Suspension Basics

[Bibio]

I am in no way a suspension guru/specialist and every single thing I have written has been information gathered from various places thought the internet and personal conclusions. If I have made any mistakes and or you have information that will help our community the please feel free to correct me and or add to this information. Hopefully we can all benefit each other by gathering our knowledge in one place for future reference.

Foreword.
There is no do it all suspension settings. How you ride and with what determines the settings you use, for instance if you mainly ride 2 up with luggage then set your bike up for this or if you mainly ride solo on roads with bad surface then set up for that. Another thing is that you cannot use your mate’s settings as every single person has a different riding style, height, weight and sitting position.

Taking the required measurements in this guide is pretty difficult by yourself so my suggestion would be to get a group of you and your friends together and have a suspension day. The only tools required assuming that you have the correct springs fitted are c spanners for your rear shocks a flat bladed screwdriver to twiddle with the clickers, sockets to fit the tops of your forks to turn the spring adjuster a measuring tape, some masking tape and a notepad.

[Bibio]

Part 1. Springs
The springs in your suspension are there to support the weight of you, your pillion (if you ride with one), luggage (if you have any fitted) and the bike. If the springs on your bike are too soft then your bikes suspension will always bottom out if they are too hard then your bikes suspension will always top out.

You are never going to get your suspension set up properly without first getting the correct springs. Fitting the correct springs for your bikes use is vital as it allows your suspension components to work in the desired range. You are looking to use as much suspension travel as possible without topping or bottoming out your suspension under every day use.

If you’re not prepared to get the correct springs for your bike then read no further as the information will be of no use.

[Bibio]

Part 2. Sag
Having the correct springs is vital but having them working in the wrong part of your suspension travel is useless this is why you must set the bike/rider sag settings as this ensures that your bike is using the correct part of your suspension failure to do this will be like having the wrong springs in that again your suspension will either top out or bottom out. There is no hard or fast rule to this setting but you must allow enough travel in either direction so in daily use your using as much travel without hitting the extremes. You can set your sag roughly using the information below but only road testing will ensure that it’s correct.

Setting your sag.
You have to set your sag with everything you use in daily riding. For instance you must be fully kitted up and sitting in the position you ride in. if you ride with a pillion and or luggage then they/this must also be on the bike when making the measurements. You will need the help of another person to note down the measurements. You can take notes of different circumstances for future reference, for instance if you mainly ride with a pillion but occasionally ride solo then take down both adjustments so you can quickly set up the bike for a given use.

When taking your rear sag measurements use the same datum for all measurements if you don’t have a decent spot then create one using a piece of masking tape as close to straight up from your rear spindle as possible. For the front measure from the bottom of one suspension leg to the top of the dust cap where it meets the fork leg on upside down forks and from the bottom of the bottom yoke to the bottom of the dust cap where it meets the fork leg on conventional forks.

It’s pretty impossible to take these measurements without the help of a second/third/fourth person during the measuring process so if you ride solo then get a friend to help. Your pillion if you ride with one will need to be present and fully kitted up and if you have luggage this will also need to be fitted and filled with contents. Your looking to take measurements from how you most use your bike and from there you can then reduce the number of things to get different settings.

Raise the rear of the bike off the ground and note down the size then raise the front of the bike off the ground and note down the size. These sizes are free length of your suspension and from this you can set the sag. An ABBA superbike stand is perfect for this but if you don’t have one you can use the side stand but be careful if you do.



With the bike on the ground sit it upright off the side/centre stand and bounce on the front and rear of the bike a few times to settle the suspension then note down the sizes using the same markers as before. If you mainly ride with luggage then make sure that it’s fitted and with it’s daily contents present. Your looking for a bike sag measurement of 5-10mm of rear sag and 25-35mm of front sag so go ahead and set it to that.



This is the tricky part. You now need to sit on the bike in your riding position with your feet on the pegs and off the side/centre stand your pillion if you ride with one also needs to be on the back and sitting with their feet on the pegs. To do this sit the bike next to a wall and stick your elbow out against the wall to steady yourself and the bike. Ideally you would like another person to hold you in that position and another to take measurements. Your looking for a rider sag measurement of 30-40mm of rear sag and 35-45mm of front sag. If the measurements fall outside of this range then you most probably have the wrong springs for your needs.



< now go back to setting your bike/rider sag with different scenarios and note down how many turns you use for each one that way if you usually ride with a pillion but fancy a ride by yourself then its just a quick turn of the preloads using your settings and off you go and if you feel you have to make any adjustments to your dampening settings while your out then note these down also for the next time >

if all has went well and your measurements have fallen in the correct sag measurements then the next thing to do is put a cable tie on one of your front fork legs just loose enough to be able to slide up and down but stay in position then slide it up against the dust cap. Next take a small piece of blu tack and stick it on the bump stop of your rear shock.

[Bibio]

Part 3. Dampening
Now that you have set your sag it’s time to start turning those clickers. If you have basic suspension your pretty stuck and will find it difficult to dial in compression or rebound but it can be done using thinner/thicker oils and opening/closing the bleed holes in your front suspension. If you have a basic rear shock with no dampening adjusters then your well and truly stuck and the only thing you can do is upgrade your shock to a better one. I’m not going to go into describing how to modify your damper rod suspension forks and will leave that to those suspension guru’s out there to advise you better.

Dampening rate can either be Hard (slow) or Soft (fast) or anywhere in between. Do not confuse this with making your suspension hard or soft as it’s a method of controlling the rate at which the spring is controlled in its movement and nothing more.

I’m not going to even attempt to explain the shim stacks and valves in cartridge type forks and rear shocks but mention that there are two types of dampening within them which are Fast and Slow rates the fast rates control sudden bumps and let more fluid pass by valves at a higher rate while the slow rate controls chassis movement.

Rebound.
Rebound dampening is the control of the spring in a downwards motion. Too much dampening will stop the spring from returning quick enough and too little will make it return too fast. Your looking to set the dampening just enough that the spring is controlled so there is no over shoot but still allow the spring to return quick enough to stop packing down.

Turn both rebound adjusters (if you have two) to full hard so they are lightly seated at there full travel then mark that position with a marker pen adjacent to and as well as the slot on the adjuster this way it gives you a indicator then back them off 1 full turn towards soft or if you have the clicker kind count the clicks and note them down.

Sit on the bike and grab the bars then pull up on the bars then push down with as much force as you can then allow the forks to come back up without pressure on them, it takes a bit of practise to get right but patience will reward.

Your looking for the motion of your front forks as they rise back up. If they come up slowly and stop abruptly then decrease the rebound adjusters (go softer) by 1 full turn. Remember to do both adjusters if you have one on each leg that control rebound. Then repeat the bounce test. Your looking to set the rebound just at the point where the forks rise up then stay there and just after the point of overshoot. So you bounce till your forks come up then go down again then add (1/8th of a turn) 1 click towards hard till they stop going down again after the bounce so they come up quick enough but without overshoot.

The rear is slightly harder to judge but is the same principle as the front but to make it easier get someone to sit on the bike while you bounce the back and watch for the point of overshoot then wind back till gone.

Compression.
Compression dampening is the control of the spring in an upwards motion. Too much dampening will stop the spring from compressing quick enough and too little will let it compress too fast. Your looking to set the dampening just enough that the spring is controlled so there is no undue movement while compressing. For instance your wheel hits a bump in the road and you don’t have enough compression dampening, it will continue to compress after it has hit the bump as there is nothing controlling the force on the spring so your wheel ends up leaving the road surface till your rebound takes over and returns it back on the road surface.

I personally find compression adjustment a nightmare to set statically so i resort in riding the bike to get it somewhere I like.

Fortunately there is help at hand in the form of your tyres. Compression and rebound problems can manifest themselves in very telltale signs in the tread pattern of your tyres. I will admit that this is where I’m still learning the art of reading tyres but from the information I have gathered it seems that there are distinctive wear patterns that emerge to help us diagnose problems. I’m going to leave cold and hot tear out of this and concentrate on just the basics of suspension signs in tyres.

The picture below is of an Avon Storm Ultra 2 tyre and is taken off the internet via Google images. The red arrow indicates the direction of travel, the green curved line indicates what I’m going to call the leading edge of the tread pattern and the blue curved line is indicating what I’m going to call the trialling edge of the tread pattern.



There are two distinct types of wear that arise from suspension problems the first is chamfering and the second is ridging. Chamfering looks like the edge has been worn away and ridging looks like a ridge sticking up on the edge.

I’m more than likely wrong with this but to much compression chamfers the leading edge. While to much rebound ridges the trialling edge. If this is correct then I would presume that these signs would disappear once the correct dampening is dialled in.

Fast compression adjustment or rear shocks is the dampening control when hitting sudden bumps. Its not to control how the shock acts at high mph speeds. So only adjust this if you find the rear a bit vicious hitting sudden bumps like raised and over painted rumble strips. Be careful of this though as it can cause your shock to blow by to much fluid resulting in loss of dampening.

[Bibio]

Part 4. Inspection
Once you have made all the necessary adjustments and after several rides check where the cable tie is on your front forks and if the blu tack has any marks on it from your rear shock bottoming out. Your looking at using 7/8th’s of your front suspension travel keeping an 1/8th in reserve if it’s not then add or subtract some preload. Same goes for the rear but it’s a bit more tricky to judge so if the blu tack looks like its been squashed lots then add a little preload if it’s not been touched try having a look at the damper rod for an indication to how much travel it’s using and subtract some preload if needs be. Then inspect your tyres for the telltale signs of dampening problems and adjust as necessary.


As I said right from the beginning I’m no expert so if you know better and would like to correct me then by all means do so or if you have any other knowledge that you would like to share on the subject then please do.

Please excuse any spelling or grammar mistakes as I’m stupid.

Must have taken you bloody ages! Thanks. A really good starting point in getting to know about suspension. I'm sure some of us will find this info very useful.

[yorkie_chris]

Overall a very helpful series of posts mate, I hope I don't seem rude by questioning a few points.

Originally Posted by Bibio

Part 1. Springs
The springs in your suspension are there to support the weight of you, your pillion (if you ride with one), luggage (if you have any fitted) and the bike. If the springs on your bike are too soft then your bikes suspension will always bottom out if they are too hard then your bikes suspension will always top out.

Remember with the pointy rear, and with any fork, which are by nature progressive. The pointy rear due to linkage geometry, and forks due to air gap.

This gives rise to a harsh feeling if springs are too soft. As you get into the progressive area and it becomes very stiff. This combined with the rapid extension allowed by weak rebound damping exaggerates the harshness.

Originally Posted by Bibio

Fast compression adjustment or rear shocks is the dampening control when hitting sudden bumps. Its not to control how the shock acts at high mph speeds. So only adjust this if you find the rear a bit vicious hitting sudden bumps like raised and over painted rumble strips. Be careful of this though as it can cause your shock to blow by to much fluid resulting in loss of dampening.

On most shocks with HSC damping adjustment the adjuster is preloading some pop-off valve on the reservoir. The vast majority of flow work is done by the piston, so no matter what you do with the adjusters you will still have most of the HSC intact. HSC clickers are a very fine adjustment tool but by going too far soft with it you may make the LSC bleed (in the middle of this lot) ineffective as all the fluid can bypass the LSC needle easily.


I would also argue that you emphasise the tyre reading a bit too much and that damper setting is done more by feel. Reasons being tyre wear can take a while to manifest itself, so how do you know your twiddling was in the correct direction.


My own take on it, bear in mind these feelings are FAR more evident when having a strong damper which has enough adjustment range to get wrong!

Rear rebound, the way I set this is to find a nice smooth corner. When rebound is too loose you will experience wallow, this feels like the shock is pumping up and down, actually quite hard, maybe twice a second. It can feel like the tyre is letting go a bit. You can attempt these corners a few times dialling in a bit more rebound each time. You should be able to feel the wallow lessen in intensity as the wheel gets brought under control.
Dial in enough to #just# get rid of this. You still need it to react fast enough, see below.

Rear rebound too hard, the best way to see this is on a corner with many small ripples or bumps. If it is too hard you will get the feeling of sliding. This is because the suspension deflects upwards on a bump, the tyre then cannot come down to meet the road, so the whole chassis drops into the bump... but drops #outward# in the corner giving the oversteer feeling. It's very unnerving.


Rear comp is harder, it's a far more subtle adjustment and getting the rebound right is far more important. Owners of single clicker nitron and hagons don't bother... just use that one clicker to get the rebound right. If you try and chase both settings with one adjuster it doesn't work.

If the rear comp is too soft, on the rear being affected by a bump, or by rolling on the power, the rear drops, this rakes the forks out and makes the bike feel like it is going straight on despite maintaining lean angle.

If too hard, it will feel like it's lacking grip and spinning up easily. But like I say this adjustment is subtle, it's important for riding fast but it's not the night and day difference that rebound gives.

[Bibio]

@ Runako. not really m8 it was just stuff i had in my head. for me the problem was putting it on paper due to the type of dyslexia i have.

@ Y_C. no rudeness involved and is exactly the kind of thing i'm looking for people to add.

Good effort then!

Been meaning to do all of this for ages but need some dry weather/people. There's and absence of both down here to help even set the sag. I fear I will have to refer to this knowledge (for the most part) next year when there's a better guarantee of both. But I'll obviously come back to this thread as and when.

Thanks both.

God job bibio, should be made a sticky, maybe there will be a small reduction in a lots of questions that look the same, next time you're down at the pub buy yourself one from me and give yourself a clap on your shoulder.

Just wanted to put a few things on the list, they should be the first things to sort before the suspension tips:
Steering Head Bearings must be in tip top shape, front and rear wheel aligment must be spot on, wrong chain tension can effect the rear damper, and tyre pressure also needs to be correct, if any of these are not 100% the suspension will never be 100% either.