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Author Topic: S4RS suspension adjustment?  (Read 2540 times)
Timmy Tucker
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« on: June 29, 2021, 10:10:28 AM »

So I need help getting the suspension on my S4RS sorted out. I don’t know if a previous owner tinkered with the settings or what, but it doesn’t handle nearly as well as my old M750 did with the standard factory suspension setup. The 750 felt like a scalpel in the turns, while the S4RS feels like a cargo ship. To put it in perspective, my dad‘s old 1100 Virago handled better than my S4RS.

The S4RS has an entire metric shit ton of understeer and feels like it’s really pushing hard in the corners. It doesn’t want to turn in quickly at all, and I have to really work the bars into a turn. At the same time, the rear end feels a little bit squishy or soft. I don’t mind the bike moving around under me a little, but the back tire just doesn’t feel planted at all. It’s like it’s just squirming around trying to find traction.

I’m 250lbs, but it’s my understanding that the factory springs should still be usable with my weight, especially since I don’t do any 2-up riding. The tires are Pirelli Diablo Supercorsas with tons of tread left, so I don’t think it has anything to do with the tires.

 I’m pretty hell-bent on doing this myself so I can learn about suspension set up. So I looked through the stickied suspension threads above, but all of the links are no longer valid. Anyway, sorry for the long story above. Here are my initial questions:


1. My first step is to make sure the suspension is in its original factory configuration before I do anything else. I can figure out most everything I need from the owners manual, except for the sag settings for the rear shock. Does anybody know what the total travel of the rear shock is? I need to know that so I can adjust my preload for a typical 1/3 “race sag”.

2. My fork tubes are currently set flush with the top triple. Is that the standard placement from the factory?

3. Are there any special tools that I will need to do this? It looks like I can accomplish most everything with a normal set of wrenches/sockets/screwdrivers etc. What am I missing?

4. Can you recommend a decent resource to help me understand what the different settings do? I understand what preload is. I’m not entirely clear on how adjustments to compression and rebound damping affect the handling, and how to tell what is needed.


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1999 M750 - "Piggy"
2007 S4RS
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« Reply #1 on: June 29, 2021, 10:30:06 AM »

Just a suggestion, look up Dave Moss Tuning on the YouTube. Some really good info.
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Timmy Tucker
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« Reply #2 on: June 29, 2021, 10:51:41 AM »

I’ll do that. I’ve seen his name come up in quite a few searches.
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1999 M750 - "Piggy"
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rule62
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« Reply #3 on: June 29, 2021, 11:01:44 AM »

Start with 30mm - 35mm of rider sag front and rear... then go from there.

This site is also helpful for clicker settings...
https://www.cycleworld.com/sport-rider/suggested-sport-bike-motorcycle-suspension-settings/
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stopintime
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« Reply #4 on: June 29, 2021, 12:45:19 PM »

Let me be a little blunt... (?) if you found your 750 to corner on rails, aiming for race settings is a miss. (1/3 is not 'race) I would recommend somewhere around 40-45mm

Spend hours and hours on Youtube to study Dave Moss. Totally worth it.

Tech specs search will tell you wheel travel front and rear. They are 130mm and 148mm

Unwind (with a special Öhlins spanner) the shock preload rings until they no longer push the spring. Same with the fork - unwind until completely 'out'. Then add a couple of assembly/mounting preload turns. Make sure the static sag is ~15mm (bike floating in air vs resting without rider) and the rest of the sag is caused by you. If you need more than 1-2 additional turns to get good rider sag numbers - the springs are wrong. Don't try to accomplish anything with wrong springs. Just don't.

Rebound is easy. Push one end of the bike down and let it jump up by itself. Find the setting that makes the bike settle after ONE jump.

Compression is harder. It requires riding and feeling. It also requires that you decide if you want a comfortable ride or better contact with the surface and wheels. Nice to have a recommended starting point - a number of clicks - but don't trust Ducati's numbers. Then find small potholes, speed bumps or other objects that obviously will challenge the suspension. Choose compression settings that feels good.

Later, you can fine tune for new levels of skills and for soecific types of riding. Road, street, track a.s.o

*********

The bike sounds like it's off geometrically. Made even worse by shitty suspension? Are you very confident you can check geometry yourself? If not, get help. You mustn't ride that bike without confidence.

In my world, it's very well worthy the money to get the WHOLE job done by a pro. Just pick one who is willing to let you watch and learn.
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« Reply #5 on: June 29, 2021, 02:08:23 PM »

Start with confirming the suspension is set to factory settings first. 

Front:
    forks should be installed 195.5mm from the top of the bottom triple to the top of the fork.
    preload 19mm.
    compression 30 clicks
    rebound  28 clicks

Rear:
    adjustable link 261 mm. from bearing center to bearing center.
    preload 11mm.
    compression 12 clicks
    rebound 13 clicks

Unfortunately I don't have specs for the ride height after you correct as needed, but if the springs are stock all should be correct.  Now set sag.  Can't get sag right, front or rear?  What stopintime said.  Now you can work on getting the bike right for you. 

My 750 turned in quicker than the 1100.  851 based frame verses ST4 based frame  (geometry) and small case engine compared large case engine (rotating mass).  After you get things sorted if you want raise the rear a bit.  I didn't because I am inseam challenged.
   
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Timmy Tucker
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« Reply #6 on: June 29, 2021, 06:56:27 PM »

Let me be a little blunt... (?) if you found your 750 to corner on rails, aiming for race settings is a miss. (1/3 is not 'race) I would recommend somewhere around 40-45mm


Haha, let me clarify…

I’ve been reading quite a bit the last few days, and I was under the impression that the term “race sag“ referred to the amount of sag with the rider fully geared up and on the bike. I’ve seen quite a few guys throwing that term around when referring to street riding, so I assumed that was the term that everybody used for it.
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« Reply #7 on: June 29, 2021, 10:16:23 PM »

Suspension set up for track is stiffer than you want for street since tracks hopefully don't have pot holes, frost heaves and various other bad surfaces.  If the roads are OK where you live 35 might be a good starting point.   
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Moronic
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« Reply #8 on: August 12, 2021, 06:26:24 AM »

OP if you're still around I hope you persevere. Handling for an S4Rs can be very sweet.

Yes the fork caps are level with the top of the fork tubes when the bike is stock. If you drop the triples in an effort to speed up the steering, the front mudguard will strike the base of the radiator on full compression of the suspension, so that's not recommended.

The rear spring should be Ohlins yellow and should have 36/105 among the other numbers printed on the side. That signifies a 105N/mm spring. If it doesn't have 105 on it, you can work out the rate from the number after the slash.

Do you need special tools? Yes and even they might not work to adjust preload on a stock S4Rs spring. These came with one nylon and one aluminium adjustable collar, and you may find that the nylon is cross-threaded and pretty hard to move at all.

Even if not, you will need two Ohlins C-spanners to unlock the collars and adjust them. Adjustment is painfully slow, and it's difficult to get the spanner well located due to interference from the piggyback reservoir. Adjustment is one tooth at a time between relocations of the spanner - maybe an eighth of a turn.

Can't remember the stock front damper settings but the rest Howie has quoted look right to me so they likely are too. The clicks are clicks back from full hard. Note that the preload quoted in mm in Howie's specs is the number of mm the spring is compressed compared with its free length - a figure useless to you and that has nothing to do with sag or how many turns you make on the adjusters.

If you are 250lbs naked you'll find the stock front springs very soft but the rear should be absolutely fine if you wind up the preload a bit. Yes the rear axle travel is 140mm to the bump stop and maybe gets to the quoted 148 with the bumper fully compressed. That suggests 45mm laden sag and you can use that much but I tend to run a little less.

As you may be aware, the S4Rs has an adjustable rod in the rear suspension linkage that allows you to adjust ride height and swingarm angle independent of spring preload (the 'raise the rear' reference from Howie's post). On a bike this old if it hasn't been adjusted and greased since new it will certainly be seized and unserviceable but there are plenty of aftermarket replacements around. Likely your problems arise from here and your being a bit weighty for the stock preload setting.

The S4Rs is set up from the factory with the adjustable link set at minimum, prioritising stability over neutrality. In that state with stock settings at the front it will want to run wide in turns and won't hold a line unless you lean off a fair bit. With you compressing the rear spring a bit extra, that alone could account for the symptoms described.

The solution could be as simple as three turns of the adjustable rod (the setting I prefer these days) and enough extra spring preload to put the sag where you want it.

I say as simple as, but it's not likely to be simple in practice. Very likely you will need to buy the aftermarket adjustable rod and then either fit it yourself or get someone to fit it who knows what they're doing. At the same time they can pull the shock and wind up the preload to whatever you think you need, perhaps also pulling the spring and replacing the nylon spring collar with a second aluminium one.

Frankly at this point I would also purchase and have fitted an Ohlins hydraulic preload adjuster - there is enough space. That way you can experiment with preload easily. If you plan to pull the shock and adjustable rod yourself, from memory of seing it done you'll need a socket wrench with an extremely long lever.

Should you also fit a firmer spring? You could but there is no half step available in Ohlins' spring range in this length, so you would need to go to a 115. You'd find that okay but firmer than optimal, just as the stock spring will be okay but softer than optimal. Your call but I'd be sticking with stock for the comfort.

Re the clickers, if you stick with the stock valving I would set the compression adjuster to full soft and then wind off rebound until it's unbearably bouncy, then restore a click. The stock valving on that shock is appalling, IMO, but many seem to persevere.

See my sig line for more on the shock.

At the front I like the rebound damping as stock but the compression four clicks softer. Recommended air gap is 170mm but I prefer a little less at 150, which helps retain some bump travel under brakes. You'll find the fork springs are pretty wimpy for your weight at 0.85N/mm and if you stick with them I'd suggest reducing the air gap further. I like 0.9 springs at the front and found 0.95s cost too much of that lovely Ohlins subtlety. If you stick with the stock rear spring I'd recommend 0.9s in the front and maybe an air gap of 140mm; if you were to go for a 115 rear spring and like a stiff set-up then you might prefer 0.95s at the front.

With the set-up right an S4Rs should feel very neutral in turns, carving beautiful arcs with no bar input and steerable on the throttle. You don't even need to hang off.

As a final thought - are your steering head bearings good, and what tyres are you running? That chassis is pretty sensitive to tyres, and works best on something sporty and pointy. Squared-off Michelin Road 3s or 4s for example will leave it feeling pretty truck-like on stock settings with extra weight on the back.
« Last Edit: August 12, 2021, 06:46:35 AM by Moronic » Logged

booger
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« Reply #9 on: August 12, 2021, 07:35:16 AM »

Wow!^ Nice comprehensive explanation.

Dunno if anybody has said this before but have you changed the oil in shock & fork yet? Also being that you are a bit heavier than what Ducati spec'd the springs for (my understanding is they spring the bikes for a 170lb rider plus or minus) so those could be corrected and the oil changed out, you may find the suspension behaves as you want it to then.

I have a S4RT with the Showa/Sachs front/rear. Searched forever to try and find the OE Ohlins front fork secondhand but no luck. In the end I opted for a full Traxxion Dynamics rebuild f/r and kind of splurged; I got the outer tubes on the fork anodized medium gray(they were plain silver before) and the inner tubes TiN coated (plain chrome stock) which were merely "feel good" cosmetics but the AK-20 cartridge kit they put in it pretty much made it perform like suspension is supposed to. I found a new in box factory Ohlins rear but Traxxion recommended I simply revalve the Sachs so that's what I did. They resprung it with a Hyperco and did a revalve. Both arrived "preadjusted" ready to install; I told them how much I weigh with gear on and my riding style etc etc. They have a shock dyno as any proper suspension shop should have and I suppose that's what enabled them to be able to "preadjust" it. The suspension works much much better now of course but I haven't played around with the settings yet. I suspect it will work even better still when I get around to adjusting it with more granularity.

I suspect the OEM Ohlins is not as good as the aftermarket Ohlins all things considered, yet their OE valving is likely better than the factory valving in the Showa/Sachs I have so you may not benefit as much as I have with a full out cartridge kit & revalve so maybe some new oil and a respring may yield what you want without spending the sheer amount I wound up spending. Lighter wheels help the handling out a lot too, I just fitted some BSTs and swapped out all the steel fasteners on the unsprung parts of the bike with titanium and also fitted a titanium front axle. So yeah, I've been working hard to improve the physics of the bike myself because I also felt like I had to manhandle it through the corners. Could have spent a little less money but with me being easily prone to budget creep on all my projects I'm not surprised. It's a good bike, it's worth it.

Traxxion also sent me a PDF of how to adjust suspension in greater detail, it's called "Suspension For Mortals" written by the owner of Traxxion. It's not Traxxion-specific, it's a handbook that details adjusting any suspension with more granularity. You are welcome to this PDF if you want it.
« Last Edit: August 12, 2021, 08:56:13 AM by booger » Logged

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« Reply #10 on: August 12, 2021, 07:48:43 AM »

Timmy Tucker I am a little heavier than you. I didn't read everything on this thread but looks like there is a lot of good information. I am lucky enough to be local to Dave Moss. He travels around and does quick suspension tunings for people for about $40-60 depending on the event and service. My S4RT has full Ohlins, DU333 rear and 999R front forks. I am pretty sure it was all stock springs. He told me he could adjust what he could but getting resprung was going to be what I really needed. The preload was set so high I wasn't getting full travel of my suspension. I rode like that for 5 years or so and finally bit the bullet and got it resprung.
 
Front I am running a 10.5  This is a tad stiff but I got my springs for $30 total, so I couldn't pass up that deal.
Rear I am running a 115   I think my Ohlins guy (Jesus at Daredevil Motorsports in Sacramento) wanted to go stiffer but the next step up is 130, that was a big jump. Not sure why they don't have an in-between.  
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Moronic
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« Reply #11 on: August 20, 2021, 04:38:50 AM »

Timmy Tucker I am a little heavier than you.

Rear I am running a 115   I think my Ohlins guy (Jesus at Daredevil Motorsports in Sacramento) wanted to go stiffer but the next step up is 130, that was a big jump. Not sure why they don't have an in-between.  


Are you bottoming the shock on a frequent basis?

I'm around the 80kg mark naked and a few years ago put in about 12,000 miles (custom saddle) on the S4Rs with a passenger of roughly 55kg. That's 135kg naked, or 300 pounds. We started with a 123 spring (not Ohlins) and came back to a 115 (Ohlins). That spring had plenty under all conditions, Including riding with the two of us and significant baggage.



Are you sure you need more spring?

And 1.05 in the front is ridiculous, IMO. Spend a few $ for .95 or even .9 and you won't know yourself.
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