Suspension gurus please help

[stemplin]

I have an 08 ec300 and would like to try and get the shiver 45's dialed in a bit. I bought the bike used and was told it was resprung for around 230lbs. I'm 240 in gear so that seemed close enough.
I ride mostly tight single track with lots of roots and small stuff and the front end really seems to deflect all over the place. I get terrible arm pump and blisters that I never got on the same terrain with my 01 300 (completely stock suspension)
I have my forks apart now and was hoping someone could give me some opinions on the shim stacks that I have.

rebound/mid stack
22x.10
22x.10
22x.10
16x.15
piston
22x.10
19x.10
19x.10
17x.10
17x.10
15x.10
14x.10
11x.20

Base stack
22x.30
piston
22x.10
22x.10
16x.10
22x.10
21x.10
19x.10
18x.10
17x.10
16x.10
14x.10

Any help/ideas would be greatly appreciated. I'm new to this whole shim stack thing, but looking to learn.

Thanks,
Scott

 

[swazi_matt]

Possibly related, but maybe the gurus could shed some light on the benefits of using aircells (sub tanks), their website says it will stop deflection

 

[GMP]

That does not look too bad to me. A little more rebound shimming maybe. Also, no mention of the MV float dimmension, or spring preload. Too little float and/or too much preload wiill ruin the ride over trail trash.

As far as subtanks, I built and used a set on my '03 that had the WP fork and they worked very well. How well they work will depend on the fork, and the ratio of air volume in the fork to tank volume. When you think of a fork, it has two springs, mechanical and air. The mechanical spring is linear, the air spring is progressive. The overall rate is a sum of these two. The higher the oil level, the smaller the air volume, and the greater the airspring rate is relative to travel. What a subtank system(one with a needle valve) does is to change the progression curve of the airspring relative to the speed and travel of the fork. It increases the air volume at lower fork speeds or short ranges of travel as the small volume/velocity of air is able to pass through the valve and into the tank easily. At longer ranges of travel like big hits, the valve restricts the airflow more, and the fork feels stiffer as the air spring effect is more. This is somewhat adjustable with the needle valve. Les built a set like mine and instaled them on his custom XR with a set of Zoke 45 forks. Worked, but not a dramitic difference. Reason is the WPs have a steeper curve. I can say for sure that the Zokes without the tanks are far better than the WPs with the tanks. So the conclusion, IMO, is that the fork should be properly dialed in in the traditional manner before subtanks are applied. If your springs are wrong, or your valving too loose, you will be riding too low into the travel, where the airspring rate starts to ramp up rapidly.

Hope this helped put some science behind the marketing. This is a basic description and there are different opinions on which type of valve should be used, etc. but the theory is the same. Subtanks are an option in some cases but not a magic bullet.

 

[stemplin]

GMP - I understand preload and will measure and post. Would you mind explaining float height, I have no idea how to determine that. Also, what exactly would you recommend for more shims in the rebound stack.


Thanks for the help.

 

[bchatt]

That mid looks pretty weird to me.
GMP: have you seen a set up like that before? Whats with that 16x.15 bleed shim?

 

[GMP]

The 16 is not a bleed shim, its a crossover in a 2 stage stack. The stack looks fairly normal to me, certainly not stiff.

By float I mean the travel of the mid valve shim stack, from the piston face until it hits the rebound tap. Anything down to 1 mm should not be a problem as far as harshness.

Rebound looks close. You can add another 22 on the bottom though.

You say its sprung for your weight, have you verified this?

It should be easy to tell if the harshness is caused by an overall stiff fork that rides high in the stroke, or a too soft fork that rides down into the stiff part of the stroke. Honestly, that valving looks pretty decent, certainly better than stock, and IMO not your main problem. The base valve could probably even be a little stiffer for your weight. Also depends on your speed, ABC?

Also, are the forks aligned correctly and the T clamps not overtightened? CRITICAL on a GasGas lower clamp!

 

[stemplin]

I have not had the spring rates verified and can't find any markings on them so I'm going strictly by what the previous owner told me.

I will measure the spring preload and float height and post.

I'm probably a middle of the pack C rider.

Where do you guys get extra shims from?

Thanks

 

[bchatt]

The 16 is not a bleed shim, its a crossover in a 2 stage stack.

I was meaning the one between the piston and the face shim in the mid.
The three 22x.1 strikes me as odd. Have you seen similar set ups? That would result in alot of float I would think.

 

[GMP]

Sorry, me bad. I was dyslexic on that stack and was thinking the 16 was on the other side against the tap. Its bad. Adds free bleed, but also adds bleed to the rebound that you don't need. This could be a good deal of your problem, lack of rebound control. Do this to the mid:

piston
22 x .1
22 x .1
19 x .1
17 x .1
15 x .1

Check the float. You can add 15s to get the float from 1.4 down to 1.2mm for starters. Don't go too tight on float at first if your not hitting big stuff fast, start here and see what it feels like. This should keep the fork up in the stroke better.

 

[swazi_matt]

That does not look too bad to me. A little more rebound shimming maybe. Also, no mention of the MV float dimmension, or spring preload. Too little float and/or too much preload wiill ruin the ride over trail trash.

As far as subtanks, I built and used a set on my '03 that had the WP fork and they worked very well. How well they work will depend on the fork, and the ratio of air volume in the fork to tank volume. When you think of a fork, it has two springs, mechanical and air. The mechanical spring is linear, the air spring is progressive. The overall rate is a sum of these two. The higher the oil level, the smaller the air volume, and the greater the airspring rate is relative to travel. What a subtank system(one with a needle valve) does is to change the progression curve of the airspring relative to the speed and travel of the fork. It increases the air volume at lower fork speeds or short ranges of travel as the small volume/velocity of air is able to pass through the valve and into the tank easily. At longer ranges of travel like big hits, the valve restricts the airflow more, and the fork feels stiffer as the air spring effect is more. This is somewhat adjustable with the needle valve. Les built a set like mine and instaled them on his custom XR with a set of Zoke 45 forks. Worked, but not a dramitic difference. Reason is the WPs have a steeper curve. I can say for sure that the Zokes without the tanks are far better than the WPs with the tanks. So the conclusion, IMO, is that the fork should be properly dialed in in the traditional manner before subtanks are applied. If your springs are wrong, or your valving too loose, you will be riding too low into the travel, where the airspring rate starts to ramp up rapidly.

Hope this helped put some science behind the marketing. This is a basic description and there are different opinions on which type of valve should be used, etc. but the theory is the same. Subtanks are an option in some cases but not a magic bullet.

THANKS that would explain why the last time i fitted them they helped in some areas but had an overall weird feel, they worked fine on my kx, but the suspension was pretty well sorted before i fitted them.

so my plan now is to get the suspension sorted out, then when i ride some super gnarley races i might fir the aircells, seem to remember them making the big rocks on slow climbs easier on the arms

 

[GMP]

That would make sense because fork movement is slow, and air can flow into the tank. You effectively remove the progressive airspring component of the total spring rate. On the WP43s, they really cleaned up the action on the small stuff (short travel).