Suspension SETUP, a 'how to' guide...

PB Forum :: Mechanics' Lounge
Suspension SETUP, a 'how to' guide...
Previous Page |
Author Message
Posted: Dec 8, 2008 at 11:46 Quote
INTRO: I explained a while ago to a few people on Pinkbike how to set up their damping and what the different adjustments do; so I figured that perhaps there are a few more people out there who have paid good money for the latest suspension system but don't 'properly' know how to get the most from it - so I took the liberty of creating this thread to explain to the best of my knowledge how to get the most from your product....

___
SAG: How much the suspension compresses under static rider weight - used so that your tyres can follow the terrain and don't leave the ground every time you go over the edge of a bump.

Amount of rear end sag is dependent on frame design (due to how much the rear wheel will move in relation to the shocks movement - ½ shock stroke doesn't always equal ½ travel) and rider preference, manufacturers recommendations vary, but as a rule: 25-30% travel for dh riding and 15-20% for xc/fr; these guideline values also apply for fork sag.

Sag is set by adjusting spring rate and preload [with coil springs], sag can be set with low speed compression adjusted to rider preference, but lockout/limited lockout (aka - propedal/pedal platform) should be switched off.

A: Eye 2 eye length
B: Stroke length

There is information contained throughout this thread for details & instructions on setting your fork & shocks sag - most of the needed info is linked here:
http://www.pinkbike.com/forum/listcomments/?threadid=60436&pagenum=2#commentid1445707
http://www.pinkbike.com/forum/listcomments/?threadid=60436&pagenum=15#commentid2161849

If needing a different spring for your rear shock, here are the links to some shock spring-rate calculators:
TF Tuned spring calculator - for all brands/frame types
Mojo Suspension (UK Fox distributor) - more specific calculator for Fox shocks

___
PRELOAD: Used for fine tuning sag, will also slightly stiffen up your shock throughout its travel.

Spring rate and spring preload should be chosen to give you the correct desired sag, damping should/is used to control the compression from there on. (commonly, frames have tuned & progressive leverage rates too in order to assist the shock in resisting bottoming out/wallowing. Although a linear type leverage rate can effectively be used with a longer stroke and/or higher oil volume shock (eg. Foes) so damping controls all the movement including ramp-up, IMO this method is best when done properly...)

Air springs do not have a preload adjustment as sag can be fine-tuned via air pressure; however, the sag of an air shock with an added air reservoir will be affected by the PSI in both chambers, so altering reservoir chamber PSI after setting sag will affect sag and can be compensated for by slightly reducing main-chamber pressure.

___ _ _
Damping...
NOTE: common speed sensitive damping adjustments effect the amount of resistance to movement by restricting oil flow, not the speed or speed range at which the resistance takes effect. - a factory re-tune would be required for the latter.


___
LO-SPEED COMPRESSION: REDUCES rider induced inputs by restricting initial oil flow.

Low speed damping when set up correctly for DH riding may feel awful when doing 'the car park test', as, if you are riding dh, even braking will cause a faster compression than you pushing the fork down, the speed at which low-speed damping restriction occurs will mostly effect the influence on the suspension of your body movements on the bike, cornering compression and pedal bob/brake dive, but won't effect higher speed compressions like stutter bumps as much [dependent on the products low-speed damping range and gradient of effect].

You will find your best setup after a few trial-and-error runs/rides, the best setting should give you the minimum small bump compliance you are happy with so as to help the fork remain extended as much as possible - this reduces the inertia your damping system has to control and leaves you with more travel for bigger impacts.

___
HI-SPEED COMPRESSION: Adds extra resistance to the forks motion when it compresses quickly to help avoid harsh bottom out.

High speed damping should not be set up around the car park, to set it up will rely on feedback from a travel indicator (lil rubber ring on stanchion) at the end of a run/impact.

It should be tuned to give 'most' [rider preference dictates amount] travel from the BIGGER impacts you'll be hitting; bottom out resistance deals with the final remaining compression (except on some shocks where 'bottom-out adjustment' adjusts reservoir volume [spring rate ramp-up]) - you should get MAX travel (aka: bottom out) on the BIGGEST impacts you encounter.

___
BOTTOM OUT RESISTANCE: Allows high speed damping to be used more 'sparingly'.

Bottom-out resistance is generally only internally or non adjustable if included on forks, most shocks use an elastomer bump-stop for this purpose, it effects the very late compression spring rate curve, or resistance if a hydraulic type is used - it usually isn't affected by compression speed and will always take its effect when the fork reaches near-full compression (position sensitive). - This feature is used as the last resort to stop a harsh bottom-out thud on the biggest hits you encounter, the same way a negative travel spring stops final extension top-out.

Some shocks label the reservoir volume adjustment as 'bottom out resistance', this is partially true, but more accurately this type of adjustment changes the progressiveness of the shock throughout its travel... which ultimately will affect bottom out.

___
RESERVOIR PRESSURE & VOLUME ADJUSTMENTS: Many shocks now ditch nitrogen filled reservoirs in exchange for adjustable pressure air reservoirs. Changing the air pressure has a duel effect of altering the shocks preload and progressivity together, it will also change any pedal platform (aka 'Propedal') threshold too. This duel effect is because air has a progressive spring rate [imagine a curve on a graph getting steeper]. For example; increasing the air pressure in a reservoir will move the start point of your shocks progressiveness further towards the steeper gradient on the spring-rate graph, increasing your initial spring-rate [preload] and making it ramp-up quicker through the shocks travel [more progressive]... and visa versa for decreasing pressure.

Air volume can be adjusted mechanically on shock reservoirs and by altering oil level [within limits] in forks with open-bath damping, again, it adjusts the progressiveness of the suspension - a smaller volume ramps-up quicker [bottoms out less], a larger volume is more linear [uses more travel more often]. Details about balancing shock reservoir pressure and volume together can be found a few posts further down...

___
REBOUND: Rebound force, unlike compression forces, are governed by only one thing - spring pressure. Its best not to view rebound damping as 'how fast your fork extends', but how much resistance to your fork extending there is. Rebound damping can also be used to help maintain bump absorption even when the fork is compressed by effectively reducing the amount of return [opposing] force the spring can apply, this aspect of rebound damping can be further explored with rebound systems that feature adjustable High and Low speed rebound damping.

The setting of rebound damping is largely rider preferential, but it should be set within the boundaries of 'packing up over stutter bumps' and 'kicking the wheel out when cornering'.

Rebound damping should generally be set up to give the fastest possible rebound speed without allowing the wheel to kick out or causing the shock to extend 'too harshly' [top-out]. The reason for this is so that the wheel will always try to return to maximum travel position as quickly as possible but in a controlled manner, thus helping to keep your tyres on the ground and keeping you higher up in the softer part of your travel so you have better stutter bump absorption.

Rebound settings between the front and back of your bike can also be correlated to control the tilt characteristic of your bike when launching off jumps, depending on rider weight distribution, e.g. faster rebound at the back can be used help to pitch your bike forward when going airborne so as to help you land parallel with the transition.

You may also want to increase your rebound damping if you have a frame that suffers from significant pedal-bob so the back end will 'pack down' more under pedalling giving you a firmer, less bouncy shock when you're cranking it - doing this can increase pedalling efficiency in nearly all bikes, possibly at the expense of a more ideal 'terrain mapping' or controlled rebound setting though.

You may also find increasing your rebound damping at the front, if your bike has relaxed geometry, may help with cornering as your weight tends to be further over the back if you have a slack head-angle - increasing the damping may help stop your front wheel 'kicking out' and losing grip when you're lent over in corners.

___ _
Finding the right setting...
Most manufacturers will give 'default' starting point adjustments for all your fork/shock's damping settings, if so, then follow these initially - If you feel the need to tinker or just want to see if you can increase performance, then try [with one damping adjustment at a time] riding with each dial in it's MIN [-] and then MAX [+] setting, see which extreme you prefer the most, then work form there adjusting your damping dial 2 clicks at a time, then fine tuning click-by-click once you get close to your preferred setting.

Remember - a 'generic' setting will not perform at its best on all types of terrain as riding spots vary. Once you become more familiar with what each adjustment on your damping units do and how it effects the ride characteristics of your bike, you will more quickly be able to adjust your fork and shock to better suit each area you ride at - try making a note of what settings best suit each of your fav' riding spots so you can quickly dial in your bike each time you go riding.

There is also a fair bit of info as regards setting up Fox 40's contained in this thread as quite a few people have queried how to get the most out of these forks - have a read through the pages first if wanting any info on setting up these forks, as chances are, your question will have been covered already.

____ _
I have decided not to cover lockout/limited lockout (aka: pedal platform 'damping', threshold adjust e.t.c.) settings here as the alterations to these settings are somewhat far more obvious and will most likely be covered in the users manual for your product, which if you don't have, can generally be found in the tech area on the product manufacturer's website (with some mfr's, relevant 'tech' documents are linked to under each respective product's section on the mfr's website or in their archives, so refer to the web-page of the exact product model you have if you can't find a general 'tech' area on their website). Essentially these adjustments just provide additional preload to the suspension, limiting its movement from pedalling/body movement forces.

Technical links:
Fox Racing Shox
Rockshox
Marzocchi
Manitou
BOS Engineering
X-Fusion
Cane Creek
Elka

____ _ _
Fork & Shock upgrade companies links - if you want to take it to the next level!...:
PUSH Industries
CR1 Engineering
Avalanche Downhill Racing
...any more? msg me if you know of any other 'performance upgrade' companies!



_ _ _ _ _

I'm happy for anyone to usefully add to this or refute what I've put in this post, I hope it will prove a useful resource to any who aren't clued up on what 'all them dials' do!

- LozSalute

Posted: Dec 8, 2008 at 12:41 Quote
Great post!

I'm just going to point out a few things in a friendly way, so don't take offense to this.

When setting sag, just to clear up rider weight, you set sag with your suspension under static load, meaning an unchanging mass. This means you must be in attack position, but slightly leaning on a post or wall to keep your weight even.

When adjusting the preload it doesn't effect the spring rate, it simply compresses it slightly so now it takes a little more weight to compress the next bit, which is no longer the first (however much you compress with preload collar). So say you have a 400lb spring, this means that it requires 400 pounds of force to compress that spring one inch, 800 for two inches and so on (may be slightly off with the second inch number, correct me if I am). So since you have cranked the preload collar in a bit, it no longer takes 400 pounds to compress the shock the first inch, the proload collar is faking the spring into thinking it is already into its travel.

Your description of the damping systems is one of the best that I have seen from a fellow PB member, but I would just like to make it clear that damping does not make the fork/shock stiffer, it slows either the compression or rebound via hydraulic resistance. If you set your sag with all compression damping full soft, then crank everything full hard, you will still have the exact same sag, however the faster hits do not give the fork enough time to compress due to the added hydraulic resistance. Again, it is a matter of faking the fork or shock into thinking something is different than it really is.

Posted: Dec 8, 2008 at 12:55 Quote
thanks for adding!tup - I agree with what you're saying!...

I've found some damping systems may slightly affect sag near their 'extreme' settings, so I mentioned that part just in case.

- and thanks for clarifying the preload part - I got my wording wrong, it doesn't change the rate (that will still be the rating of the spring), it shifts the start point of that rate

Salute - I've altered the wording now to accommodate the bits you've mentioned! - Loz

Posted: Dec 8, 2008 at 13:55 Quote
ctd07 wrote:
thanks for adding!tup - I agree with what you're saying!...

I've found some damping systems may slightly affect sag near their 'extreme' settings, so I mentioned that part just in case.

- and thanks for clarifying the preload part - I got my wording wrong, it doesn't change the rate (that will still be the rating of the spring), it shifts the start point of that rate

Salute - I've altered the wording now to accommodate the bits you've mentioned! - Loz

Bingo, that's pretty much exactly what I was saying there accept a WHOLE lot shorterSalute

Posted: Dec 8, 2008 at 14:18 Quote
Salute

we need more threads like this and stickied so people can help others when asking how to's.

Posted: Dec 8, 2008 at 14:34 Quote
This is good - well written, factually correct, and easy to understand. Nice job!

Posted: Dec 12, 2008 at 6:18 Quote
I'm going to go ahead and sticky this, if any of the staff have any objections feel free to PM me. Nice guide!

Posted: Dec 12, 2008 at 6:38 Quote
gabor wrote:
I'm going to go ahead and sticky this, if any of the staff have any objections feel free to PM me. Nice guide!

Salute

Posted: Dec 25, 2008 at 20:27 Quote
deliciously nerdy!
subscribed.

Any tips on a dhx 5.0 (coil or air)? I've always wondered what are upsides/downsides to the size of the boost valve chamber and/or the pressure in it. It seems to me (from riding one) when you run a larger chamber with high pressure you get a more linear bottom out resistance? Is this true? Or am I talking out my ass? And if that's so, what would be the advantage to running a smaller chamber (aside from possibly more bottom out resistance?)

Posted: Dec 26, 2008 at 5:15 Quote
EDITED:

you're pretty much dead on
check here for Fox's explanation of the DHX system.

The chamber size (adjusted by turning the bottom out resistance plug) affects the rate of increase of the spring rate - the pressure in the reservoir basically affects the start point of that rate, and contributes to the initial and overall 'stiffness' of the shock.

Having a larger volume with a higher pressure will give you more mid-range compression resistance too because, as you stated, the resistance is more linear.
- a better setting for faster flowy trails

Having a smaller volume with a lower pressure will allow you to use your travel more often [better small bump sensitivity] and still have resistance against big hits.
- better for slower bumpier 'tech' trails

Done properly (by adjusting the reservoir pressure in relation to the reservoir volume), both setups would require the same amount of force to reach bottom out, just one way would have more mid range resistance.

The effect of the of the propedal may also become slightly more noticeable the higher the pressure inside the reservoir, as by increasing the reservoir pressure you will slightly increase the shocks 'preload' too. This could be compensated for by slightly reducing your main-chamber pressure/preload; or by slightly reducing your propedal effect [not an option with newer DHX air shocks, which just have an ON/OFF switch].

Posted: Jan 1, 2009 at 4:57 Quote
question,what spring rate should i use? im 160lbs. using a giant glory dh with a fox dhx 5.0,im currently using a 450 spring rate which is kinda stiff

Posted: Jan 1, 2009 at 5:11 Quote
dhwows wrote:
question,what spring rate should i use? im 160lbs. using a giant glory dh with a fox dhx 5.0,im currently using a 450 spring rate which is kinda stiff
heres are some useful calculators, the mojo website is probably more accurate for Fox shocks
Mojo
TF Tuned

Posted: Jan 1, 2009 at 6:42 Quote
nice one! thanks!

Posted: Jan 1, 2009 at 11:42 Quote
Hi, I have a question aswell. I have a keewee chromoeight and I dont know what the name of the suspension design is because its an unusual one. this means that I cant use a spring rate calculator. I weigh 200lbs and have a fox vanilla rc shock, can anyone help me with the spring weight i need?
cheers.

Posted: Jan 1, 2009 at 12:19 Quote
AirForceOne wrote:
Hi, I have a question aswell. I have a keewee chromoeight and I dont know what the name of the suspension design is because its an unusual one. this means that I cant use a spring rate calculator. I weigh 200lbs and have a fox vanilla rc shock, can anyone help me with the spring weight i need?
cheers.
Its a basic single pivot with a linkage to 'displace' the lower shock mount so as to maintain the desired wheelpath whilst also keeping the shock position and therefore CoG low.

For the Mojo calculator [which I'd recommend for Fox shocks as I don't think the DHX shocks use the same damping system as other shocks] you don't need the linkage type, on the TF Tuned website, I'd go with the single pivot option.

- Nice bike btw!tup

Previous Page |

 
Your subscriptions
no posts

Copyright © 2000 - 2014. Pinkbike.com. All rights reserved.
dv92 0.016176
Mobile Version of Website