modify old springs rather than replace?

[Guest Gfacter]

Well that's what they did for me. I am happy with the way they feel, but still a little unsure about the mechanics. I always thought the spring rate was determined by the size of the wire?

For me the bike is stiffer and I have plenty of adjustment room for sag settings.

[SAFE-T]

RMR Suspension told me the same thing - basically that the materials and manufacturing of many OEM components are superior to aftermarket, and can be modified to perform similarly to - and sometimes better than - what is available from the performance aftermarket.

Also, springs don't wear out but fork fluid does.

[fallzboater]

Well that's what they did for me.  I am happy with the way they feel, but still a little unsure about the mechanics. I always thought the spring rate was determined by the size of the wire?

For me the bike is stiffer and I have plenty of adjustment room for sag settings.

<{POST_SNAPBACK}>

The wire size, coil diameter, and number of free coils are used to calculate the spring rate. A coil spring actually works like a torsion bar, each unit length of the wire will twist a certain amount with a given torque. So, a longer bar will twist more for a given torque, and a coil spring will be softer with more free coils (longer wire).

There's no reason a coil spring can't be made stiffer by shortening it, but it's often not done properly with respect to overall suspension design.

[lizard]

Yeah, what fallzboater said!

Another way to think about is compare it to an air filled tire vs. solid tire. A solid tire is intuitively going to give you a harsher ride due the the lack of "give" or high spring rate. In the air filled tire, the air is the "spring" in that it "gives" with the amount of "give" being adjustable by varying the pressure. If you remove part of the spring and replace it with a solid object you have increased the effective spring rate just like adding more air pressure in a tire increases the spring rate.

Just another way to try and get your head around the idea. :rolleyes:

[Guest]

to more specifically adress some of your questions:

they would definately have to put some sort of spacer in to take up the length they chop out. this configuration will definately tighten up the suspension - and could be done in such a way that the result would be very close to what you'd get with their replacement springs.

the factory springs may or may not be coiled with a process that makes them less susceptible to stress concentrations or other plagues of asymmetry - i don't know about that. it's a reasonable claim.

what's going to happen to the springs with age is they'll become shorter from being deformed and not springing back all the way. so the spring pitch will change slightly... to really capitalize on the extra stiffness you'd have to shim them to fit your fork length (ie. you'd have to adjust for the change in length like this company is doing when they snip them).

shimming them will decrease your travel. so will putting in new springs that are stiffer.

there does come a point where you'll reach coil bind (where the springs compress to the point they're sitting on each other... that would be bad - but i don't really know at what length/coil pitch stock or modified springs would get to the point of being in danger of that happening. i'm inclined to think it'd be at some point beyond the life of the rest of your average bike.

[HispanicSlammer]

shimming them will decrease your travel. so will putting in new springs that are stiffer.

Not necessarily so there is a lot of excess length in the spring, in terms of binding.

The vfr spring has a total length of 375mm or darned close to 15 inches, the fork itself has a total travel of 120mm (where it will bottom or top out due to the cartridge or the bushings whacking each other),which leaves you with difference of 255mm of extra length in the spring that is not being used. If you allow for binding of the spring coils to the point where the coils actually make physical contact with each other (coil diameter 5mm x #of coils 26) = 130mm of binding length, giving you a true free length of non binding travel 245mm - 120 = 125mm of excess spring travel!

You can shim the fork spring 125 mm to where it will bottom out the fork tubes - before the spring binds on itself!

I will write a how to on how to cut springs to a desired length and spring rate, & how to measure it with an ordinary bathroom scale! attach this topic to it! The only way you can get less travel over a bump is by increasing the damping or increasing the spring rate. Shimming cannot increase the spring rate, the spring rate is constant! All that does is lift the bike up, the ground is the ground, the spring is constant pushing down on the spring with a shim will just lift up the bike, you weigh the same so does the bike so the spring pushes back lifting the bike up! So says Newton!