Ohlins Preload

[posplayr]

EDIT 6/29/2012 I should mention in this thread that after I up graded my Ohlins I got a next stiffer spring set and the wollowing pretty much went away. However I also changed to 18" wheels (170/60-18 rear tire) and radials so I'm sure it was the combination of both. Basically A flexible side wall and a under sprung weight contributed to the wallow.

Anybody fiddled with their Ohlins preloads? I get a little wallow in fast tight corners (70 mph+) especially when I have my camping gear on top(ridding the 831100ED). Generally the bike handles very well under fairly aggressive ridding. This wallow adjusted by extra weight on the rear is my only complaint.



I was not sure how the preloads adjusted so now both shocks are off and I have decided to should move the static adjustment clip ring(on the left) . By measurement the adjustment collars (on the right) give a 1/2" of adjustment. Collars are intended to be made on the bike without removal. Now that I have it apart I see I have been running on the lowest preload as well.

I guess I should mention the shocks were set for my weight (I might have told them 200 lbs at the time) by Ohlins when we all did the group buy.

So here is my question, for anybody that has used the adjustment collars how much do they typically change the ridding and do they provide more than enough adjustment? I'm debating whether to change the ring by 1,2 or as much a 3 grooves. (leaning toward 2 groves as I write this).

Pos


Update:

Added ony one of the clip ring grooves and set preload to max. Just around town it is very firm and a little bit of bounce. I may set it back to mid range but need to get out into some twisties to really feel the diff.

[Mark M]

I would have to say that preload is going to do very little for a wallow, that is typically a rebound damping issue. If you are running significantly heavier, then adding preload will restore your ride height, but extra damping is what is needed to control the motion. How much static and laden sag are you running? Your description of a "little bit of bounce" also sounds like a lack of rebound damping to control the spring you have on there.

Mark

[posplayr]

Mark

I would have to say that preload is going to do very little for a wallow, that is typically a rebound damping issue.

I might be using the wrong term. There is a tendency for rear spring compression in a high speed turn to cause body roll (initiated from the rear). It is worse when I have a load on the back like the the camping gear in my signature. It is not an undamped mode, but seems to be strictly a function of rear swing arm compression in a turn.

If you are running significantly heavier, then adding preload will restore your ride height, but extra damping is what is needed to control the motion.

As mentioned above it is worst at highspeed banked irregular curves (which compress the swingarm at a bank angle) and seems worst with the camping gear which is probably 50 lbs. Stiffening the rear seems to reduce the compression and I'm guessing makes the tendency to roll reduce.

How much static and laden sag are you running?

I don't know and will not go so far as say it doesn't matter, but I dont have much choice at this point as other than to change the preload and see what happens. The Ohlins were set for a 200 lbs rider , and the front is set very stiff and so the front ride height is up. In front I have an uncut progressive spring with the racetech emulator set to zero preload and 15 wt oil. The emulator is 14mm so that is like having maximum fork preload (which is 13mm)

Your description of a "little bit of bounce" also sounds like a lack of rebound damping to control the spring you have on there.

Bounce may have been a poor choice of words given the discussion. I think the rear spring was so stiff, that the swing arm is not compressing as much and transmitting more force to the rider(me). There is nothing under damped about the ride; it is harsh. Moving back to the mid preload position reduced this significantly.

http://www.lkjh.biz/bike/california/santa_barbara/camino_cielo/

I did a test ride on Camino Cielo after a readjustment on a low speed very twisty road. This is after I added 1 fixed groove to the preload (0.150") and went to the middle of the preload (0.200 above minimum) which added a total of 0.350 to the spring compression from where I had been riding the Ohlins.

The bike handles great at low speed and even though it was a rouch road, it was not excessive. Most of the twisties are between 10-30 mph. After I got off of Camino Cielo, traveling at 60-65 through a 45 mph marked curve there seemed to be less of the compression/roll tendency but I really need Hwy 33 to test that out.

Final note, these are virtually brand new Ohlins from the group buy last year. They have at most 4K miles on them. I did not spring for the adjustable ones. These only have preload adjustment.

My Gixxer will have a fox double clicker on the rear so, I will not be motivated to try to make the GS do more than it is willing to .

Jim

[salty_monk]

I feel something somewhat similar on the G sometimes. More so with the cases on it & loaded.

I personally don't think it's anything to do with the shock, I think it's bump induced frame or swingarm flex. I've run at several different combinations of preload & damping (albeit on much poorer quality shocks) with no marked changes observed....

Is that a possibilty with your setup do you think?

Dan

[posplayr]

Dan

I think it's bump induced frame or swingarm flex. I've run at several different combinations of preload & damping (albeit on much poorer quality shocks) with no marked changes observed

The most noticeable has been when I was loaded with all the camping gears and going through a relatively high speed turn and noticeable rear suspension compression.

The rear seems to attempt to roll into the turn in phase with a compression of the rear suspension. It is well damped , but if you happened to hit several undulations in the road that at your speed are in phase with the mode, there is a constructive build up albeit well damped.

It seems to being driven by some asymmetry (e.g. swing arm , frame or bias ply tire flex). I will have a bandit swinger with radial 170/60-18 on the rear with the new conversion so I will be able to see if that helps.

For now I only have a single degree of freedom in making any adjustment and that is in the rear preload ALONE. I was thinking that the stiffer the preload is, the less compression and therefore the less this mode seems to be excited. Right now I'm not sure as I was only able to do some moderate 60 mphs turns.

For the purpose of this thread, I was not really trying to get into so much detail, but rather ask how much of an adjustment on a Ohlin (clip rings or collar adjustment) is noticeable and how much is too far in terms of stiffness.

The more I write, the more I'm starting to think it might be rear tire sidewall flex phenomenon. If the rear gets extra load due to road undulations while in a banked turn, the compressed rear sidewall might have a tendency to squeeze the wheel to the outside of the turn (increase yaw into the turn) and give this effect. Just thinking it threw; not sure.

Jim

[first timer]

did you get a tunning manual from ohlins when you got the shocks? it tells you how to set up you static sag and your ride sag. Might want to call ohlin and see if they can send you a copy.

I used one to set up my SV after my race tech springs in the front end. it was easy to use and helped alot.

I seemed to have lost the pdf but i will see if i can track it down.

I know what Jim is talking about, when Laura and I were riding his bike it seemed like his back end was a touch loose, my thought was under dampening, or loose swing arm bearings. I have felt frame flex and and it doesn't feel loose when it happens, just a hyper extention and a springy feeling.

[posplayr]

Rear Sag and Ride height

OK here are some numbers I measured tonite which my wife begrudgingly helped me with.

Originally I had the Ohlins installed as I got them from the factor set for my weight 200 lbs with the preload collars at minimum.


As described previously, I lowered the clip ring by one groove (0.150") and moved the preload finally to the middle (0.200"). So now I have an extra 0.350"=8.9 mm preload from before.



The rear static sag numbers (unweighted) are 3.2 mm (after adding 8.9mm preload)
The right height with me on it (no shoes , helmet or jacket) 28 mm

The static sag is low because I just got finished adding all of the preload. The ride height at the low end but will settle more into the range with gear weight of 20-25lbs added (boots,jacket,helmet,pants).

Pos

OK Comments?

Ryan,

or loose swing arm bearings.

The bandit arm should solve that.

What do you think of the sidewall flex theory?

[Mark M]

The rear static sag numbers (unweighted) are 3.2 mm (after adding 8.9mm preload)
The right height with me on it (no shoes , helmet or jacket) 28 mm

Your laden sag is pretty good, but the lack of static sag indicates the spring rate is too low for your weight. Adding preload is a crutch for this condition and will result in a fairly harsh ride combined with easy bottoming and dropping through the stroke in corners. Pretty much what you describe in your first post. If you have the option, stepping up to the next stiffer spring rate would likely work out better for you.

Mark

[posplayr]

Mark

I appreciate you comments, but I'm confused about the last one.

but the lack of static sag indicates the spring rate is too low for your weight.

The sag is with me off of the bike, and there is only 3mm of sag because I added a 9mm of preload. I added preload to see what happens and to see if the rear wobble would go away. Apparently this preload might have little effect on wobble effect.

If I reduce the preload, I'm sure the static sag will increase again (by the amount of 9mm of preload I put in?)

I won't be surprised if I'm overloading the rear spring when loaded with an extra 75 lbs of riding gear and camping gear, as that is why i was trying to add more preload. However I'm not so sure that the lack of static sag which I created is an indicator of weak springs.

Also lets keep this in context, Ryan felt it when he was riding with Laura on the back (he is 150 lbs she is 100 lbs but right on the back) and I feel it (without camping load) when attempting to chase down a late model GSXR 750, and a couple of Buells. At almost anything under 50 mph it doesn't show up. For me it is laying over about as far as my case guards will allow, at 50+ mph on an uneven road when it is very noticeable. It keeps me at 60 mph rather than going to 80 mph.

Jim

[isleoman]

Pos,

I've had the Ohlins on my bike for at least 20 years, in fact they had a different part number back then. My adjustable collar has been lowered over time to compensate for my increase in weight. Mine are set on the fifth ring down from the top. I had them rebuilt by the local GMD a few times over the years. I'm sure they fiddled with the original oil weight

I don't experience the handling issues your talking about, either with my current USD forks or the stock forks that were highly modified. I know my wife weighs more than your camping gear and it still doesn't wallow around and we've done quite a bit of triple digit sport touring. My buddy weighs about 165 and we'll trade bikes and he never has a problem using my set up for 220.

I bought some new Ohlins during the group buy and had them set up for my current weight. I know the springs are black. I'll have to count down the rings for you. The new ones are the 13.25" long units designed for the CBR1000/900s.

My advice is to just write down your original settings (I know you would) and start moving in both directions till your happy.

[posplayr]

isleoman

My adjustable collar has been lowered over time to compensate for my increase in weight. Mine are set on the fifth ring down from the top.

In the pics you can see which grove the clip is it. If the upper most is unusable then it was set to 4th groove. I think I told Ohlins I weighed 200 lbs with hopes I would stay below 195. I'm now at 208 lbs so I guess I fibbed a little. I just moved the clip down one on Sunday (not shown in the pic). I have the black spring as well. Other than oil weight, we are probably running about the same. Note those weights are in my birthday suit .

I'm starting to think that I am dealing with a tire issue. I'm using the Pirelli Sport Demons 130/90-17 on the rear and 100/90-19 on the front with stock rims. I think they are inflated to about 36/33 psi respectively. The rear tires are a little flat on center from the two GSR trips, but the first time I had any evidence of the problem there was only 1500 miles on them and I was returning from Yosemite.

Up front I have progressives springs(un cut), racetech emulators, 15 wt oil, zero preload and a fork brace. My Yoshi pipe runs right down the center, so when I drag something it is now tending to be my case savers (thank you very much they are going to stay on).

Thinking back about some recent rides, it seems like if I'm sitting forward with legs pressing the tank and below 60 mph I never feel any hint of anything but very solid ride and handling. Bill (Chef) at 6'6" and 300+ lbs has ridden the same bike with 2 comments from him after he first rode it were "best handling GS he has ridden" and "confidence inspiring". Given my late in life endeavor into motorcycle, I was happy as I planned to make the bike safe in the handling department first then work on power.

In the most pronounced experiences I have had with the phenomenon, there has been a definite suspension loading to roll effect. When the rear suspension loaded, the bike rolled further into the direction of turn. As it unloaded, the roll angle cam back out. It was stable and did not grow. It was enough that I held the throttle constant and did not accelerate any faster in the turn.

At the time I did not know if this was a normal gyroscopic effect or what. I did read up on suspensions and rear wheel weave and there was a suggestion that it was made worse by weight located high and to the rear. I assumed it was normal. I'm starting to think not.

I have the stock GS1100E aluminum swing arm. While I did not replace the needle bearings, they don't even seem to have run dry and seemed to be in good working order so i simply greased them and reassembled. I don't suspect the swing arm as that would promote issues even in a straight line and that just doesn't happen.

This is a virtually new shock and set virtually the same as yours.

The tires are really the only thing left so here is the theory.

Weight/loads between the wheels tends to load both front and rear wheel equally. Any weight behind the rear axle will tend to LOAD the rear wheel and actually UNWEIGHT the front. This loading of the rear wheel and unloading of the front wheel will cause an increase in the rear wheel side way flex and side slip angle. This in turn creates an additional side force and therefore even more body lean. This can not occur when riding straight as all the forces are straight down and there is no side slip angle.

I would have considered frame flex to be a possibility, but if it was then your bike would have the same effect. It is possible that it comes from swing arm flex, but you don't seem to think that you have experienced that. I will recheck my swing arm bold for tightness, but the evidence suggests some type of flex, and the tires are the most likely candidate.

If the above is true, then I should be able to install a stiffer rear tire and make it go away. I have the Bandit arm and 170/160-18 planned for this summer. Maybe I'll just swap the swing arm first to rule that out.

Pos

P.S. Mike I set up the forks as recommended by you and Joe Nardy; thanks again that was very helpful.

http://www.thegsresources.com/_forum/showpost.php?p=861452&postcount=33

[isleoman]

Pos, When I had the stock forks and swingarm and Ohlins I was running bias-ply tires. I think I ran a Perrelli Lazer 33 in the front and a Bridgestone BT45 or something like that in the back.

Now days I run the BT021 Bridgestones front and rear. Love em. They wear beautifully on the GS, they don't wear as well on the FZ1. Tend to develop flat spots and cupping in the front.
No cupping on the GS at all and I have more than 6k on them.

[salty_monk]

Where did you get your tyre pressures? Avon recommends 36F 42 Rear for my bike... A little more pressure should help to stiffen the sidewall.

[posplayr]

Dan,
Manual say 24 and 28 psi and it goes up from three depending upon riding load. How many sacks of concrete do you typically carry on that skunk?.

So your saying I should just bone those babies up till they squeel?.

Will check what the rating is at lunch.

Jim

[isleoman]

Those pressure might be ok for the track but they seem low for the street. I think Monk will be closer to the target. I would have suggested 36 front and 38 rear. 24 seems way low.