Preload/Shock Absorber

[wackettrw]

Please explain to me (in layman terms, and without the use of complicated tools and devices), how to manually tune the suspension on my 1999 R1100RT sports tourer by adjusting the stock adjustment mechanisms (i.e. preload and damping adjustment mechanisms). The manufacturer's 25 page owner's manual is no help at all. Perhaps if you explained how to manually tune the suspension for the following 2 extremes, I would make minor in-between adjustments, when required.


TOURING:
When I travel for 2-3 months straight during the
summer or touring down south during the 4-week
mid-winter semester break, I travel with an extreme
load (weight) to include 2 fully loaded oversized-lid
stock saddle bags, a top bag, a fully extended stock
tank bag, a very large army-sized duffle bag
(completely full of camping gear) strapped across the
passenger seat (the duffle bag also substitutes as a
backrest), plus I'm no light-weight to begin with. In
total, assume I weigh in at just below the maximum
carrying capacity load limit for the RT when
camping/touring.

versus

SPORT:
Local riding with no tank bag nor top bag, saddle
bags nearly empty or sometimes completely removed,
making the RT like a "sport" bike.



I remember being told (by a BMW salesman when I
bought the bike new 5 years ago) to sit on the bike on
level ground in front of a large storefront window.
Look at the reflection in the window and adjust the
preload knob/wheel until the bike is level, which
changes based upon load I am carrying. Then ride the
bike with the load I am carrying, and set the damping
screw/nut adjustment mechanism until the bike does not
bottom out on a bump/pothole nor is too stiff/hard a
ride. Is this satisfactory? Other suggestions?

Please note that I am not the least bit mechanical.
I ride my BMW motorcycles, I do not fix it! All the
maintenance is done by authorized BMW dealers at home
or away when I travel. Please KEEP IT (your
explanation) SIMPLE STUPID (referring to the KISS
principle, not you).

[lorazepam]

Depends on what you weigh, as to how to adjust it for "sport" riding. I am rather "densely" packed at 250 pounds, and I just crank up the preload all the way, and put the rebound damping about 3/4 of the way up. I can put close to max load on with camping gear and riding 2 up so this works for me. I prefer a firmer suspension when riding solo, and with my weight, I just leave things where they are, and when I am looking for hundredths of a second at the track (fat chance) I will tweak it further. Until then I will leave the settings in one place. Just my .02 worth.

[dlearl476]

I am of the opinion that you want your bike to handle the same in all instances. You change the settings to compensate for the weight you're carrying, not a riding style you "think" you're using. Basically, you want your bike to react to your input the same whether you're out "sportriding" or fully loaded motoring down the freeway on your way to a rally weekend. To that end:
Kroon Suspenion Set-up (http://www.ohlins.nl/UK/suspsetup.html)
and
Ohlins Set-up (http://www.ohlins.com/pdf/ultimate_tuning_bike.pdf)
are two I know of. I'm sure a Google search for "motorcycle suspension Set-up" would hit on scores more.

And if I could add one little personal note: Take copius notes and only change ONE thing at a time. It's time consuming (but fun!) when you do it, but once you know your best personal settings, it's a snap to go from fully loaded to stipped for fun. And your bike is predictable in both situations.

And I just read your KISS bit. If I were you, I'd take my bike to a race shop. Somewhere you have a good feeling about the techs taking you seriously, and offer money to help you set up your bike. A good shop will enjoy the challenge, and in the end you'll have the numbers you need to change the set-up yourself as needed.
Me, I find the more I know about my bike and the more I do myself, the greater enjoyment I have of using it. I myself like to play with suspension settings mid-ride. That way I get instant feedback. But I HAVE had race tuners help me get the initial set-up. Mostly cause I live alone and it takes at least two people to set the sag properly.

[lorazepam]

True Dave, if you have aftermarket suspension, getting a competant shop to help with setup is a good idea. BMW shocks are not exactly racing material, and the settings are limited, and the shocks wear out pretty fast (20-30k miles). I wouldn't go to a shop, I would see if you can get a mechanic you trust from your BMW shop to help on a sunday. The race guys will be in your pocket for a grand or more before they turn a wrench.

[wackettrw]

You guys are missing my points. If I'm running at full weight/capacity of the motorcycle (i.e. touring) versus lowest possible weight (sport riding), which way do I turn the pre-load and the shock absorber damping.
That is, at full load do I turn the pre-load towards 'S' or 'H' (which I guess stands for soft & hard)? At lowest possible weight, towards 'S' or towards 'H'?
At full load do I turn the damping knob clockwise or counter-clockwise? At lowest possible weight which way do I turn the damping knob?
I know I willl learn to adjust the above 2 settings based upon the load I'm carrying, but I don't even know which way to turn the pre-load screw and the damping knob, and for what reasons. I don't even know what adjustment is used for what purpose. That is, does the pre-load set the bike level and the damping knob sets the shock from bottoming out OR is it just the opposite????
Also, please comment on my sales rep's comments of looking at reflection in mirror for initial shot at setting the pre-load screw & the damping knob.
Sincerely,
Richard

[kbasa]

Let's explain how a shock works a little and then this'll make more sense to you.

The spring of the shock carries your weight. If you raise the bottom of the shock, you'll raise the rear of the bike, which is helpful if you have an extra person or more stuff on the back. On your bike, that's going to be in the "H" direction. There are some guidelines for determining what the proper height is and the manuals at the Kroom site will probably help you determine what that height should be.

So, you've got your weight supported by the spring and you're riding down the road. Without an ability to damp the movement of the spring, you'd just pogo on down the road every time you hit a bump. The shocks other function is to damp the movements of the spring. It does that with what it termed "rebound damping". Basically, if you find yourself bouncing down the road you need more rebound damping. Again, they're probably calling "more" by the "H" value. If your bike doesn't pogo, you should be fine. Be sure to understand that the rebound damping adjustment won't keep your bike from bottoming out - that function will come from your spring.

OK, so now you've got all these knobs and levers and you've got ways to adjust them. You've also got an opportunity to really screw them up. So, before you do anything else, get a little notebook and take some notes. Note how many turns each of the adjusters are from either full in or full out. Mark it as your base. If you get things all screwed up, you'll be able to get back to where you started. Also, as you find an adjustment that works for you and your wife or you and your stuff, you'll be able to quickly adjust the suspension to those values because you've got it written down and stuck in the tail cone of your bike.

Now, as far as which way to turn the damping knob, I'm not familiar with your shock. But if you've got the starting value written down, do what engineers around the world do - make it way too big and see what happens and then make it way too small and see what happens. This should show you how the know works pretty quickly. In one direction, your bike will pogo and in the other direction, it'll be strangely harsh.

Make sense?

[Mr. Frank]

I'd be interested in hearing where people set the rebound damping on the stock shock on the R11xxRT. I have mine in the middle of the range because I don't have a better idea.

[wackettrw]

You guys are really confusing me on setting the preload and damping. Let me see if I got this straight, based upon my knowledge and what you have said:

First set the preload. This is done to get the bike level based upon the load/weight I am carrying at the time. I turn the preload wheel/knob clockwise towards 'high' to raise the rear of the bike. Conversely, I turn the preload wheel/knob counter-clockwise towards 'low' to lower the rear of the bike. This leveling needs to be done with the rider (& passenger) on the bike with the load/weight (tank bag, top bag, side saddlebags, etc) that is to be carried for that ride.

Second, after the bike is level by setting the preload, now the damping screw has to be adjusted between soft (S) and hard (H) to set the amount of damping to prevent the shock absorber from bottoming out (i.e. soft) and the ride being too stiff (i.e. hard).

Normally, the shock absorber damping screw can only turn 1/2 to 1 full turns maximum (i.e. minor adjustments are all that are needed), while the preload wheel/knob can make numerous turns between low (low weight/load, sport riding, 1 up, no bags, no extra equipment, no passenger, etc) and high (heavy load/weight, with passenger, loaded tank bag, top bag, saddlebags, etc).

If I got the above incorrect, please so advise where. Also, if anyone can answer the Hattiesburg, Mississippi rider's question about determining where to set the damping screw (other than keeping it in the middle), would be appreciated. Is the only answer 'feel' the 'bounce' when riding and adjust the damping screw accordingly?

Sincerely,
Richard

[kbasa]

You understand it perfectly.

Set the ride height by adjusting the preload.

Ride it a little. If it bounces a couple times after you hit a bump, add more damping. If it doesn't, back it off a little until it does and then add just a smidge more to get rid of the bouncing.

:thumb

[dlearl476]

>You guys are missing my points.

And you missed mine. "Teach a man to fish...."
Oh well, I tried.

[wackettrw]

TO: KBasa (Dave Swider)
Dave,
Regarding your last comments, as follows:

"You understand it perfectly. Set the ride height by adjusting the preload. Ride it a little. If it bounces a couple times after you hit a bump, add more damping. If it doesn't, back it off a little until it does and then add just a smidge more to get rid of the bouncing."

Question #1:
By "adding more damping", do you mean turn the damping screw clockwise towards "hard" (H)? Conversely, by "back it off", do you mean turn the damping screw counter-clockwise towards "soft" (S)?

Question (or Comment) #2:
I'm not so sure about your comments about "bouncing". I do not believe a bike should "bounce" at any damping setting, unless your shock absorber is defective. A shock absorber dampens (i.e. stops multiple bounces) at any setting. However, if the damping is set too "soft" you could bottom-out on big bumps, and if the damping is set too "hard" (i.e. firm) you will be jarred when you hit a bump (just like a chopper without rear suspension). In either case, if you "bounce" more than once, your shock absorber is defective no matter what the damping setting, in my view. If I'm wrong please comment/explain.

I have really appreciated all the comments on this subject, including going to a professional to learn how to do it correctly. I believe most motorcyclists do not know how to adjust the preload and damping correctly. I have asked Motorcycle Consumer News, BMW Owner's News (via "The Wrench"), David Haught (spelling?) of Proficient Motorcycling, etc to do an article (in layman's terms) on the subject.

Hope to see you all at the Northwest Passage Rally in Spokane, Washington in mid-July 2004.
Regards,
Richard W. Wackett

[kbasa]

Originally posted by wackettrw
TO: KBasa (Dave Swider)
Dave,
Regarding your last comments, as follows:

"You understand it perfectly. Set the ride height by adjusting the preload. Ride it a little. If it bounces a couple times after you hit a bump, add more damping. If it doesn't, back it off a little until it does and then add just a smidge more to get rid of the bouncing."

Question #1:
By "adding more damping", do you mean turn the damping screw clockwise towards "hard" (H)? Conversely, by "back it off", do you mean turn the damping screw counter-clockwise towards "soft" (S)?

Adding more damping, and I'm making an assumption since I'm not sure how your shock works, would be moving it toward 'H'. You can always experiment and make it way to big and see what happens and then make it way too small and see what happens. You won't break the shock by experimenting.



Question (or Comment) #2:
I'm not so sure about your comments about "bouncing". I do not believe a bike should "bounce" at any damping setting, unless your shock absorber is defective. A shock absorber dampens (i.e. stops multiple bounces) at any setting. However, if the damping is set too "soft" you could bottom-out on big bumps, and if the damping is set too "hard" (i.e. firm) you will be jarred when you hit a bump (just like a chopper without rear suspension). In either case, if you "bounce" more than once, your shock absorber is defective no matter what the damping setting, in my view. If I'm wrong please comment/explain.

You're looking at damping as resistance to compression of the shock. That's actually the spring's job. Damping controls resistance to extension of the shock. If the damping is set too soft, the shock will cycle a couple times after you hit a bump. When shocks fail, that's what goes on them: the damping loses its ability to resist extension. If you have the damping set too low, you'll get the same effect.

The spring on your shock will offer the same amount of resistance to compression throughout its travel. It will be tuned for a weight range. If it's too hard for you when you're alone, it might be better when you're loaded. Kind of like how a pickup truck rides better with a lot of stuff in the bed. The preload adjustment for your spring only sets the ride height.



I have really appreciated all the comments on this subject, including going to a professional to learn how to do it correctly. I believe most motorcyclists do not know how to adjust the preload and damping correctly. I have asked Motorcycle Consumer News, BMW Owner's News (via "The Wrench"), David Haught (spelling?) of Proficient Motorcycling, etc to do an article (in layman's terms) on the subject.

Hope to see you all at the Northwest Passage Rally in Spokane, Washington in mid-July 2004.
Regards,
Richard W. Wackett

You bet. :)

[wackettrw]

Dave,
I will have to think about your comments in your last response, namely,:

1. "damping controls resistance to EXTENSION [emphasis added] of the shock" absorber,

2. "if the damping is set too soft, the shock will cycle a couple of times after you hit a bump.", and

3. "When shocks fail" ... "the damping loses its ability to resist EXTENSION [emphasis added]."


As a real layman/novice in the mechanics of vehicle suspension, I thought, but certainly do not know for sure, that when shock absorbers fail, the shocks:

1. compress AND extend too easy ... as if their up & down damping effect is lost/leaked

2. the vehicles drops down (shock absorber doesn't hold the vehicle back from falling ... i.e. compressing the spring), and

3. there is nothing holding back the spring from bouncing up & down forever, but gravity.


I thought a spring was made to have the ability to stretch and compress within a certain weight range to soften the ride, while the shock absorber prevents the spring from continuing to oscillate up & down. If the shocks are defective or worn out, the springs would take over and oscillate almost continuously when bumps or dips in the road are hit.

I appreciate your time & effort in educating me.

Sincerely,
Richard

[kbasa]

Originally posted by wackettrw
Dave,
I will have to think about your comments in your last response, namely,:

1. "damping controls resistance to EXTENSION [emphasis added] of the shock" absorber,

2. "if the damping is set too soft, the shock will cycle a couple of times after you hit a bump.", and

3. "When shocks fail" ... "the damping loses its ability to resist EXTENSION [emphasis added]."


As a real layman/novice in the mechanics of vehicle suspension, I thought, but certainly do not know for sure, that when shock absorbers fail, the shocks:

1. compress AND extend too easy ... as if their up & down damping effect is lost/leaked

2. the vehicles drops down (shock absorber doesn't hold the vehicle back from falling ... i.e. compressing the spring), and

3. there is nothing holding back the spring from bouncing up & down forever, but gravity.


I thought a spring was made to have the ability to stretch and compress within a certain weight range to soften the ride, while the shock absorber prevents the spring from continuing to oscillate up & down. If the shocks are defective or worn out, the springs would take over and oscillate almost continuously when bumps or dips in the road are hit.

I appreciate your time & effort in educating me.

Sincerely,
Richard

We're real close here. :)

I'll explain the damper portion a little more thoroughly and maybe this will help.

Some shocks have an adjustable ability to control compression damping. This can, if turned up real high, make the motorcycle feel harsh and buggy like. However, that portion of the shocks characteristics aren't adjustable for you. You only have control over rebound, no?

All shocks do, to some extent, control compression damping, which, in combination with the spring, provide the resistance to compression.

You're using the stock BMW shock, right? In that case, you only have an ability to control rebound damping (and not over a very wide range at that) and the ride height (preload).

But yes, if you have the rebound damping too soft, your bike will act exactly like the shock is worn out. It won't damp out chassis oscillations in one cycle like you'd like as an ideal.

Woooo..... :)

[Mr. Frank]

Hi Dave,
You are correct. The stock shock on the RT has only rebound damping. It does not have compression damping.

[wackettrw]

Dave (& Frank),
Thank you very much for all the help on setting the preload and damping on my 1999 R1100RT and understanding the concepts behind suspension tuning. I really do appreciate it. Look for me as a volunteer at the Registration booth at the Northwest Passage Rally. I'll buy you two a beer in the beer garden one evening ... in payment for all your help.
Richard W. Wackett

[kbasa]

Originally posted by wackettrw
Dave (& Frank),
Thank you very much for all the help on setting the preload and damping on my 1999 R1100RT and understanding the concepts behind suspension tuning. I really do appreciate it. Look for me as a volunteer at the Registration booth at the Northwest Passage Rally. I'll buy you two a beer in the beer garden one evening ... in payment for all your help.
Richard W. Wackett

Yer on, Rich!

I'll be the guy on the BMW, wearing a Tshirt.

:)

dave

[dlearl476]

Originally posted by wackettrw

.... I believe most motorcyclists do not know how to adjust the preload and damping correctly. I have asked Motorcycle Consumer News, BMW Owner's News (via "The Wrench"), David Haught (spelling?) of Proficient Motorcycling, etc to do an article (in layman's terms) on the subject.
Regards,
Richard W. Wackett

What, the ones I posted weren't good enough for you? :cat FWIW, MCN DID an article on suspension set-up a couple of years ago. I used to have it saved to another hard drive, but a crash took care of that. I know the guy I got it from and I'll see if I can get a link for that one.

Until then, here's another one from Ohlins. I didn't realize the one I previously posted was more product info than generic "how to".

Suspension Set-Up (http://www.ohlins.com/pdf/07241-02.pdf)