Suspension

 Suspension Baseline Settings

Do not send your suspension off to get re valved until you have gotten a solid baseline of suspension settings. Today’s bikes come with pretty good suspension and the average rider would only need to dial in the compression and rebound, sprung correctly for rider’s weight, and proper sag settings.

Springs

This is the first step in customizing a suspension set-up just rider weight. It is also the first step in getting better suspension performance out of your bike. Below is a basic chart of what spring rate you’ll need compared to rider weight.

Spring Rate Chart
Rider Weight Shock Springs (KG) Fork Springs (KG)
130-140 lbs. 4.8 .38
140-150 lbs. 4.8 .38
150-160 lbs. 5.0 .39
160-170 lbs. 5.2 .40
170-180 lbs. 5.4 .41
180-190 lbs. 5.6 .42
190-200 lbs. 5.8 .43
200-210 lbs. 6.0 .43
210-220 lbs. 6.3 .44
220-230 lbs. 6.7 .45

Measuring And Setting Sag

Setting the sag is very important to the handling of your bike. Too little sag in the rear places more weight on the front end and to much sag will take away weight from the front end (will try to lift the front end). View the video below for more information. Here’s a link with more information on setting sag.

Here’s a few extra tips.

  1. Bike should be race ready with all equipment (fuel tank filled, any accessories etc).
  2. Rider should be in full riding gear.
  3. Rider should be in normal racing position while another person holds the bike upright.
  4. Setting Sag Video

Fork Installation

The proper installation of the front forks is essential to proper suspension operation. This procedure will ensure that the front forks are parallel and not binding.

  1. Place bike on stand that will allow the front tire to be off the ground.
  2. Install forks in the triple clamps, ensure that both forks are the same height in the clamps (refer to your owners manual for correct dimensions). Also make sure the bleed screws are towards the front, this will make bleeding the air from your forks easier.
  3. Apply engine oil to threads of the pinch bolts.
  4. Tighten each pinch bolt (alternating pattern) in the top clamp to 220inlbs. (refer to owners manual for torque specs)
  5. Next tighten the lower clamp pinch bolts (alternating pattern) to 168inlbs. (refer to service manual for torque specs). Over tightening the lower clamp pinch bolts could result in mid-stroke harshness.
  6. Install front wheel assembly, first pry the brake pads apart with a screw driver before bring the wheel into position. This helps the front disk to be installed between the pads as the wheel is installed.
  7. Before tightening any of the axle pinch bolts go ahead and fully tighten the axle nut (refer to service manual for proper torque specs). If needed you can tighten the right side pinch bolts just to hold the axle while you tighten the axle nut. Make sure you loosen the right side pinch bolts before you proceed any further.
  8. Next step can be done two different ways. Spin the front wheel and abruptly apply the front brake, repeat this a few times or remove the bike from the stand and compress the suspension a few times and place bike back on the stand.
  9. Tighten the left side (caliper side) axle pinch bolts to spec (refer to service manual).
  10. Spin the wheel again and abruptly apply the front brake, repeat a few times or take bike down off the stand and compress suspension a few times and place back on stand.
  11. Final step is to tighten the right side axle pinch bolts.

Fork Install Video

Suspension Fluid

Burnt up and contaminated suspension fluid can cause the following:

1) Excess internal wear to your shock and fork cylinders from poor lubrication.

2) Increased stiction (resistance to initial movement) as your fluid looses it’s lubrication / slippery properties.

3) Inconsistent and reduced damping at elevated temperatures because the viscosity properties have deteriorated.

Oil change frequency in your car is determined by mileage; oil change frequency in your bike is determined by time.

Shock Oil Change Frequency Analysis:

To control your suspension movements, a piston plunges through oil creating resistance (damping) and generating heat. By the end of a moto your shock fluid can reach up to 300°F. This extreme temperature is achieved because the shock is relatively small and has very little surface area to dissipate the heat. Additionally the shock is shielded from cooling air by the air box.

A good rule of thumb is that for every 10° F rise in temperature, the life of suspension fluid is cut in half. Under 200° suspension fluid will last a long time. Once suspension fluid reaches about 200°, the polymer chains begin to burn up and the viscosity stabilizers break down. So to determine oil change intervals we must look at the time the oil spends above 200°. We will call this “Time At Elevated Temperature”. High performance suspension fluids last about 20 hours at elevated temperature before suffering significant viscosity breakdown and loss of lubrication properties.

To determine oil change frequency, the rider must determine when his shock has experienced “20 Hours at Elevated Temperature”. A good rule of thumb is to subtract 5 minutes from every ride since it takes about 5 minutes to get the shock over 200°.

If a MX bike races a 20 minute moto, it counts as 15 minutes at temperature. Thus if you ride 4, 20 minute sessions, you put 1 hour on your shock fluid. So 20 days of riding use up your 20 hours of oil life. If you ride once a week, your oil is cooked in about 5 months. Obviously if you ride twice a week, you should change your oil in half that time.

If a desert bike races a 2 hour and 35 minute race, it counts as “2 1/2 hours at temperature”. Thus if you race or ride for 8 extended sessions you use up your 20 hours of oil life. At 2 races or extended riding sessions a month, your oil is cooked in 4 months. And remember a 1 hour spirited ride with your friends before the race adds another “55 minutes at temperature” and shortens your oil life further.

Fork Oil Change Frequency Analysis:

Fork oil does not get very hot because forks do less work than the shock, there are two forks full of almost a quart of oil, and there is allot of surface area to dissipate the heat. Thus from a temperature standpoint, fork oil should last a long time. However, fork oil suffers extreme contamination from the sliding action inside the forks and the spring twisting and creating chips. These small metal particles become suspended in the oil and act as sandpaper in the oil.

Because of all the contamination, the fork oil should be changed often. To make your life simple, I recommend changing the fork oil when ever the rear shock is serviced. This ensures that both front and back are maintained on a regular basis and will minimize wear to your valuable components.