Fork set up: what´s better for dh?

chillindrdude · Jan 29, 2012

i run 30% sag at minimum. i like the extension from sag in the chop to get that 'stick to the ground'/absorption feeling. i run fairly slow rebound, 2-3 clicks from half, but no more than 2/3rds to full slow. i run half low speed compression to minimize fork dive and bobbing on the gas. i run about 1/4-1/3 to full high speed compression. i want some plushness on big hits, but want support as the bike goes thru mid-stroke.

look at your owners manual, or tech/tuning section for your fork. i usually start at recommended settings, and then go from there.

marshalolson · Jan 29, 2012

time runs.

play with settings.

use settings that give fastest results.

armada · Jan 29, 2012

soft spring and a lot of compression is the faster setup IMHO, and u neem more sag

baca262 · Jan 29, 2012

if you like to plow, softer spring/firmer valving, if you like to jump over nasty stuff, firm spring/softer valving. this is really your personal preference. you can also plow with the firmer spring but it won't be as forgiving as the softer spring.

SCARY · Jan 29, 2012

I play with this all the time.Luckily for me,I have a Dorado and you can tune the initial part of the stroke separately from the mid/last part of the stroke.So, I can use a stiffer (air) spring and also use a fair amount of compression while still having a a supple initial stroke.And...the knobs work when you turn them.Its the perfect fork.

norbar · Jan 30, 2012

Actually as I got faster I decided to drop a bit of sag. It feels like it carries speed better (didn't measure) but what's the most important it stays higher in travel than around 30% and I like that a lot. I still run normal amounts of damping.

saruti · Jan 30, 2012

what norbar said is true
and with head angles this days... it is working better that way.

norbar · Jan 30, 2012

Imho try the lowest sag you can get away without loosing traction. I went overboard at first but decided to try it. Didn't like it, added pressure and it is perfect now.

staike · Jan 30, 2012

Yeah faster people seem to run less sag. I'm running 25% and that feels perfect to me and matches my shock very well. A friend that's faster runs his at around 20% and my slow little brother at around 30%.

norbar · Jan 30, 2012

I'm not really sure it's only for faster people. I'm pretty sure most of the forum here would have smoked me but unless your local trails are really low speed less sag is quite good. I think it's more to do with the track and your riding style. You can adjust to less sag.

William42 · Jan 30, 2012

hard compression, hard spring (~10% sag, comp about 3/4-4/5 of the way in), and as fast rebound as I can get away with without it jittering make me the fastest, but it also sucks for riding experience and tends to blow up my hands after two runs. I have much more FUN and can ride longer with more normal 15% sag and comp damping at around 50% with a bit of progression toward the end. Rebound I still like to run pretty fast.

4130biker · Jan 30, 2012

Stiff feels good to me- jumps better pumps better, but there is a point where it's too far. A funny thing was pointed out to me a while back on this forum- as I reduced travel on my bike I would have to go with a stiffer spring, or be bottoming out more often on my demo 8. Really the big bikes can feel short travel with a stiff set up but be there to save your ass and bike when you comPletely smash something. So with lighter dh bikes, I can see why freeride bikes are kinda less and less common...
Seems like stiff should be faster on most things if you can hang on!

StabprimoMonkee · Jan 31, 2012

I like my drinks and my bikes stiff.

time-bomb · Jan 31, 2012

marshalolson said:
time runs.

play with settings.

use settings that give fastest results.

profit.

fixed

nybike1971 · Feb 1, 2012

DMdh said:
That´s right for sure, but if you are an agressive rider you´ll need more damping if you dont want to blow constantly through the travel.
At this moment for example: 69 kg with gear on, and using red spring on my boxxer(72-85 kg) with shim stack to offer more hs damping and compression dial set to minimum(lsc)

If your lsc is set wide open, you are not going to feel much at all from the hsc shim stack as most of the oil is flowing through the lsc port. Even full closed, the needle on the Boxxer is pretty blunt and doesn't really close down completely. A stiffer HSC shim stack will make things even more unbalanced and essentially almost never crack open.

As far as stiff or soft spring, simple damped oscillator arguments show that the fastest bump response time is achieved with the stiffest spring and lowest damping that allows for that particular fork extension. In practice, that means that you will have the fastest responding suspension (both in compression and rebound) by using the stiffest spring that still allows you to achieve full travel.

Go-ride had an interesting article a few years ago on setting up sag and their main point was that we set up sag on a level surface and ride the bike on steep downhills. For that reason they recommended roughly 20% sag up front, because it turns into 25-30% with the weight shift when you point the bike down a steep track.

I personally end up right around 25% sag up front. I am 170lbs and ride a red spring in a 2010 Boxxer with one spacer, LSC two turns out from full closed, HSC a few clicks in on a shim stack modified to be somewhere between 2010 and 2011 stick damping (less harsh at high-speed than 2010 but with more LSC support than 2011).

norbar · Feb 1, 2012

nybike1971 said:
If your lsc is set wide open, you are not going to feel much at all from the hsc shim stack as most of the oil is flowing through the lsc port. Even full closed, the needle on the Boxxer is pretty blunt and doesn't really close down completely. A stiffer HSC shim stack will make things even more unbalanced and essentially almost never crack open.

As far as stiff or soft spring, simple damped oscillator arguments show that the fastest bump response time is achieved with the stiffest spring and lowest damping that allows for that particular fork extension. In practice, that means that you will have the fastest responding suspension (both in compression and rebound) by using the stiffest spring that still allows you to achieve full travel.

Go-ride had an interesting article a few years ago on setting up sag and their main point was that we set up sag on a level surface and ride the bike on steep downhills. For that reason they recommended roughly 20% sag up front, because it turns into 25-30% with the weight shift when you point the bike down a steep track.

I personally end up right around 25% sag up front. I am 170lbs and ride a red spring in a 2010 Boxxer with one spacer, LSC two turns out from full closed, HSC a few clicks in on a shim stack modified to be somewhere between 2010 and 2011 stick damping (less harsh at high-speed than 2010 but with more LSC support than 2011).

I think I ran more sag with my stock RS damper but when I switched to Avy Cart and complained about the fork being a bit too low in it's travel Craig suggested running no more than 20% sag. I was suprised but tried it and it performs better.

baca262 · Feb 1, 2012

DMdh said:
But you are talking about a boxxer team or wc, and mine its a rc

me thinks you want an avalanche cart.

norbar · Feb 2, 2012

DMdh said:
Well, then you´re wrong.

You just don't know it yet

ianjenn · Feb 2, 2012

norbar said:
You just don't know it yet

Or maybe he just wants a Dorado?

baca262 · Feb 2, 2012

norbar said:
You just don't know it yet

Full Trucker · Feb 2, 2012

This thread is suffering from way to much conjecture and way too little stopwatch.

baca262 · Feb 2, 2012

now seriously, you do have a point. but the motion isn't nowhere near a decent damping cartridge, construction or performance-wise.

Steve M · Feb 3, 2012

nybike1971 said:
If your lsc is set wide open, you are not going to feel much at all from the hsc shim stack as most of the oil is flowing through the lsc port. Even full closed, the needle on the Boxxer is pretty blunt and doesn't really close down completely. A stiffer HSC shim stack will make things even more unbalanced and essentially almost never crack open.

As far as stiff or soft spring, simple damped oscillator arguments show that the fastest bump response time is achieved with the stiffest spring and lowest damping that allows for that particular fork extension. In practice, that means that you will have the fastest responding suspension (both in compression and rebound) by using the stiffest spring that still allows you to achieve full travel.

Go-ride had an interesting article a few years ago on setting up sag and their main point was that we set up sag on a level surface and ride the bike on steep downhills. For that reason they recommended roughly 20% sag up front, because it turns into 25-30% with the weight shift when you point the bike down a steep track.

I personally end up right around 25% sag up front. I am 170lbs and ride a red spring in a 2010 Boxxer with one spacer, LSC two turns out from full closed, HSC a few clicks in on a shim stack modified to be somewhere between 2010 and 2011 stick damping (less harsh at high-speed than 2010 but with more LSC support than 2011).

Unfortunately simple mass spring damper theory isn't especially accurate with bikes, as the force input at the axle is only in a single direction, and the rider is far from a rigid mass. It does give you some useful tools to compare different setups though, although the numerical result of a given calculation is on its own fairly useless.

Boxxer R2C2 valve geometry is worthy of a thread of its own, and particularly with the stock shim stack, "traditional" means of looking at the interaction between LS and HS can pretty much be thrown out the window. In stock guise (for 2011 at least - haven't dyno'd a 2012 yet), the compression adjusters are ineffective.

Full Trucker said:
This thread is suffering from way to much conjecture and way too little stopwatch.

We've done some testing on exactly this actually, and statistically proved that between two different compression settings on a particular fork (no other changes, same valving and all) on a particular section of track, you could be approximately 2.7% faster on average. This means that over say a 5 minute course, you could potentially be about 8 seconds faster (or slower) based entirely on that one setting - crazy hey?

Basically, on reasonably steep or rough terrain, the fastest setup is firm and typically also quite dead. The rougher and steeper it is, and the better a rider you are, the more this is true, whereas on smoother, flatter or particularly tight bermed stuff, the opposite can be the case.

It gets to the point where you pretty much need to be hitting the gym just to be able to hold on for a whole run, because it gets uncomfortably harsh - to the point where many riders, myself included, are limited by physical fitness before they reach the limitations of the bike. I can ride faster for 1 minute on an extremely harsh setup, but am slower overall on a 5 minute course because I don't have the fitness/strength to hold onto that kind of setup and ride it hard for that long.

mantra · Feb 3, 2012

Steve M said:
Boxxer R2C2 valve geometry is worthy of a thread of its own...

Feel free to start one

Should be verry interesting for a lot of people!

baca262 · Feb 3, 2012

+1 from me.

Verskis · Feb 3, 2012

Steve M said:
Basically, on reasonably steep or rough terrain, the fastest setup is firm and typically also quite dead. The rougher and steeper it is, and the better a rider you are, the more this is true, whereas on smoother, flatter or particularly tight bermed stuff, the opposite can be the case.

If by "dead" you mean "not poppy", I agree on that part.
But I'm curious about your arguments on firm setup being less advantageous on smoother, flatter and tight-bermed courses? I'd think in those circumstances it would be especially bad to have a soft, wallowy setup. And in steeper and rougher courses, wouldn't one need a softer setup to get maximum traction?
Of course too soft fork is bad on a steep track, as fork dive isn't desired on those circumstances, but I would think the suspension's ability to keep the wheels on the ground is also very important.

Actually, I'm very interested in hearing theories, why is stiffer setup faster? Is it because of minimal geometry changes and predictable handling?

norbar · Feb 3, 2012

Yeah I was also suprised about that bermy flatter track. I tend to run a ton of LSC on those.

StabprimoMonkee · Feb 3, 2012

It's about energy dissipation not about some arbitrary magic value.

Steep, rough tracks - a lot of energy that needs to be dampened. Flat track - not so much.

norbar · Feb 3, 2012

StabprimoMonkee said:
It's about energy dissipation not about some arbitrary magic value.

Steep, rough tracks - a lot of energy that needs to be dampened. Flat track - not so much.

Yes but also berms were mentioned. Also flat tracks if you race require pedalling.

Steve M · Feb 3, 2012

Let's establish one thing here: for the moment I am only talking about how FAST a certain setup is - not how comfortable, poppy, playful or fun it is.

Verskis said:
If by "dead" you mean "not poppy", I agree on that part.
But I'm curious about your arguments on firm setup being less advantageous on smoother, flatter and tight-bermed courses? I'd think in those circumstances it would be especially bad to have a soft, wallowy setup. And in steeper and rougher courses, wouldn't one need a softer setup to get maximum traction?
Of course too soft fork is bad on a steep track, as fork dive isn't desired on those circumstances, but I would think the suspension's ability to keep the wheels on the ground is also very important.

Actually, I'm very interested in hearing theories, why is stiffer setup faster? Is it because of minimal geometry changes and predictable handling?

StabprimoMonkee said:
It's about energy dissipation not about some arbitrary magic value.

Steep, rough tracks - a lot of energy that needs to be dampened. Flat track - not so much.

Basically stabprimomonkee is correct - energy dissipation is the key issue. In some instances, you want the bike to be absorbing as much energy as possible, in as short a period of time as possible; these occasions are typically when you're trying to hit rough stuff particularly fast - especially when you have stuff like say a small drop on steep ground into a loose sketchy corner. The longer the bike takes to deal with the landing of that drop and return to something vaguely like a steady state, the less time and space you have to prepare yourself (body position, braking, line choice etc) for the section of track you're coming into. Keeping the wheels on the ground is desirable but you need to consider the critical times that this needs to occur, because it occasionally is a factor that needs to be compromised somewhat for the sake of stability. Obviously, good tuning seeks to minimise how much you need to compromise, but only a bridge salesman would tell you that you can have your cake and eat it too.

Other times, the bike is absorbing energy that you are intentionally putting into it, that you want back but aren't necessarily getting returned. Pumping berms or jumps is where you feel it the most obviously, but our research basically shows that it comes down to situations where your body is behaving actively rather than passively. A lot of the time, a rider on a DH bike is "coping" with rough terrain by acting something like a weird spring/damper unit (a lot more complex than that obviously), but low frequency inputs allow the rider to move their body fast enough to pro-actively interact with the suspension - this means pushing down at the appropriate times, allowing the bike to come up at the appropriate times, etc - all the actions we associate with "pumping" in general. From our observations, this appears to be a primarily biomechanical reaction rather than something that is strongly associated with a particular degree of skill, partly because more skillful/fast-acting riders tend to be riding substantially faster into given terrain anyway. Anyway, basically in terrain where you are able to ride more aggressively and pump more, with less roughness or steepness, your optimal setup will be less damped and occasionally slightly more stiffly sprung.

For those who have ridden Whistler, compare riding B-line with riding Canadian Open, both chainless. On a steep, rough track like CO, you don't have issues with generating enough kinetic energy because it's almost all coming from the gradient of the trail rather than directly from rider inputs, and most of the time all you want the bike to do is not kill you, in other words you just want it to be extremely stable and predictable after each major input to the bike. On B-line, all you want to do is pump each corner and each little dip. If the damping is too heavy, each time your body loads up the suspension either through pumping motion or just through cornering g-forces, more of the energy your body is putting in is being dissipated, and less is being returned as force over a displacement that you can use to push off the ground to gain speed. In other words, a livelier setup with less energy dissipation is useful for these kinds of trails. For novice riders, there is no need to have Aaron Gwin levels of compression damping, all that's going to do is hurt traction, hurt their hands, and make the bike feel lethargic and sluggish, because they aren't riding at the speeds or on the kind of terrain where the bike really needs to be stable above all else.

When it comes down to it, for "real" DH courses, the compromise you invariably make is how comfortable the bike is to ride - I can give you a setup that will have very low overshoot and very short time to settle, and most riders will say it feels horrible. On decent DH racecourses, it will be faster than a livelier/more compliant setup, provided the rider can deal with the harshness. That's not to say that's what everyone wants out of their suspension though!

Steve M · Feb 3, 2012

norbar said:
Yes but also berms were mentioned. Also flat tracks if you race require pedalling.

If you need more support in berms, you should usually be looking at spring rates moreso than your damping. Pedalling efficiency is another thing altogether, in that case, the closer to locked out and the more resistance there is to movement, the better the bike will pedal. I suggest adding up how much time you spend pedalling on your local DH trails and work out whether pedalling efficiency is really a big factor in that regard, because you will almost certainly be compromising something if you're making major changes to your suspension just to increase pedalling efficiency slightly.

Also I should clarify on "firmer" as used above: typically your fork spring rate should not need to change significantly from one course to another (unless the gradient is massively different), but you may find you really need to play with the LSC settings depending on gradient. On steeper/rougher terrain you will typically want, if anything, a lower spring rate on the rear, with more compression damping (typically slightly less rebound to allow for the lower spring though). This tends to give a dead feel, with less kick, but within reason, good stability too. Going nuts in this direction can make your bike harsh though.

In short:
- flat/smooth stuff: less comp damped fork, slightly softer fork spring and/or stiffer rear spring, less comp damping in the rear. Rebound adjusted to suit at both ends.
- steep/rough stuff: more comp damped fork, slightly firmer fork spring and/or softer rear spring, more comp damping in the rear. Rebound adjusted to suit at both ends.

StabprimoMonkee · Feb 3, 2012

And something I can confirm from my observations.

Fast setups are fast, but don't leave out on your interval training. Because you will hurt, bitch.

Fork set up: what´s better for dh?

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