Setting Sag the Race Tech Way
Static Sag or "Race" Sag is the amount the bike compresses from fully extended, with the rider on board.
Here's how to measure it the Race Tech way. It is a little different than how you may have done it before but is far more accurate and consistent.
If you use this method your Sag measurement will be consistent within 1mm.
Consult your DVS Custom Setup Sheet or Product Search for recommended Spring Rate, Preload and Sag.
ERROR #1: If your Sag number is way too low (with our recommended spring rate and preload) you are probably using the wrong procedure. More than likely you are taking your first measurement with the bike on the ground instead of off. Using this incorrect procedure you will notice that your Sag number will not change with changes in Preload.
These instructions include the use of a Sag Master as well as a Tape Measure. A Sag Master makes life much easier. Sag is measured directly with no subtracting required.
The Sag Master has a pin on the back. The pin goes into the hollow axle and the tape is extended vertically and locked in to a reference mark on the chassis.
This is why you see the tape starting from the axle instead ot the other way around.
A regular tape measure can be used but it requires a little more math. We will include this.
1- Put the bike on a stand and the wheel off the ground.
Make a mark on the fender or side panel that is close to vertical. Be sure the wheels are the same distance off the ground (many bikes will tilt forward when put on a center stand.)
ERROR #2: Not measuring vertically. If the tape measure is angled the Sag number will be decreased dramatically (measures too low).
Sag Master - Put the pin on the back of the Sag Master into the hollow rear axle. Extend the tape and lock it in so the end aligns with the mark on the plastic.
Note: Do not force the Sag Master body into any particular position. Allow it to go to the top of the hollow axle and let the pull on the tape to orient the body.
Tape Measure - Measure the distance from the rear axle to the vertical point.
This is L1 for a Tape Measure. (It is the end of the tape, in other words "zero", for a Sag Master.)
If you don't have a Sag Master, at least use a metric tape measure. Much easier.
2- On a dirt bike put the rider on the bike in full gear (yes, I know the guy in the picture isn't wearing his) and have them stand on the pegs. The reason for standing is simple - it is consistent. Seats on dirt bikes are very long. If the rider sits on the seat in different locations it will throw the measurement off.
On a road bike the procedure is the same except the rider should be in standard riding position - not standing (the position of the footpegs on different street bikes are all over the place).
The best way to balance the bike is to have the rider grab onto something. (Not leaning against the wall as shown in this pic.)
ERROR #3: Having someone else hold the bike up. It is much easier for the rider to balance the bike by himself rather than fight for balance with the person holding the bike.
ERROR #4:Gripping the bike with your knees or putting weight on the bars with your hands.
Compress the rear suspension slightly (about 15mm - 1/2") and then SLOWLY release it back up - particularly at the end. If there were no drag in the linkage the bike would continue to come up a little more.
ERROR #5: Bouncing up and down on the bike. If you bounce the bike there is no way to tell where it will end up.
3- Sag Master - Read the number to the reference mark. There is no need to subtract since the tape was locked and zeroed at full extension.
Tape Measure - Measure to the reference mark.
ERROR #6: The rider jiggles the bike. If the rider is not still the number may change.
This is L2
If there were no friction in the linkage it would come up a bit further.
4-Lift up on the rear slightly (about 15mm) and SLOWLY let it come down - particularly just before you let go.
If there were no friction it would continue to drop a bit more.
The Stiction Zone - The distance between pulling up and pushing down is caused by friction. We call this distance the Stiction Zone.
Make sure the rider is still. Do not let the rider bounce around on the bike.
See ERROR #5: Bouncing up and down on the bike. If you bounce the bike there is no way to tell where it will end up.
5- Sag Master - Read the number to the reference mark. There is no need to subtract since the tape was locked and zeroed at full extension. Average the two measurements to get the Sag number.
Tape Measure - Measure between the same two points. In this picture we are using a regular tape measure.
This is L3
Stiction Zone - The difference between lifting up (L2) and pushing down (L3) is caused by friction. We call this the "Stiction Zone". The greater the Stiction Zone the more friction there is. If it is more than 4 or 5mm the linkage needs attention.
Sag is calculated by averaging L2 and L3 and subtracting it from fully extended.
Sag = L1 - ((L2 plus L3)/2)
Sag = the original measurement minus the average of L2 and L3
Note: FREE SAG is the amount the bike compresses with the weight of the bike only - no rider. Use the same method as outlined for Sag.