It's NOT preload!

[5w30]

I have to ask: did you read my reply to the OP? The one that I linked to just above? Did that not explain why some people would feel the adjuster doesn't adjust preload (when you and I know that it actually does).

I read your post #20 (several times) and think you make a very good case that the "adjuster" is there to fine tune the desired spacer length...which in turn changes ride height but in order for the adjuster to actually change preload it has to compress the main spring and whether that happens depends on the relative spring strength between the main spring and the top out spring.

Can you say the adjuster is a preload adjuster if the main spring is not compressed at all? That is what actually happens on a ZX-14 fork. If you screw the adjusters in 15mm the end result is that the also fork "grows" 15mm, all the spring compression is in the top out springs. Doing the same test on the C14 forks (which are externally identical) the end result is that the fork only "grows" 10mm, which would lead one to conclude that the main spring has compressed 5mm and the adjuster is a partial preload adjuster. Why the difference...the C14 has shorter and stronger top out springs. When the forks are installed on the bike and weight is applied, the results are the same, the ride height for both forks has increased by 15mm as a result of the adjustments.

I haven't tried to do any measurements on the FJR's forks so I don't know what the relative spring strength is between the top out springs and the main springs but I would guess that a 15mm adjuster change (on OEM springs) is going to compress the main spring by 5mm or less, making it a partial preload at best....and that number could change substantially up or down (maybe to zero) if the forks have aftermarket springs and spacers. When you change the preload on a shock (has to be a aftermarket since the OEM does not have preload adjustment in spite of what Yamaha calls it), the spring compresses the exact amount of the adjustment applied, however, that is not the case with the forks when top out springs are involved....and unless you do some careful measurements you do not know what preload, if any, you are actually getting, however you will always get the same amount of ride height change (adjusted for fork angle) that you applied with the adjusters...and that is why I prefer to call the adjusters ride height adjusters rather than preload adjusters.

Does what you call the adjusters make any difference in performance or safety? Absolutely not! Does the amount of actual preload applied by the adjusters make any difference in performance or safety? Same answer...the main springs are going to compress the same total distance once weight is applied whether preload is applied or not. Likewise, the adjusters change the ride height the same amount whether preload is applied of not.

I did, and again just now. It was refreshing to see you more or less straighten the matter out. This sentence though... it isn't true. Unless I'm just misunderstanding what you mean by "appear to change"..

When the fork is unweighted the total length of the fork will appear to change as you vary preload because there is a spring on the cartridge that acts as a buffer to soften top-outs.

When the fork is unweighted you aren't going to see any change in the length of the fork by tampering with preload. It just isn't going to happen. The fork is at full throw, how is the length going to change?

Getting back to the dirt bike reference... when you tighten the collars on your rear shock, increasing preload, do you think you just made the shock longer?? Not at all. Will it be "longer" under the same load (assuming spring compression is occurring) than it was before you tightened the preload, yes it will, because it will ride slightly higher in the stroke. Once you remove any spring compression from the equation (unweighted), or if the component is already topped out in its throw (unweighted), preload impacts overall length absolutely zero.

 

[MCRIDER007]

Yeah, we've had this discussion before. I don't think we have had this discusssion

Suppose that the FJR1300 did not have top out springs. If that were the case then these would qualify as preload adjusters in your definition because the main spring would be compressed at full length, right? How would it change how these adjusters affect the way the suspension rides? It would be completely identical to how it works now. Right up to the point where the suspension tops out, which it really never should anyways. If the FJR did not have top out springs then the adjusters would qualify as preload adjusters because they would be compressing the main spring only but (as you said) the ride would be the same up to the point the suspension tops out and doesn't have the top out springs for a soft landing.

Besides, it takes some amount of force to compress those top out springs, so in actuality as the top out springs are compressing (and fork lengthening) the main spring is being compressed somewhat as it delivers the added force to the top out springs.I think that is the same thing I said.

I really do not see what the difference is that the fork elongates because of a top out spring compressing or not. The effect of screwing in the adjuster is exactly the same as adding additional spacer distance above the spring: it raises the loaded suspension's ride height and that is all. That is all that spring preload ever does whether there is a hard top out or a spring buffered one.

The fork getting longer does not serve any useful purpose, it just demonstrates that the top out springs are being compressed rather than the main spring. I agree that spring preload in the forks is the same as adding a spacer (the adjuster is just an variable spacer) and a backdoor way to increase ride height , preload does a bit more in the shock but that is a different subject.

PS - DId you ever read the PM I sent you about the ES spring rate?

 

[MCRIDER007]

I did, and again just now. It was refreshing to see you more or less straighten the matter out. This sentence though... it isn't true. Unless I'm just misunderstanding what you mean by "appear to change"..
When the fork is unweighted the total length of the fork will appear to change as you vary preload because there is a spring on the cartridge that acts as a buffer to soften top-outs.

When the fork is unweighted you aren't going to see any change in the length of the fork by tampering with preload. It just isn't going to happen. The fork is at full throw, how is the length going to change?

Try it and take some careful measurements before and after. When you say the fork is at full throw, I think you are saying that it is fixed in place internally. Not true, the bottom on the fork tube is trying to lift/compress the top out springs that are located on the outside of the cartridge. The adjuster pushes down on the main spring but at the same time it is lifting up on the fork cap/fork tube. Its hard to measure when the forks are on the bike but very easy to see when the forks are on a work bench.

If you try to measure with the forks on the bike, you need to pull the axle or do both forks at the same time.

 

[5w30]

Topout springs just muddy the waters. Some valid points were made regarding them. None the less, regardless of the transfer percentages between topout springs and main springs, when you tighten preload you are increasing compression resistance in the spring system which in turn will cause them to ride higher in their range of motion at a given load.

 

[MCRIDER007]

Topout springs just muddy the waters. Some valid points were made regarding them. None the less, regardless of the transfer percentages between topout springs and main springs, when you tighten preload you are increasing initial compression resistance in the spring system which in turn will cause them to ride higher in their range of motion at a given load.

This is true for a shock, not a fork. As Fred said, a fork rides higher because the preload adjuster acts as an additional internal spacer.

 

[Old Guy]

I have to ask: did you read my reply to the OP? The one that I linked to just above? Did that not explain why some people would feel the adjuster doesn't adjust preload (when you and I know that it actually does).

I read your post #20 (several times) and think you make a very good case that the "adjuster" is there to fine tune the desired spacer length...which in turn changes ride height but in order for the adjuster to actually change preload it has to compress the main spring and whether that happens depends on the relative spring strength between the main spring and the top out spring.

Can you say the adjuster is a preload adjuster if the main spring is not compressed at all? That is what actually happens on a ZX-14 fork. If you screw the adjusters in 15mm the end result is that the also fork "grows" 15mm, all the spring compression is in the top out springs. Doing the same test on the C14 forks (which are externally identical) the end result is that the fork only "grows" 10mm, which would lead one to conclude that the main spring has compressed 5mm and the adjuster is a partial preload adjuster. Why the difference...the C14 has shorter and stronger top out springs. When the forks are installed on the bike and weight is applied, the results are the same, the ride height for both forks has increased by 15mm as a result of the adjustments.

I haven't tried to do any measurements on the FJR's forks so I don't know what the relative spring strength is between the top out springs and the main springs but I would guess that a 15mm adjuster change (on OEM springs) is going to compress the main spring by 5mm or less, making it a partial preload at best....and that number could change substantially up or down (maybe to zero) if the forks have aftermarket springs and spacers. When you change the preload on a shock (has to be a aftermarket since the OEM does not have preload adjustment in spite of what Yamaha calls it), the spring compresses the exact amount of the adjustment applied, however, that is not the case with the forks when top out springs are involved....and unless you do some careful measurements you do not know what preload, if any, you are actually getting, however you will always get the same amount of ride height change (adjusted for fork angle) that you applied with the adjusters...and that is why I prefer to call the adjusters ride height adjusters rather than preload adjusters.

Does what you call the adjusters make any difference in performance or safety? Absolutely not! Does the amount of actual preload applied by the adjusters make any difference in performance or safety? Same answer...the main springs are going to compress the same total distance once weight is applied whether preload is applied or not. Likewise, the adjusters change the ride height the same amount whether preload is applied of not.

I did, and again just now. It was refreshing to see you more or less straighten the matter out. This sentence though... it isn't true. Unless I'm just misunderstanding what you mean by "appear to change"..

When the fork is unweighted the total length of the fork will appear to change as you vary preload because there is a spring on the cartridge that acts as a buffer to soften top-outs.

When the fork is unweighted you aren't going to see any change in the length of the fork by tampering with preload. It just isn't going to happen. The fork is at full throw, how is the length going to change?

Getting back to the dirt bike reference... when you tighten the collars on your rear shock, increasing preload, do you think you just made the shock longer?? Not at all. Will it be "longer" under the same load (assuming spring compression is occurring) than it was before you tightened the preload, yes it will, because it will ride slightly higher in the stroke. Once you remove any spring compression from the equation (unweighted), or if the component is already topped out in its throw (unweighted), preload impacts overall length absolutely zero.

I agree with you here, though I haven't really been into my FJR forks. The length of the fork may change with spring compression when it's changed because the sag will change. But get the front end off the ground, and I can't see the length of the tube changing from minimum to maximum preload.

FWIW, this is actually what I was referring to in post #11. The tubes would have to stay the same length -- you couldn't change one without changing the other.

 

[Fred W]

See, the sag settings is where things get confusing, caused by the top out springs:

Many people will use a ty-wrap on the inner fork leg as an indicator of fork sag, but because there are top out springs built into the FJR fork, measuring the distance that the fork moves from fully extended when unweighted to fully weighted is not a great way to measure the bike's relative ride height during adjustment.

When you make an adjustment to increase the ride height by cranking down on the pre-load adjuster, the effect is to both increase the unweighted fork length (by compressing the top out springs) and also to increase the bike's resting height when weighted, but the increase in the height will not be the difference in fork extension, only a part of that.

The amount that you actually vary the ride height will be exactly the amount that the adjuster is moved in since when the bike is weighted its weight is fully supported by the main spring.

Trying to come up with an example of how this might work out (took me a while and I actually got it backwards the first time):

Suppose that you crank the adjuster in by 10mm and that causes the top out springs to increase the unweighted fork leg length by 7mm. But the fully weighted bike will actually sit 10mm higher on the adjusters, so the fork is compressed 10mm less at rest when weighted than it was previously. What you would measure with the ty-wrap method would be a 3mm change, but what you really got was a 10mm change in ride height.

Increasing preload can never actually increases spring tension. It can't. The spring is what it is and will compress a given amount for a given amount of load. If some of that spring compression has happened before adding the weight it is simply subtracted from the total and the fork rides higher, but with the same spring rate from there.

So what good is increasing preload? It will increase the ride height at that end of the bike, which affects front to rear weight bias and alters steering geometry. That is all that it does. It will not make the suspension "stiffer".

 

[Uncle Hud]

<yawn>

No rain forecast for this evening. Where are my keys? I'm going to pre-load, post-load, and test out my suspension for about an hour.

 

[Fred W]

You know... if this stuff doesn't interest you, you don't have to read it. There is a deliriously interesting thread on this very forum titled: "What's the weather like where YOU are today". <big yawn>

Just sayin'...

 

[Shane]

I knew a road racer that liked to dink around with his front ride height all the time. I would occasionally pit for him at BIR, which is also where I learned to balance wheels/tires from the Michelin guys.

My friend used to alter his ride height by loosening the fork clamps and just raising or lowering the forks a few mm's in the clamps.

Worked for him. Makes sense to me.

Shane

 

[Fred W]

Makes all kinds of sense.

In a racing environment a subtle change in steering angles can make or break you, and the needs vary by track, surface, conditions, etc. For us road riding jamokes the requirements are far less constrained. We may aspire to be Rickey Racers, but the reality is often (usually?) something else

Like my good friend Hud, who knows that I was just messin' with him anyway, I just dial up some damping and add some rear shock preload on my ES when wifey is on the back, and enjoy the ride.

What's not to like?

FWIW - I didn't get out yesterday nor today even though temps were soaring into the near spring time ranges. Think I better go out and adjust my suspension some more...

 

[Uncle Hud]

^^^^^^ You betcha, FredW. Us southerners adjust our suspensions based on "hard ride" or "soft ride"; or occasionally "babe on the back". Takes care of everything in a lot fewer than 70 postings.

 

[BobCo]

It seems as if this is dying down a little. Here is a little fuel for the fire. It's Race Tech's page that discusses the relationship of the top out spring to the fork spring preload. There's a spreadsheet link on the page that helps with setting up a new fork spring when there is a soft top out spring involved. Interesting stuff.

https://www.racetech.com/page/title/Fk%20Preload%20-%20Relaxed%20and%20Actual

 

[John d]

Preload - What does it do? - by Sonic Springs

 

[Old Guy]

I knew a road racer that liked to dink around with his front ride height all the time. I would occasionally pit for him at BIR, which is also where I learned to balance wheels/tires from the Michelin guys.
My friend used to alter his ride height by loosening the fork clamps and just raising or lowering the forks a few mm's in the clamps.

Worked for him. Makes sense to me.

Shane

Very common. My ZRX forks are raised in the clamps about 10mm.

 

[TripperMike]

Personally I prefer to have my forks as far down as possible in the triple clamp. I kinda dig that "chopper" look.

 

[Redfish Hunter]

At turns boring, silly, and irritating, this thread has nevertheless been educational. I still cannot help but wonder if Mr. Ashe was not just stirring **** on purpose or... At any rate, when Fred W starts having to work to explain himself and MCRide007 starts really talking suspension, I start listening. Several others chimed in with some Good Stuff as well. Thanks for all the information gentlemen.

Meanwhile, on my ES, can I call it pre-load or not?

And Hud? I never seem to have to worry about adjusting suspension for a "babe on the back seat". What am I doing wrong here?

 

[Fred W]

Yeah, it's still preload on the ES (just like on any other bike), but the adjusters for the front forks have gone AWOL on our ES models. The only ride height (preload) adjustment we have is electronic and at the back end only. The only adjustments at the front end are for compression and rebound damping, which do not affect the ride height at all.

The good news (for me anyway) is that I feel no need to change the preload / ride height of the forks on my ES, and generally only change the rear preload setting based on added weight, to get the bike back up to level. Most added weight is right over the back wheel anyway (saddlebags, trunk, passenger).

Now, I am not Hud, but I did stay at a Holiday Inn Express once. I'd have to surmise that what you are doing wrong must be that you are scaring away the attractive ladies with your ugly mug, 'cause as we all know, the FJR is a chick magnet.

~~~~~~~~~~~~~

The page linked to by John d is pretty clear except there is one mistake in the text:

Let's assume that we have a pair of fork springs, each with a rate of 50 lbs/inch. The pair then have a combined rate of 100 lbs/inch. That means that it takes 100 lbs. to compress the fork the first inch, another 100 lbs. for the second inch, (total of 200) and so on. Also assume that the bike and rider together place a 300 lb load on the front end. If the fork is assembled with zero preload then the springs will compress 3 inches and the fork will compress 3 inches total. How much additional force does it take to compress the next inch?? 100lbs. Now say we add an inch of preload. The first 100 lbs of bike weight don't cause the forks to move, the next 200 lbs. make it compress 2 1 inches. The spring though is still compressed 3 2 inches and it still takes 100 lbs of force to compress the next inch.

I think they just had a little brain fart there, because otherwise everything they said makes perfect sense.

~~~~~~~~~~~~~~~~~~~

Now, just to prove that we aren't complete idiots for this stuff not being easier to fathom, here's a quote from the RaceTech web site linked to by BobCo above:

In many cases we recommend replacing the stock "long, soft, top-out springs" with our Reactive Spring Series. They are not as stiff as the old days but are not nearly as soft or as long as the new-fangled ones. Testing has shown the proper top-out spring can drastically affect traction particularly when leaned over in the turns.

I take exception to that last sentence. I do not see any way possible that changing the top-out spring would have any affect on traction. The top out spring is never compressed during actual riding, especially not mid turn. The only time the top-out spring would be compressed at all is when you hit a bump or rise in the road so big that it would have totally unweighted the bike (think "getting air") long enough that the forks would have time to extend fully (against the resistance of the rebound damping) and would have otherwise "topped out". Other than that they just make setting the sag a bit trickier, as noted in the rest of the article.

That sentence makes me think that maybe even they don't fully understand what is happening all the time, so we are in pretty good company.

 

[John d]

~~~~~~~~~~~~~
The page linked to by John d is pretty clear except there is one mistake in the text:

Let's assume that we have a pair of fork springs, each with a rate of 50 lbs/inch. The pair then have a combined rate of 100 lbs/inch. That means that it takes 100 lbs. to compress the fork the first inch, another 100 lbs. for the second inch, (total of 200) and so on. Also assume that the bike and rider together place a 300 lb load on the front end. If the fork is assembled with zero preload then the springs will compress 3 inches and the fork will compress 3 inches total. How much additional force does it take to compress the next inch?? 100lbs. Now say we add an inch of preload. The first 100 lbs of bike weight don't cause the forks to move, the next 200 lbs. make it compress 2 1 inches. The spring though is still compressed 3 2 inches and it still takes 100 lbs of force to compress the next inch.

I think they just had a little brain fart there, because otherwise everything they said makes perfect sense.

~~~~~~~~~~~~~~~~~~~

Fred, your new math doesn't work for me.

 

[MCRIDER007]

~~~~~~~~~~~~~
The page linked to by John d is pretty clear except there is one mistake in the text:

Let's assume that we have a pair of fork springs, each with a rate of 50 lbs/inch. The pair then have a combined rate of 100 lbs/inch. That means that it takes 100 lbs. to compress the fork the first inch, another 100 lbs. for the second inch, (total of 200) and so on. Also assume that the bike and rider together place a 300 lb load on the front end. If the fork is assembled with zero preload then the springs will compress 3 inches and the fork will compress 3 inches total. How much additional force does it take to compress the next inch?? 100lbs. Now say we add an inch of preload. The first 100 lbs of bike weight don't cause the forks to move, the next 200 lbs. make it compress 2 1 inches. The spring though is still compressed 3 2 inches and it still takes 100 lbs of force to compress the next inch.

I think they just had a little brain fart there, because otherwise everything they said makes perfect sense.

~~~~~~~~~~~~~~~~~~~

Fred, your new math doesn't work for me.

Doesn't work for me either.......