Ducati Monster Forum

M900 DU440 Ohlins base settings.
Checked the manual courtesy of sponsor Motowheels.
Compression 12 clicks
Rebound 14 clicks
Preload 11mm


Any tips or hints with this shock?

I'm 90-95kg/200-210 in gear and rider sag is about 30mm.

Cheers.

I run that shock with stock valving and like it. I couldn't tell you how many clicks I'm running. I do use the remote to adjust the compression based on how the roads are. I don't mess with the rebound.

Eric did change the spring on mine to a 10.0, IIRC, and I probably have closer to 15mm preload.

I'll check my spring code. What do you weigh at?

It's been 17 years since that spring went on. I might have weighed 190-195 in gear at the time.

It might be a 10.5 too. I can check the code if you need me to. I do know it isn't the one that it came with.

My experience with springs is a heavy spring with 15mm preload feels more compliant than a light spring with heavy preload...over 15mm.

True about spring rate and preload. If my spring is in the 10-11 range it should be workable (hopefully). It is a nice shock and a bonus it came with the bike.

Set the damping according to the manual and it feels great. Very poised and composed but reasonably supple.

That's very good news.  :)

I've not used that shock.

If you wanted to experiment, first place I would go from here would be to back off the rebound damping. I would probably go eight clicks - which should put it close to full soft - and see how she feels then.

If that's a lot more supple, but pretty bouncy, add rebound click by click until it starts to kill the supple. Then back off a click.

That's assuming supple is what you want.

But you probably have thought of this already.  ;D

Thanks man.
Is that 8 more clicks of rebound damping on top of the 14 out? It feels pretty good at the standard settings.
The standard compression damping setting of 12 out is more damping than I thought would be supple but I guess it controls the shock from collapsing too quickly and packing down.
The shock looks old but works well and its hard to know how much its been messed with inside but boy it feels great. No accounting for reading the instructions ;D.

Well, "feels great" is what you want. So you're there. The rest is just a bit of icing that may be available for this particular cake or may not.

Ohlins specs count the clicks from full hard, as I expect you know.

From memory that shock will have about 21 clicks total range on each adjuster.

So 12 out on compression is roughly nine up from minimum, out of 21. If the shock works well there, that says a lot for the compression valving: you are pretty much in the middle with the adjuster, which is optimal. You can go harder or softer, to taste or to suit the conditions.

Similarly, 14 out on rebound is roughly seven up from minimum, out of 21. So about a third of the possible rebound adjustment range.

My suggestion was to back it off a further 8 - that is, in total 22 out. Well, the adjuster will probably freewheel after 21, so you will then be at minimum rebound.

The point of going there is just so that you can see if the shock feels freer and more supple. I think Ohlins sometimes specs more rebound than we want on rough Aussie roads. The result is a rear end that feels a bit rough or fatiguing on the bumpy bits, although it is really nicely tied down on the smooth bits.

Certainly the case with mine. I think I am three or four rebound clicks softer than Ohlins spec, on what is a standard Ohlins rebound stack. Fairly recently I decided I wanted a bit more control, and deducted just one of those clicks - i.e. went a single click back towards full hard from where I had been. The difference on bumpy bits from just that single click was profound.

So I reversed that change pretty soon. If I were racing, I might wind on more rebound. But for the road, a setting right on the edge of too bouncy works best for me.

The only reason I suggested winding off the full extra 8 (or 7, probably) was so you could see what she felt like at minimum rebound. As an alternative, just wind off four.

The change, when the shock stops packing down and instead recovers fully from each bump is quite noticeable. It feels almost as though the rear brake had been dragging and suddenly it's released.

Hope that helps some. It may well be that on that shock, Ohlins spec is spot-on.

OTOH it might also be that the rebound stack is identical to what they use on my DU333, for which they also recommended 14-out. I think I've settled on 17 out, but could be a click either way.

 

The OEM Ohlins I started with for my 750 wasn't what I would call supple.

I suspect your shock has been tuned.
Perhaps mine had been tuned the other way before I got it.
We'll never know.  :-\

I'm still running that Penske, and remain quite impressed how well it works straight out of the box.  [beer]

Keep in mind the knob on the shaft controls a needle/orifice valve, and generally the Ohlins have little or no check-valve on that circuit.
So when you turn the knob, it changes both compression and rebound.

The knob on the reservoir is usually just a needle/orifice valve and check-valve so it does compression only.

Thanks mate. The shock has been on the bike for all of its four owners, so that's awhile. It works real well as does the 440 on GK's M900Sie. Both quite supple yet controlled. We are both pretty heavy so maybe the compression valving is correct for us. ;D

I would agree with Speeddog, as they come  Öhlins dampers tend to be "sporty" rather than supple.

When I do a base setting on the rebound, I bounce the forks / shock, and watch how they rebound; the forks should do just a small top-out and resettle slightly, and the rear should just not do that 8i.e., top out slowly but not re-settle). That gives a fair starting point, the rest is up to personal feel and preferences, and type of ridng, of course.  I prefer to start all settings on the soft side, since to firm settings can feel deceptively fine, especially on smooth surfaces, when in reality beeing to firm. The procedure is not my idea, it´s been described often enough in varous articles and it works well for me. 

Below a shock dyno graph, showing the effect of changing rebound with compression unchanged (Öhlins DU5034, intended for S4RS Monster, but with shimming softened). There is a small effect on the compression as well, but I do not think us mere mortals will feel the difference.
 
(https://farm5.staticflickr.com/4700/39819789732_e1e3909ba9_b.jpg) (https://flic.kr/p/23EJQbQ)Skärmklipp 2018-01-23 09.41.58 (https://flic.kr/p/23EJQbQ) by torbjörn bergström (https://www.flickr.com/photos/125016045@N02/), on Flickr

I think the Penske has a check valve in the rebound adjuster, to eliminate this effect. It also has useful high speed / low speed adjusters. My expert / professional friends rate the Penske highly.

As for springs, again a matter of personal taste, I believe. As long as the sag numbers are within reasonable limits, the difference in spring stiffness will not be that big. personally, I prefer softer springs with more preload since it allows more suspension movement. The Öhlins for the "ST generation" Monsters came with 100 N/mm springs, and an ST4S came with 95 N/mm; I have that spring on my DU5034 on the M800.   

Thanks man [thumbsup]. Interesting graph.

Mine from a 851, bought and renovated over 15 years ago.
No moddings.
Spring: 1095/31-95  230. 27 mm threads showing.
I'm 93 w/o gear.

"Set the damping according to the manual and it feels great. Very poised and composed but reasonably supple."

Same here. Maybe 1-2 clicks-done!
Same procedure on 3 Ducs now...

Did you have the stock spring on yours?

It had a 1091-31/95, then I swapped in a -34/100.

Currently running a 600 lb/in spring on the Penske.

180# in street clothes, likely pushing 200# with gear.

Do you recall how much preload you needed to get the desired sag?

The only reason I ask is I don't find my Ohlins harsh at all and the stack is OEM with a stiffer spring.

On install, I set 17mm for the /95 spring, 13mm for the /100 spring.

But I was running the hydraulic preload adjuster, so it could have easily varied a good bit from that.
And I like running quite a bit of sag.

My Ohlins could have been fiddled with before I got it, 10 years old then and no way to tell.

You've made me re-evaluate my weight estimation. 200 in shorts and 210-220 in gear. The 440 is so composed and road holding is superb, but it's touring plush with the 110lb GLW riding pillion. Brings to mind your description of the compression damping as "firm". I think the spring code is well erased with time, but I may just adjust a click or two and fine tune spring preload.

That Penske was a beautifully crafted shock. It was a whole kilo+ lighter than the oem Sachs/Boge too.

So set the damping at stock spec and adjusted from there. I note that backing off the comp damping only lets the shock fall into its stroke too quickly so it stays at the base setting of 12 clicks out. I can fine tune overall compliance Vs control via the rebound clicker which still clearly has an effect on either fast or slow speed compression damping. I suspect it affects high speed comp damping while the comp knob controls slow speed comp damping or how quickly the shock falls through its stroke. So I'm using the comp knob to provide control and composure of the rear end while using the rebound wheel to manage overall compliance. Does this sound correct to you suspension guys?

I've never touched the rebound. I only adjust the remote reservoir and am happy.

Keep in mind...I never felt the vibration of a left main bearing that was failed.

The vet suspects the piston had been hitting the head for quite some time.

It's all perspective. :P

...which reminds me...I need to call him about the replacement motor that I also blew up... [bang] [bang] [bang] [bang] [bang] [bang] [laugh]

 ;D

Hard to say from where I sit. In practice, my approach follows ducpainter's. Difference being that I reached my preferred rebound setting from trial and error. I have found a rebound setting that works everywhere, and I adjust compliance with the compression knob.

If you take a look at the chart MonsterHPD posted:

(https://farm5.staticflickr.com/4700/39819789732_e1e3909ba9_b.jpg)

you can see that the rebound adjuster has only a small effect on compression damping, and that what effect there is becomes more prominent at high deflection speeds. (Upper curve is compression, speed rises left-to-right, chart shows rebound and compression at a range of settings for the rebound adjuster.)

So as the chart shows, using the rebound adjuster has a way bigger effect on rebound than compression.

However, adjusting rebound affects compliance, because it affects the ability of the shock to recover from one bump before it encounters the next.

Therefore my guess is that what you are feeling when you use the rebound clicker is the effect of the rebound damping on compliance at different settings (and not so much the effect of the rebound clicker on compression damping).

That is only a guess, obv.

It occurs to me - and this too is only a guess - is that the shock has too much rebound at the Ohlins reccommended rebound setting. So it is packing down a bit.

Have you tried running four clicks less rebound than Ohlins rec?

Thanks. That's exactly where my adjustments ended! That really helps explain what I'm feeling with the shock. And yes, I have the rebound now set at 18 clicks , so 4 more clicks out from the oem setting of 14.  [thumbsup]I first tried 16, then 18 and it's a good compromise. Playing with the compression has given me no joy and reducing  compression damping lets the shock collapse too quickly while increasing compression damping creates a harsh ride over sharp bumps. The stock compression setting works quite well.

This doesn't sound quite right. Might just be the language you've used. But I would expect the effect of a single click on the compression knob to be subtle. And therefore that you could use that clicker helpfully to tune your ride for different conditions.

I would expect ride compliance to improve as you wound off compression, and without any downside when you're just tooling along in a straight line.

Adding compression from minimum should then progressively firm up the rear for when you're working the bike.

It may be that the OEM compression setting is as firm as you ever need. But you should get more comfort (albeit less stability) as you wind the adjuster in the direction of soft.

Interesting that you like 16-18 out on the rebound. As I've said above, that's about where I am (on a different shock, but one that may well have the same rebound stack).

"Seriously, I feel one single click of compression but the rebound is less stark, but noticeable."

Edit
Testing has shown me that high speed (sharp edged bumps) are easily felt with a single click but low speed not so much. Rebound is felt more per click  for slower more rounded pot holes an d depressions causing severe packing if I went too far. After lots of testing I now think the rebound is the more intrusive adjustment

I have kept a record of all my adjustments, so I have set the compression damping knob all the way out (-12 clicks) to take it out of the picture and play with the rebound damping at 16 and18 clicks out (-2 & -4 from stock). A ride through the local hills left me feeling some packing at 16 clicks so now I will play with 18. Once I'm happy with rebound damping I'll add some compression damping and see how I feel. You guys are correct about there being plenty of built in compression and rebound damping on these shocks and my mistaking packing for compression harshness because the bike is well composed with all clicks out on the compression knob and I can feel the bike staying down or packing on deep, long potholes or hanging up on the crest of bumps with oem rebound settings.
Thanks for your guidance fellas.
On the track I find suspension set up so much easier.

Sounds like you're on to it now.  :)

Good luck, and keep us posted.

Thanks again fellas.
Cheers.

Still fooling around with the shock.
Comp damping all the way out.
Rebound damping played with from a baseline of 14 out. Trying 18 out, 20 out, 22 out, 24 out, etc and back again to see what I like as a compromise.

Whatever happend to
"Set the damping according to the manual and it feels great. Very poised and composed but reasonably supple." ??

Sooo easy to get lost in suspension fiddling....
And what spring do you have?

I can't get lost if I know the oem settings. ;)
But it is very easy to get lost, albeit suspension or engine tuning if you dont document your changes. I have eliminated the compression damping and focused on the interaction between the rebound damping and spring.
Since I have the oem settings (which are good minus 4 clicks on rebound), I can experiment and learn. I write down my impressions and get a feel for what the shock is doing by setting at extremes and also making 2 click adjustments at a time.  I can say that the adjusters still work on an old shock. As I stated earlier, the spring code has long since worn off so the spring rate is a mystery until the shock is serviced when the spring can be removed and tested.

Another thing I found was in relation to adjustments on the fly, I always hated the look of the compression gas cannister up near the tank (mine is near the shock), but I now appreciate the ability to make changes on the fly. The County I ride in has some roads that are in great condition (down here that means bumpy but not dangerous) and then roads that may cause a sedan to crash, so I found that there is not one single correct setting (that seems obvious), but everyone seems to be looking for that magic bullet when two or three settings for different roads/riding is more realistic. The gum tree roots can lift the road between rides or a pot hole form overnight so the road conditions are dynamic.
Active suspension would be an advantage around here. On the bad roads the sport bikes get smashed by the adventure bikes and motards and on the good roads the sport bike guys are waiting on top of the mountain with their helmets off..

For me  it's about learning and documenting. I have some note books laying around.. I take my hat off to suspension guys. I have found suspension fine tuning relatively easy when working with race track suspension set up by a pro, because you start with an excellent base line, but what can be very difficult is finding a reliable base line when dealing with street suspension and vastly different road conditions. I don't know about you guys but I have a much easier time setting up forks than shocks.

Thanks mate. Testing this out.
Cheers.

...and in the end, you'll set the rebound at the factory setting...+ or - a click...

set the compression at factory, and adjust as necessary. [evil]

Have fun. :-*

Probably. ;)

I also tested at minimum damping all round and it still handled very well. Not bad. Good to have options.

MHPD, Speeddig and Moronic, I'm following your advice and running minimal damping all round with a click here and there. Very happy.

Well, happy is good.  :)

Great way to get a feel for your options.

Cheers.

Setting of 21 out of 24 clicks from the recommended 12 for compression. Had it all the way out for comfort but felt the shock compress and fall into it's stroke too quickly. Rebound is 18 clicks out from recommended 14.

Edit: Was able to compensate for adding those few clicks of compression damping to stop the shock falling through its stroke too quickly by backing off the rebound from 15-16 to the 18 and this removed any harshness and slight "packing". Interesting interface between the damping circuits.
Thanks for the feedback you blokes. [thumbsup]

Interesting Tony, that is within a click or two of where I have ended up for general cruising. (Different shock as you know, although as I have said above I suspect the rebound stacks are identical.)

Yes, with a bit of extra compression you can get away with less rebound. Strangely, an Ohlins tech I was talking to at an Australian GP in the 90s offered me that as an example of advice he might give to a rider. He said the rider might ask for more rebound to control oscillation at some point on the track, and he might suggest instead a bit more compression, which would reduce shock deflection and thus give the rebound a bit less to do.

Are you really happy now?  :D

Yeah, I am less aware of the shock working and more aware of tyre feedback. The sense of feel has given me a lot more confidence.

Out of interest, I checked the range of settings on the damping adjusters. Compression had 25 clicks then a dead stop with no more movement so that was nice and clear. Rebound on the other hand went to 60 clicks out before freewheeling  :o. I think minimum rebound damping may be around the 25-30 click zone. Anyone able to clarify this?
Cheers.