Ohlins forks on S4RS very stiff - Ducati.ms - The Ultimate Ducati Forum
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post #1 of 22 (permalink) Old Aug 12th, 2019, 10:34 am Thread Starter
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Ohlins forks on S4RS very stiff

I love my S4RS but itís beating me to death on my local roads. I could find no adjustment settings on the forks that alleviated this. The forks started leaking so I replaced the seals last winter, verified that the spring rate was correct for me, and replaced the fluid with the documented volume from the top of the tube. I did not bother measuring the amount that came out as it wouldnít have been correct anyway due to leaking profusely on both sides for a while. Also , the forks were so harsh I wasnít sure they werenít overfilled to begin with. I used 5w synthetic fork oil, Spectro , IIRC. Nothing was found wrong internally, and the forks were thoroughly cleaned.
What Iíd like to know is , if youíre happy with the forks, what fluid you are using ? What was the fluid height you set ? What compression and rebound adjustment are you happy with ? Please do not give me the ď everybodyís different ď speech. Iíve heard it all. If youíre not going to give me some baseline settings, please donít respond at all. The suspension on this bike is downright punishing. Before I send them to someone for professional work Iíd like to exhaust all options.

'96 Ducati SS900CR, '07 S4RS, '06 Busa, '77 Bonny,
'00 Superglide, '85 Sportster, '78 SR500
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post #2 of 22 (permalink) Old Aug 12th, 2019, 11:35 am
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I love my S4RS but itís beating me to death on my local roads. I could find no adjustment settings on the forks that alleviated this. The forks started leaking so I replaced the seals last winter, verified that the spring rate was correct for me, and replaced the fluid with the documented volume from the top of the tube. I did not bother measuring the amount that came out as it wouldnít have been correct anyway due to leaking profusely on both sides for a while. Also , the forks were so harsh I wasnít sure they werenít overfilled to begin with. I used 5w synthetic fork oil, Spectro , IIRC. Nothing was found wrong internally, and the forks were thoroughly cleaned.

What Iíd like to know is , if youíre happy with the forks, what fluid you are using ? What was the fluid height you set ? What compression and rebound adjustment are you happy with ? Please do not give me the ď everybodyís different ď speech. Iíve heard it all. If youíre not going to give me some baseline settings, please donít respond at all. The suspension on this bike is downright punishing. Before I send them to someone for professional work Iíd like to exhaust all options.
I'm thinking your fork oil is too heavy...ohlins, despite the number 5 on the bottle is near water...other than that I'm 175lbs running a 9.5 spring with an 80cm air gap with 4 turns in from all the way out on rebound and 20 turns out on compression...your tire is ultimately going to tell you what you need...but I hear your complaint..I went up a spring rate and left my settings as before and it hurt to move my arms after a long ride...I'd recommend a lighter oil and open up your compression and rebound a bit ...perhaps remove some fluid too just be careful your not slamming into the bottom of the stroke under extreme situations

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Last edited by Buhgaboo; Aug 12th, 2019 at 11:50 am.
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post #3 of 22 (permalink) Old Aug 12th, 2019, 12:39 pm
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There’s actually two damping circuits to consider— low speed damping that’s controlled by how many clicks you set — and high speed damping that’s controlled by the internal shim stack.

Compression damping is what makes a bike ride “hard” on bad (normal) roads. You want to dial in as little as possible without making the bike handle poorly. This takes a bit of experimentation. Not enough compression in front causes fork dive. You can bottom the forks on hard braking. Too much causes the bike to loose control on bumpy turns and feel too busy.

Too much compression in the rear will wreck your spine and cause the back to bounce all over bumpy corners. Too little will make it feel sloppy. A little compression damping here goes a long way.

When you hit most bumps, the low speed damping controls how quickly you stop bouncing. Too quickly and the bump feels jarring, too slow and you find the bike bouncing for several cycles after which gives you the feeling that there’s not enough control of the bike movement. So you set damping to strike a personal balance between jarring and bouncy. Adjust your damper for full soft, and again for full hard. Ride around to understand the effect of the range of adjustment available.

When you hit a quick bump like a pothole, the hydraulic fluid just can’t flow fast enough through the small adjustable orifice that you use to set low speed damping discussed above. So there’s an internal shim stack that lifts like a pressure relief valve to allow more fluid flow and consequently less damping during the event. After the high speed suspension movement event, the shim stack returns to its normal closed position.

There are shim stack replacement kits like the Race Tech Gold Valve that allows you to have some additional velocity sensitive damping adjustment. The idea here is that the gold valves (I’m quoting) “lets the damping rate be optimized for small, low velocity, fork motions where oil is forced between the valve disk and body, but lets the spring open up the valve to provide more oil flow when large/fast fork movements occur. By adjusting the tension in the spring you can tailor when and how far the valve opens, that is, when the transition between damping that's good for small bumps and damping best for big hits occurs.”

So, as you ride, make a distinction between slow and fast bumps as they affect ride quality — then you’ll know what to do.

I'd start by decreasing low speed compression damping to its lowest click setting and take a test ride to understand your adjustment range using your current fork oil viscosity and to see if your problem is low speed or high speed damping. If the problem is low speed damping related, gradually raise the damping to suit your personal comfort level.

Last edited by Strega; Aug 12th, 2019 at 3:29 pm.
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post #4 of 22 (permalink) Old Aug 13th, 2019, 12:06 am
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i have a customer who probably weighs 90 - 95kg at a guess. he is running i think a 0.90 and 0.95 spring, or maybe 0.85/0.9, forget now. i think his have been played with - knowing him, i'm sure they would have been.

ohlins 1309 oil (19 cst at 40 degrees) set to 85mm with white guide in, but not spring. i think it was 95mm, and he wanted to try a little higher. spec is 170mm. settings c: 12, r: 10, p: 2.5 turns.

sounds like something is wrong to me if they're too harsh. is the valving original?

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post #5 of 22 (permalink) Old Aug 13th, 2019, 10:08 am Thread Starter
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I donít know whether the forks have been played with or not. I tried to contact the PO but wasnít successful. Iíve now dialed compression all the way out but havenít tried it yet. Itís not just comfort, the front tire is not maintaining road contact very well either. Bumps in the middle of curves could be challenging. I thought the 5w fluid would be comparable or maybe even make things a little more compliant, but it didnít. Everything internally looked fine.

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post #6 of 22 (permalink) Old Aug 13th, 2019, 10:51 am
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In stock form those forks are usually under sprung for most riders, when they first came out we though the front brakes were strong but it was mostly due to dive.

I may have missed it but where are they too harsh?
everywhere?
bottom of stroke?
mid stroke?
As mentioned be sure to differentiate between high speed damping and low speed, remember we are talking shaft speed.

Is the bike chassis otherwise stock?
Does it have clip ons.ape hangers or oem bars?
Has the rear ride height been raised or lowered?

Were you ever happy or did the problem come with the oil change?
Is the bike using all its travel under maximum conditions?
Have you measured travel?

I have had a oem ohlins bike come in where the rebound adjuster had been jammed closed internally due to improper assembly I also bought a set of used ohlins that had been screwed up internally by a prior owner including welding of the cartridge body and a large house fly being in the valve stack... I kid you not!
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post #7 of 22 (permalink) Old Aug 13th, 2019, 10:57 am
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Originally Posted by duc96cr View Post
I donít know whether the forks have been played with or not. I tried to contact the PO but wasnít successful. Iíve now dialed compression all the way out but havenít tried it yet. Itís not just comfort, the front tire is not maintaining road contact very well either. Bumps in the middle of curves could be challenging. I thought the 5w fluid would be comparable or maybe even make things a little more compliant, but it didnít. Everything internally looked fine.
Think of compression like a volume knob for feedback...too much and you feel everything...too little and your on a cloud...but if your rebound is out to far the bike will pogo in the corner...if it's too tight it will skip off the bumps....also if the rebound doesn't match the rear it will feel very unstable mid-corner as if the bike is rocking back and forth....a simple way to adjust the rebound is to look at the tire tread....if the forward edge is wearing down it's too fast and needs more damping, clicks to the right....if the trailing edge is worn it's too slow, clicks to the left....same for the rear but only look at the tread were your on the throttle...everyone's shock is too fast when coasting and will give you the wrong read...

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post #8 of 22 (permalink) Old Aug 14th, 2019, 5:35 am
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the way i see it you have 3 options.

1/ keep complaining about it.
2/ pull it apart again without any real idea of what you're looking for.
3/ send them to someone who knows.

only #3 is going to help you.

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post #9 of 22 (permalink) Old Aug 14th, 2019, 8:49 am Thread Starter
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I like to fix things myself if possible. I wonít learn much if I send them out. When I assembled them last winter I had the wrong oil height but someone here corrected me and I lowered it. It is summer here belter so Iím not going to disable the bike until cold weather. Iíll send the forks out then if Iíve had no success. I donít have a ton of experience on adjustable forks but Iíve rebuilt them several times before with no problems. I havenít had any issues with the others. I did the GSXR conversion on my SS with no problem and good results.
In Michigan we have a wide temperature change that causes the roads to compress and form peaks at the cracks, some roads every 10-20 ft. Those little peaks are what the forks donít handle. I have those roads near my house. The Ohlins forks donít seem to want to handle those small risers, sending the jolt straight to me. This is not the case with the Showas on my SS or Busa. The springs are .90 in both Ducatis. I weigh 195# in full gear and both bikes weigh about the same.
I have a zip tie to indicate fork travel and will go for a ride today. Iím thinking I may change to lighter fluid to reduce damping as my next step.
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post #10 of 22 (permalink) Old Aug 14th, 2019, 4:54 pm
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are the shims stacks original/correct/appropriate? that's really all that's going to effect harshness. oil height won't, unless they're full to the top.

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