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Discussion Starter · #1 ·
So yeah, there are lots of spring calculators on line, even some mfgs publish or provide guidelines for choosing a spring rate, but what spring rate is right for a person can vary greatly depending on use, suspension, etc...

What makes choosing a coil spring more complicated than choosing an air spring rate is the obvious stuff: need to install a completely different spring, which is not really a trail side task.

So, for baseline, yes, a calculator gets you in the ballpark, but then what? Do you change rate based on feel? Do you change rate based percentage of travel used? Do you keep going up on spring rate until you no longer bottom out or you can't feel your testicles ;)
 

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Spring calculator to get a good idea. Feel is typically next. If it feels great, you're done. If not check sag. If you're sag is close to what you should run, figure out what knobs to adjust.
 

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I can't comment on air shocks and forks because I've always rode coil but I set up by sag. I like to go with the lightest spring rate without constant bottoming and potentially having the spring deflect and rub the shock body. Also take into account your riding style. For instance, I ride fast and smooth and don't do drops to flat or session rocks.
 

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I have always used the calculator then gone by feel. All that really matters in the end is if it works how you want. Generally if your leverage curve is linear you should go a touch stiffer and if it’s progressive stick with the recommended rate to start
 

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100% maths based on ride frequency. Do not use sag.

Give me your bike wheelbase, chainstay length, head angle and rider weight.
Where does suspension design factor in with that math? After 20 years of custom shocks and quality aftermarket springs, I can sit on a bike and immediately now what needs to happen with spring rate, pre load* and sag. I'm good enough to be able to drop the rear end to the ground and it just sticks without too much fiddling around.

*Oil filter tight on the preload ring. After that I'm going with a different spring rate.
 

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Discussion Starter · #7 ·
Okay, I'll play: 2019 GG Shred Dogg, Fox 36/160mm, Bomber CR

87kg nakid
WB 1246mm
CS 423mm
HTA 65.3 deg
Travel 140mm

100% maths based on ride frequency. Do not use sag.

Give me your bike wheelbase, chainstay length, head angle and rider weight.
 

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Where does suspension design factor in with that math? After 20 years of custom shocks and quality aftermarket springs, I can sit on a bike and immediately now what needs to happen with spring rate, pre load* and sag. I'm good enough to be able to drop the rear end to the ground and it just sticks without too much fiddling around.

*Oil filter tight on the preload ring. After that I'm going with a different spring rate.
Suspension design changes leverage.

Feel is your final check that you got it right.
 

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Okay, I'll play: 2019 GG Shred Dogg, Fox 36/160mm, Bomber CR

87kg nakid
WB 1246mm
CS 423mm
HTA 65.3 deg
Travel 140mm
Fork you're halfway between 45 and 50 lb/in
Rear shock is 400lb/in.
For those who care about sag, when balanced over the BB you'll have about 25% rear and 17% front.

If you ride like a complete nutter, you can bump those rates up. But they're your starting points.
 

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Give me your bike wheelbase, chainstay length, head angle and rider weight.
I wonder if you get the same result as what I ride:
100 kg
2015 Knolly Warden Alu Large:
* Wheelbase: 1189 mm
* Chainstay: 429 mm
* HA: 65.5 deg
* rear travel: 150 mm
* Front fork 170 mm lyrik, so HA may be changed slightly, but I run 30% sag so it may even it out (bike is designed for 160 mm fork)

Have DHX2, keep in mind tend to lean over my rear wheel a lot (probably this is why I have problem with using full travel of fork....) and in North Vancouver Canada - steep, roots, rocks.
 

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I have owned many coil shocks and not once have I ended up w/ less than 3 steel coils and hopefully one Ti spring. Yes I started w/ multiple calculators, analytics & finger crossing but even if something feels ok I need to "go no go" on the tuning process.
 

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Discussion Starter · #13 ·
I started with 400# and I could bottom it out just bouncing up and down in the garage, upped it to 450# and rode it and hard over the weekend (30k technical ride/4K climbing) and bottomed the shock throughout the ride but not overly so; it was comfortable.

Swapped to a 500# spring this morning and did a short mellow ride on my backyard trails, max 0.5m drops and was still using all of my travel. Got a 550# spring in the bullpen, hate to go too stiff but I'm worried about how it'll handle bigger drops if I don't increase my spring rate.

Oddly enough, my previous GG bike, a 2018 aluminum Smash had similar geo, CS 429, same travel, in theory the same suspension, running a RS Super Deluxe RCT with a 400# spring worked just right.

Fork you're halfway between 45 and 50 lb/in
Rear shock is 400lb/in.
For those who care about sag, when balanced over the BB you'll have about 25% rear and 17% front.

If you ride like a complete nutter, you can bump those rates up. But they're your starting points.
 

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I started with 400# and I could bottom it out just bouncing up and down in the garage, upped it to 450# and rode it and hard over the weekend (30k technical ride/4K climbing) and bottomed the shock throughout the ride but not overly so; it was comfortable.

Swapped to a 500# spring this morning and did a short mellow ride on my backyard trails, max 0.5m drops and was still using all of my travel. Got a 550# spring in the bullpen, hate to go too stiff but I'm worried about how it'll handle bigger drops if I don't increase my spring rate.

Oddly enough, my previous GG bike, a 2018 aluminum Smash had similar geo, CS 429, same travel, in theory the same suspension, running a RS Super Deluxe RCT with a 400# spring worked just right.
Are you actually bottom it out hard, or are you just getting to and touching the bottom out bumper?
 

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Are you actually bottom it out hard, or are you just getting to and touching the bottom out bumper?
Yeah that's the thing about the bottom out bumper... I thought I was bottoming my #500 (after starting at 400) but it turns out I was gently using 80% of the travel.
 

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Discussion Starter · #16 ·
Are you actually bottom it out hard, or are you just getting to and touching the bottom out bumper?
It's all relative. I use the bumper to determine where I am in the travel "use"; not really worried about sag these days, so if I find I'm using all of my travel popping off a 12" rock, it's not hard to see how dropping a five foot ledge is gonna be a problem.

Coils are inherently better for small bumps, even a stiffer spring still does that better than an air can, so I'd rather have too high of a rate than one that is too low.

We can't realistically expect a small rubber bumper to handle hard bottom outs, so in my mind bumping spring rate until I use 80-90% of my travel on a normal ride will lead to 100% or more use on a "complete nutter ride".
 

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I started with 400# and I could bottom it out just bouncing up and down in the garage, upped it to 450# and rode it and hard over the weekend (30k technical ride/4K climbing) and bottomed the shock throughout the ride but not overly so; it was comfortable.

Swapped to a 500# spring this morning and did a short mellow ride on my backyard trails, max 0.5m drops and was still using all of my travel. Got a 550# spring in the bullpen, hate to go too stiff but I'm worried about how it'll handle bigger drops if I don't increase my spring rate.

Oddly enough, my previous GG bike, a 2018 aluminum Smash had similar geo, CS 429, same travel, in theory the same suspension, running a RS Super Deluxe RCT with a 400# spring worked just right.
The correct spring rate isn't determined by bottom-out. It's determined by ride frequency. You need to use compression damping (or more travel) to prevent bottom-out.
140mm ain't that much. The shorter your travel the more compression damping you need.

If you over-spring to prevent bottom-out you end up with a harsh and jiggly ride that needs more rebound damping to stop it bucking. The end result is over sprung and overdamped.

I run a bit firmer and faster that the first numbers above. Using the same frequency I ride for your application bumps your rear spring rate to 460 lb/in.
 

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I wonder if you get the same result as what I ride:
100 kg
2015 Knolly Warden Alu Large:
* Wheelbase: 1189 mm
* Chainstay: 429 mm
* HA: 65.5 deg
* rear travel: 150 mm
* Front fork 170 mm lyrik, so HA may be changed slightly, but I run 30% sag so it may even it out (bike is designed for 160 mm fork)

Have DHX2, keep in mind tend to lean over my rear wheel a lot (probably this is why I have problem with using full travel of fork....) and in North Vancouver Canada - steep, roots, rocks.
I get 57 lb/in front and 530 lb/in rear using the same ride frequency as myself. Sag would be approx 24 and 14%, but a hundred little factors change that.

This is a little oversprung in the back (vs a comfort tune) as I mentioned with Nurse Ben.
 

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Cool. I run 550 spring right now, but was thinking about going to 500. You are right, sag is now at approx 25%. Will see how 500 + more compression damping feels. Thanks!
 
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