Explain how a spring rate changes static sag

flymoto
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flymoto
So I'm trying to set up my suspension. Got a stiffer spring in at the moment. I have 40mm static sag, but how would a softer spring lower the number? Surely it would be the other way round. I don't understand the mechanicals of this after a lot of thinking I thought I'll come to vital! Is it that the stiffer spring is shorter and requires less pre load? Fried my brain this has.

Cheers
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scooter5002
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scooter5002 3/4/2017 9:12am
3/4/2017 9:12am
Static sag is an indication that you have the correct spring for your weight. When on the bike, you want the recommended ride height, whatever it may be for your bike. When off the bike, the bike should drop 25-35 mil under its own weight. A spring that is too soft will leave you with no static sag, with the proper ride height. Conversely, too stiff on the spring rate will leave you with too much sag.
flymoto
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flymoto 3/4/2017 9:30am
3/4/2017 9:30am
Thanks. I understand the ranges. I have 40mm at moment with 100 race. And i know that I probably need to go softer. But surely if the spring was too soft it would drop more under its own weight? Can some one put it in stupid terms how a softer spring would give me less static rather than more? Am I been stupid?

Thanks
Honda Man 66
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Honda Man 66 3/4/2017 11:05am
3/4/2017 11:05am
You have to crank down on the soft spring so much to get the right sag that when you get off the bike, the spring is compressed so much that it raises the back of the bike up.
Paw Paw 271
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Paw Paw 271 3/4/2017 11:48am
3/4/2017 11:48am
Honda Man 66 wrote:
You have to crank down on the soft spring so much to get the right sag that when you get off the bike, the spring is...
You have to crank down on the soft spring so much to get the right sag that when you get off the bike, the spring is compressed so much that it raises the back of the bike up.
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flymoto
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flymoto 3/4/2017 2:09pm
3/4/2017 2:09pm Edited Date/Time 3/4/2017 2:14pm
Understood. So if I go down a spring rate, IIl have to add more preload to the spring, which will then push the bike up, reducing the amount the bike drops (static sag). Right?

So you don't want too much preload, but don't want it topped out either? My thinking was more preload, equals less travel right? And also eliminating the softer first part of the stroke on small chop etc?
RussB
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RussB 3/6/2017 3:31am
3/6/2017 3:31am
flymoto wrote:
Understood. So if I go down a spring rate, IIl have to add more preload to the spring, which will then push the bike up, reducing...
Understood. So if I go down a spring rate, IIl have to add more preload to the spring, which will then push the bike up, reducing the amount the bike drops (static sag). Right?

So you don't want too much preload, but don't want it topped out either? My thinking was more preload, equals less travel right? And also eliminating the softer first part of the stroke on small chop etc?
Correct.

No, preload has 0 effect on travel. A spring that is too firm will restrict travel however.

From my experience I would highly recommend you try a softer spring, I did and I really liked the results. For £80 it is a very cost effective modification. Worst case you don't like it and sell the spring on ebay for not loads less than what you paid.
Acidreamer
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Acidreamer 3/9/2017 9:29am
3/9/2017 9:29am
You need to understand how springs work. Springs are rated at different stiffness levels. The level you need is entirely based on the weight the springs need to hold up. Springs also tend to work best within certain ranges of tension or preload. You dont want a super compressed spring with tons of preload, but also dont want a loose spring with no tension. All of this comes into play to get your bike set up in the sweet spot range of height for optimal handling.

So like they said, softer springs will require more preload which forces the shock to extend more. The correct spring will put the shock length in the correct range.

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