Fox and other online spring calculators doesn't take into account for the leverage curve. Yeti and PUSH do.

 

But I was told that the curve doesn't matter..that it's the average ratio that ultimately determines the correct rate...also in my specific case the leverage rate is progressive but linear with no funny irregularities so I would have thought it would work pretty well with the FOX calculator... and then again for bikes as progressive as mine it is saying subtract another 100lbs off the figure it gives that is already 100lbs lower than PUSH. So basically FOX advises 250lbs and PUSH 450lbs....like wtf?? Might aswell play pot luck.

 

FOX and TFTune always quoted 50# less for me. Went through 3 bikes with coil shocks, all were quoted 50# less than what I should have bought to achieve ~30% sag

 

i didn't know push had their own spring calc. i've used the yeti and it seems decently accurate. i've been on a 500# spring. tftuned and fox are always 50# lower than what i expected.

got a link to the push spring calc?

 

Not a PUSH calc just the spring that came with my PUSH 11.6 or at least the spring that should have came until persuaded Darren I would prefer 25lbs less... I would get a Sprindex to find my ideal rate but supposedly the accuracy and spring tolerances are miles off so it won't actually tell me what rate I prefer.

 

I found PUSH's suggested spring rate to be pretty accurate for my 11.6 built Yeti. I would assume Yeti's suggested spring rate would also be fairly accurate. PUSH knows what works since they build and test the 11.6 to work with a specific frames leverage curve. Yeti knows what works since they engineered the frame and tested what works best with their leverage curve. At that point, the main variable is the rider and how they are positioned on the bike.

 

Using the average leverage ratio gets you close, but there is going to be some variation. Using average leverage ratio works for getting you the spring rate that gets you to bottom out at a certain vertical acceleration without considering damping. Depending on the progression, that may leave you too soft or too stiff around sag or the mid stroke. Then there's damping characteristics. IFP pressure and design can affect the total shocks spring rate. HSC should also be considered, if you have a setup that feels stiff in the mid stroke but uses all the travel, you could back off spring rate a bit and add HSC. Then there's just personal preference. One company may have a coil shock Engineer that likes a higher natural frequency and another company that likes them lower. I would say, use the calculator that factors in the setup that you're actually running. If Yeti's suggestion is factoring the fact that it's a PUSH shock, use that. If Yeti is giving a generic suggestion for a coil spring and PUSH is considering your specific Yeti, use that. Those both hold more value over a calculator that uses average leverage ratio. You may still not like the result, which is why most people start with the cheapest coil they can get, adjust as necessary, then eventually get a nice lightweight spring of the rate they choose. Just like air shocks, it's rare for the pressure chart to be bang on, you've got to fine tune it from there.

 

The thing is I don't have any practical way to measure my sag accurately...I know some say sag is not too important but at least it would be good to know what ballpark I am in... because for example it's not only the difference in suggested spring rates that is the problem here but it's also the fact that what Yeti says creates a certain sag percentage calculators like the FOX one are saying my sag percentage with that same coil is much lower. This is taking into account adding all the weight bias measurements etc correctly into the FOX calculator. As you can see the FOX calculator is telling me that with a 450lb spring I will be getting 22.8% sag... the Yeti one is saying a 450lb spring will give me 21mm of sag..which on a 65mm stroke shock equates to 32.3% sag. Now my bike has a relatively straight leverage curve nothing wild..all the correct data has been inputted into FOX and if I had to take an eyeballed guess, there is no way my shock is sagging to 32.3% with a 450lb spring when I sit on the bike which Yeti is claiming it will.
These are wildly different sag figures for a given rate...so either the FOX one is complete BS or both are not accurate as I don't believe I'm getting the amount of sag Yeti is stating I am with that spring either. Wish there was an easier way to measure it on a coil. I could try a zip tie around the shaft but don't know how accurate that is going to be.

And bare in mind further still FOX recommends take off another 100lbs if your bike is greater than 25% progressive...so basically FOX is saying a 350lb spring will give me 29% sag but take off another 100lbs on top of that for my bikes high progressivity (250lbs) and Yetis is saying a 450lb spring will give me 32% sag....I mean come on that isn't even remotely close or in the ballpark...both are opposite ends of the scale practically.

 

Reverse components makes a revised version of their sag checker for coil shocks. It will fit any coil

 

With your data put into the Fox calculator, I get a 385lbs spring rate for 30% sag, so a 400lbs will be good for 28%?

When I used the Fox for my bike, it was spot on.
Why bother, if you know what is best for you by trying it out? My SD has a scale, and it shows the sag I wanted to achieve, but who cares if you can feel it is right?

 

Did you input all the same data I used? I changed the weight bias to 65% rear as that is roughly what my bike equates to...but also there is info at the bottom of the calculator that says subtract another 100lbs for bikes over 25% progressive.

 

I paid for a calculation after trying various ones
My dilemma is the four Ohlins springs I have are a bit off in measured spring weight (got them checked as well)

Bike Spring Rate Calculator - Advanced - Rear Spring Only (Shockcraft)

This is a complex frequency based spring rate calculator to determine rear spring rates for Trail and Enduro MTB.Enter rider weight, bike weight and unsprung weights as well as bike geometry numbers to get the most accurate starting point for bike setup.

www.shockcraft.co.nz

 

I paid for a calculation after trying various ones
My dilemma is the four Ohlins springs I have are a bit off in measured spring weight (got them checked as well)

Bike Spring Rate Calculator - Advanced - Rear Spring Only (Shockcraft)

This is a complex frequency based spring rate calculator to determine rear spring rates for Trail and Enduro MTB.Enter rider weight, bike weight and unsprung weights as well as bike geometry numbers to get the most accurate starting point for bike setup.

www.shockcraft.co.nz

But is it only for PC or can you use it on Android phones too?

 

Well either way I just measured the sag with the elastic band method. Remember PUSH recommends 450lbs...Yeti also says 450lbs and states that will give me 21mm of sag which is around 33%.

Well with a lighter 411lbs Ohlins spring I'm getting 18mm of sag... after a few rough calculations and comparisons it seems the FOX calculator is much closer to what is true than what Yeti is saying.

Yeti is saying 450lbs will give me 21mm sag or around 33%...FOX is saying 450lbs will net me around 23% sag and so far the FOX seems to be correct.

I'm fine with PUSH and YETI suggesting recommended rates even if they are too firm or lower sag....

I'm not fine with YETI stating their recommended will give me 33% sag when in reality it's closer to 23%...are they measuring sag on a 35 degree incline or what??

I will buy Dougals calculator because why not...but I'm expecting results much closer to FOX than YETI.