Suspension feels much better with pillion - what to do?

[bluremi]

I skimmed through the suspension setup thread but couldn't figure out the answer to my question.

I have a stock 2008 FZ6 with the factory rear preload setting. I live in NYC (bumpy roads) and am 5'11" 160lbs.

When riding solo I feel like the rear suspension is incredibly jarring, to the point where I stand up on the pegs to avoid back/neck pain when going over bumps or dips (of which there are thousands in NYC).

However, when my girlfriend who weighs about 115lbs is on the back I feel like the suspension is perfect. I can feel the road but it absorbs bumps effortlessly. This is how I want it to behave all the time, since I do 95% of my riding solo.

Can you guys give me some advice? Is preload adjustment enough? If I need to get aftermarket parts, I'm at a loss for the best approach...

 

[beatle]

When you say "factory rear preload setting" what do you mean? You should be able to reduce the preload.

 

[FUHL]

When you say "factory rear preload setting" what do you mean? You should be able to reduce the preload.

Even so, that is not going to change the spring rate or dampening of the shock.

 

[bluremi]

When you say "factory rear preload setting" what do you mean? You should be able to reduce the preload.

I just mean the setting hasn't been changed from the factory setting.

 

[outasight20]

I know exactly what OP is referring to. First off, you should be adjusting the preload on the rear shock up to the highest setting (7) when riding with a passenger. When riding alone, I usually keep the preload around 3 to 4. This makes the bike a little more squishy over bumps and reduces the ride height.

In your case, you should try reducing the preload all the way down to 1 and report back on how it feels. How much do you weigh? I'm about 200 pounds with all my gear on.

 

[FinalImpact]

You're over sprung for your weight, so the spring is riding around "topped out" which makes it harsh.

That said, lowering the spring rate which is good for solo riding AND then adding a passenger would likely make the rear squat so much it would not be comfortable to ride. << FWY: This means spring replacement.

Spring rate is how much load it can carry.
Preload is how much compress the spring to obtain it working height.

All info above is correct! Check the current setting and move it down 3 #. Going from 6 or 7 to 1 may be a bit much. Be careful. :thumbup:

 

[bluremi]

Thanks for the input. Based on this excellent article explaining what preload does, it sounds like the suggestion is to:

1- Lower the preload, since my current amount of preload is too high. When I sit on my bike solo, the piston is sitting near the top of the shock, causing the ride to be harsh.

2- If after lowering the preload it still feels harsh on solo rides, I should consider changing to a softer spring.

Regarding #2, google says I can change just the spring and leave the shock alone. Would that be enough to smooth out my ride, or do I need to change the shock as well to something with compression and rebound controls?

 

[FinalImpact]

^^ Go to racetech and enter your weight on the scale for the FZ6 and see what spring rate you come up with.

2008 FZ6 Rear Shock:
Eye to eye: 300 mm (11.82")
Travel: 50mm (1.97")
Setting #1 light: 175.2mm (6.90")
Setting #7 firm: 165.8mm (6.53")
Installed length MANUAL SAYS: 172.0 mm (6.77 in), doesn't say what setting tho, suspect #3.

Range of preload: 9.4mm (0.37")
Coil OD: 77.6mm (3.055")
Coil Dia: 11.76mm (0.463")
Spring free length 185.0 mm (7.28")
Spring rate K1: 12.99 kgf/mm (727.45 lb/in), 127.40 N/mm


FWIW: addressing the front is not a bad idea either. Its a non linear spring with a starting rate too low and final rate near equal to the rear. Most find a linear spring (i.e. same rate up front) makes the bike more predictable in the corners. Much more pleasant to ride.
IIRC ~ 0.74kg/mm to 1.20Kg/mm

As for the shock, its about preference and matching it to the forks. The two should offer a balance of damping rates that work together.

Just an observation but those who cruise and commute generally seem ok with ride quality.
Those who play in the corners may want better control. Mine has some changes to bother ends...

 

[bluremi]

Dropped the preload down to 1 (bent my key in the seat lock even though I read a post warning me about it, DUMB)

The ride is much smoother now, thanks for the advice.