Before you even begin to tackle the tough job of dialing in suspension, you need to know what type of riding you will be doing. Whether its trail, MX, TT, desert, or woods racing, proper suspension will make you faster or allow you to ride longer with out getting tired. After you have decided which type of riding is most important to you, you can start to set up your quad's suspension to best suit you weight, ability, and the terrain.
When setting up your suspension a good place to start are at the A-arms and swing arm. There are lots of good (over priced) aftermarket brands to choose from, but the real decision is what width A-arms and length swing arm do you need. Your probably wondering what wider A-arms do, and do I need? At most racing events there is a set width limit that your quad can be(usually 50''
. They measure the quad from out side of your front wheels. In MX, TT, and desert you want to be at the limit, because the wider the front is the less roll you will have, and it also creates more control and stable ride. But if you are riding XC or trails that have trees, you are going to need shorter or stock length A-arms so that your quad will be able to fit between the narrow areas that the trees create.
The swing arm is also a major part in setting up your suspension. A longer swing arm from 1 to 2 inches longer will give you better straight-line stability but will take away traction under acceleration. A shorter swing arm is good for TT racing or hard packed, slick MX track. You would use the longer swing arm if you have plenty of traction and especially if you race desert or off road, where you need straight-line stability.
The wider aftermarket A-arms and a longer swing arm also create a better controlled suspension travel and more adjust ability. When purchasing wider A-arms it will be recommended that you replace your standard shocks to help the performance of your quad. Reason being is the geometry and shock mounting points of the new a-arms will not work with a stock length shock. The A-arm and swing arm manufactures will also recommend the length and travel shocks that are right for you and your quad.
What is Next
First start wit the ride height (sag) of your quad. This measurement is taken on flat ground, with the rider in full gear sitting on the bike in normal position. It is very important that the rider always sits in the in the same spot on the bike while taking the ride height, or each time you check it will be different. Also try to have about the same amount of gas in the tank. Now measure from the ground to the bottom of the frame, either in front or behind the foot pegs. Just make sure you measure it from the same spot every time. To raise the ride height you will need to tighten the spring pre-load adjuster to put more tension on the spring. To lower the ride height you will need to loosen the spring pre-load adjuster.
Most manufactures have different ways to do this. Some have a threaded collar (or large thin nut) that you can twist to increase or decrease pre-load. Some have a whire clip that slides into groves in the shock body. Here you would raise or lower the clip into a groove to make the adjustment. No matter which is used, the job is much easier if the quad is jacked up and the shocks are free of dirt.
Setting the Ride Height
TT racing - 4-6 inches
MX - 6-8 inches
Trail riding - 7-10 inches
Desert - 8-11 inches
If the track or course that you are on is smooth with out big jumps, you want your quad low to the ground, so that the quad can turn well. But when the quad is low it will not take jumps or bumps as well. If the track is rely rough, then raise the quad up so that it can handle those conditions.
There has to be a balance between turning the quad and handling the track. 1 inch of ride height change can make a difference. This is something you need to experiment with. You should bottom lightly at least once each lap on the track or else your not using the full travel of your shock. You don't want to bottom hard though which that will wear out parts faster and you.
If you are going to use the stock a-arms, swing arms and shocks, the factories typically set a quad up for an average rider who weighs 165lbs and rides a variety of terrain. All quads, every make or model, have different spring rates, because of the different leverage ratios on the shocks. This is because of different sized A-arms on the front, and swing arm lengths also differ greatly.
The spring rate is how strong the resistance is when a spring is compressed. We rate springs in pounds, when a spring is compressed one inch and the force is 300 lbs then the spring is a 300lb spring. A lot of springs are rated in kg/mm (metric). So to convert a 300lb spring into metric you would divide the pound rating by 55.88 or if you want to convert kg/mm (metric) to lbs you would multiply the metric by (55.88=5.4 kg, x 5588=300 pounds.
Spring rate is a very important part in making your quad handle. So by working to achieve the correct ride height measurements, you will find out you need a stiffer or softer spring. If the spring preload is adjustable, you would ultimately like the adjustment mark to end up in a middle position so there is room for adjustment either way.
The stacked springs make a progressive spring rate. All springs get progressively stiffer when compressing through its stroke, but they have a level progression. A progressively wound spring starts off softer and then gets a lot stiffer that a straight rate spring. When using the multi spring stack you can adjust where the progression changes through the stroke. When you use a normal progressive spring, the progression is set and cannot be changed. Also with the multi stack springs you can have crossovers to fine-tune your spring even more. The crossover change the point of progression. Crossovers are the spaces that are stacked on the shock body between the springs to change the bottoming point of the short springs in the spring stack.
Generally when you have a three stacking stack the 2 short springs are softer than the bottom spring. So if you have a 3 spring stack one long spring and 2 short springs, and do not use crossovers, you will have a softer rate. This happens because the short springs are allowed to use their full stroke, which gives you a softer spring rate. The crossovers really help you tune your springs progression. Changing the crossover by 1/8 inch make a big difference. This is also something that you need to experiment with.
What to Look For
Remember that you use the spring's pre-load to set the ride height. Spring preload also stiffens of lightens your spring rate. If you find the ride height you want but keep bottoming you should use a stiffer spring.
But if you use to stiff a spring your quad will not transfer the weight properly and you will lose traction and also have a rough ride. And if you springs are to soft then the bike will have excessive bottoming and to much body rolling (feels like all the weight is on 1 front shock). There is not a perfect setup that will work for everyone. The aftermarket companies that you buy your suspension from will get you in the ball park, but you will still need to tune your quad to best suit you.
Setting the Adjusters
When setting the compression adjuster, remember that this is basically your low speed adjustment. On most of to days shocks the high speed adjustment is only changed internally. The compression adjuster is generally located at the top of the shock or on the reservoir. You want to turn this in as little as possible. The further out, the softer the ride will be and the more traction you will get and the more the wheels will stay on the ground. How ever, to handle constant bumps like desert or rough woods riding, it may be necessary to use a stiffer setting. Never keep the dial all the way in as it may cut off oil flow.
Remember the faster you get from one bump to the next, the faster you want to rebound. For example on a flat MX track with the occasional jump, you can go with a slower setting to keep the quad low in the rear for better traction. For a whooped-out road or rough trail, you need quicker rebound to reset the shock for the next compression stroke. If you quad doesn't rebound before the next bump, it wont be using all of its travel. Do this bump after bump and the shock will pack up and the shock will stop moving. Also if you quads shock packs it will kick side to side.
However if you rebound is set to fast it can cause the quad to kick off the face of the first bump it hits. So again this is an area that has to be experimented with every time you change terrain you ride in.
So with any suspension changes you will have to spend time adjusting all of the components of the shock to get the right balance for your riding ability and terrain..