Correct spring rate

[Grichka]

Hi there,
Since I do not seem to find any good info on the net about spring rate, I’ll try asking you guys !
I just received and installed my new Fox DHX2, which came with a 450x2.4 spring.
I am 95kg with equipment, and the SAG with this coil is at ~20mm, when it should be at ~15/16mm according to ridefox.com.
My bike travel is 150mm, my shock travel is 55mm, what would you guys recommend to install, 500lbs, 525lbs, 550lbs, more ?

 

[Forever Wild]

Another data point for you. I’m 100kg. I use 650# and happy with performance.

 

[Doomanic]

Spring Calculator - TF Tuned

Spring Calculator - TF Tuned are experts in mountain bike and bicycle suspension service and repair, including setting-up the for you and your bike

www.tftuned.com

586-622 according to that.

 

[Grichka]

Thank you Doomanic! What is the difference between « Single pivot / DW Link » and « 4 bar / VPP » , I don’t understand what those things mean ?
And as the coil coming with the shock is 2.4, am I still ok to get a 2.8 ?

 

[Doomanic]

Single pivot bikes are just that; they hae a single pivot point and no lickages, like the Oranage Surge;

Your Levo is a 4 bar/VPP design.

And as the coil coming with the shock is 2.4, am I still ok to get a 2.8 ?

2.4 or 2.8 what?

 

[Grichka]

I see, thank you for the explanation, very useful.

By 2.4 or 2.8 I meant the coil travel (or length), because with the 450x2.4 actually on, the pre load adjuster is only at the middle of its screw, so I guess I could also go with a longer coil, like 2.8 ? Or would that mess with the whole suspension ?

 

[Doomanic]

I’m pretty sure that if you need more than 2 turns of preload your spring rate is wrong.

If you can fit the longer spring and still have the correct preload adjustment it’ll be fine. Heavier than the shorter spring though.

 

[Grichka]

Oh I am sure that my actual spring rate is wrong. I have to find a bigger one, I just wanted to know which one.
Thank you for your help, I will keep an eye for a 600x2.4 or 2.8.

 

[Forever Wild]

Oh I am sure that my actual spring rate is wrong. I have to find a bigger one, I just wanted to know which one.
Thank you for your help, I will keep an eye for a 600x2.4 or 2.8.

You should consider a 2.4 length vs a 2.8 length. I took out a 500x2.8 and replaced it with a 650x2.8 and it was a very tight fit going in. The two springs looked the same side by side but the 650 was hard to compress and that made the job difficult. A 650x3.0 would have been virtually impossible.

Also, have you considered a progressive spring like a VALT coil spring? I did not and second guessing myself on not doing more research on a progressive spring.

 

[Grichka]

Is your pre-load screw at the end of the screw thread when it starts touching the spring ? Because mine start touching the spring when it is screwed half way already, that's why I am considering getting a spring a bit bigger, like 2.6 instead of 2.4.

I saw those VALT progressive springs, I'm not sure if they're really good or not. How do they work ? The more you compress, the harder it gets to be compressed ?

 

[Doomanic]

I saw those VALT progressive springs, I'm not sure if they're really good or not. How do they work ? The more you compress, the harder it gets to be compressed ?

Yes.

 

[Forever Wild]

Is your pre-load screw at the end of the screw thread when it starts touching the spring ?

500x2.8:

1. Collar was 1.5 turns of pre load (easy to turn). 2. When collar backed off it was not touching (barely)

650x2.8

1. The collar is fully backed off (no preload).
2. The collar is currently touching spring and hard to turn if I try to apply some preload.

In summary:
The 650x2.8 gives me less sag for my 100kg weight. Bottom bracket sits higher and I have less pedal strikes. The low speed bump compliance is better. I felt the preload I was applying to improve my sag on the 500x2.8 was making the the spring too stiff and didn’t ride as well as my 650# spring.

 

[Grichka]

Thank you for your detailed exemple, appreciated!