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Discussion Starter · #1 ·
EDIT: I'm an idiot, apparently I posted this same question last year. Feel free to disregard. I can't delete this post, so I guess I'll just leave the wall of text below. :madman:

I have a 2018 Santa Cruz V10 with a Fox coil shock on it, custom code DDWR, info from the Fox website product lookup:

2018, DHX2, P-Se, TiN, LSC, LSR, Santa Cruz, V10.6, 8.75, 2.75, 500 lbs/in, CF, Standard Logo

This is my first coil shock, and I'm a bit confused by a few things. The Setting Coil Spring Preload section on Fox site has a big scare warning:

WARNING: Tighten the preload adjuster just until the spring no longer moves, then preload no more than 2 full turns. Preloading the spring more than 2 full turns may cause the spring to coil bind when the shock is bottomed out. This can cause damage to the shock which could lead to a loss of control resulting in SERIOUS INJURY OR DEATH.
I assume "until the spring no longer moves" means to tighten the collar until it just barely contacts the spring, i.e. the spring is no longer loose to shake back and forth. But... that point is significantly different for each of the following 3 cases:

  • shock is not attached to bike (zero compression load from bike weight)
  • shock is attached to bike, bike is resting on wheels (positive compression load from bike weight, so collar will contact loose spring sooner)
  • shock is attached to bike, bike is suspended from seatpost (negative compression load from bike weight, so collar will contact loose spring later, maybe? assuming plunger can extend past resting state)
Which one of the above should I be using? In the presence of this confusion, I chose the first one. With the shock removed from the bike, I turned the collar until it put a light pressure on the spring, and then I added two more complete turns.

Then, I went out and rode a pretty easy blue DH trail with no real drops or anything (Coaster @ Northstar for those familiar), and at the end observed that the shock had already used its full stroke even for that mild trail. This seems wrong, so I had two ideas:

1) Since it supposedly unsafe to add more preload... I need a stiffer spring. But using the Fox Spring Rate Calculator, I came up with 500lbs/in (i.e. what I already have). FWIW, I used all the defaults already filled in the form, changing only my weight (185lb with all gear), the rear wheel travel (8.5in) and the shock stroke (2.75in). So that idea would appear to be out.

2) Maybe coil shocks are supposed to use their full stroke much more easily than air shocks? I don't know. I've hit pretty big jumps and drops on this bike, and obviously it uses its full stroke on those too, but I've never felt a rough bottom out sensation that bothers me, and I notice the bumper is thick rubber... so maybe I should just not worry about this? It still seems weird that it would bottom out on pretty tame trails.
 

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You're totally over-thinking this.

You can tighten up the spring with the shock on the bike. The idea is to snug up the spring so it doesn't move up and down to start. That's it! If you're worried about the weight of the bike compressing the shock, then tighten the preload collar so the spring is snug, then lift the bike by the seat to make sure the shock wasn't compressing under the weight of the bike.

Preloading a spring is for helping you get to your sag point, but if you go past 2 full turns of the collar (after the spring is snug on the shock, on the frame) before you get to the required/desired sag, then you need to go up a spring rate at least.

You might not feel a harsh knock when you bottom out, but do you bottom out often??? Once in a while isn't terrible, but at full bottom out is when you lose traction. The idea is to avoid bottoming out so the wheel remains 'suspended' in order to keep traction with the ground.
 

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Keep on Rockin...
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You're totally over-thinking this.

You can tighten up the spring with the shock on the bike. The idea is to snug up the spring so it doesn't move up and down to start. That's it! If you're worried about the weight of the bike compressing the shock, then tighten the preload collar so the spring is snug, then lift the bike by the seat to make sure the shock wasn't compressing under the weight of the bike.
Yep.

If the weight of the bike is "pre" pre-loading, just snug down the coil while holding the rear end off the ground by the seat. Probably a "hair splitting" proposition anyway.

I've been told dialing "perfect" sag via preload is way over-rated or even not advised. If you have the proper spring rate whether your sag ends up at say 20, 25, or 30% it doesn't really matter.

One can argue that proper spring rate is not established by getting proper sag with your coil, but rather by a mathematical formula that predetermines your spring rate (which incidentally should give you the right amount of sag anyway. Might be a chicken and the egg sort of thing).
 

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Discussion Starter · #4 ·
You're totally over-thinking this.
Yeah, I do that. :lol:

You might not feel a harsh knock when you bottom out, but do you bottom out often??? Once in a while isn't terrible, but at full bottom out is when you lose traction. The idea is to avoid bottoming out so the wheel remains 'suspended' in order to keep traction with the ground.
I'm not sure how often it is, but I suspect it happens too often, since as I noted it happens at least once even on pretty mellow trails. The only place I've ridden this bike is Northstar, and I do have a problem cornering as fast as I want to and keeping the back end from washing out. I had just chalked that up to (a) lacking skill and (b) incredibly dry dusty/bumpy berms. But maybe you're right and I'm bottoming out early in the turn. Should I just increase compression damping to try to address that? Thanks!
 

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Discussion Starter · #5 ·
I've been told dialing "perfect" sag via preload is way over-rated or even not advised.
That makes sense I think. Two full turns of the preload collar only changes the sag by less than 0.1"... according to the Fox spring rate calculator the difference between 0 and 2 turns is 25% sag vs 23% sag respectively. That difference is negligible.
 

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The Riddler
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Yep.

If the weight of the bike is "pre" pre-loading, just snug down the coil while holding the rear end off the ground by the seat. Probably a "hair splitting" proposition anyway.

I've been told dialing "perfect" sag via preload is way over-rated or even not advised. If you have the proper spring rate whether your sag ends up at say 20, 25, or 30% it doesn't really matter.

One can argue that proper spring rate is not established by getting proper sag with your coil, but rather by a mathematical formula that predetermines your spring rate (which incidentally should give you the right amount of sag anyway. Might be a chicken and the egg sort of thing).
agree with this. if you watch the fox dialed series from the world cups, jordie says something about how greg minnar doesn't use any preload because it doesn't matter and just makes the shock work less like it's supposed to.
 

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No known cure
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Avalanche says 1.5 to 4 turns. Outside that, you need a different weight spring. I like just enough preload to keep the spring from rattling.
 

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I generally snug up the spring, then one full turn for good measure and leave it at that.

The11..go up a spring rate. If you want, get a cheap steel one off pinkbike or something so you're not out a bunch of money. Once you find the right one, then splurge and get an SLS or Ti spring. DO NOT crank up your compression just to help with bottoming. You'll make your bike handle worse.
 

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No known cure
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I generally snug up the spring, then one full turn for good measure and leave it at that.

The11..go up a spring rate. If you want, get a cheap steel one off pinkbike or something so you're not out a bunch of money. Once you find the right one, then splurge and get an SLS or Ti spring. DO NOT crank up your compression just to help with bottoming. You'll make your bike handle worse.
I treat it like an oil filter. Turn to snug, then a quarter turn or more. And like you mentioned, once I have spring weight dialed, I spring for Ti spring.
 

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Electricdownhill805
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Lifting up the seat with the shock installed was a brilliant idea !
You saved me so much stress overthinking this feeling like something wasn’t right adjusting the preload and I was correct lifting up the seat the coil was very loose
You're totally over-thinking this.

You can tighten up the spring with the shock on the bike. The idea is to snug up the spring so it doesn't move up and down to start. That's it! If you're worried about the weight of the bike compressing the shock, then tighten the preload collar so the spring is snug, then lift the bike by the seat to make sure the shock wasn't compressing under the weight of the bike.

Preloading a spring is for helping you get to your sag point, but if you go past 2 full turns of the collar (after the spring is snug on the shock, on the frame) before you get to the required/desired sag, then you need to go up a spring rate at least.

You might not feel a harsh knock when you bottom out, but do you bottom out often??? Once in a while isn't terrible, but at full bottom out is when you lose traction. The idea is to avoid bottoming out so the wheel remains 'suspended' in order to keep traction with the ground.
 
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