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Front fork Pre Load adjusting

nickrides

Mini Bike
Forum Subscriber
Gents
So I got back form a 1400 mile loop around Utah and NV. I brought a wrench with me to adjust the preload on my front forks springs which I thought were too " Loose" I continually put more and more preload on them until one day I thought I had gone too far. I backed off the pre load a bit and whala
I think I found a nice balance of stiffness and good feeling of being planted.
I put a ziptie around one fork leg to see how much compression I was getting.
I think doing this while on a tour was a good way to figure out what worked best for me.
Being on the bike all day for 5 days you get a good feel for it.
Best
Nick
2014 C-14
 

Daytona_Mike

Member
Member
Pre load (Also called SAG...Also called Chassis Geometry) cannot change the 'stiffness' or 'Looseness' or 'tightness' of the springs.... or any spring... that is reason is why we have to change our springs to match our weight ... .... Just saying.... Pre load raises and lowers the height of the chassis. The goal of any preload setting is to be 1/3 into the the shock travel. Raising the chassis reduces that 1/3 .. depending on how far you were in to that 1/3 to start with. Too much preload raises the chassis too high ....reducing that 1/3 to very little...among other things,,, then the shock easily tops out...... lifting the tire off the road.... loosing contact with the road... not a good thing.
 
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nickrides

Mini Bike
Forum Subscriber
Mike
I have read from you the above before.
When I started my trip I could see on my ziptie around my fork leg that I was getting about 90-95% full compression.
I slowly cranked in more preload until I was getting maybe 80% full compression after a few hours riding.
Then I went down a 40 mile section of road that was fairly rough and I didn't like the ride, too harsh, so I backed off the preload a bit and found I had reached a happy medium for my bike at my weight.
I liked my suspension feel before all this and I like it better now.
To me it does feel stiffer and more planted, if that makes sense.
I don't follow you on the lifting the tire off the road thing...
Nick
2014 C-14
 

Daytona_Mike

Member
Member
Hi Nick. yeah.. its not that the bike is stiffer.... adding preload your chassis is now higher.. taller.... your forks are more extended then they were. I do not know what your weight is or how much luggage you had on the bike so your bike might have started out with your suspension overly compressed (Too much SAG). So the lifting of your tire off the road thing: When your shocks extend outward to its full length....like going over a hill.. or lets say a drop in the road.. the forks are trying to reach out and stay in contact with the road.... by increasing the pre load too much.. that 'reaching out' is reduced and if reduced too much (too much preload) the shock 'Tops out'.. reaches its limits.. can no longer reach out very far and keep in contact with the road. Make sense?? I see this a lot in the quad world.. everyone in the quad world wants ground clearance.. they crank the preload all the way in to raise the bike up as far as they can... the shocks are completely topped out.....fully extended cannot reach out at all.. which makes the quad super rough riding and dangerous, terrible handling.... most of the time the tires are not on the ground.. If you have a chance.. find some ones bike that has upgraded the suspension.. AK20's.. Ohlins.. Penske and take it on a rough or wash board type road. THAT IS when you will feel that 'planted' confidence inspiring feel. It wont even feel like your on a C14. On the other hand.. maybe you shouldn't. It gets expensive.
 
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Daytona_Mike

Member
Member
Unfortunately these stock C14's have no Compression damping adjustments and the valving is not the best. Raising the chassis to compensate changes the rake and trail - weight balance front to back- (handling). . its best to read up and know what these adjustments do before making changes.
 

laker9142

Member
Member
I completely agree with Daytona Mike. I don't think the word 'preload' should even be used pertaining to motorcycle suspension. Its a complete misnomer that causes nothing but confusion.
 

connie_rider

Member
Member
{Not a suspension expert, but I think}
Many confuse spring rate with Preload.
Preload is the correct way to describe the initial compression of the springs.
ie; You use preload to compress the springs and raise the suspension.

The springs are pre-loaded/compressed to set the sag..
Setting the sag adjusts how much suspension travel you have available.

Spring rate is the force that is required to compress the spring over a distance.
The spring rate effects how much the suspension is compressed/rebounds during suspension travel.

Sag, "and" spring rate work together to adjust ride height and how much travel is used.

Damping is used to control the rate that the suspension moves.
Compression Damping is the damping during suspension compression.
Rebound damping is the damping during suspension extension.

All must work together..

Ride safe, Ted
 
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laker9142

Member
Member
I'm not a suspension expert either. But I do have a basic understanding of how it works. I'm not trying to undermine what you're saying Ted, I'm just expanding on it with my own words. You are correct that people misunderstand the word "preload" and now you've thrown in the term "sag". Sag has an actual definition of, how far the forks compress from the point where the bike sits under its own weight, as compared to the point where the bike sits with the rider on board. My C14 has a sag of 40mm with the springs supplied by Traxxion. It is set by the spring and is non adjustable. If you want to change the sag you have to change the spring.

Pre load really has no definition, if you want to call it pre-compression, that's a closer meaning. But said pre-compression does nothing but allow the spring to fit, into a predetermined cavity of a certain length, as designed by the engineers. Once the bike is sitting on the ground and the forks are compressed past that pre-determined length, then the pre-compressed length is irrelevant unless you your doing wheelies or otherwise raising the bike off the ground.

Setting sag, and adding preload, are wives tails and myths. The so called spring adjusters on top of the forks only adjust the ride height of the front end. Therefore I only refer to those adjustors as "ride height adjustors". I keep mine cranked all the way in for max ride height to compensate for the rather generous 40mm of sag specified by Traxxion and their spring choice. I did ask them about that and they said 40 was good for a bike like mine. Sport bikes are around 32 and race bikes even less.

As far as springs and damping go, I like to keep it real simple, so here's my take on them. Springs absorb the energy from the tire hitting the bump, and stores that energy until the spring rate overcomes that energy, and releases it back out to extend the compressed fork. What Ted said is absolutely correct also for both spring rate and damping. I just said it differently.

Damping simply controls the speed at which the spring both absorbs and releases energy.

Now if you can find somebody who can specify exactly which spring rates and which damper settings go together for a given situation, then you've got a suspension expert. If you call somebody for suspension advice and they start talking about setting "sag" and "preload", just hang up.
 

turbojoe78

Member
Member
This guy mentions "preload" and seems to be concerned with measurements. (sag?)
He must not know what he's talking about?

 

connie_rider

Member
Member
Hi Laker. Most are used to calling it pre-load adjustment, and even the Kawasaki Manual call's it pre-load adjustment.
But, I agree that adjusting the spring pre-load adjusts the ride height, so you can call it Ride height adjuster.
It's just a difference of what we call it, and {I think (??)} we agree on it's use.

But, I say "I think" because you said: "My C14 has a sag of 40mm with the springs supplied by Traxxion. It is set by the spring and is non adjustable".
There, we have a disagreement, because the "Pre-load/ride height adjuster" changes sag,
and the "combination" of spring rate & pre-load controls ride height.
You even said; "I keep mine cranked all the way in for max ride height to compensate for the rather generous 40mm of sag specified by Traxxion and their spring choice".
A assure you that "cranking it in all the way" has adjusted {decreased} your sag.
ie; In the video above, cranking in all the preload, decreased the sag {with 275 lb rider aboard} 1/2".

Ride safe, Ted
 
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nickrides

Mini Bike
Forum Subscriber
What I thought my problem was, was that I did not have enough preload on my front springs as I could see from my ziptie on my shock leg was that I was bottoming out, or very nearly bottoming out, while riding, either through hard braking or bumps in the road.
I put in more and more preload until the bottoming out stopped, it seemed to feel much better.
I should get a helper out there today and actually measure some stuff.
I will and post up what I find.
That Vid with Dave Moss is a big help
BTW I'm 225 5'11' -I tour with minimal gear, very little really, a CC and some hand wipes.
Nick
2014 C-14
 

connie_rider

Member
Member
Nick, (I 🤪) have a thought..
If you "almost" used all your travel,,, that is not (necessarily) bad.
{ie; were you riding hard? /did you feel it bottom out?}
You want to be able to use as much of the available travel as possible.
Because; You want the travel to be as long as possible without bottoming out.
ie; The longer the travel, the longer the damping system has to control things (and the smoother the ride).

I suggest that you do check sag.
See what the sag is now. {where you currently have the pre load adjusted} and then compare that with the pre-load cranked all the way in, and all the way out. {As Dave Moss did in his video above}

NOTE: We need Daytona Mike {or other} to come in here and help (correct me) as I can get over my head real quick.
ie; Mike... "Helppppp"!!

Ride safe, Ted

PS: I like this this video as it covers the sag adjustment process and explains things well.
{Watch video from the start....}
Using this process, my bike is set at about 35-38mm of sag. (with a (short/fat) rider aboard)

 
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laker9142

Member
Member
I'm not sure about that Ted. When I say cranking it all the way in I mean turning the adjuster clockwise. If you'll notice the guy working on the zx14, he turns those adjusters in, or clockwise, and the front end comes up .50". So its actually the ride height that changes.

I'm working on a little project that i hope will show, in pictures, what I'm trying to say in words. And pictures are worth a thousand words!

And I acknowledge that everyone uses the term "pre load". I just don't like it because, as shown in that video above, all it does is change the ride height. I suppose when you raise the front a half inch, you do gain a half inch of rate gain just before you bottom out. But I've never bottomed out!
 

connie_rider

Member
Member
I'm enjoying this discussion as it's making me think, and I'm hearing idea's from others.
"I admit", I'm over my head here.
All my posts should start with; "I think", because I sure don't "know" what is correct.
Which is why I'm asking for more knowledgeable people to join the discussion and correct my/our errors.

Dealerships, and most riders seldom take the time to set sag/damping before riding a bike.
A few years ago, I started trying to learn more about suspensions.

I watched video's, experimented, and talked with others to learn the little {I think} I {kinda} understand.

"I think"
It is possible to set sag, and (because of friction/stiction/improper spring rate} have poor ride height.
Mike talked about it;
Raising the chassis to compensate changes the rake and trail - weight balance front to back- (handling).
Its best to read up and know what these adjustments do before making changes
.
NOTE:
Sag is set static. {with the bike not rolling}.
After setting sag, damping is also set static. {our stock suspension allow only rebound damping adjustments}

{I think}
... Ride Height is not necessarily the same as static sag, because the suspension is moving and friction/stiction/air flow effects things differently.
... Ride damping is not necessarily the same as static damping, because the suspension is moving and friction/stiction/airflow effects things differently.
After setting sag/damping {statically}, you have to ride the bike and make adjustment's as needed.

Ride safe, Ted

PS: Nick adjusted his bike's {front??} preload {to his preferences} while on a long ride. "Well done" Nick!
But, he didn't mention if he adjusted the rear, adjusted damping, or set sag before the ride (??)
I suspect that when he checks his sag, he'll discover that he has too much sag and too little damping.
 
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laker9142

Member
Member
Most times it helps to understand how things are made to understand how they work. In this case we have 4 things we're dealing with;
1) A spring

2) The weight of the bike, and weight of bike plus rider.

3) The damper rod..... Which isn't even needed for setting ride height and sag, (this is clearly shown in the following pictures). All three pictures show that once the load of the bike exceeds the "preload" of the spring as confined by the damper rod, the damper rod becomes irrelevant. (I do concede that the spring is "preloaded "when confined by the damper rod. But it's the only time the term preload is used appropriately). To clearly show that this is true, I completely removed the nut from my simulated damper rod and nothing happened, And that series of measurements began with NO preload. The bike weight just sat there on the spring and didn't move. You can prove this on your own bike by setting an explosive charge inside the fork on the damping rod. Remotely trigger the charge and sever the damping rod. Nothing will happen to bike as it sits on the spring.
This also shows that since the damping rod is irrelevant, then there is no way to "add tension" to the spring. The spring must be in a confined state to add tension to it, and there is nothing there to confine it. Because we just blew up the damping rod!

4) A jack screw, also known as the "preload" adjustor. Which can only change the initial ride height. This initial ride height is more commonly recognized as the first number of the sag calculation. Its use is clearly shown in that Moss video. Since the bike in his video clearly moves up a half inch as cranks the jack screws "in"..... it did not compress the spring and add "tension" as he implies.

I completely disagree with Moss when he says that turning in the "preload" adjusters somehow adds tension to the spring. There are only the 4 things listed above in this situation we're talking about. There is no silk hat involved. In order to add tension to a spring you have to compress it. What he's saying is a myth. If somebody can explain to me what he's talking about, please do. But don't just send a link to another video.
He also says some odd things about the hydraulics helping with ride height, then he says "but it really shouldn't". Talk about adding confusion to something that already seems to confuse people.

So my pictures convey 2 things

1) Space under the nut, or no nut at all is needed, when the bike weight exceeds the preload of the spring. (The threaded rod and nut simulate the damper rod)

2) When you add a .490 spacer ((simulates our jack screws (or preload adjustors if you want)) it moves the weight of the bike up .490! There is no magical tension added to the spring.

3) The sag created when the rider climbs on the bike, after the bike is already sitting on the ground, is the true sag. Mine is 40mm. And it can not be changed without changing springs. For all the reasons stated above.

4) Comments and arguments are welcome! If I'm wrong, then I am really confused and would like to know where I went astray.

Also I just noticed that the rider weight, and bike plus rider measurements, are reversed in the picture WITH .490 spacer, WITH nut. I'd change it but the picture thing is harder that the rest of it.
 

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bmidd

Member
Member
I completely disagree with Moss when he says that turning in the "preload" adjusters somehow adds tension to the spring. There are only the 4 things listed above in this situation we're talking about. There is no silk hat involved. In order to add tension to a spring you have to compress it. What he's saying is a myth.
When you increase preload on a fork or a shock, you are increasing the force exerted by that spring. When increasing preload, you are decreasing sag and making the bike ride higher, that's common knowledge. I think you are getting hung up on Dave using the word Tension, you have to remember he's English and speaks proper English.
You said Traxxion sold you springs that give you 40mm of sag, I'm going to assume that's with the preload adjusters fully out. You say you crank them all the way in to raise your ride height. Have you had anyone measure your sag after you wind them all the way in? It won't be 40mm anymore. Your spring rate gets you in the ball park for sag, it can be adjusted with your preload adjusters.
Have you added Traxxion compression and rebound valving, or did you just install springs? I ask because I have found the C14 suspension to be utter shit. As an experiment, I've sent off an OEM shock to be rebuilt and resprung and I have a leftover set of ZX14 forks that I'll rework this winter and throw on the front. If the experiment doesn't make much of a difference, I'll throw a Penske on there and call it a day. The OEM shock has zero rebound control, even worse than an OEM Z14 rear , which responds nicely to a Traxxion or RaceTech rebuild and gives you 90% of a nice Penske.


On another note, Dave is a fountain of knowledge and will respond to Facebook questions or emails, if you want to reach out to him. If you want to lose yourself for about a week, send me a PM and I'll give you my Dave Moss login and you can browse his paid videos to help you in your quest. He goes into in depth detail on suspension theory and walks you through tearing into your own. Max @ Traxxion also has lots of old videos on YouTube they have uploaded, called Suspension for Mortals and has lots of good info.
 

TireguyfromMA

Member
Member
The ZX14 is lighter than the C14. The springs in the forks on the ZX14 are under sprung, or to soft. If you take the forks from a ZX14 and put them on a C14 you will not be able to get your sag set to 35mm +/- 5mm. Even with the preload adjusters turned all the way in your probably going to be in the 45mm range. If you send the ZX14 forks to Traxxion to be reworked, make sure you let them know the forks will be fitted onto a C14 so they can put the right springs in. I know all this from trying to help another COGer set the sag on his C14 recently using a SLACKER V3 Digital tool. Watch Dave Moss use this tool.
 

connie_rider

Member
Member
3) The sag created when the rider climbs on the bike, after the bike is already sitting on the ground, is the true sag. Mine is 40mm. And it can not be changed without changing springs. For all the reasons stated above.

4) Comments and arguments are welcome! If I'm wrong, then I am really confused and would like to know where I went astray.
Laker, sorry, but you are incorrect.
I think your confusing "spring rate" with "Preload".
"Spring rate" can not be changed without changing springs.
But, "Sag" and "is" changed with preload adjustment.

I studied your photo's to try to understand what you are showing.
... I see something in your photo's that is different than what you see.
You interpret your photo's as prove there is no change in sag.
I look at the same photo's and they show me that sag is occurring.

NOTE:
"The preload adjuster" is an adjustable spacer that changes the force which is applied to the top of the spring.
It changes the force on the spring by changing how much the spring is compressed.
(It pushes between the top of the shock and the top of the spring)

For Now, look at your #5 photo only. {as it's the most basic}
...In your photo #5 you have 2 identical springs.
.....On the right spring, you have 2 weights. {they demonstrate Bike weight/rider weight}.
That (right) spring is partially compressed by the weight of the blocks. {it is sagging due to the combined weight}

On the left spring, you have 3 weights. {it demonstrates Bike weight/rider weight/*preload adjuster}.
** The 3rd block is acting as a preload adjuster and pushing down on the spring.
That (left) spring is more compressed by the weight and additional height of the blocks. (it is compressed more because of the additional weight/spacer)
Note that the left spring is compressed more than the right spring.
So the top of the left spring is lower than the right spring.
But, the top of the block on the left is higher than the top of the block on the right.

{For this discussion, Lets say the top of the upper block (on the right) is 6" off the table and represents the top of the shock}.
,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,{Lets say the top of the upper block {on the left}, is 6 3/4" off the table and represents the top of the shock).
ie; The top of the block on the left is 3/4" higher then the block on the right spring...

So, if the Right block is 6", and left is 6 3/4"; you can see a difference of 3/4". {ie; the sag decreased}

Ride safe, Ted
 
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laker9142

Member
Member
Ted, I appreciate that you've presented an actual argument to what I'm saying. One of the hardest things about it is trying to present it so its understandable. I've deleted a dozen other pictures that were much to tedious. But tomorrow I'm going to take 2 more pictures that will plainly show,,,,,,when you add the .49 spacer to the stack, the bike weight goes up .49. So if that's true, that means the spring did not compress, correct?

Also in pic 5, the .75 spacer is aluminum and was not meant to be a third weight. I do concede that it did compress its spring about .050. Ill do it again with a piece of plastic so it doesn't influence the spring (as much). and regardless of height off the table, the point of that picture was just to show that when you set a certain weight on a spring, it doesn't matter that you jacked it up .75. the spring compresses the same amount.

I apologize to the original poster for hijacking this thread. I was just agreeing with Daytona Mike. Then I got bored on Thursday afternoon and decided to prove it. Which I did. Now I need to figure out how to explain it.

In your paragraph above under Note and in parenthesis you say, (it pushes between the top of the shock and the top of the spring). This indeed is the crux of the matter. And I say this is false and I have offered proof. Just need to make it more clear.

Here's a thought to consider, the bike weight is just sitting on top of the spring with nothing but gravity pushing it down(like picture 5). If you disconnect the damping rod, and lift the bike off the ground, the forks will fall apart leaving the wheel and lower legs on the ground. And since my picture showing no nut on top of the threaded rod (damping rod), effectively eliminates the damping rod from the assembly. That means that nothing else remains in the assembly to (as you say) push against. The bike is simply sitting on the spring.
 

connie_rider

Member
Member
Good discussion!!
Like you, I retyped my note multiple times to try to find the right wording.

Ted, I appreciate that you've presented an actual argument to what I'm saying. One of the hardest things about it is trying to present it so its understandable. I've deleted a dozen other pictures that were much to tedious. But tomorrow I'm going to take 2 more pictures that will plainly show,,, when you add the .49 spacer to the stack, the bike weight goes up .49. So if that's true, that means the spring did not compress, correct?
No, the spring did compress because there is more force being applied to it by the length of the spacer.

laker9142 said:
Also in pic 5, the .75 spacer is aluminum and was not meant to be a third weight. I do concede that it did compress its spring about .050. Ill do it again with a piece of plastic so it doesn't influence the spring (as much). and regardless of height off the table, the point of that picture was just to show that when you set a certain weight on a spring, it doesn't matter that you jacked it up .75. the spring compresses the same amount.

It's better that it is aluminum, because that shows' that the change is because of the length of the adjuster, not the weight of the material.
But, no,,, the spring did not compress the same amount... {see below marked %%%%%}
I apologize to the original poster for hijacking this thread. I was just agreeing with Daytona Mike. Then I got bored on Thursday afternoon and decided to prove it. Which I did. Now I need to figure out how to explain it.
In your paragraph above under Note and in parenthesis you say, (it pushes between the top of the shock and the top of the spring). This indeed is the crux of the matter. And I say this is false and I have offered proof. Just need to make it more clear.
Here's a thought to consider, the bike weight is just sitting on top of the spring with nothing but gravity pushing it down(like picture 5). If you disconnect the damping rod, and lift the bike off the ground, the forks will fall apart leaving the wheel and lower legs on the ground. And since my picture showing no nut on top of the threaded rod (damping rod), effectively eliminates the damping rod from the assembly. That means that nothing else remains in the assembly to (as you say) push against. The bike is simply sitting on the spring.
That is true even with the forks intact.. {The weight of the bike is setting on the spring}

Try this;
The pre load adjuster is an adjustable spacer that is located between the top of the upper fork tube and the top of the spring.
*The preload adjuster passes thru the top of the upper fork tube.
*The bottom of the preload adjuster is setting on top of the spring.
*The bottom of the spring is resting on top of the damping rod.
*The bottom of the damping rod is setting on the bottom of the lower fork tube.

NOTE: During assembly the spring is compressed approx. 2" to assure that it holds the 2 fork tubes apart.
Visualize;
,,,, Wheel off ground; tubes are at full extension.
,,,, Wheel on ground (with bike and rider weight on top, and pre load adjuster NOT extended); upper tube moves down as spring is compressed by weight.
When the preload adjuster is extended, it compresses the spring more.
When the spring is compressed it develops more force. {due to the coils being deflected} and pushes back.
Result;
,,,, Wheel on ground (with bike and rider weight on top, and pre load adjuster extended); upper tube moves down as spring is compressed by weight, "but" due to the increased force from the spring being compressed, the upper fork tube moves back up.

%%%%% NOTE: The amount of preload extension is not the same as the amount of fork tube extension}
Using 3/4" of extension by the preload adjuster.
That 3/4" pushes the spring down only a portion of that amount.
{for now, let's assume the spring is compressed only 3/8"}
As the spring is compressed, it develops more resistance and pushes the upper fork tube up.
{for now; Let's assume the upper fork tube goes up the remaining 3/8"}
So {in this case} the 3/4" of adjuster extension results in 3/8" of spring compression and 3/8" of fork tube extension. {result is 3/8" less sag}

Geez, this is hard to type.

Ride safe, Ted
 
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connie_rider

Member
Member
NOTE: In this discussion, I'm been describing a typical motorcycle fork. {like the ones used on a C-10}
In a cartridge fork {used in a C-14} the spring/preload adjuster works the same, but the shock is assembled differently.

"Yes", I know my notes are too long...

Ride safe, Ted
 
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laker9142

Member
Member
I've included 2 pictures. One shows the cartridge that goes inside the fork, the other is a modified picture 5, with the weight of the spacer reduced so it wont influence the spring. The shims shown combine to a spacer height of .747. Also shown is a .750 joe block for comparison. There is no 50/50 split.

The bottom of the spring sets on the cartridge body, which is bolted to the bottom fork tube. And thus moves in unison with the tire. The damping rod is the skinny shaft inside the spring, it threads into the fork cap. That fork cap also doubles as a jackscrew (preload adjustor). I wont mention the damper rod again because it does nothing in regard to our conversation.

So again we have a spring, bike and rider weight and a jackscrew. Nothing else.
When you put the same weight on the same spring, you will get the same amount of compression every time. Regardless of jackscrew height. (See picture 5) (And all my other pictures too).

Also when you hit the same bump at the same speed you will get the same amount of spring compression, every time.

With all that being said, I'm pretty much out of bullets. Unless you can explain to me where that 50/50 split comes from! It you can explain that with facts supported by evidence, then I will delete all my posts on this thread, replace them with a large banner that says Ted Is Great. And Ill buy you a beer!
 

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Just Cliff

Member
Member
It you can explain that with facts supported by evidence, then I will delete all my posts on this thread, replace them with a large banner that says Ted Is Great.
Ted is great? Well that's just damn funny right there.

You two have continue this discussion at my house & have a seminar using my bike. Then maybe I can keep up with Ted. :rolleyes:
 

laker9142

Member
Member
Sounds good Cliff. I plan to be there for Thursday evening festivities. Just mounted up a new set of Metzeler M9rr's, highly recommended and good reviews. Ive never tried Metzelers before, Hope to get there and back!

Just how big a feller is Ted anyways?
 

connie_rider

Member
Member
OMG, Laker's gonna be there too.... ?? {What the heck is your name?}
Yahoo. We can argue for hours.. {Got to get my thinkin' hat on}.

I admit; I didn't realize that we were talking about a cartridge fork, and I'm not familiar with their assembly.
Also; I don't see the jackscrew in your photo?
But; {regardless of it's location} it works the same.
The jackscrew pushes against the spring to preload {pre compress} the spring.

You did ask for proof. Sooo,,,
Are you familiar with Newton's third law of Motion?
For every action, there is an equal and opposite reaction.
The statement means that in every interaction, there is a pair of forces acting on the two interacting objects {In opposite directions}.

Visualize; that the "weight" of the bike is setting on top of the partially compressed spring.
,,, So, the weight of the bike is held up, by the force stored in the compressed spring).
ie; the spring is compressed until it develops enough force to support the weight of the bike. {Sag}
Next; Visualize; that a screw jack {pre load adjuster} is screwed out between the top of the fork and the spring.
{ie; That screw jack pushes down on the spring, "and" up on the fork tube}.
As the spring compresses, it becomes "more" resistant to compression.
As the spring resistance increases, it develops enough force that the {balanced} weight of the bike "rises"... {& Sag decreases}

Note that when you hit a bump, the spring compresses "exactly" the same "amount" as it did before preload was added.
In both cases {with and without preload} the amount of movement is the same because the spring rate does not change.
But, {because we added preload and raised the bike} there is more travel available..

Ride safe, Ted

PS: Cliff has always been jealous of my mustache.
PS II: I drink Shiner Bock
 
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laker9142

Member
Member
Hi Ted, the names David. Yes we'll have to continue this discussion over beers. That will help! lol.

But what your not getting is that, the equal and opposite reaction, is that the bike weight goes up. Not that the bike weight somehow compresses the spring. Its simply impossible unless you make the bike heavier.

But we're not getting anywhere here so I hope to see you at Cliffs!
 

connie_rider

Member
Member
Ok, David. We'll continue to discuss {not argue} over beers.
I suspect that we're misunderstanding one another, more than disagreeing with each other.

Until we meet, ponder these.
1) From Dayton Mikes post {Reply #4} its not that the bike is stiffer.... adding preload your chassis is now higher.. taller.... your forks are more extended then they were.

2) Form your recent post. is that the bike weight goes up. Not that the bike weight somehow compresses the spring. Its simply impossible unless you make the bike heavier.
I agree that making the bike heavier will compress the forks. Bike is setting there. No weight is added. Only the preload adjuster was moved/extended.
Extending it/Pushing down on the spring with the preload adjuster, pushes up un the upper fork tube and down on the spring. {Pre-compressing the spring}

3} Go to reply #( and watch Dave Moss adjust the suspension on a ZX-14.
At 1:55 Dave measures the front forks and says their too low. Sez; "We need to put quite a bit of pre load in".
At 3:00 Dave cranks all the pre-load in.
At 3:45 Dave remeasures the front end and it is higher.
It rose from 2 3/4" to 3 1/4" extension. {the front of the bike is 1/2" higher}
..... It went up because Dave cranked in preload. {at 3:00}

Ride safe, Ted
 

laker9142

Member
Member
Dang Ted, you're a tough nut...to crack! But it seems like you're coming around. I agree with almost everything you said in that last post except the part in parenthesis about pre compressing the spring. It kinda sounds like that 50/50 split thing you mentioned earlier.

I want to clarify what I said and you quoted. when I said "the bike weight goes up", I should have said "the weight of the bike goes up higher from the ground". The bike doesn't gain weight.

I've got a hypothetical for you that may help, but first I need to know if you agree with the statement that, 'the same weight on the same spring will produce the same amount of compression, every time'.

So I'm leaving now. Taking the long way to Cliffs and splitting it into 2 days. Stopping at a couple poi's.
 
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