[mullen119]

Seems like there has been a lot of talk on here about Manitous ABS+ damper and how good it is. I have been playing around with the HSC shim stack over the last few months and figured i would make a "how to" guide so others can do the same. It only takes 15-20 minutes and once you get a shim stack set up for your weight, The ABS+ damper is even better!


Use a 2.5mm allen wrench to take the top cap off. Take it off carefully!

Be careful not to loose the little ball bearings and springs, They are very tiny and easy to loose track of.When you reassemble, it doesnt matter where they springs and bearings go as long as they are across from each other.

Once the top cap is off, unscrew the damper from the leg and pull it out. Pull is out slowly and you wont loose very much oil. Keep a rag near by because you will loose a little no matter what.
Damper after being pulled out.

At the very top of the damper, there is a place for a 10mm wrench to hold the damper while you use a 13mm socket to unscrew the nut on the bottom of the piston.

One shim that is used as a check valve and a spring are under the piston. This just allows oil to flow freely back into the leg after the fork is compressed and re-extended. When reassembling, The spring goes back with the wider end toward the piston and the skinnier end toward the nut.

Close up of bottom of piston

Close up of top of piston

Shim stack installed

My 2010 drake has 6 compression shims stock. 3 the same size, and 3 that get progressively smaller in a pyramid shape. Lighter rider can remove shims to allow the HSC to open with less force, while heavier riders will want to add shims. Endless possibilities for shim configurations, So if you try this, post your weight and shim stack.


Reassemble same way you take it apart. Make sure the LSC is all the way open(counter clockwise) when you put the damper back in the leg. Oil height should be 87mm from the crown when fully assembled. If your careful taking it apart you shouldn't loose a significant amount of oil, but always check to make sure.:thumbsup:


<b>Key points from that this thread has turned up:</b>

1. Thanks to Solitone, we have the Manitou ABS+ tuning guide which includes dyno charts and many different shim stack combinations. Its probably the single best find this thread has produced (thanks Solitone)

This link should work:
<a href="https://goo.gl/JaqWO">https://goo.gl/JaqWO</a>

2. Spring rate needs to be set up correctly. I get PM's and hear of people trying to get their fork to feel right when it is way under/over sprung. Spring rate trumps damping and should always be set up correctly prior to trying different shim stack configurations.

3. A good place to order shims is MX tech.
MX-Tech Suspensions

 

[Dougal]

Is that a dished piston? With the outer ring protruding slightly more than the inner seat which the centre of the shims are compressed against?

 

[mullen119]

Is that a dished piston? With the outer ring protruding slightly more than the inner seat which the centre of the shims are compressed against?

yes, there is a small lip that the shims sit on top of. From memory I would say is about half a mm tall

 

[Dougal]

yes, there is a small lip that the shims sit on top of. From memory I would say is about half a mm tall

Cool, there's another tuning dimension manitou have given you. By relocating small shims to under the largest one you can reduce the preload on the shim stack and have it opening sooner.

Basically now you've got platform starting point on top of all the usual shim stack options. By closing the freebleed it's a total platform.

 

[mullen119]

that's a great point dougal. I never thought about it, but that would open up even more options.

 

[half_man_half_scab]

So, for a total shim newb here, do you remove one of the largest diameter shim to decrease HSC? Conversely, do you add a shim equal to the largest diameter shims to increase HSC?

What do you torque the nut to?

Is there some place I can read about the underlying mechanics of how this shim system works?

 

[PMK]

Yes the stack preload can be a good tuning option for those that understand it.

Currently Race Tech has this option with their G2 series Gold Valves.

Race Tech takes it a step further by allowing the preload shim the ability to run different diameters that alter the port area.

Those wanting to understand more should do some searching about Penske dampers. There should still be tech articles about the various piston or valve body designs.

Also, remember, that as you unload the stack, you almost always must firm the stack. The downside of running a non preloaded stack is in most instances you will increase HS damping and often create deflection issues.

PK

 

[Mr.P]

Subscribed. (great thread!)

P

 

[JLantz]

I have the Drake '10.

I am not a suspension engineer.

How does rider weight affect the purpose of the shim stack?

 

[mullen119]

I have the Drake '10.

I am not a suspension engineer.

How does rider weight affect the purpose of the shim stack?

The purpose of the HSC shim stack is to open as a "blow off" when oil pressure builds up because it cant get through LSC circuit fast enough. Heavy riders are going to create more pressure then lighter riders, causing the shim stack to open on smaller hits that a heavier rider may not want it to open on. On the other side, lighter riders will have to hit a much bigger hit to get the same shim stack to open. Think of it as a 250lbs person is going to be much harder on a fork then a 150lbs person, So them same shim stack on the same fork will feel a lot different to those two people.

 

[mullen119]

So, for a total shim newb here, do you remove one of the largest diameter shim to decrease HSC? Conversely, do you add a shim equal to the largest diameter shims to increase HSC?

What do you torque the nut to?

Is there some place I can read about the underlying mechanics of how this shim system works?

You can add and remove any size shim, you will get the biggest effect by adding or removing the biggest shims, but for fine tuning, you can change any of them. There is also different shim thicknesses that you can use for more tuning options.

I couldnt find a torque number for the nut. I just snug it down fairly lightly and have not had any problems, But if anyone find a torque number it would be good to know.

use google to find information on shim stacks, Lots of good information out there:thumbsup:

 

[PMK]

Took a moment and found a link to the Penske site info.

http://www.penskeshocks.com/files/Adjustable_Manual.pdf

Later pages discuss the various piston design formats.

Pretty technical but should be more than enough information to make your brain hurt.

Granted it is not bicycle specific in title but is applicable.

PK

 

[mullen119]

Good link PMK

 

[Dougal]

I've got an introduction to shim stacks on the www.dougal.co.nz website below, because it's frames (yeah it needs updated), but follow this path
www.dougal.co.nz
-> click to enter
-> Suspension
-> Advanced tuning tab will turn up below. Read the basic tuning one first

The Penske one is a gold mine once you've got a handle on it.

 

[mullen119]

I've got an introduction to shim stacks on the www.dougal.co.nz website below, because it's frames (yeah it needs updated), but follow this path
www.dougal.co.nz
-> click to enter
-> Suspension
-> Advanced tuning tab will turn up below. Read the basic tuning one first

The Penske one is a gold mine once you've got a handle on it.

Thats a great link dougal. It explains shim stacks in detail and it written in a way that I would think a noob would understand pretty easily.

 

[Dougal]

Thats a great link dougal. It explains shim stacks in detail and it written in a way that I would think a noob would understand pretty easily.

Thanks, I always appreciate good feedback.

 

[mullen119]

here is a good place to buy shims. I still need to measure the shims ID and max OD. I will do so and post them when I get a chance.

 

[derby]

Thanks, I always appreciate good feedback.

Dougal, did the quake affect your area?

 

[Dougal]

Dougal, did the quake affect your area?

Hi Ray

I live about 450km away so that quake and the aftershocks were just able to be felt here. But I do have a lot of friends and also family in Christchurch. So far every report I've heard from people I know is good, but it is still early days and there are a lot of people still to get news from.
It will be some time before the extent of the casaulties are known.

 

[mullen119]

Hi Ray

I live about 450km away so that quake and the aftershocks were just able to be felt here. But I do have a lot of friends and also family in Christchurch. So far every report I've heard from people I know is good, but it is still early days and there are a lot of people still to get news from.
It will be some time before the extent of the casaulties are known.

Good to hear you are ok dougal, Hopefully all your friends and family are as well.