Friday, 8 April 2011

Motorcycle Suspension : Diagnosing and Resolution

Here is a simple suspension diagnosis and troubleshooting for your motorcycle. 


FRONT

Adjustment locations: 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.
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 tucks 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 nor 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.


REAR

Adjustment Locations: Rear Shock
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.


Mark Thompson has spent the past 20 years racing motorcycles and managing Race teams and riders. 

He now runs theTrackbikes Website along with a number on Internet Ventures


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