Fork oil, need input.(gsx400e)

[John Park]

You're redefining spring rate here. Rate is defined as the force required to deflect the spring a given amount. The key here is that it's the whole spring. You're looking at an arbitrarily defined section of the spring. Within that context you are correct, the deflection per wind is the same. But there are more winds per unit length, and so the total deflection is greater for a given force. That's the definition of "softer".

I agree; but the rate difference only becomes apparent past the point of coil bind. Up to that point you may as well have wound the same length of wire evenly to the spec length. That's what I was trying to say. It's only when coil bind takes a section of the spring out of the equation - no longer the 'whole spring' - that the 'difference' becomes apparent.

We both know how it works; it's just making that function understandable to those who haven't figured it out yet.

This has been a really informative thread. It's also impressive that you actually make the springs. I had assumed that you had them made in some fab shop to your specs. Bravo.

[RichDesmond]

I agree; but the rate difference only becomes apparent past the point of coil bind. Up to that point you may as well have wound the same length of wire evenly to the spec length. That's what I was trying to say. It's only when coil bind takes a section of the spring out of the equation - no longer the 'whole spring' - that the 'difference' becomes apparent...

Hmm, I'm not sure what you're saying. If it's that winding part of the spring with tighter coils, versus winding the same length spring with the wider coils, makes no difference that's not true.
If you wind a spring with "x" coil spacing over the whole length you'll get one rate. If you wind the spring with "x" coil spacing over half it's length, and "1/2x" spacing over the other half it will be softer initially, and then stiffer after the more closely wound section coil binds. The reason being that up until coil bind the total length of wire available to flex is greater, and after coil bind it's less.

[John Park]

Hmm, I'm not sure what you're saying. If it's that winding part of the spring with tighter coils, versus winding the same length spring with the wider coils, makes no difference that's not true.
If you wind a spring with "x" coil spacing over the whole length you'll get one rate. If you wind the spring with "x" coil spacing over half it's length, and "1/2x" spacing over the other half it will be softer initially, and then stiffer after the more closely wound section coil binds. The reason being that up until coil bind the total length of wire available to flex is greater, and after coil bind it's less.

Exactly.

I fully understand the principles; well, the basic physics anyway. I think you missed 'with the same length of wire', which would involve increasing the spacing initially and then going narrower.

I guess that until you come up with a spring for the 'soda straw' forks we'll just have to futz with air or cut and spacer. No rush, just a hint.

[derwood]

Exactly.

I fully understand the principles;

apparently not

[John Park]

apparently not

What is it that you think I don't understand?

I'm saying that - until coil bind sets in - a given length of spring wire, wound to a specific length will have the same rate even if you wind one part wide and another part narrow. I don't think you really got the equal length of wire aspect. Of course if you start winding one part closer you will end up with more length of wire being employed to get to the same overall length of spring, and it's going to be softer - up to coil bind.

The point is that by cutting off a section of the spring it gets stiffer. Cutting the close wound end gets you to coil bind earlier, shortening the spring even more. That's all I was trying to share with those who want to stiffen the front end of a Twin.

I actually do understand the principles. Compared to the physics I work with in my job, this is pretty simple; and yes, part of it involves working with springs.

[RichDesmond]

Exactly.

I fully understand the principles; well, the basic physics anyway. I think you missed 'with the same length of wire', which would involve increasing the spacing initially and then going narrower.

I guess that until you come up with a spring for the 'soda straw' forks we'll just have to futz with air or cut and spacer. No rush, just a hint.

I did miss the "same length of wire part". Given that constraint, the initial rate should be the same, and then stiffer after coil bind of the more closely wound section.
Not an experiment I've done though, something else to put on the list for the winter.