suspension explained page1

[indie]

ok bear with me i couldnt post this all on 1 page so 3 will do

DAY 1 - What is “suspension” all about?

Your bike suspension is designed primarily to absorb the imperfections in the roads, and ensure that tyres keep contact with the roads. Most bikes suspension are based on a spring like you would find in a pen, mattress or trampoline but much stronger. To stop the spring from bouncing the tyre like a yoyo; the rate the spring moves up and down is controlled by “dampers”.

Dampers are “like oil filled bicycle pumps”. The pump will move faster or slower depending on the size of the hole the oil is being pumped through and the thickness of the oil. All bikes have both a spring and dampers. My bike has the spring on the outside of the damper on the rear wheel (called rear shock) but the front wheel suspension has the springs within the dampers hence you cannot see them. They are called the front forks.

The suspension for your front wheel is independent from the back wheel and can react differently to road and riding conditions.

Where did I start?
Before I touched the bike, I located the handbook for my bike as supplied by the manufacturer. The handbook contains details on what can be adjusted and where on the bike the knobs and screws are for setting up your bike front and rear suspension. Also it details the manufacturers recommended suspension settings for your bike. If you have aftermarket (third party) suspension, contact them.

Depending on your bike you may be able adjust some, all or none of the following

* Preload (Spring tension, based on your weight)
* Damping (speed the spring squashes and returns to normal )
o Compression (advanced damping control, speed the spring squashes)
o Rebound (advanced damping control, speed the spring returns to normal after been squashed)

Note that compression and rebound are part of damping.

After I had established what I can adjust on my bike and how to adjust it, I got a pen and paper and wrote down my bikes current settings so that I can return the bike to it if I make a mess of things. On my bike, this meant counting “clicks” as I turned the screws for the compression and rebound clockwise or anti-clockwise. Preload is easier to note and record as you can see what “notch” the rear spring is on and what “ring” the front is on.

The manufacturer has spent a lot of time and money on research and development and they have a financial incentive to ensure that my bike handles well, therefore the manufacturers recommended suspension settings for your bike will not be that bad. Compare what your current settings are for your bike against the manufacturers setting. If they are different, and you think your bike could handle better, have a go at setting your bike to manufacturers recommended settings.

You should be able to fiddle with your suspension and bring it back to the settings recommended by the manufacturer or your original setting before you go any further. Do not read any further unless you are competent with the above and acknowledge that this whole article is purely for information only. Please do not fiddle with your bike, then injure yourself and then blame me.

DAY 2 - SET UP BIKE TO YOUR WEIGHT (PRELOAD)

To set up your bike you will require the proper tools as recommended in your bikes handbook, usually a long screw driver, spanner for the front and a funny looking tool for the rear preload and tape measure!!. You will need patience and time. It is best to set the bike up where you are most likely to use it i.e. on the roads or race track.. Ensure your bike is in good working condition, including replacing dodgy fork seals, lubricating linkage, and changing fork or shock oil and you have correct tyre pressure . If you are unsure of your tyre pressure and it is a track bike use 32psi front, 30psi rear.

Twiddling with setting randomly will not get you far. You suspension can be broken down to the following

* Front wheel
o Preload
o Damping Compression
o Damping Rebound
* Rear Wheel
o Preload
o Damping Compression
o Damping Rebound

If your bike does not have some of these setting then you will have to compromise on the setting of your bike or buy aftermarket suspension if necessary. You really should set up your bike in the right order. It is best to start with the preloads, front and rear as this is based on your weight and relatively easy to set up, then work your way down.

Rear Preload
Whatever your weight, when you sit on the bike, you want the bike to squat just a little bit (about 30mm) but not too much. You want to ensure that the bulk of your rear suspension travel is available for when you actually ride the bike as opposed to supporting your heavy frame. At the same time you should have a little bit of sag left. If the bike drops too much then increase preload and if you are very light and the bike barely moves under your weight, then soften the preload.

Below is a more detailed explanation. This is easy to set up but can be a bit confusing so just follow the steps one at a time.

Step 1


Step 2


Step 3


Step 1: First find the fully UNLOADED length of your rear suspension. Put your bike on its centre stand. If you do not have a centre stand find a means of lifting the rear wheel up under the engine so that there is no weight (including the weight of the bike) on the rear axle and wheel. Measure the distance between the rear axle and a fixed point directly above like a bolt or mark. Note this measure measurement. Do not use a rear wheel bike stand as there is still the weight of the bike on the swing arm.

Step 2: Find the NORMAL length of you rear suspension. This is amount the suspension drops under the weigh of the bike alone without the rider. Put the bike on level ground and bounce it up and down to free any stickiness. Measure between the same two points as above, i.e. the rear axle and the fixed point directly above.

Step 3: Find the fully LOADED length of your rear suspension. This is the length of the suspension with the rear wheel on level ground and the rider seated on it in his normal riding position in full biking garb. First bounce up and down on the seat to loosen the suspension then get into your normal riding position with all weight on the bike and both feet on the bike. To prevent yourself from falling of (if you have not already) lean the bike against a wall and get your mate to measure between the same two points as above i.e. rear axle and the fixed point directly above.

Next thing is to understand a couple of buzz words. “Static sag” and “Rider sag”.

RIDER SAG is the difference steps 1 and 3. This is the amount the bike drops when your heavy arse sits on the bike.
STATIC SAG is the difference between step 1 and step 2. it is how much the bikes weight acts on the rear suspension or how much you can lift the bike rear without the rider on it before it tops out.
A top racing suspension company suggest that rear wheel rider sag should be around 30-40mm and static sag should be around 5-10mm. However this many vary depending on your bike and manufacturer. The more rider sag you have, the softer the bike suspension will be. I personally use 35mm for road and a few track days use.

Therefore if your rider sag is less than 30 mm then your preload is too hard, if it is more than 40 mm, then it is a bit soft. Once you have set your rider sag as close as possible to 30-40 mm, next check your static sag. If you have more than 10mm then you may need stiffer springs. If however, if your static sag is less than 5mm or you have no static sag then your springs may be too hard for your weight.

If you have to compromise then try to have at least a bit of Static sag in order to stop the bike from topping out.


QUOTE
Note that books, videos, media and pub acquaintances will all have different opinions on the naming and figures quoted above (and below). I find that I get fewer complaints with the current labelling system than I would with other labelling systems.

Avoid being obsessed with numbers and naming systems. I will try to explain the underlying principles of setting up your own bike. There are too many scenarios and permutations surrounding the effects of tweaking each setting that it would take me forever to cover them all. Therefore I will only touch on a few of the more common effects.