How to adjust your suspension
To get the most out of your motorcycle, it's essential not to neglect your suspension settings.
Here are some basic rules.
1st point:
Setting the shock absorber pre-load, known as the SAG
Start by placing the motorcycle on a tripod so that the wheels don't touch the ground.
Then take a tape measure and measure the distance between two marks. We'll take the 1st mark at the saddle fixing nut. The second at the rear wheel axle.
Example: 645 mm
Next, we'll take this value with the rider on the bike, wheels on the ground. The rider must be fully equipped, and the bike must be fully fuelled. So we'll need one person to measure, and another to hold the bike and rider in balance by the handlebars. The value found is called RACE SAG.
Example: 545 mm
Our race SAG is therefore 100mm.
below are the basic values from 125 2T and 250 4T.
In motocross, 100mm
Supercross 95 mm
Enduro 105 mm
The greater the downforce, the more stable the bike, but the less manoeuvrability. Conversely, the less downforce you have, the more manoeuvrable the bike will be, but you'll lose stability when accelerating in a straight line.
Now that we've passed this stage and adjusted the spring preload to suit the discipline and the rider, we're going to control the dead travel called FREE SAG.
This time, the bike's wheels should touch the ground, so compress the suspension once or twice and let the bike return to its natural position. Measure again between the two marks.
Example: 35 mm
35 mm is the correct value - it can vary by +/- 5 mm.
If your value exceeds 40 mm, the shock absorber spring is too hard.
If your value doesn't reach 30 mm, your spring is too soft.
In both cases, replace your shock absorber spring!
2nd point:
Hydraulic adjustment screws.
The hydraulic principle of a fork or shock absorber is to laminate oil through one or more pistons and valve stacks. However, there are auxiliary passages to significantly modify the oil flow through these circuits.
These famous adjustment screws, called TEN for relaxation and COMP for compression , act over the entire suspension travel. Today, most shock absorbers have a "slow" compression circuit, i.e. for low speeds and "fast" for high speeds. Some forks, notably the KAYABA PSF 2 fitted to the new 450 CRF 2015, offer the option of setting the compression slow and fast and the rebound slow and fast.
The compression acts on the hardness of the break-in and the rebound on the time it takes for the suspension to return to its initial position.
We'll now look at the types of settings adapted to different circuits and climatic conditions. If you're riding in dry weather on a concrete surface with precarious grip, the settings won't be the same as if you're riding on clay soil with just the right amount of water and maximum grip, for example.
Loose ground :
In conditions of perfect grip, the track will tend to break up quickly, with deep ruts and holes in the braking and acceleration zones.
Your standard suspension settings should be made on this basis, finding the best compromise.
Muddy terrain :
Mud accumulates on the bike, which can in some cases weigh it down by as much as 15 kilos. The basic hydraulic settings are similar to those for soft ground, but you'll need to compensate for this increase in weight by adjusting the spring preload.
Reduce shock absorber spring preload from 100 to 95 or even 90mm.
Air fork - increase air pressure
Spring fork without preload device replace springs if possible with a higher spring rate, otherwise compensate with hydraulics by increasing compression.
Hard terrain :
Circuit with a very hard texture, with ruts in jump calls, turns...
Compression and rebound must be freed up so that the wheels remain in contact with the ground as much as possible, to avoid the sensation that the suspension is " tapent ".
Tune fork and shock settings in the same way
Sandy ground :
On soft ground, you need to keep the front end as precise as possible and avoid the fork plunging.
To do this, raise the front of the vehicle as much as possible.
Increase the shock absorber pre-load from 100 to 105. The hydraulics remain more or less standard.
For the forks, you need to firmly brake compression, lower the fork tubes to the level of the upper tee, if possible install tees with higher offsets than the original to gain in stability, and position the rear wheel at the end of the swingarm to increase the length of the bike.
For air forks, significantly increase pressure within the limits of the manufacturer's standard.
For spring-loaded forks, install higher-rate springs.
Supercross
This discipline requires a very rigid chassis, with maximum precision. Supensions need to be very firm to withstand big jumps and woops... but also to be forgiving in the event of a mistake.
Shock absorber preload 90 mm
Adjustments in harmony between front and rear :
Highly braked compression
Slightly braked rebound to avoid climbing too high in jumps.
Maximum-pressure air fork
Fork with springs adapted to firmer springs
Firmer spring shock absorber
