spring rates

[dlaing]

I'm presently running 38 mm laden sag and 20 mm unladen sag, with a Wilbers 641 custom order shock and 95 N/mm (543 lbs/in) spring. (sag delta = 18 mm).

 

With the previous OE Sachs shock and OE 532 lbs/in (93 N/mm) spring, I was last running a 40 mm laden sag and a 14 mm unladen sag. (sag delta = 26 mm).

 

Q: BUT RATCHET, RATCHET! You only went up a measly 2 N/mm (11 lbs/in) on a shock re-spring rate?!?!?

 

A: Yes, Glasshoppel. . . Please pay attention now, and observe carefully how this allowed me to hit my sag delta target with the spring rate upgrade -- not quite, but very nearly *dead-nuts*:

 

The sag delta dropped by a great whallopping 31%.

 

SNIP

Hope this helps.

 

Yes, this helps! Thanks for the reply...even the amusing tangential rant.

And thanks for the term sag delta. Did you make that up? I like it....seriously!

 

You did NOT go up a measly 2N/mm (11#/in), because your measurement of the Sachs OEM spring is WRONG, as I previously suggested, but now with the evidence that you provided.

While your sag delta numbers cannot precisely determine what the Sachs spring is, we can get pretty close, assuming your sag measurements are consistent and accurate.

We simply take known spring rate of the Wilbers shock, 95N/mm multiply by delta, 18, then divide by delta, 26 which gives us the measurement of the Sachs OEM spring, ~66N/mm (377#/in) (31% difference from the Wilbers)

So you went up 29N/mm (166#/in), not 2N/mm(11#/in).

And no, the 2:1 leverage ratio does NOT change the math.

So, the answer to Gavo's question is that it is theoretically approximately a 65 N/mm spring, but since reality differs a little from theory and measurement, it could be as high as a 75 N/mm spring (~425#/in) or maybe lower than 65N/mm, but I doubt it.

[Guest ratchethack]

Yes, this helps! Thanks for the reply...even the amusing tangential rant.

And thanks for the term sag delta. Did you make that up? I like it....seriously!

Well Dave, I’m sincerely pleased that you apparently understood the concept of ‘sag delta’, and its value. Don’t know if I was the one who came up with it or not. Could be. I started using it while shopping spring rates and setting up the Guzzi. I found it particularly helpful. None of the boys at GuzziTech had heard of it, but that was many years back. . .

. . .your measurement of the Sachs OEM spring is WRONG, as I previously suggested. . .

Hm. That's quite the bold claim for someone whose best unsubstantiated, wild, flyin' guess is, "theoretically approximately. . . it could be as high as a 75 N/mm spring (~425#/in) or maybe lower than 65N/mm, but I doubt it."

 

But I appreciate the challenge, Dave -- (such as it is). . . Let’s explore this a little, shall we?

 

I provided the following direct measurements (and multiple cross-validated backup sources for all the measurement data -- and the rate calculator ) – all easy enough to verify by just about anyone hereabouts, in my previous post:

 

OEM Sachs shock spring

Wire Diameter, .436"

Coil Diameter (center to center), 2.712"

Number of Free Coils, 5

[calc] 532 pounds per inch (93 N/mm).

 

SPRING RATE CALCULATOR SOURCE:

http://guzzitech.com/springrate.html

Other than the rate itself, where, exactly, do you disagree with any of this^, what are your numbers, and what sources are you using?

While your sag delta numbers cannot precisely determine what the Sachs spring is, we can get pretty close, assuming your sag measurements are consistent and accurate.

We simply take known spring rate of the Wilbers shock, 95N/mm multiply by delta, 18, then divide by delta, 26 which gives us the measurement of the Sachs OEM spring, ~66N/mm (377#/in) (31% difference from the Wilbers)

HOLY SCHNIKIES, Dave! If you’re gonna bring in your infamous Purple Planet math again, we’re gonna hafta transport this whole thread hundreds of light-years across space-time to Remulac, and I (for one) prefer riding my Guzzi on the Blue Planet, where we don’t hafta deal with those pesky 7-dimension reverse polarity gravity wells – not to mention the noxious nitrous oxide atmosphere. . . Not sure wot all that might be like, but I'm pretty sure I'm not interested. . . Do Guzzi’s even run on Remulac? If so, do they run forwards or backwards from an Earth perspective? Enquiring minds. . .(well, you know). . .

 

I recognize your math technique here, having seen it many times before. But I'm afraid Math instructors here on the Blue Planet tend to take a mighty dim view of pre-selecting a "theoretically approximately" desired range of results before you start a math problem, and then reverse-doctoring the numbers by haphazardly dividing and multiplying any numbers that happen to be handy with neither rhyme nor reason until you get back to something that looks like it might pass for the results you really, really wanted. . .

 

It's mighty curious that you're willing to trust both my "before" and "after" spring rate upgrade sag measurements (particularly in the case of the "before" numbers, which are nearly 4 years old), since you're hardly in a position to validate them. But somehow, you trust these numbers enough to attempt to use them to calculate a spring rate with them, and you present your "theoretically approximately" range of wild, other-worldy calculated result as valid. . . And yet, having embellished this extension of faith with a great big slice of extra-terrestrial mathematics, you're somehow not willing to trust my direct measurements of the springs themselves, (which, you and just about everyone here ARE in a position to validate!) How to explain the hypocrisy and inconsistency behind that?!?!

 

One thing’s becoming increasingly clear from an Earth perspective -- it’s obvious why it’s taken you over five years (I think?) and coming up on your 3rd try (and counting) to get your shock spring rate right. . . (I got mine right the first time.)

So, the answer to Gavo's question is that it is theoretically approximately a 65 N/mm spring, but since reality differs a little from theory and measurement, it could be as high as a 75 N/mm spring (~425#/in) or maybe lower than 65N/mm, but I doubt it.

Um, this is just me, but I’d be mighty surprised if Gavo would swallow this one^, Dave. Ditto anyone else on this planet. . .

 

Just gotta ask: On Remulac, is it customary to smile when you use the word, “reality” followed by the word, "differs"?

 

Lookin' forward to your Sachs spring dimensions and rate calc.

 

Oh -- Do provide them in Earth units of measure -- ¿Por favor?

[GuzziMoto]

Well, well, Quazimodo.

Blah, blah, blah......

 

Err. . . Is this^ from some other thread?? Some other Forum?? Romper-Room??

 

Without taking anything I posted out of context above, (or anywhere else, ever), please show me where I as much as hinted that preload has anything wotsoever to do with spring rate.

 

Please explain why you found yourself compelled to babble aimlessly about progressive springs here, since it has absolutely NOTHING to do with anything that anyone in this thread is talking about, least of all myself in the post you appear to be responding to.

 

These two can be answered together.

No, you did not directly post that preload effects spring rate. But one of the two links you posted did say that. Now, I don't hold you responsible directly for what someone else says but if you post a link to info as sources to support your claims then what info the link contains is part of the discussion. And the second link you posted said

"Preload: the amount the spring is compressed when it's not supporting any weight. Some preload is necessary just to keep the spring in place when the suspension is fully extended. More preload is used to increase ride height and increase the apparent spring rate. More on this later."

and

"Preload adjustment is good for small changes in spring stiffness, but no substitute for selection of the right spring rate."

These statements in part suggest that spring preload effects spring rate and that is not true.

And I mentioned progressive springs only because I know you and others use them and it is worth pointing out that they are different when it comes to preload not effecting spring rate. With progressive springs the amount of preload effects the spring rate. Period. If that is "babble(ing) aimlessly" then too bad.

And as for preload not being relevant to a discussion on spring rate and ride height/sag settings.... huh?. Only you could say that with a straight face. Spring rate, bike/rider weight, and preload are the only factors that effect ride height and sag. Seems relevant to me...

 

This^ must be some kind of desperately bad attempt at a joke, but I can’t imagine who might find it amusing. Please read my post for the first time and get your facts straight.

 

This^ must be some kind of desperately bad attempt at a joke (Part II), but I can’t imagine who might find it amusing (Part II, B ). Please read my post for the first time and get your facts straight (Part II, C).

 

These two can also be answered together.

If you don't understand that a 1:2 ratio of shock travel to wheel travel means that with a 500 lb spring (which means that 500 lbs of force will compress the spring 1") 250 lbs of weight (force) will compress the shock 1/2" and the wheel/suspension will compress 1" is opposite to what you assert, then it is not on me to teach you as you clearly will not listen to me. But others may read your comments and take them as fact so it is them that I am trying to help. The leverage ratio between the shock and the rear wheel travel at 1:2 is dividing the effect of the spring in half so that to get "X" change at the wheel you have to apply double "X" change at the shock. At the front because there are two springs the opposite is true. The effect of a change in spring rate is doubled (a 2:1 ratio) by the fact that there are two springs holding the front end up.

Neither one of these statements is opinion. They are what they are. The only way you can change the outcome of these effects is to change the inputs into the equation. The ratio at the rear is likely not a straight 1:2 ratio and is likely on a curve while the ratio at the front will only change if you change the number of springs being used. But I made it clear that it was you that established the "1:2 ratio", not I.

 

Without taking anything I posted out of context above, (or anywhere else, ever, -- I’ve lost count of which Part), please show me where I even as much as hinted that, “the difference between the two is the only number you need to know”.

 

I'm sorry, you did not say it was the only number you need to know.

You did say..

"For those still interested and capable, but possibly not accustomed to the term, ‘sag delta’ (laden sag minus unladen sag), it’s the ONLY single measurement number that directly relates spring rate to load. When tuning suspension, it’s a very handy number to use for comparison purposes when setting up and balancing the chassis, since it cuts all the usual unnecessarily confusing, irrelevant, and useless foolishness and folderol of preload considerations OUT of the picture. "

Thanks for pointing out my mistake (although when you said "it’s the ONLY (emphasize yours) single measurement number that directly relates spring rate to load" I thought you meant the ONLY when you apparently meant something else). My bad.

This time around, Quazimodo...

Blah, blah, blah....

 

There’s always hope, you know.

I am not so sure there is "always hope".

For example, I used to "hope"that you would stop with all the name calling and insults and actually limit the discussion to facts, but I can't see that ever happening. What would you have to say?

 

Edit.. Sorry that was mean. I apologize. Hatchet Wacker does provide good info in many cases. He just doesn't seem to know the difference between what he knows and what he thinks he knows.

[GuzziMoto]

Yes, this helps! Thanks for the reply...even the amusing tangential rant.

And thanks for the term sag delta. Did you make that up? I like it....seriously!

 

You did NOT go up a measly 2N/mm (11#/in), because your measurement of the Sachs OEM spring is WRONG, as I previously suggested, but now with the evidence that you provided.

While your sag delta numbers cannot precisely determine what the Sachs spring is, we can get pretty close, assuming your sag measurements are consistent and accurate.

We simply take known spring rate of the Wilbers shock, 95N/mm multiply by delta, 18, then divide by delta, 26 which gives us the measurement of the Sachs OEM spring, ~66N/mm (377#/in) (31% difference from the Wilbers)

So you went up 29N/mm (166#/in), not 2N/mm(11#/in).

And no, the 2:1 leverage ratio does NOT change the math.

So, the answer to Gavo's question is that it is theoretically approximately a 65 N/mm spring, but since reality differs a little from theory and measurement, it could be as high as a 75 N/mm spring (~425#/in) or maybe lower than 65N/mm, but I doubt it.

dlaing, you are correct in that you can figure out the OEM spring rate (at least pretty dang close) if you have accurate numbers on the sag with the old spring and accurate numbers with the new spring as well as an accurate rate for the new spring. But I believe you are incorrect that the ratio of rear shock travel to rear wheel travel does not enter into it. It does, but opposite the way Hatchet Wacker says it does. The 1:2 ratio means that a 50 lb increase in spring rate at the shock would have a 25 lb net effect at the rear wheel since the rear wheel only moves half as far relative to the rest of the bike for a given amount of shock movement. This means that while an increase of 50 lbs in spring rate at the shock would only result in an extra 25 lbs being required to compress the rear suspension 1". This fact coupled with the measurements Hatchet Wacker provides leads me to think that his numbers don't add up. And rather then try to figure out what the actual rate change is it would be easier to measure a stock spring myself. Just a matter of time to get to it.

 

Edit... After thinking about it I think you are correct that the ratio doesn't enter into it as all measurements are taken at the rear wheel and are comparable as a percent. The ratio is only going to determine the wheel travel for a given shock travel and thus only effects results at the wheel relative to changes at the shock as hard numbers not percents. The percents will be the same. Sorry dlaing. I think you're right.

[Guest ratchethack]

I am not so sure there is "always hope".

Um, Quazimodo. There are of course, exceptions. . .

 

HINT: You aren’t providing any value to this discussion, you’re not amusing, and you clearly don't have much beyond the slightest clue about the topic at hand. The evidence that you aren’t sincerely interested may be easily seen in the astonishing trail of everything that you’ve got backwards here – and that you continue to get backwards -- at least partly because you very evidently aren’t paying much attention.

 

You seem to be desperately seeking attention and ego gratification here. May I suggest that since you have yet to bring anything of value here, this is not the place for you. Why not find a parking lot somewhere, where you can practice some true exhibitionism by engaging in your previously mentioned parking-lot parading and posing behavior with your Guzzi? That way, you get to engage in your favorite “crabs-in-a-bucket” posturing one-upsmanship contests to your heart’s content with equally developmentally-challenged fools, talk trash, count Koo, etc. . . and you don’t have to pretend anything on the Forum – I’m sure you look the part. . .

 

Good luck, and do try to have some fun.

[GuzziMoto]

Um, Quazimodo. There are of course, exceptions. . .

 

HINT: You aren’t providing any value to this discussion, you’re not amusing, and you clearly don't have much beyond the slightest clue about the topic at hand. The evidence that you aren’t sincerely interested may be easily seen by the astonishing trail of everything that you’ve got backwards here – and that you continue to get backwards -- at least partly, no doubt, because you aren’t paying much attention. <_>

 

You seem to be desperately seeking attention and ego gratification here. May I suggest that since you have yet to bring anything of value here, this is not the place for you. Why not find a parking lot somewhere, where you can practice some real exhibitionism by engaging in your previously mentioned parking-lot parading and posing behavior with your Guzzi? That way, you get to engage in “crab-in-a-bucket” posturing one-upsmanship contests to your heart’s content with equally developmentally-challenged fools, talk trash, count Koo, etc. . . and you don’t have to pretend anything on the Forum – I’m sure you look the part. . .

 

Good luck, and do try to have some fun.

 

No ego involved here, at least on my part.

I just don't want to see somebody read something here and assume that because no one pointed out how wrong it is that it must be right and then base decisions they make on bad info.

I see your response to having it pointed out that you are wrong hasn't changed.

The quality of your insults has little to do with whether you are right or wrong.

But I imagine it makes you feel better.

You speak of providing "value" to this discussion, but what sort of "value" are you adding, when you post info that ranges from slightly wrong to completely wrong.

As I said, not everything you post is wrong but sometimes you get out on the thin ice of your own knowledge and don't seem to know it.

If you have some sort of argument to support your claims then by all means bring them out for all to see.

As for your insults to me I don't care. Your words are feeble and weak, old man. They mean nothing.

Post up something to show how superior your knowledge of motorcycle suspension to mine and put me in my place. Otherwise, it's just noise.

[Dan M]

No ego involved here, at least on my part.

I just don't want to see somebody read something here and assume that because no one pointed out how wrong it is that it must be right and then base decisions they make on bad info.

You speak of providing "value" to this discussion, but what sort of "value" are you adding, when you post info that ranges from slightly wrong to completely wrong.

As I said, not everything you post is wrong but sometimes you get out on the thin ice of your own knowledge and don't seem to know it.

If you have some sort of argument to support your claims then by all means bring them out for all to see.

As for your insults to me I don't care. Your words are feeble and weak, old man. They mean nothing.

Post up something to show how superior your knowledge of motorcycle suspension to mine and put me in my place. Otherwise, it's just noise.

 

From my perspective on the sidelines just reading the content of this thread, the name calling started with you. Perhaps you think people are calling you names when you read Quasimodo but the truth is, spell-check does that to your screen name. (I know, spelling and grammar are not on your list of priorities, I'm just pointing out a fact here)

 

Back to the original topic. I'm just curious. You have piped up here to tell others they are full of it but I have not read what your personal set up is. So can you tell us what you have on your V11? Spring rates? Shock brand? Damping settings? Sag measurements? Your weight with gear?

How about some useful information instead of just noise?

[gavo]

I didn't think such a simple question would cause such a drama I only asked because I'm going to try a new spring on the sachs shock as I was browsing this site http://teknikracing.rtrk.com.au/?scid=28689&kw=4315973. But it appears I'll have to measure my spring myself to get an accurate answer or strip it and take it to the experts( the real ones not the virtual ones)

[raz]

You guys confuse me. If we're talking travel (and assuming 2:1), the shock will compress 2 cm from a 1 cm wheel movement. And 20 mm more preload gives 10 mm higher rear. Right?

 

To compress a 400# spring 1 inch, we apply 400 lbs at the spring. That is the same as 200 lbs at the wheel (or rather the seat). But as the swing arm only move 0.5 inch when we do this, the "effective spring rate" is still 400#. Is that right?

[Guest ratchethack]

You guys confuse me. If we're talking travel (and assuming 2:1), the shock will compress 2 cm from a 1 cm wheel movement. And 20 mm more preload gives 10 mm higher rear. Right?

No. The shock will compress 1 cm for every 2 cm of wheel (spindle, axle) travel. Adding 1 cm preload on the shock spring collar will raise the rear 2 cm.

 

Best be careful and deliberate with this stuff, or you'll quickly find yourself off in the tall grass, Raz.

 

To compress a 400# spring 1 inch, we apply 400 lbs at the spring. That is the same as 200 lbs at the wheel. . .

Correct^.

 

. . . the "effective spring rate" is still 400#. Is that right?

Here's where the semantics can get tricky. Careful. . . the "effective spring rate" at the wheel spindle is half what it is at the shock, and the effective spring rate at both (with a straight rate spring) is always constant, regardless of preload.

 

Make sense?

[Dan M]

No. The shock will compress 1 cm for every 2 cm of wheel (spindle, axle) travel. Adding 1 cm preload on the shock spring collar will raise the rear 2 cm.

 

This is interesting and maybe I'm over thinking this.

I understand the ratio and if you lengthen the shock by 1cm you would realize 2cm at the wheel but wouldn't adding 1cm preload only change the wheel by 1cm assuming it is carrying the same load and working against a 2:1 ratio?

[Guest ratchethack]

This is interesting and maybe I'm over thinking this.

I understand the ratio and if you lengthen the shock by 1cm you would realize 2cm at the wheel but wouldn't adding 1cm preload only change the wheel by 1cm assuming it is carrying the same load and working against a 2:1 ratio?

Nope.

 

Again, the semantics can get tricky, and though this stuff is pretty simple, it IS pretty easy to get confused. . . if you over-think, you can easily get turned around. . .

 

Think of it this way. If we assume (as I b'lieve you have above) that the load represented by the combo of bike and rider is a constant, and the rate of the spring is a constant, when you crank in preload, this simply moves the effective spring pressure up the linear rate curve (actually a straight line with straight rate springs, and no bell-crank linkage multiplier, as with the Guzzi).

 

It's 1:2 shock preload to wheel travel, same as it's a 1:2 eye-to-eye increase to wheel travel. But when you crank in preload (regardless of eye-to-eye shock length), both laden and unladen sags decrease by the same number, and the sag delta remains the same.

 

Make sense?

[Dan M]

Nope.

 

Again, the semantics can get tricky, and though this stuff is pretty simple, it IS pretty easy to get confused. . . if you over-think, you can easily get turned around. . .

 

Think of it this way. If we assume (as you have above) that the load represented by the combo of bike and rider is a constant, and the rate of the spring is a constant, when you crank in preload, this simply moves the effective spring pressure up the linear rate curve (actually a straight line with straight rate springs, and no bell-crank linkage multiplier, as with the Guzzi). When you do this, both laden and unladen sags decrease by the same number, but the sag delta remains the same.

 

Make sense?

 

 

Sorry, I'm still foggy here. Let's say the ratio was 1:1 and you compressed the spring by 1cm and all else was equal. I'd expect the wheel movement to be 1cm. But, if the spring is working against a 2:1 ratio wouldn't the wheel movement be half?

[Guest ratchethack]

Sorry, I'm still foggy here. Let's say the ratio was 1:1 and you compressed the spring by 1cm and all else was equal. I'd expect the wheel movement to be 1cm. But, if the spring is working against a 2:1 ratio wouldn't the wheel movement be half?

Nope.

 

I understand how you're thinking about this, Dan.

 

Try this:

 

The spring is working against a 2:1 ratio before, throughout, and after a preload change. The increase in load carrying capacity (weight supported) achieved by adding preload is constant -- that is, you add the SAME load carrying capacity for every increment of added preload.

 

Since load, rate, and swingarm ratio are all constants, regardless of what they are, both shock movement to wheel movement and preload change to wheel movement are also constant -- that is, 1:2.

 

Does that help?

 

EDIT: Egads, I've just had to edit this to make it right. You're makin' me work waaaaaay too hard, and I'm supposed to be on vacation! Important festivities will soon be underway, and I gotta go.

 

EDIT: Egads (Part II) I've had to change another term above to make it right!

[GuzziMoto]

From my perspective on the sidelines just reading the content of this thread, the name calling started with you. Perhaps you think people are calling you names when you read Quasimodo but the truth is, spell-check does that to your screen name. (I know, spelling and grammar are not on your list of priorities, I'm just pointing out a fact here)

 

My first post in this series used the name "Hatchet Wacker" (which I did not make up, but after he began calling me Quasimodo I began to return the favor and use various derivations of his name for him), and commented that his post was "almost coherent and correct" I then followed by pointing out the inaccuracies in his post (which was more then the accuracies), conceding that at least one part could be considered a matter of opinion/point of view, and finished by agreeing with him that there was plenty of info on the subject out there in internet land but pointed out that you can't believe everything you read on the internet. Some of it is wrong. I used this very thread as proof of that with out naming Hatchet Wacker specifically. In total, I would say less then 5% of my post was even referencing Hatchet Wacker directly and while not sugar coated or wrapped in pretty bows in really don't see any serious insults in it.

His response on the other hand was almost completely full of insults and devoid of any facts or positive info.

So if you see me in that exchange as the bad guy, I fine with that.

As for my name, my spell checker doesn't do that. But if it did I am smart enough to know how to stop it.

 

Back to the original topic. I'm just curious. You have piped up here to tell others they are full of it but I have not read what your personal set up is. So can you tell us what you have on your V11? Spring rates? Shock brand? Damping settings? Sag measurements? Your weight with gear?

How about some useful information instead of just noise?

I don't see how telling others how I set up my wifes V11 is helpful to others. Telling them how to set their bike up correctly could be useful, but that is not my job. As mentioned there is plenty of info already posted on that very subject there for the reading. My concern and the reason for correcting the errors in Wackers post is that many here and others browsing through may not know that what he said was not 100% fact and if no one questions it they may believe it to be so. I do not worry about every little inaccuracy, but when there is more wrong then right I feel compelled to speak up. If that is not a good thing to you or anyone else here then I encourage you to skip my posts.

But if you feel how my wifes V11 is setup will help you, well I am not crazy enough to post info on the internet about my wifes weight but I will give some info about the components. It has a Penske shock built and valved for her weight and style. After putting it on all I had to do is take a couple clicks out of the compression. Where it ended up matters little as the valving is specific to her shock. The spring rate would relate to her weight so you will have to guess. The preload and sag is pretty much standard fair. I didn't have to adjust it after Penske built it. They do good work.

The fork I have the stock springs in and sag is okay (woops, I may have said too much), but I did modify the valving so that the fork actually had compression dampening. As delivered there was only rebound dampening and a slightly adjustable hydraulic bump stop. That required blocking off oil passages in the cartridge to force oil to go through the piston instead of around it. I have mentioned this before but either no one else has forks like this or no one else has thought it is a problem.

The fork mods made a world of improvement turning the harsh feeling front end into a much smoother but sharper feeling ride as they no longer bottomed over every decent size bump and reacted much quicker to front end inputs. No sign of the Twitchy Red Frame Demon either (no steering damper either, that was also a huge improvement but as it was bad it is not a fair comparison).