Wilbers progressive fork springs installed, but...

[LucasD]

... the instructions were in German. The pictures were clear though, so
I really couldn't screw things up that bad. :)

While I notice an improvement, it's not quite what I was
expecting, having read so many posts about what an
amazing difference the springs made for other people.

Anyway... the service manual states that the springs
should be installed with the tighter pitch at the bottom of
the fork, while Wilbers' instructions include a picture and an
"achtung" stating that the springs should be installed with the
tighter pitch at the top of the fork.

I installed them per the service manual, but I'm wondering
if it really makes a difference.

[Jonnylotto]

Always go with the manufacturer. There's a reason they want the tighter pitch up top. (Don't ask me, I use Sonic Springs straight rate).

[LucasD]

I went with the service manual because the stock springs
were progressive and Suzuki installed them with the tighter
pitch at the bottom.

Maybe some physics major can explain why they'd work
better installed one way versus the other. :?

[MATTMAN]

Just put one one way and one the other. :lol: ...... :shock:

Anyway it shouldn't be too hard to swap them around.

[Basses5]

Always go with the manufacturer. There's a reason they want the tighter pitch up top. (Don't ask me, I use Sonic Springs straight rate). Tighter pitch should be at top so spring can get "progressively" stronger the more it's compressed. :roll:

[greywolf]

Coil bind would happen on the bottom too.

[Basses5]

Coil bind would happen on the bottom too.Yes I agree but the tighter coil displaces more oil resulting in a higher oil level and if the new ones have a more massive tighter coil resultant oil level would be higher.

[greywolf]

Now that makes sense.

[LucasD]

I sent the question to Wilbers and got this reponse from Klaus Huenecke:

"No, it does not matter technically, the spring will work correctly either
way. The reason we say to install it with the tighter wound ends up is, that we want to reduce the unsprung weight on the wheel by as much as possible."

I guess I'll take them out and flip them over.

[greywolf]

Since the trapped air can add a little to the resistance to compression, bound coils down could be a little stiffer since they displace more oil and the air volume is therefore smaller. The unsprung weight thing was in my mental hard drive but apparently in a bad sector. :wink:

[Jonnylotto]

I sent the question to Wilbers and got this reponse from Klaus Huenecke:

"No, it does not matter technically, the spring will work correctly either
way. The reason we say to install it with the tighter wound ends up is, that we want to reduce the unsprung weight on the wheel by as much as possible."

I guess I'll take them out and flip them over.

Now that doesn't make sense...the entire spring is "unsprung weight"

[greywolf]

Nope. It's continuously variable. The top of the spring goes with the fork tubes/sprung wieght. The bottom goes with the fork legs and internals/unsprung weight. More coils on the bottom increases unsprung weight. When the fork gets compressed 5", the inertia of the lower end has to be overcome enough to move 5" in relation to the sprung mass of the bike while the top doesn't move at all.

[bill l]

Nope. It's continuously variable. The top of the spring goes with the fork tubes/sprung wieght. The bottom goes with the fork legs and internals/unsprung weight. More coils on the bottom increases unsprung weight. When the fork gets compressed 5", the inertia of the lower end has to be overcome enough to move 5" in relation to the sprung mass of the bike while the top doesn't move at all.

Hi Greywolf,

I'm not picking on you, I'd like your input on this. I understand the logic of what you said here. And it makes sense for a straight rate spring over large, slow-compression bumps. But I just installed some progressive springs and had to ponder the up/down spring thing. Your explanation most accurately (I beleive) describes the currently accepted logic. So it seems a good place to post an alternate point of view. I opted to install the tightly wound end to the bottom of the fork. Here's why: The tighter end is weaker and will respond significantly over small, rapid road irregularities - when unsprung weight is most critical. With the tight coils at the top of the fork the remainder of the spring will have to travel up the fork tube to compress those weaker coils at the top - and become unsprung weight moving upward with the axle. With the softer (tighter) coils at the bottom, the axle can react while the remaining spring above remains relatively inert. Could this be what Suzuki has in mind or do you know if it's more complex than that? Thanks,

Bill

[RichDesmond]

I sent the question to Wilbers and got this reponse from Klaus Huenecke:

"No, it does not matter technically, the spring will work correctly either
way. The reason we say to install it with the tighter wound ends up is, that we want to reduce the unsprung weight on the wheel by as much as possible."

I guess I'll take them out and flip them over.I wouldn't bother. While Klaus is absolutely correct, the difference orientation makes in unsprung weight is tiny compared to the rest of system.
Flip them the next time you change fork oil. :)

[greywolf]

I think in either case the difference will be so small as to be unnoticeable.

[RichDesmond]

Hi Greywolf,

I'm not picking on you, I'd like your input on this. I understand the logic of what you said here. And it makes sense for a straight rate spring over large, slow-compression bumps. But I just installed some progressive springs and had to ponder the up/down spring thing. Your explanation most accurately (I beleive) describes the currently accepted logic. So it seems a good place to post an alternate point of view. I opted to install the tightly wound end to the bottom of the fork. Here's why: The tighter end is weaker and will respond significantly over small, rapid road irregularities - when unsprung weight is most critical. With the tight coils at the top of the fork the remainder of the spring will have to travel up the fork tube to compress those weaker coils at the top - and become unsprung weight moving upward with the axle. With the softer (tighter) coils at the bottom, the axle can react while the remaining spring above remains relatively inert. Could this be what Suzuki has in mind or do you know if it's more complex than that? Thanks,

BillBill,

If you don't mind my jumping in:

You're overthinking this. The force is felt in the whole spring at once. It doesn't, in any practical sense at least, start at one end and travel to the other. In other words, the spring doesn't know, or care, which end it's being compressed from.

[Compared To What?]

Bill,

If you don't mind my jumping in:

You're overthinking this. The force is felt in the whole spring at once. It doesn't, in any practical sense at least, start at one end and travel to the other. In other words, the spring doesn't know, or care, which end it's being compressed from.

Exactley. . . . . . .

[bill l]

Bill,

If you don't mind my jumping in:

You're overthinking this. The force is felt in the whole spring at once. It doesn't, in any practical sense at least, start at one end and travel to the other. In other words, the spring doesn't know, or care, which end it's being compressed from.

My point was that over small bumps the soft 20% of the spring is compressing more (per inch of coils) than the other 80% of the spring, not that the compression was traveling from one end to the other. It makes sense to me to have the soft end at the bottom in order to cushion the spring above it and effectively increase the sprung weight of the spring itself, at least over small bumps where it matters. If 80% of the spring has increased upward travel (in order to compress the weaker top coils) there is definitely some added unsprung weight - probably much more than having an extra two or three coils on the bottom.
Ok, the bottom line is that there isn't much difference so this is really more of a mental exercise. I think the logic has been underthunk (new word?) and that only heavy end/light end has been taken into consideration. I'm throwing in lighter/stiffer spring action and the logic appears to oppose the benefit of an extra two or three coils of sprung weight on top.

[Tollster]

The unsprung weight thing was in my mental hard drive but apparently in a bad sector. :wink:


Regularly schedule maintence is in order....please "Defrag" immediately to prevent further loss of sector!

[RichDesmond]

My point was that over small bumps the soft 20% of the spring is compressing more (per inch of coils) than the other 80% of the spring, not that the compression was traveling from one end to the other..This is true. Doesn't matter which way the spring is oriented, that's what happens. It makes sense to me to have the soft end at the bottom in order to cushion the spring above it and effectively increase the sprung weight of the spring itself, at least over small bumps where it matters. If 80% of the spring has increased upward travel (in order to compress the weaker top coils) there is definitely some added unsprung weight - probably much more than having an extra two or three coils on the bottom.The soft end isn't cushioning the stiff end, the whole spring is compressing. The difference in unsprung weight is so tiny compared to the rest of the system (wheel, disks, calipers, tire, sliders...) as to be completely unimportant.
Ok, the bottom line is that there isn't much difference so this is really more of a mental exercise. I think the logic has been underthunk (new word?) and that only heavy end/light end has been taken into consideration. I'm throwing in lighter/stiffer spring action and the logic appears to oppose the benefit of an extra two or three coils of sprung weight on top.Nope, the lighter/stiffer action has no effect at all. There is the unsprung weight difference that's real, but far to small to matter.

[bill l]

The soft end isn't cushioning the stiff end, the whole spring is compressing.

Yes, the whole spring is compressing and the spring itself doesn't care. It only knows it has to occupy a smaller space. How much mass *travels upward with the axle* does matter. To exaggerate, think of a progressive spring with an 80/500 lb rate. Put the 80 lb rate coils down and, relative to the axle, the 500 lb rate coils will be sprung weight (they'll essentially act as a spacer) and will be suspended (cushioned) by the 80 lb section. Now flip the spring. In order for the 80 lb coils on top to be compressed, the 500 lb coils will have to *travel upward with the axle* to compress them. No difference to the spring itself, but a big difference in how much of the spring is unsprung weight. You're right though, practically speaking it is a non issue.

[FlyingFinn]

As soon as you guys are done discussing which way to install progressively wound springs, we could move to talking about which takes more energy to compress, air or water.

--
Mikko

[RichDesmond]

As soon as you guys are done discussing which way to install progressively wound springs, we could move to talking about which takes more energy to compress, air or water.

--
MikkoI was thinking something theological might be appropriate, like; How many angels can dance on the head of a pin?? :p

[FlyingFinn]

We'll cover that next. But only after the water vs. air issue has been fully analyzed. :rolleyes:

--
Mikko

[bill l]

We'll cover that next. But only after the water vs. air issue has been fully analyzed. :rolleyes:

--
Mikko

Well, If you guys could weigh your bladder and then your head, turn yourselves upside down and see which expands more. . .

[FlyingFinn]

Very damn funny! But I'm going to let that one go and forgive you only because of your famously good avatar ;-)

In case someone doesn't know what is the story behind this "water vs. air" thing, just take a look here and read few posts into the thread:
http://www.advrider.com/forums/showthread.php?t=213875

--
Mikko

[V-Tom]

Out of curiousity, roughly how much do springs weigh? Roughly how much does the unsprung part of the front fork/brake/wheel and tire assembly weigh?

..Tom

Yes, the whole spring is compressing and the spring itself doesn't care. It only knows it has to occupy a smaller space. How much mass *travels upward with the axle* does matter. To exaggerate, think of a progressive spring with an 80/500 lb rate. Put the 80 lb rate coils down and, relative to the axle, the 500 lb rate coils will be sprung weight (they'll essentially act as a spacer) and will be suspended (cushioned) by the 80 lb section. Now flip the spring. In order for the 80 lb coils on top to be compressed, the 500 lb coils will have to *travel upward with the axle* to compress them. No difference to the spring itself, but a big difference in how much of the spring is unsprung weight. You're right though, practically speaking it is a non issue.

[RichDesmond]

Out of curiousity, roughly how much do springs weigh? Roughly how much does the unsprung part of the front fork/brake/wheel and tire assembly weigh?

..TomA pair weighs ~3lbs. The difference in unsprung weight between the soft end and the stiff end would only be a few ounces though. At a very rough guess the rest of the unsprung weight should be 30-40 lbs.

[garry]

I think the more interesting question is the progressive rate vs straight rate one. The OP didn't sound too impressed by the spring change.

I just installed some straight rate Sonic Springs and the difference is great IMO. And I'm a light guy (180 in gear). I hammered on every bumpy road I could find last night (some dirt, some paved) and the harshness in the front is gone. Good stuff. Works well with the Wilbers spring on the stock shock upgrade I did a few months ago.

[hbonser]

Water won't compress... What's was this thread about now? I forgot...

Oh, yeah... springs in the fork.

What's the consensus on which is better for a heavy rider (250#)? Stiff straight rate springs or progressive springs?

Thanks.