[nms:front forks,6,0,50,tbk,]