Swapping Forks, wheels, and swing-arm.

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Re: Swapping Forks, wheels, and swing-arm.

#46 Post by Off Road » Sat Nov 23, 2013 9:40 pm

So, I'm going to wrap this up by giving you a few Opinions, and 1 real Fact,
Then I'm going to go read my book, and let this thread fade away.


Opinions regarding the use of R1 suspension parts.

Most modern bikes have a steep rake angle, and a small fork offset.
When modern front ends, (wheel, forks, trees), are installed on an RZ, it will increase the bikes rake and trail. This will slow the steering.

The small offset moves the front wheel closer to the motor, which adds more weight to the front end, This will slow the steering.

The small offset will also shorten the wheelbase, This will quicken the steering.

The shorter wheelbase, will increase weight transfer, and decrease maximum baking ability.
A longer swingarm, would help solve this.

But with the wide tire, and big brakes, the bike will still have really awesome brakes..

The relatively large (120/70) front tire will increase rake & trail, and slow the steering.
A smaller 120/60 front tire would steepen rake, reduce trail, and decrease unsprung weight, which will all help in keeping the wheel in contact with the road.

An RZ with an R1 front end, would probably benefit from having a longer swingarm, to restore some of the length lost by the small fork offset,
and an increase in rear ride height, (longer shock or shorter dogbones), to decrease the rake and trail.

And IMHO, the wheels (3.5" F, and 5" rear), and tires, are too big and heavy for the RZ.
Added weight that's not needed, and reduces performance.
But, that's just my personal opinion, which don't mean squat, because what do I know?

There are also lots of good reasons for installing R1 parts (cost, performance, availability, personal preference, etc.)




Opinions regarding the use of FZR400 suspension parts.

I'm probably just biased, but I think the FRZ400 swap is a great choice, at least for a street bike.

The tree's have a larger offset than the R1.This helps to decrease the trail, and retain the length of the wheelbase.
The FZR wheels are relatively small (3" F, and 4" R), which means they're lighter., which means less unsprung weight
The tires are also relatively small (110/70 F, and 150/70 R)., which also makes them lighter as well.
The front tire is really small, compared to an RZ or R1. This really helps to reduce the trail, and quicken the steering.

Compared to an R1, the FZR wheels and tires look pretty small, Compared to and RZ, they look huge.
I think they're the perfect size for and RZ, bigger and better than stock, without being overly big and heavy.
The FZR has larger bakes and they work super.
I installed EBC prolight disc, which are lighter than stock, and reduce unsprung weight.
The front forks are 38 mm, and a bit more rigid than the RZ forks,
Fork springs/damping were designed for the heavier FZR, so they didn't have enough sag , when put on the lighter RZ, but the spring rate seems to work good with the bike.



And finally, IMHO, The biggest improvement that you get, from installing a newer front end, is the ability to run some good radial tires.
The Bridgestone BT016 radials make the bike handle a lot better than the BT45's.



So, after all my assumptions and calculations, and then riding the bike, and evaluating the suspension mods, there is 1 thing that I do know for a fact. 100% guarantied.
If I ever do another track day, the bike with the FZR suspension, will definitely be my new track bike, because it's way better than my old RZ track bike.
Last edited by Off Road on Sun Nov 24, 2013 1:08 am, edited 2 times in total.

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Re: Swapping Forks, wheels, and swing-arm.

#47 Post by Off Road » Sun Nov 24, 2013 12:37 am

Off Road wrote: Fork springs/damping were designed for the heavier FZR, so they didn't have enough sag , when put on the lighter RZ, but the spring rate seems to work good with the bike.
I wrote that, and then started thinking about my sag, and forks springs, and spring rate, and suspension load, and sprung and unsprung weight.

The FZR springs were engineered by Yamaha to work on a 400 pound, full fairing, FZR400.
I've removed that bike, and replaced it with a naked, 330 pound RZ, which reduces its sprung weight by 60 pounds or so.

This greatly reduces the ratio between sprung and unsprung weight. Which reduces the wheels ability to stay in contact with the road.

In order to improve this, I could add more sprung weight, or install stiffer fork spring.
More weight's a bad idea, and stiffer springs will give a harsher ride.
And I already have a really small diameter front tire, which is also transmits more force to the frame.

Then I should reconsider the damping, which was also originally setup for the heavier FZR400.


So, which set-up will give me the best stability, and the quickest steering, and allow me to get through the corner faster?
Stiffer springs, or softer springs?
More damping or less damping?
More rake/less rake?
More trail/less trail?
Longer wheelbase/shorter wheelbase?
Bigger tires/smaller tires?

I don't have a friking clue.


Quote: "All engineering design is the art of compromise, the best bike is the one whose designer has achieved the best overall compromise for the intended purpose,"

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Re: Swapping Forks, wheels, and swing-arm.

#48 Post by Off Road » Sun Nov 24, 2013 1:20 am

OK. Just one more small speech, and then I promise, I'll STFU. :smt005
I've manged to babble on, for 4 pages, and by now, even the most patient forum member, is wondering why I've developed a sudden obsession with suspension setup.

1- Motorcycles at rest, (as in not moving), fall over. Moving motorcycles have stability.
And hundreds of different forces, all interact, and affect how much stability the bike has.
And that's really interesting shit, IMO.

2- "The best you've ridden, is the best you know".
My 83 Rz handled better than my LC.
My 90 RZ had much better front brakes, than the 83.
The FZR brakes are way better than the 90 RZ brakes.
BT016 radial tires are way, way better than BT45's

After you've ridden something better, it's hard to go back. You want to ride something that's even better, and it's addictive.
If I can learn a few things, and improve the handling of my RZ, then that's a really worthwhile thing.
But first, I need to understand what all the suspension components are doing, how they interact, and how changes to the setup will affect the bike.


So why exactly, do I want/need razor sharp handling on my street bike.

1- Unexpected sand and gravel, in the middle of a familiar corner.
2- The idiot in a car, that doesn't see me, and runs a stop sign.
3- Another idiot in a car, that doesn't see me, and changes lanes.
4- Somebody's stupid dog, that runs out from behind a parked car.
5- And the nice set of tight, twisty corners, on a quiet country road, that I know of. :smt003

In situations like these, I want my tires to have a firm grip on the road, so that I can relax, and truly enjoy the adrenaline rush, that we get from riding a motorcycle..

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Re: Swapping Forks, wheels, and swing-arm.

#49 Post by Off Road » Fri Nov 29, 2013 10:31 pm

Off Road wrote:OK. Just one more small speech, and then I promise, I'll STFU.
And I was wrong, again. Oops my bad.


I spent some more time reading Tony Foale's book on motorcycle chassis design, and then wrote down some of the cool stuff to post here.
But, the information wasn't really clear in my mind.
Read some more, and wrote down more info, Read some more, wrote some more, Read more, wrote more.
And in the last week, I've written a series of pretty long posts, about stuff that will really be of No Use to anybody.
However, in the last post, there are a couple of bits of info, that may be helpful to some people.

The first 3 posts also have some pretty neat info, but they were mostly written to help me get things straight in my mind.
I'm posting them here, for the people who enjoy the journey, as well as the destination.


The guys that are interested in math, physics, motorcycle suspension, and then more math and physics, might might find it interesting.
If you think those subjects somewhat dull, then this really isn't the post for you.

I installed an RZR400 swingarm on my bike, this decreased my swingarm angle,
which decreased the anti-squat.
I was interested in learning more about how it would affect the bike.

Tony Foale has a whole chapter on Squat and Dive, so I looked at it last night.
The chapter starts with Load Transfer, and a page of math on how to calculate it.
Then moves on to Center of Gravity, acceleration limit lines, virtual pivot points, and I was lost and confused.
I read through all 50 pages in the chapter, and in the end, none of it made much sense. :smt017


Moved on to something easier. The appendices.
Rake and Trail, a 4 page glossary of terms, unit conversions, gyroscopic affects.
Still need to look at that more, but a spinning wheel behaves different, depending on whether you turn the axle (left/right), or tilt it (up/down).



Next was Physics of Motorcycles, With detailed descriptions and explanations on:
Basic Trig., Units of Angle, Speed, Velocity, Acceleration, Mass, Inertia, Moments of Inertia, Weight, and Momentum,
Next were Newtons 3 laws, followed by Force, Weight, Moments, Torque, Work, Energy, Power, Adding Velocities and Forces.

And then we got to Centripetal and Centrifugal Force. Interesting.
I've known about these forces, and have taken them as a fact, for all my life.
But Tony makes a pretty compelling argument, to say that one of them may not exist. :smt005


Quote Tony Foale:
"Centripetal and centrifugal forces are the two opposing parts of the Newtonian concept that for every force there is an equal and opposite reaction, for the case of an object following a curved path.
Centripetal is the inward force and for vehicles that is the lateral tyre force pointing toward the turn centre,
centrifugal is the conceptual force trying to make the vehicle move outwards away from the centre.

As to whether centrifugal force exists is the subject of a long running argument between purists and pragmatists.

Without centripetal force the vehicle will go straight and this force is necessary to cause the forward momentum to change direction,
in reality there is no force trying to make the vehicle move away from the turn centre, all it wants to do is carry on in its current direction.

Consider a mass on the end of a piece of string being swung around. Most people will talk about the tension in the string as being centrifugal force generated by the mass trying to fly away from the centre.
The implied assumption being that the mass is pulling outward (centrifugal). Actually it is the string that is pulling the mass inward (centripetal) to change its direction of motion, which otherwise would be in a straight line.
If we release the string, the mass doesn't fly outward, it simply continues in a straight line tangential to its instantaneous velocity at the moment of release.
If the mass had been subject to a centrifugal force, then it would have flown radially outward from the centre.
In fact its motion will be at right angles to the outward direction at that instant."



So, Centrifugal force might not exist. Didn't see that one coming.

And if you think that's funny, then you're going to like this.
Imagine that you pull away from a stop, hard on the throttle you pull a huge wheelie, and all the weight transfers to the rear wheel.
Guess what. It didn't happen, because there is no such thing as 'weight transfer'.

Quote:
"Weight is the gravitational attraction of all the particles in the bike towards to the centre of the earth, and for convenience we usually consider the sum of these forces to act through the CoG.
Neither acceleration nor braking can cause this weight to transfer elsewhere.
As a result the use of the term ‘load transfer’ is preferable."




The next appendix was on Analysis of Mechanisms.
Virtual pivots, Virtual Swingarms, Instantaneous Force Center.
Started by evaluating a 4 bar linkage (4 pivot points), and calculating the Virtual Pivot, or Virtual Center.

Quote:
"The significance of this virtual centre is that we could replace the original 4 bar linkage with a 3 link version pivoted at the virtual centre.
This then becomes the only connection between the reference frame and the mechanism.
Perhaps of more use to us is that, the virtual pivot is the only point that forces can be passed between the links and the frame. The virtual centre is also called the “Instantaneous Force Centre”.

These properties of the IFC provide us with some simple methods for the analysis of suspension behaviour, in particular squat and dive characteristics.

These methods are detailed in more depth in chapter 9 on Squat and Dive."

Duh. Wish I knew that earlier.


Finally, I glossed through the last Appendix, which detailed how to calculate your Center of Gravity.


Armed with my new found knowledge, I tried chapter 9 again.

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Re: Swapping Forks, wheels, and swing-arm.

#50 Post by Off Road » Fri Nov 29, 2013 10:38 pm

Chapter 9 - Squat and Dive, my second attempt at trying to understand what the hell is going on.

Didn't go well. :smt017
Back to reading Appendix 5, again.

Velocity is speed with direction.
When referring to rotating objects, it's known as angular velocity

Mass is the amount of matter in an object.
And then there's the rotary version of Mass, known as the Moment of Inertia.

Momentum is Mass x Velocity.
And the rotary version of Momentum

Reread Newtons 3 laws on Physics, and then on to Force.
Force is the ability to change momentum, and is defined as Mass x Acceleration.
When evaluating motorcycles, Load can also be considered as a Force.

And on to a discussion on Weight vs. Mass.
Weight implies that the Force of Gravity is acting on an object.
And he closes the chapter by saying:

Quote:
"It is very important to fully grasp the differences between weight and mass in order to get a good understanding of motorcycle behaviour."

OK, I've wasted another night, but I've got this. Bring on Chapter 9.

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Re: Swapping Forks, wheels, and swing-arm.

#51 Post by Off Road » Fri Nov 29, 2013 10:44 pm

Chapter 9 - Squat and Dive, Third time around.


When we apply a force to the bike (accelerating or braking), it will cause a load transfer, from one wheel to the other,
If we're accelerating, the load transfers to the rear wheel, compresses the spring, and the bike wants to squat.
At the same time, a force is being applied to the frame, through the swingarm.
This force is trying to push the bike forward, and since the swingarm is at an angle, it also tries to push the rear of the bike up, (anti-squat).

The sum of the chain force and swingarm force, apply a resultant force at the Virtual Pivot Point, and this force is balanced by an equal force at the tire contact patch.
The Virtual Pivot point is determined by the swingarm angle, and the angle of the chain, relative to the swingarm.

So, the Virtual pivot changes with suspension movement, and applies a Force at different points on the frame.
A steep swingarm angle places the Virtual Pivot up high, and produces a large antisquat.
A shallow arm angle places the Virtual Pivot lower, and creates less antisquat.

Ummm. Great, But damn, that was the long journey to get to something that I thought I knew 3 months ago,

A steeper swing-arm angle creates more Antisquat.

Now, what does it all mean?
How much antisquat do you need?
What happens if you have too much, or too little?
How do determine how much antisquat the bike has?

Good questions, but I'm not there yet. Still got another 36 pages in this chapter.

But, I did find a few nuggets if info that might come in handy, for some folks.
They're coming up next.

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Re: Swapping Forks, wheels, and swing-arm.

#52 Post by Off Road » Sat Nov 30, 2013 12:41 am

OK. This is the post where I give you "My Opinions", on the information that I read.
This is the info that I think will actually be helpful when making changes to my suspension.

When we accelerate or brake, there is a load transfer that causes the bike to sag or dive.
This changes rake and trail, and really doesn't improve the bikes handling
The load transfer also changes the contact pressure, between the tire and the road, which reduces the amount of grip that's available.

Reducing load transfer (sag and dive), provides better grip, and improves braking and acceleration.
If a bike has 100% Antisquat, then the antisquat force is equal to the squat Force,
and the rear of the bike will not rise up, or squat.

The "average Japanese motorcycle, (circa 2002)", had 133% Antisquat when the swingarm was fully extended (steep angle).
And this dropped to 30% antisquat, when the swingarm was fully compressed.
When the swingarm was in mid suspension, the antisquat was 100%.

LOL, went looking for the info that I saw in the Chapter Summary, and got sidetracked by a heading called Acceleration.
Three pages of charts and graphs, that say 100% antisquat will give the best grip, and fastest acceleration.




Quote:
"Over the past decade or so, increasing emphasis has been placed on anti-squat values as an important setup parameter.

This aspect of machine setup is not always properly understood and it is often thought that the swingarm angle is the critical dimension but this ignores the influence of sprocket size and location,
others consider the anti-squat angle (as shown in fig. 9.6) as more important, this is much better but still ignores the influence of the CoG height over load transfer and so still gives an incomplete view of the problem.

the concept of anti-squat percentage was introduced. This parameter takes into account all
the factors involved in the squat / anti-squat process and so is much better for comparison purposes.

A value of 100% anti-squat means that driving forces will have no influence over suspension loads and so will give a very neutral feel."


Quote:
"As the anti-squat percentage varies so much with suspension compression it is impossible to specify an optimum value suitable for all machines,
like suspension and geometry settings it has to be done to suit particular tracks and riders. Whilst the anti-squat percentage will partially determine the bike’s attitude, for a given driving force, and so affect handling, it was shown that the dynamic transient effects can be most important.

As an extreme example, if we have a machine with pro-squat then on opening the throttle there will be a tendency to momentarily lift the rear wheel.
In a straight line this might only cause a small loss of traction and maybe chattering but whilst cornering could be the precursor of more serious problems."




Here's an interesting comment regarding Swingarm Pivot location, and what might happen if you change it

Quote:
"keeping with fig. 9.11, if the swing-arm pivot is lowered by a little over 25 mm. then at full extension the anti-squat will be reduced to a more desirable 100% from the original 133%.

A heavy price has to be paid at the other end of the suspension range though, here the anti-squat will change from 30% to about – 34%.
A strong pro-squat tendency in other words."


Please refer to his previous quote, re pro-squat and a small loss of traction in the corner.



OK, it's getting a bit clearer for me. The big things that affect antisquat are:
Swingarm angle, Sprocket size, Sprocket location (relative to swingarm pivot), and the influence of the Center of Gravity height over the load transfer.
And the Center of Gravity is only affected by little things like, rake, fork offset, fork length, swingarm length, wheelbase, rider seating position, bar height, and...


And then, right in the middle of a chapter devoted to Squat and Dive, we go back to the basics, under the heading titled "Preload".
Too funny. I thought I know all about sag & preload, six months ago. :smt005
It can be used to increase ride height, and reduce fork dive.

I never thought about how preload affects the load transfer, and helps keep the tires on the road.

Quote:
"We have seen that due to the effects of load transfer, either wheel can be relieved of load. Commonly called wheelies and stoppies,
these actions cause the forks and rear suspension units to react against the top-out springs or rebound stops.
Accordingly we should expect that the degree of spring preload will have a significant effect on the transient responses of the suspension during these manoeuvres.

There are two principal aspects of greater preload in these circumstances;

• The static loaded position of the suspension is closer to the rebound stops, and so there is less suspension movement available before topping-out. So that occurs more often.

• The preload force means that when the suspension does top-out, it does so in a harder fashion."





Lets say the spring rate on the forks and shock, are 50 pounds per inch of movement.
We add 1' of preload to both ends, and when we're on the bike, there is another 1" of rider sag.
This means that there is now 100 pounds on both the forks and shock (50 preload, and another 50 compressing the springs 1").

If we brake hard, and transfer 50 pounds of load, onto the front wheel, and off the rear,
then the rear shock will extend 1', and top out.
It can't get any longer, so if we brake harder, and transfer more load to the front wheel,
then the rear tire will lose contact with the pavement..

The same goes for the front end when accelerating. After 50 pounds of load, is transferred to the rear wheel,
the forks well extend 1" and top out. Any more load transfer, will result in a wheelie.


Now, if we remove the 1" preload spacer, and the get back on the bike.
We again apply 100 pounds to the front and rear springs, and they sag 2".

Now if we accelerate, and transfer 51 pounds of load off the front wheel, instead of doing a wheelie coming out of the corner, we still have 49 pounds of force on the front wheel.
We will now have to transfer 100 pounds of load off the front wheel, before topping out the forks.

The same applies to the rear shock. if we have no preload, and 2" of travel,
then we will have to transfer 100 pounds of load off the rear wheel, before topping out the shock,
Instead of the 50 pounds of weight transfer that was needed when there was a 1" preload spacer.

Tony also stated that "increased preload tops out the suspension in a harder fashion".

When you brake hard, you transfer load off the rear wheel, onto the front wheel.
As the load on the rear decreases, the spring extends, and the rear of the bike raises
Since the tire is still on the ground, the spring has pushed the bike (sprung mass), away from the wheel.

Well, an object in motion, (our bike, moving away from the wheel), tends to stay in motion.
So when the shock tops out, the bike will keep moving up, and the tire will leave the ground, for a fraction of a second.

If you have more preload on the shock, there will be more force pushing on the bike, and when it tops out, it will lift the bike more, and the tire will be further off the ground.

Now, All this may not be relevant on street bikes, because Tony designs race bikes, and this all happens in miliseconds, but after doing some evaluation and modeling, he said this:

Quote:
"The dark curve shows the motion with no rear spring preload, in this case the rear wheel stays on the ground.

The light curve is when the same rear spring is preloaded by 25mm.
This is enough to cause the rear wheel to start hopping with an increasing magnitude, which would probably lead to the rider easing off on the brake."


It's definitely something else to think about.


So, decreasing preload, increases the amount of fork/shock travel, before topping out.
As load is transferred, under hard acceleration and braking, this increases the time that both tires are in contact with the pavement, providing grip.

However, decreasing preload (increasing sag), shortens the forks and shock, and decreases the amount of travel, before they bottom out, under compression.

In addition, the shorter forks, steepen the rake, reduce trail, and shorten the wheelbase.
The shorter wheelbase increases load transfer, which increases contact pressure, which decreases grip.

And again, I'm amazed to see that even small changes to one part of the suspension setup, affect the whole bike,
and changes that improve performance in one area, may hurt performance in another.
Last edited by Off Road on Sat Nov 30, 2013 2:00 am, edited 1 time in total.

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Re: Swapping Forks, wheels, and swing-arm.

#53 Post by Off Road » Sat Nov 30, 2013 12:45 am

And finally, in the Summary of Chapter 9, Tony Foale closes with these few thoughts, which do nothing to inspire the would be suspension tuner.


Quote:
"There are an infinity of suspension settings possible with any individual motorcycle, but there is no such thing as the optimum setup.

Something that works well in one set of conditions may lead to problems in others.

The best one can hope for, is to achieve a compromise that works reasonably well under most of the expected situations to be faced by any machine.

it is sometimes very difficult to determine just what adjustments need to be made.

We’ve seen how settings at one end can affect the response at the other, therefore there are times when it is difficult even to decide at which end adjustments should be made."



And I thought this suspension swap was going to be tough. :smt003

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Re: Swapping Forks, wheels, and swing-arm.

#54 Post by Off Road » Sat Nov 30, 2013 1:48 am

So, did I waste my time, or was my 20 hours of reading, a useful thing.

It does confirm my thought that I need more front sag (less preload).
My bike has excellent stabililty, so the increased sag will, steepen the rake, decrease the trail, and wheelbase, and quicken the steering.
The increased sag will also improve tire contact with the road.

On the down side, the shorter wheelbase, will put more load on the front end, increase the load transfer, increase the contact patch pressure, and reduce grip.


My bike also has a shallow swingarm angle, which has reduced the rear ride height.
So, I want to shorten the dogbones, to steepen the swingarm angle, and restore the ride height.
This will further steepen the rake decrease trail, and again, it will quicken the steering.

The steeper swingarm angle will also increase the antisquat, and this may or may not be needed.

I have installed a smaller front sprocket, which will increase the antiquat.
And I have reduced the un-sprung mass of the bike, which means that I need less antisquat force.
And I have have cut down my seat, and installed clip-ons.
Both of these have changed the bikes center of Gravity.
Which is also going to have and affect on the amount of antisquat that's required.

But, it's going to take a few more hours of reading to find out how the Center of Gravity affects the amount of antisquat that's needed.

So, when Winter ends, in 6 months, and all the reading and calculating are done, I still won't know anything.

The only way to find out how, the suspension changes will affect the bikes handling, (or if I'm skilled enough to notice the affects), :smt005
is to make the changes, test ride the bike, and see what happens.

Damn, I'm really missing Summer.

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Re: Swapping Forks, wheels, and swing-arm.

#55 Post by Off Road » Sun Dec 08, 2013 8:34 pm

I posted the following in my project thread, but not many people read that crap, so I'll repeat the info here,



Off Road wrote:
Off Road wrote:
RZResurection wrote:This is what we all need. A nice, infinitely-adjustable suspension linkage

Image

Something like that would be awesome, ...

A shock with a ride height adjustment, would make this sooo easy.
A rear shock with ride height adjustment would be a good way to go, or so I thought.
Then I read Yamaha's explanation on how the progressive rear suspension works.

Image


Using the above diagram, lets say we use up 1/3 of the travel when we sit our 200 lb. ass, on the bike (rider sag).
The rear axle is at point B, the shock spring has compressed by the amount of l1, and the bottom of the shock is at point b.



With no load on the bike, lets install an adjustable shock, and "shorten" it, so that it bolts to the link at point b.
Now when we use up first 1/3 of the rear wheel travel, the spring will compress by the amount of l2, instead of l1.
Compressing the spring more, means that more force is required, even though the rear was travel was the same.

During the second 1/3 of the wheel travel, the shock will compress by the amount of l3, instead of l2.
Again the spring compresses further, and the spring rate increases.

In addition, since the effective spring rate has increased, when we put our 200 lb body back on the bike, there will be less rider sag.




On the other hand, if we "Lengthen" the shock, so that full extension puts the bottom of the shock, where it connects to the link, at a point lower than point a.

Lets assume that shock is long enough so that the first 1/3 of the travel takes it to point a, the spring has compressed by an amount that is Less than l1.
During the second 1/3 of the wheel travel, from point A to point B, the the spring compresses by the amount of l1.
And during the final 1/3 of wheel travel, from point B to point C, the spring compresses by the amount of l2, instead of l3, as it would with the oem shock length.
Since the spring compressed less, for the same 1/3 of the travel, it required less force, which means that the effective spring rate is decreased.

In addition, since the spring rate has decreased, when we put our 200 lb body back on the bike, there will be more rider sag.






So, from what I've read, the following changes will happen, when you install a LONGER rear shock.
- Rake will get steeper
- Trail will decrease
- Swing arm angle will get steeper
- Anti-squat will increase
- Sag will increase
- Effective spring rate will decrease

Now, all of the above is just "my opinion", and should be treated as such.
The info could be full of errors, but since I don't have any better ideas, I'm going to proceed with the following plan.

On the purple project the rear sag is as follows.
Static sag - 5 mm
Rider sag - 30 mm

The difference between the two value's is 25 mm.
I've been told, and it makes sense, that if the difference is too big, then you may need a stiffer spring.
How much difference is too big? Don't know. One fellow suggested a good value would be 20 mm.

It's possible that my shock spring might be a bit on the weak side.
so, I don't want to install a longer shock, and further decrease the spring rate.


That leaves me with using shorter dog-bones, to decrease rake and trail, steepen the swingarm angle and increase antisquat, without affecting the spring rate.

mkane
Posts: 921
Joined: Wed Feb 20, 2013 11:43 pm
Location: Cloverdale, CA

Re: Swapping Forks, wheels, and swing-arm.

#56 Post by mkane » Tue Jan 07, 2014 11:35 am

All very informative. A modded rz may be heading in my direction. I believe R1 parts were used in the conversion.

mkane
Posts: 921
Joined: Wed Feb 20, 2013 11:43 pm
Location: Cloverdale, CA

Re: Swapping Forks, wheels, and swing-arm.

#57 Post by mkane » Tue Jan 07, 2014 11:20 pm

According to the paperwork that came with the bike the linkage if from an r6. have no idea what the swinging came from. Wheelbase is 57". With a bit or tweeking I may be able to make it 56 1/2.
Image

krmiller70
Posts: 107
Joined: Sun Jul 14, 2013 8:38 pm
Location: Eden Prairie, MN

Re: Swapping Forks, wheels, and swing-arm.

#58 Post by krmiller70 » Wed Mar 19, 2014 4:38 pm

Ok. After reading through the hundreds of pages of suspension theory,geometry, leverage ratio's etc...
I have some questions perhaps those of you who have done this would know.

I have a Works Performance Shock with a stock swinger on my RZ 350. No idea what the length is, as the PO installed it.

I acquired an aluminum FZ 600 swinger with the 'H' link already on it less the stock FZ dog bones.

When making the swap to the FZ arm utilizing the FZ 'H' link. Can you, or should you use the stock RZ dog bones or would this cause the rear end to drop or lower the static ride height?

My goal is to keep the rear ride height as close to stock or a little higher as possible. I am using the stock front forks and have them in the stock position on the upper triple clamp. PO claims he installed Progressive fork springs, although it still has the 'air fork' caps on them?

Thanks

dinamos
Posts: 106
Joined: Fri May 20, 2005 12:52 am
Location: Burlington, ON, CA

Re: Swapping Forks, wheels, and swing-arm.

#59 Post by dinamos » Mon Jan 19, 2015 2:24 am

Sorry Offroad, it's been a while since this post but, I was wondering if you ever did a weight scale on either the F! or FZR conversions relative to stock. Just curious. BTW, a great post.

dinamos

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