Help me understand Pre-load

[oldbike54]

Dusty...
You said... “it pushes the swing arm down...” BS
You SHOULD have said...”it pushes down on the swing arm..” Yes.
Tusayan understands..(as usual..).

 OK , the force is applied downward to the swingarm . How does that change what is happening ?

 Dusty

[Huzo]

OK , the force is applied downward to the swingarm . How does that change what is happening ?

 Dusty

It doesn’t, but I’ll hammer away at the misconceptions one by one.

[oldbike54]

It doesn’t, but I’ll hammer away at the misconceptions one by one.

 Oh please do .

 You do understand that in effect a spring is still a lever , even by your definition . In fact , the force applied won't work unless it is applied to something , in this case the ground . Lay on your back and do a push up , what happens ?

 Dusty

[Huzo]

Oh please do .

 You do understand that in effect a spring is still a lever , even by your definition . In fact , the force applied won't work unless it is applied to something , in this case the ground . Lay on your back and do a push up , what happens ?

 Dusty

Not by my definition it’s not..
Where’s the pivot ?


I do understand the concept that the force won’t work unless it’s applied to the ground..
Archimedes said..
“Give me a place to set my foot and I will move the world..”
If I lay on my back to do a push up, what happens..?
I go to sleep.
This should be in “Thread drift..”

[bad Chad]

A few of you have made some helpful comments, thanks.

But the rest; I might as well asked to explain in detail the actions and reactions of all sub nuclear mater/anti-matter, in a  bowel of Quantum mechanics with a large sprinkling of String Theory tossed on for flavor!

My next question will be, "What's the correct motor oil to use preserve the freshness of my tires?

[John Croucher]

So, I have a Magni Swing arm on my Tonti frame bike.  When adding preload, where is this lever action pushing?  From the gear box to the upper shock frame mount?  From the bell crank section to the torque arm and lower frame?  Or a combination of both?  Does the will base get shorter as the swing arm folds up?  Does the rear wheel axle move in an arc around the front swingarm mounting point or does it move in a slope/angle? 

And why does the bike squat now instead of raising the rear of the bike with a Magni swingarm? 

What good is preload or sag on a shaft drive bike if the torque causes the swingarm to drive under the bike, top out the shocks and making the rear shocks useless while accelerating?

There is an awful lot going and trying to make it all work in an imperfect world is impossible.  I find that sitting in the lazy boy has the best seat of the pants feel and the best handling characteristics.  Warm in the winter, cool in the summer, always dry and the view changes as I move the chair around the house. 

Explaining all the various functions and variable is one thing, making it all work together and make each individual rider happy all the time, never going to happen.  My back is killing me this morning and I just got out of my $2,000 bed. 

[Huzo]

Preload basically just changes the ride height.

Or that is my understanding.

This bloke seems to be universally loved..
He is correct and we should have stopped here..

[John Croucher]

A few of you have made some helpful comments, thanks.

But the rest; I might as well asked to explain in detail the actions and reactions of all sub nuclear mater/anti-matter, in a  bowel of Quantum mechanics with a large sprinkling of String Theory tossed on for flavor!

My next question will be, "What's the correct motor oil to use preserve the freshness of my tires?

Heck, we did not get to stiction or how the mounting eyes with rubber bushing influence a shocks performance.  Or how duel or multi rate springs really do not work because the lighter portion is preloaded out to support the bike and rider without bottoming out the shock. 

[Huzo]

A few of you have made some helpful comments, thanks.

But the rest; I might as well asked to explain in detail the actions and reactions of all sub nuclear mater/anti-matter, in a  bowel of Quantum mechanics with a large sprinkling of String Theory tossed on for flavor!

My next question will be, "What's the correct motor oil to use preserve the freshness of my tires?

What happens here Chad is that in an attempt to enter the fray, all sorts of extraneous argument and irrelevant analogies, can be inserted into the debate that only serve to contaminate the facts.
Can you give me three names that helped and three names that didn’t ?
I’ll come up with two that helped..
Wayne Orwig and Tusayan.

[Huzo]

Heck, we did not get to stiction or how the mounting eyes with rubber bushing influence a shocks performance.  Or how duel or multi rate springs really do not work because the lighter portion is preloaded out to support the bike and rider without bottoming out the shock.

Off you go then..
BTW..
It’s dual, what’s happening between some of us here is a duel..

[bad Chad]

Ah, Huzo, that would be a to vulgar display of my power!   All I can say is, "you know who you are!"

[Huzo]

   All I can say is, "you know who you are!"

I do believe that can be the problem Chad.
Sometimes you don’t..

[80CX100]

I sense regret from Chad that he posted such a simple question, and we all realize now, that just like life, "suspension" is a miracle.

Discussions, arguments,& posts like this, can be like life itself, "Will the Circle be Unbroken"

Interesting comment from John in regards to the Magni swingarms, I came close to buying a former race bike once, that had a Magni rear end, so I've always been interested in the engineering.

I recently watched a VRRA racer, who is a very competent respected builder, suffer a catastrophic failure his first test race on the track,with his home built/designed Magni style swing arm on his Guzzi. The solid steel brackets and welds completely blew apart at the anchor points in the swing arm pivot area, very obviously some huge forces at play, that neither he nor I fully understood.

It has been a fruitful discussion, I will continue to crank my preload so the bike doesn't wallow going around a corner,lol,,, but now I realize, from the article Ryan posted,that my understanding of damping was backwards; the first thing I'm going to try this spring is lighter damping settings on my rear shock on the CalVin to see if the wheel responds quicker to changes in the road surface, going around rough corners.

Tks

Kelly



 

[pressureangle]

So, I have a Magni Swing arm on my Tonti frame bike. 
1. When adding preload, where is this lever action pushing?  From the gear box to the upper shock frame mount?  From the bell crank section to the torque arm and lower frame?  Or a combination of both?  Does the will base get shorter as the swing arm folds up?
 
2. Does the rear wheel axle move in an arc around the front swingarm mounting point or does it move in a slope/angle? 

3. And why does the bike squat now instead of raising the rear of the bike with a Magni swingarm? 

4. What good is preload or sag on a shaft drive bike if the torque causes the swingarm to drive under the bike, top out the shocks and making the rear shocks useless while accelerating?

There is an awful lot going and trying to make it all work in an imperfect world is impossible.  I find that sitting in the lazy boy has the best seat of the pants feel and the best handling characteristics.  Warm in the winter, cool in the summer, always dry and the view changes as I move the chair around the house. 

Explaining all the various functions and variable is one thing, making it all work together and make each individual rider happy all the time, never going to happen.  My back is killing me this morning and I just got out of my $2,000 bed.

1. 'pushing' at the front end of the arm. See #2.

2. The *axle* moves;
  a. In an arc the radius of the height of the triangle created by the swingarm and reaction rod theoretical intersection, when they intersect in front of the axle;
  b. In an arc the radius of the length of the swingarm and rod, when they are equal length and parallel;
  c. In a reverse arc difficult to calculate when the swingarm and rod intersect theoretically behind the axle (they never do, in my experience)

3. The bike squats because with the parallelogram linkage, the shaft jacking is countered by the suspension geometry, and the weight transferred to the rear under acceleration is free to compress the suspension, as with other bikes (ignoring chain jacking)

4. Well...something is better than nothing. Sag still works until the jacking effect removes it.

For you mechanical engineers, let's not fall into the 3rd decimal place on my mathematical descriptions.

[zedXmick]

So everyone says cranking in more preload changes the ride height on your bike. The shock measurements between eyebolt holes never changes no matter how much preload you crank in. The ride height never changes. You only change ride height if your shocks have adjustable eyebolts.

[tazio]

Say what?

[kirby1923]

So everyone says cranking in more preload changes the ride height on your bike. The shock measurements between eyebolt holes never changes no matter how much preload you crank in. The ride height never changes. You only change ride height if your shocks have adjustable eyebolts.

Thanks! I needed that.

This subject is getting way to serious. (as in way off the deep end)

:-)

[Huzo]

So everyone says cranking in more preload changes the ride height on your bike. The shock measurements between eyebolt holes never changes no matter how much preload you crank in. The ride height never changes. You only change ride height if your shocks have adjustable eyebolts.

Direct your attention to centre stage folks..
Behold one of the greatest comedians to ever tread the boards...!
The incomparable zedXmick...

[SmithSwede]

Huzo said to Dusty:  “And KOF mate.”

What does KOF mean?

[oldbike54]

Huzo said to Dusty:  “And KOF mate.”

What does KOF mean?

 King of Fleece

 Dusty

[Huzo]

Thanks! I needed that.

This subject is getting way to serious. (as in way off the deep end)

:-)

The great man Albert Einstein was once quoted as saying..
If you can’t explain something simply, you probably don’t understand it yourself..
I didn’t think I complicated it too much..

[jacksonracingcomau]

So everyone says cranking in more preload changes the ride height on your bike. The shock measurements between eyebolt holes never changes no matter how much preload you crank in. The ride height never changes. You only change ride height if your shocks have adjustable eyebolts.

All so very true, until you bolt them to a bike
Then what huzo says, frame height changes
Or, what dusty says, swinging arm goes down
Either way,  eye to eye distance changes
Let’s call it suspension travel
Adjust to weight

[Huzo]

Huzo said to Dusty:  “And KOF mate.”

What does KOF mean?

I would have been more accurate if I’d put KoF...(King of Fleece)
(He gave me those lovely badges for my V85, I gave those eagle things the arse..)
Sorta’ like the “of” in AoA...(angle of attack)

[kingoffleece]

I'm touched............ ............in the nice way!

[pressureangle]

Thanks! I needed that.

This subject is getting way to serious. (as in way off the deep end)

:-)

Sorry, he's dead wrong.

[Ncdan]

I’ve turned those dials every which way in every combination imaginable and can’t tell little to no different in the ability of being able to control a particular motorcycle in any particular riding conditions or road type.  So there’👍

[zedXmick]

All so very true, until you bolt them to a bike
Then what huzo says, frame height changes
Or, what dusty says, swinging arm goes down
Either way,  eye to eye distance changes
Let’s call it suspension travel
Adjust to weight

Of course that goes without saying...suspension travel.  Only thing you change with more preload is sag setting, you don’t change “ride height”.  Now the shock below let’s you add “ride height” by adjusting Lenght adjuster.

[Huzo]

A few of you have made some helpful comments, thanks.

But the rest; I might as well asked to explain in detail the actions and reactions of all sub nuclear mater/anti-matter, in a  bowel of Quantum mechanics with a large sprinkling of String Theory tossed on for flavor!

My next question will be, "What's the correct motor oil to use preserve the freshness of my tires?

Regarding your question relating to correct oil for your tyres, you’ve inadvertently stumbled upon the only topic in the world that I am not an acknowledged expert on...
But I can give an educated guess if you wish..(which I’m sure will ultimately be proven to be completely correct..)
Now on the topic of sub atomic particles an Quantum/String Theory..?
That’s another matter entirely..
I’ve put the full stop on all there is to know about science.
You could say I put the “period” in “periodic table..”

[Huzo]

Only thing you change with more preload is sag setting, you don’t change “ride height”.

Well, yes you do..
You see if you had 30 mm of sag with your weight on your bike, then you wound on some pre load..
You would have less sag when you jumped back on...Yes ?
So, if you have less sag after winding on pre load (let’s say 20 mm) then it means your seat has sunk 10 mm less than before..
Now things are getting hazy here, but what do you think that would have done to your ride height ?
There is always a third possibility here and that is that you may be just winding us up..(as it were).

[Tom H]

I fully understand what Zed is saying especially with the example of the shocks.

I do agree with Huzo as well. If you set X amount of sag and your bike is too low, add more preload to raise the seat/lower the swingarm.

Now I do like the shocks in Zsd post. Set your sag and if your bike hits every speed bump, screw out the eye. Make your 12" shock a 12.25".

Tom