more damping = more plush

[Adammoto]

When would more compression damping make a fork feel more plush?

I see this sometimes in testing, but I don't undersand why. Any theories out there?

[Dwight_Rudder]

No, not unless the forks were bottoming. Less damping = plush.

[wblake]

is there a chance if you increase damping too much (like trail bike for mx) to get plusher because of the pressure built up to be reliefed through the high speed???

[mog]

if you don't have enough damping you ride the air spring , this is very progressive in nature and can feel harsh if you get inti the steep part of the curve when you are not actually needing to

[sasqach]

perhaps if the shimstack needs work when aftermarket valving is put in.

[hrpufinstuff]

Are you still riding the same setup as last weekend? It felt like the little chop was very plush, but anything that caused you to get into the HS circuit resulted in a spike. I'd have to agree with mog that you're getting too far into the stroke, too fast. Maybe more initial damping would help the transition.

On that choppy trail, it was hard to really test but it felt similar to a slow rebound, as if it was too far into the stroke, causing the big mid stroke spike. Much of the trail was no problem, but you would ocassionally get a big whack from a 3-4" rock.

[DaveJ]

When would more compression damping make a fork feel more plush?

I see this sometimes in testing, but I don't undersand why. Any theories out there?

Most excellent question.

In my book, a damper or damping mechanism is anything that decreases the consequences of a direct blow or hit…usually between something that is moving (such as your body and brain) and something that is not going to move, (such as the ground or a big rock).

So when you jump off the local bridge into the lake or river below, the water acts to damper the blow of what would normally be a very hard surface...resulting in a very dead person.

So yes, in the case of the water and things like boxing gloves and trampolines, more damping means a more plush connection between two solid things rushing towards each other.

In a fork, when most of us talk about damping we usually think of the hydraulics, which in this case is a fluid attempting to move about from one chamber to the next via a series of holes or circuits.

As it does this shifting, it pushes back or cushions the blow to keep one part of the bike from slamming down onto another part of the bike. The rate at which the fluid moves from one section to the next actually creates a cushion, much like two pieces of flat steel that are isolated from each other by a twelve inch thick piece of foam.

So yes, hydraulic fluid, when allowed to move about, will push back and behave exactly like a big piece of foam. So in many ways, when you make it harder for the fluid to move about, the foam becomes more dense like…and of course, the easier the movement, the less the foam effect.

So the goal is to have just enough (firm but plush) without having too little (blow-through, bottoming) or too much (stiff, harsh). This means that sometimes adding more, means a smoother ride, and sometimes removing some means a smoother ride. Go figure.

Where it gets really tricky is what we mean by more or less because the compression and recycling of the suspension never happens at the same speed (velocity). This is where we come up with the general classifications of low, mid and high. In other words, sometimes you need less low speed related damping and more high-speed related damping, or more high and less low…and the list goes on. In other words…when the circuits in which the fluid moves through are tuned in just the right way, you create the equivalent of a 12 inch thick piece of foam that is going to behave radically different based on how quickly the two items that it holds up (or apart) come together. Tricky stuff...and this is why suspension tuners make gobs of money and drive fancy cars.

By the way, just for the record, that little screw that you turn only effects a small portion of the entire range at which the damper does its job. In many ways, the screw is a lot like the air or fuel screw on a carb. It can have a big effect on performance, but it’s not the main jet.

?

[Adammoto]

Thanks all for the responses.

By the way, just for the record, that little screw that you turn only effects a small portion of the entire range at which the damper does its job. In many ways, the screw is a lot like the air or fuel screw on a carb. It can have a big effect on performance, but it’s not the main jet.

I'm not just spinning clickers, I have been revavling a bunch in the last month. I think I'm on number 8 now.

Example where more damping = more plush:

The stock KTM XC valving is firm at low speeds but plush on high speed, sharp edged hits. The fork rides tall and is skittish on chop, but it responds really well to big rocks.

Liking the high speed response of the stock, but wanting to soften low-speed, I tried (a bunch of) softer base valves. This gives the low speed a nice feel, but it gets harsher as shaft velocity increases. Fork is NOT bottoming. It feel like it hydro-locks. Strange thing is, when I look at the two damping curves side-by-side (Restackor), the damping coefficient produced by my modified stack is lower than stock throughout...

Seems that firmer low speed makes more travel available for harder hits?? If that's the case, maybe this is an inherent trade-off?

MOG - I doubt that I am reaching the air spring as you suggested. The harshness is on sharp rocks, not necessary giant rocks...2" sag and a 3-5" bump (total travel of >7")

Edited October 3, 2011 by Adammoto

[hrpufinstuff]

Example where more damping = more plush:

The stock KTM XC valving is firm at low speeds but plush on high speed, sharp edged hits. The fork rides tall and it skittish on chop, but it responds really well to big rocks.

Seems that firmer low speed makes more travel available for harder hits?? If that's the case, maybe this is an inherent trade-off? Unless perhaps I am reaching the air spring as MOG suggested - though I doubt it with 2" sag and a 3-5" bump (total travel of >7")

"The fork rides tall and it skittish on chop, but it responds really well to big rocks." That's exactly what I felt with the stock forks as well.

When I rode your bike, I'm fairly sure the harsh hits happened while still in the first half of the stroke. What was your float set at then?

[Adammoto]

"The fork rides tall and it skittish on chop, but it responds really well to big rocks." That's exactly what I felt with the stock forks as well.

When I rode your bike, I'm fairly sure the harsh hits happened while still in the first half of the stroke. What was your float set at then?

Float was at .6 when you rode it. The midvalve was close to stock but had one shim removed and no bleed shim on the rebound side (which I think adss some bleed to the MV compression side). The base valve was altered substantially though. It was a single stage with less damping overall.

Here are the stacks you rode

BV

24 x .1 x 4

22 x .1

20 x .1

19 x .1

18 x .1

17 x .1

16 x .1

14 x .1

9.5 x .3

16 x .25

Reb

d 20 x .1 (3)

13 x .1

16 x .1

15 x .1

14 x .1

13 x .1

12 x .1

10 x .20

16 x .25

MV

12 x .1

20 x .1 (3)

18 x .1

16 x .1

10 x .2

10 x .1

MV: (0.6 float)

This is what I changed to this weekend. Somewhat lighter base valve but the big change was going to .9mm float. Also added the bleed shim on rebound stack.

BV

24 x 10 (4)

22 x 10

20 x 10

18 x 10

16 x 10

14 x 10

10 x .3

10 x .3

10 x .3

backer plate

Reb

15 x .1

3 (d) 20 x .1

13 x .1

16 x .1

15 x .1

14 x .1

13 x .1

12 x .1

10 x .3

16 x .25

MV

12 x .1

20 x .1 (3)

18 x .1

16 x .1

14 x .1

10 x .2

.9 mm float

This was a pretty good compromise between HS/LS plushness. Next I want to go back to a 2-stage base valve combined with about 1mm float and a slightly ligher stack on the MV. It never ends...

[jwaseman]

hr,

Have you tried/tested without the bleed shims? On paper it looks like you have

gobs of bleeds, don't know what that translate at the bars since I have not tried bleed shims. It seems right now if you are getting a spike at sharp rocks which is a high shaft speed situation you need a slightly stiffer setting somewhere to isolate you better from the bars. I would start at the bleed shims. Pull rebound and comp. bleed shims. If its a little too much resistance, then pull a 20 out on the mv comp. it will also increase the float of that value.

keep that in mind too!

I guess this where it can get tricky, softer or stiffer= plusher.

Jw

[wblake]

hey adammoto, i notice you only use 2" front sag, how did you come up using that with your cc forks...i run 3 inches and i like it and i find it plush at low and high speed damping....but then again am a beginner rider!!!

[grayracer513]

I'm curious as to why you're bleeding AND floating the mid. The bleed seems redundant with float.

[Adammoto]

hey adammoto, i notice you only use 2" front sag, how did you come up using that with your cc forks...i run 3 inches and i like it and i find it plush at low and high speed damping....but then again am a beginner rider!!!

It was just a rough estimate to show what range of travel we're experiencing harshness.

I'm curious as to why you're bleeding AND floating the mid. The bleed seems redundant with float.

Gray, that is the stock configuration of KTM XC models (at least in 2011).

The KTM rebound piston does not have a bleed hole like Kayaba and Showa products. They use bleed shims instead. Some guys drill their own bleed hold in the piston and remove the bleed shims. FWIW, I ran the fork with no bleed shims or bleed hole for quite a while (Factory Connection sets it up that way).

stock 2011 250/300 XC

BV

24 x .1 (3)

16 x .1

24 x .1 (3)

23 x .1

22 x .1

21 x .1

20 x.1

19 x .1

18 x.1

17 x .1

16 x .1

15 x .1

14 x .1

9.5 x .3

16 x 2.5

Reb

15 x .1

3 (d) 20 x .1

12 x .1

16 x .1

14 x .1

13 x .1

12 x .1

10 x .3

16 x .25

MV

12 x .1

20 x .1 (3)

18 x .1

16 x .1

14 x .1

10 x .2

0.6mm float