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Discussion Starter · #1 ·
I posted this on the tech board and got a very technical treatise on how to set up your suspension for a race bike, then two diametrically opposed answers and I am still in the dark and I know that you, tom will have a clear, concise and understandable explanation and here is my previous post:


Join Date: Oct 2007
Location: southern Illinois
Posts: 315


preload setting on 1800
Recently on a gropup ride I was told that increasing the preload to max would make for a more comfortable ride. This flies in the face of my body of assumed knowledge. So today while on a 200 mile ride in the Smoky Mts, Blue Ridge Parkway and surrounding areas , I upped the preload on the rear suspension from our usual two up of 5 to the max of 25 without telling my wife. Toward the end of the ride she spontaneously remarked that the jarring sensations she normally feels in her spine from road imperfections such as transverse tar strips and "bumps" when crossing road/bridge pavement surface areas didnt affect her as much today.
Seems that increasing the preload to max would create a harsher ride for the passenger [sitting right over the rearwheel] than having the preload set to 0.. Some of you engineer types please explain this to an uneducated country doctor. Thanks
Andy:shrug:
 

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I'm not in the same league with Tom Finch but I will offer up an opinion. If your previous setting was allowing the suspension to bottom out over big bumps, then that would account for the jarring as the suspension travel stopped when it still needed more travel to soak up the rest of the bump. By increasing the preload, you are starting out with the suspension higher up in its travel plus more resistance to the bump input, BUT the suspension does not bottom out, so you don't get the jarring when it comes to a sudden stop.

To put it another way, by increasing the preload, you are placing the rear shock more in the middle of its range of travel and lessening the likelyhood that the shock will bottom out. Over smaller bumps, the lower preload setting might give you a smoother ride as long as you do not bottom out the shock.

I am amused when people say "Oh, you have to have it set on XX for the best ride". The "right" setting varies for the type of road you are on, how much your bike is loaded, and whether you have followed Fred Harmon's instruction on removing air from the hydralic preload system.

Okay Tom, how did I do? Did I make sense or was this just so much more dribble from a nin-cum-poop? :coffee1:
 

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My last name is not Finch either but, my first name is Tom. However that still doesn't put me anywhere near his level of expertise!
The link I sent you was indeed about race suspensions. However, it gave you the basics for setting the preload for any bike.
Maybe a simpler explanation will work:
Raise the preload to max.
Then load your bike with the various ways you will ride it. Such as one up, 2 up, solo loaded, 2 up loaded, with and with out trailer. You get the idea.
With each of these situations and with an assistant positioned to watch the rear of the bike:
Slowly lower the preload setting until your spotter tells you the bike just started to drop. Check the readout and note the reading for each of the situations you will ride, as listed above.
Now you have a list of the preloads to set for each of your ride situations.
If you really want to be creative, while doing the preload procedure:
Park the bike 25' from a wall(garage wall maybe) on a level floor. With the bike in the vertical position measure from the floor to the center of the high beam headlamp bulbs. Measure this same distance from the floor onto the wall and draw a straight horizontal(parallel to the floor) line on the wall you can see seated on the bike.
Place the auto headlamp adjuster knob in the most up position.
With you on the bike, and using the adjusters on the headlamp assembles(I reach mine from under the fairing) covering one headlamp, adjusting the other, aim the headlamps so the "hot spot" is just below the line you drew on the wall.
Now as you load the the bike for each of your riding situations, check the headlamps on the wall, as needed turn the auto adjust knob to maintain the hot spot just below the line and put a small mark on the bike in line with the new knob position.
Now you have a list of presets and marks to align the auto headlamp adjuster to.
 

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Discussion Starter · #4 ·
suspension preload

Mark, I understand about bottoming out on large bumps and setting the preload higher makes it less likely that y0u will bottom out on the same bump. Also i believed that the higher the preload setting the more one would feel the smaller pebbles and irregularities that do not cause the bike to bottom out. What I dont understand is why my wife perceived a smoother ride with the preload set at max, especially when during the previous 300 miles the bike never bottomed out and was set at 5. As I mentioned in my original post, my friend on the same ride stated that setting the preload to 25 on his 09 seemed to make the ride smoother for him and his wife.

I have always run the preload to 25 when playing solo in the twisties.

Thanks for your responses and please dont take offense, but I would still like to hear from Tom Finch.
 

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Are you sure you don't hit the stops? The wife says she feels a lot more on the pilliopn than I do in the front. We ride about 18 empty and 20-22 loaded. The pillion sets on top of the stops and is less forgiving when it bounces. Just a thought. BTW I always thought it would make a more harsh ride, but I guess when the weight is equalized it just works. YMMV
 

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Discussion Starter · #6 ·
rear preload

I am sure I dont bottom out-hit the stops- without knowing it as I am quite conscious of it and hate when it happens on rare occasions. Whenever I see one coming I stand up on hte pegs and when two up I increase the preload.
Andy
 

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The 1800 rear suspension is quite unique. The spring is linear but the linkage is not. Very well thought out.

Think of a chain tied to a fixed point like a wall. Just picture a 1/2" chain about 6 feet long and the anchor point on the wall is about waist high. You hold the other end in you hand and walk backward away from the wall so as to pull the chain out straight.

At first, when you are near the wall, there is very little opposition to you stepping backward as the chain hangs almost straight down.

As you approach the 5 foot distance, the chain starts to straighten out and really is hard to continue stepping backward. Interestingly, you can not pull the chain totally straight with your bare hands. As you struggle to hold the chain near straight, a 30 pound child can grab the chain in the middle and pull you back toward the wall.

However, as the chain sags, it soon reaches a point where you can oppose the 30 pound child's pulling down on the center of the chain.

The Wing suspension is a little like the chain hooked to the wall, but it only has two links in the chain.

The "wall" is the cross bar that the center stand mounts to, and the force tugging on the other end of the chain is the swing arm as the wheel is forced upward by load. The child's weight is representative of the fixed rate spring of the rear shock.

As the suspension setting approaches zero, the chain is allowed to approach straight because the opposition is moved up away from the chain center. The nearly straight chain quickly straightens further when the wheel is pushed up by a bump and soon the bump can not overcome the resistance of the spring because the two-link chain is too straight.

Now, on the otherhand, if the setting is at max or 25, the chain is forced to be in more of a state of sag, and the more the sag, the easier it is to "Move away from the wall." These two views are not to scale and are sketches.



Further, the section of the "chain" that is attached to the Swing Arm is made into a lever which rotates, compressing the suspension cartridge as it does, and since this lever rotation is resisted by the suspension cartridge, the resistance is maximum when the suspension cartridge centerline is farthest form the other end of the lever which occurs as the "chain" links approach straight, multiplying the increase in force as the swing arm reaches its upper limit of travel.

In the view below, forward it so the left. Sorry for the reversal but only photos I had.



This is truly and ingenious system which can be tailored by the engineers to achieve a large amount of non linearity, making it take a very high force to actually bottom the suspension out and preserving a low spring rate at the other end of the travel.

That is why the compliance is higher when running the suspension setting higher, yielding a better ride on the rough stuff.
 

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As I should have come to expect, I am in awe of Tom's detailed analysis and great photo and graphic tutorial. The simply analogy of a two link chain and a 30# child is brilliant. Andy Cserny was right to ask Tom to respond. Thanks Tom!
 

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Mark
I feel that I should get a video recorder and get Tom to sit down and make a video of all of this stuff. If I had more brain cells and could understand just a little of what he is teaching, then I would be a very smart man. Never going to happen though...me getting smart.
 

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Discussion Starter · #10 ·
question for tom

Thanks Tom, as always you came through brilliantly and I want to thank you for educating us so lucidly and eloquently. It is now 11PM, I am just about to finish my second beer, so will have to re read your post in the am to really get a grip on it. Just amazes me to no end that you can figure all this out. People often ask me why I became a doctor and I tell them I wasnt smart enough to be an engineer.
Thanks again Tom
Andy:bow::bow::bow:
 

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OF COURSE everythig Tom said is correct. (and Tom and I have discussed this subject several times in the past on and off-line)

My KISS version of the reason is:

1) The actual spring rate and shock damping (at the shock) ARE Constant throught their travel

2) HOWEVER, the linkage ratio of the suspension (this is the amount of wheel travel to shock/spring travel) is NOT Constant. Rather it is over 3:1 at full extension of the suspension and about 2.1:1 at full compression of the suspension. (Another way of saying this is that the mechanical advantage of the load/impact that compresses the spring/shock DECRESES as the shock is compressed)

3) The NET effect of 1 and 2 above is that it takes more force to move the suspension an inch in the latter half of its travel than it does to move it an inch in the intial (extended) part of its travel.

4) THUS the ride is SOFTER in the intial parts of travel and HARDER in the later parts of travel (as it nears full compression)

5) The higher the number of the suspension adjuster (~25) the closer to the intial SOFTER part of the travel you will be operating in and the lower the number (~1) the more you will be to the HARDER latter part of the travel.

6) In the REAL world the OEM spring on a GL1800 is WAY WAY WAY too soft. Thus, even with just a single rider of average weight on board it needs to be set at 25 to get the proper amount of loaded SAG (~35% ~ 1.5") to keep the suspension operating in the softer part of its travel range.

7) Setting the suspension at less than 25 with the stock spring also greatly increases the likelyhood of a "soft bottoming" where the dense anti-bottoming foam on the shock shaft starts to be compressed and to "assist" the spring and shock and thus make the spring/shock rate go WAY up quickly. This is the harshness you feel when you hit a big bump even if you don't totally bottom out. This probably is more the casue of the harshness most feel than the gradual decrease in linkage ratio discussed above.

There is a MYTH (unfortunately perpetuated even by some of the good folks at Traxxion) that increasing the suspension setting number (sometimes called the "preload") make the bike ride Harder/Stiffer. THIS JUST IS NOT TRUE on the GL1800 or on any bike that has progressive suspension linkage and is not so over sprung that it is constantly "topped out".
 

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Dang guys! Sooo complicated.

Why don't you get Fred H.'s DVD set and watch (learn) about the rear suspension :shrug: I like visual aids:thumbup: Oh, the manual is good too...(disclaimer :doorag:). Thanks, Mark!

In my humble opinion,,urgh!~ Sam is correct. The shock (spring) is constant in it's ability to travel, compress/extend. The movement, i.e., 0 to 25 number represents the "hydraulic linkage", now see Fred's video. As the linkage moves...so moves the total spring, which at time gets sprung into action by the bumps in life,,,if you ride! Furthermore Sam's arguement is correct in the spring's sprang/sprung (compression/extension).

Now is the time to SPRING into action and go ride, tis the season, laddy. Play with your settings until you find what's right for you.
 

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Thanks Tom, as always you came through brilliantly and I want to thank you for educating us so lucidly and eloquently. It is now 11PM, I am just about to finish my second beer, so will have to re read your post in the am to really get a grip on it. Just amazes me to no end that you can figure all this out. People often ask me why I became a doctor and I tell them I wasnt smart enough to be an engineer.
Thanks again Tom
Andy:bow::bow::bow:
What amazes me is that you did not understand what Tom said after just one beer! ****, I didn't get it and all I have had is coffee!!

After reading this, my pre-load is going to 25! Done!!!


Thanks TOM!!
:grin2:
 

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Kind of amazing the time line of this thread.

In an only slightly related subject, it has been a long time since I have heard anything about the failing of the weld on the frame cross bar to which the center stand and suspension links attach. That is a very good thing and seems to say that the giant recall of the 2002-2004 models for rewelding and what ever steps were taken from then until now by the Honda factory, have been successful.

My feeling is that the fix was a bandaid when reversing the receiving sockets to face forward would have been the logical progression, is a bit steeped in my belief that much of what goes on in our world is tainted by the fact that fear of a lawsuit is far larger than desire to do the right thing.

If the sockets that receive the cross bar faced forward, the crossbar could not have been yanked backward by the suspension even if the weld was entirely omitted accidentally. Putting a weld in tension is always the least preferred way of making a joint, followed by welds in shear and then welds in compression which are the least risky. (I know that the cross bar provides other functions in the frame weldment than to anchor the suspension links, but I am speaking here of only the failure when the suspension links pulled aftward on the cross bar. The other functions would not be affected by reversing the receiving sockets.)

However, it seems that making a case that there was a temporary failure in welding quality was thought to be better than admitting that the design was flawed, which reversing the direction of the receiving sockets would have indicated.
 

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I think I learned more in 10 minutes of reading these threads about GL1800 Suspensions than my 4 years of riding my wing.. Hopefully now my 2005 GL 1800 will have a softer ride than my 2004 Harley Davidson Dyna Superglide FXDI. Growing up I have always thought the Goldwing was compared to the comfort of a Cadillac or Lincoln like riding on a cloud. It took my by surprise when my Harley had a softer suspension. Although I think the Harley suspension is a little too soft. Thank you Tom and others for all your help.
 

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I think I learned more in 10 minutes of reading these threads about GL1800 Suspensions than my 4 years of riding my wing.. Hopefully now my 2005 GL 1800 will have a softer ride than my 2004 Harley Davidson Dyna Superglide FXDI. Growing up I have always thought the Goldwing was compared to the comfort of a Cadillac or Lincoln like riding on a cloud. It took my by surprise when my Harley had a softer suspension. Although I think the Harley suspension is a little too soft. Thank you Tom and others for all your help.
Tom was a good man, sadly he’s not with us anymore, but his knowledge lives on!
 
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