[milehi]

What's the go to calculator? I'm 170 geared up and am on a 400# with the preload backed off as far as I can and it still feels oversprung. Sag is at 30%. Compression is backed all the way out. It's a RS Super Deluxe on a 2018 GG Smash.

 

[stripes]

Which shock?

 

[milehi]

Which shock?

RS Super Deluxe Ultimate coil. 400#ish has always been in the ballpark for me. I have no prior experience with these shocks but it doesn't sink into the travel how I like with 35% sag (only getting 30) when I sit on the bike. I'm also not getting full travel, even when racing. I might send it out for a tune or pick up a Jade that I can play with.

ETA I've gone as low as a 350# spring on my Ventana (140mm and thanks for those rockers) and the spring deflected enough to rub the shock body on the CCDB. That shock was sent to me direct from Cane Creek with a 400# spring which I went back to but with a Ti spring.

 

[the-one1]

Either a retune will make it feel better, or a 375# spring.
Maybe a Sprindex will work for you.

 

[Monty219]

I run a 450# spring on the same shock on a 2018 megatrail. I weigh in at 200lbs + a few pounds of water and tools i carry on bike instead of on back. My +30 lbs and +20 (or 25?) mm travel dont make for a direct comparison. But i can say i run it at 30% sag and use full travel regularly but have never had a harsh bottom out in 3 years (maximum of 6’ huck to flat for comparison purposes). At 170# you should be within the standard compression tune range so i would guess a lighter spring would be the most likely solution. As previously mentioned a springdex sounds like a good route (I haven’t tried one but would if i was questioning spring weight).

as far as a calculator goes, i dont know of one. I think it would be hard to do, due to variation in spring rate curves and personal preference but it is an interesting idea.

 

[brash]

take the calculators with a grain of salt, there is so many variables with kinematic designs etc where it would be considered a "rough guide" only.

for a FSR/4 bar this one is close,

Coil Spring Calculator (Beta) — The Suspension Lab

Calculator to help estimate the appropriate coil spring for your bike

thesuspensionlab.nz

Having the bike modeled in linkage and using the inbuilt calculator is the best, but to most is not accessible. A sprindex is also a good solution as mentioned.

Unfortunately the one big caveat with coil shocks (besides the sprindex now) is that it may take 2-3 spring rates before you settle on one. Knowing a bikes kinematic with it's start/finish leverage ratio will give you a very good estimated guess to work off. From my past experience I use this rule of thumb:

10-18% progressive: 25% sag
19-24% progressive 30% sag
25+% 33-35% sag

 

[TraxFactory]

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

 

[Jayem]

Spring tolerance is pretty shitty too. It's totally possible that you can have a "350 that is more like 385 or a "400" that is more like 365.

 

[cxfahrer]

The Fox spring calculator gives you many options. For me it was spot on with a Superdeluxe. 28% I wanted and thats what I got.
The SAR spring is high quality steel.

 

[milehi]

Spring tolerance is pretty shitty too. It's totally possible that you can have a "350 that is more like 385 or a "400" that is more like 365.

The 400# spring seems very "robust". I have plenty of free time and Eibach is three miles from my office. I may check in with them.