General Guide to Setting Static & Loaded Sag - Suspension
Posted: Mon Aug 12, 2013 12:28 am
I used this as reference when setting up mine and I was blown away by how good the results were. I did it on my own (ie. no extra hands to help as suggested). I tied string around fork tubes to measure front, and for the rear set up a height scale using clamps, a bit of rod and a metre rule.
Article quoted from www.TRXuk.TRX850.com:
STATIC SAG
The one main thing that most suspension articles miss is the most crucial - setting the sag correctly.
The sag range will be the same for everyone but some will find that they need to change springs to get
into the right range. Race bikes, generally, need harder setting than road bikes as they ride on smoother
surfaces. Road bikes have a huge range of dips, bumps and potholes to cope with so need to set slightly
softer.
Most people will have different preload settings, thanks to differing weight but all will need to be in the
same range for your suspension to work at it's optimum range, namely it's middle third.
Without the sag set right the damping will never be able to work at it's best, as it will be trying to
overcome the effects of a badly set spring. Don't forget that your pride and joy has been designed to work
with a hugely varying type of rider on board. It has to cope with very heavy riders to very light riders.
Aggressive riders to steady riders and all points and weights in between. Basically it's a compromise.
It's amazing that people will spend hundreds, even thousands of pounds on suspension components and
twiddle with them all day and night but never take the time to set the sag correctly and never get the bike
handling any better!
So what is sag? There are two types;
• Static : the amount the bike settles under it's own weight.
• Loaded : the amount the bike settles with a rider on board.
You need to set both the static sag AND the loaded sag, just doing one or the other is only getting half the
story. To do this you will need.
• A tape measure.
• A pen and paper.
• Tools to adjust the front and rear preload.
• Three strong friends.
Setting Static Sag
Setting the static sag is easier than the loaded but it will still need a set of strong hands to keep the bike
off the floor while you take your measurements.
Front
1. Lift the front of the bike off the floor using the same side stand method. Measure from the bottom yoke
to the top of the stanchion. This is measurement A.
2. Drop the bike back onto two wheels and take the reading again. This is measurement B.
3. Subtract measurement B from A. This is your front static sag reading. Keep a note of it just in case you
want to change it back. Ideally you are looking for 10-20mm on a race bike and 20-25mm on a road
bike. Either compress the spring or loosen it off to get in this range.
Rear
1. Lift the back wheel of the bike off the floor by pulling the bike over on its side stand.
2. Measure from the centre of the rear wheel spindle to a point on the tailpiece that is directly above the
spindle. (Mark that point on the tailpiece for the future reference)
3. Write down the measurement and call it reading C.
4. Put the bike back down on it's wheels and hold it upright. Let the bike settle under it's own weight.
Measure the distance from the spindle to the tailpiece. This is reading D.
5. Subtract D from C and this is your rear static sag. Keep a note of it just in case you want to change it
back. Ideally you are looking for 5-10mm on a race bike and 15-20mm on a road bike. Either compress
or loosen off the spring to get into this range.
Loaded Sag[/u
]Now to take into account the rider's weight. Sit on the bike and have one friend steady the front, one
steady the back and the other ready to measure. Sit the bike upright. Now WITHOUT touching the front or
rear brakes bounce up and down a few times in the seat and then assume your normal riding position.
Front and Rear
1. Measure the front of the bike as for measuring the static sag. This measurement E. Subtract E from A
and try to obtain 25-35mm on a race bike and 35-50mm on a road bike
2. Measure the rear of the bike using the same mark as previously. This is measurement F. Subtract F
from A and this is the rear loaded sag reading. Try and get between 20-25mm on a race bike and 30-
40mm on a road bike by adjusting the preload as before.
If you can't get in these ranges for BOTH Static and Loaded then you will need to change the spring for a
harder or softer one. Harder if you're outside the range and softer if you are inside the range. Now go and
ride and feel the difference!
Article quoted from www.TRXuk.TRX850.com:
STATIC SAG
The one main thing that most suspension articles miss is the most crucial - setting the sag correctly.
The sag range will be the same for everyone but some will find that they need to change springs to get
into the right range. Race bikes, generally, need harder setting than road bikes as they ride on smoother
surfaces. Road bikes have a huge range of dips, bumps and potholes to cope with so need to set slightly
softer.
Most people will have different preload settings, thanks to differing weight but all will need to be in the
same range for your suspension to work at it's optimum range, namely it's middle third.
Without the sag set right the damping will never be able to work at it's best, as it will be trying to
overcome the effects of a badly set spring. Don't forget that your pride and joy has been designed to work
with a hugely varying type of rider on board. It has to cope with very heavy riders to very light riders.
Aggressive riders to steady riders and all points and weights in between. Basically it's a compromise.
It's amazing that people will spend hundreds, even thousands of pounds on suspension components and
twiddle with them all day and night but never take the time to set the sag correctly and never get the bike
handling any better!
So what is sag? There are two types;
• Static : the amount the bike settles under it's own weight.
• Loaded : the amount the bike settles with a rider on board.
You need to set both the static sag AND the loaded sag, just doing one or the other is only getting half the
story. To do this you will need.
• A tape measure.
• A pen and paper.
• Tools to adjust the front and rear preload.
• Three strong friends.
Setting Static Sag
Setting the static sag is easier than the loaded but it will still need a set of strong hands to keep the bike
off the floor while you take your measurements.
Front
1. Lift the front of the bike off the floor using the same side stand method. Measure from the bottom yoke
to the top of the stanchion. This is measurement A.
2. Drop the bike back onto two wheels and take the reading again. This is measurement B.
3. Subtract measurement B from A. This is your front static sag reading. Keep a note of it just in case you
want to change it back. Ideally you are looking for 10-20mm on a race bike and 20-25mm on a road
bike. Either compress the spring or loosen it off to get in this range.
Rear
1. Lift the back wheel of the bike off the floor by pulling the bike over on its side stand.
2. Measure from the centre of the rear wheel spindle to a point on the tailpiece that is directly above the
spindle. (Mark that point on the tailpiece for the future reference)
3. Write down the measurement and call it reading C.
4. Put the bike back down on it's wheels and hold it upright. Let the bike settle under it's own weight.
Measure the distance from the spindle to the tailpiece. This is reading D.
5. Subtract D from C and this is your rear static sag. Keep a note of it just in case you want to change it
back. Ideally you are looking for 5-10mm on a race bike and 15-20mm on a road bike. Either compress
or loosen off the spring to get into this range.
Loaded Sag[/u
]Now to take into account the rider's weight. Sit on the bike and have one friend steady the front, one
steady the back and the other ready to measure. Sit the bike upright. Now WITHOUT touching the front or
rear brakes bounce up and down a few times in the seat and then assume your normal riding position.
Front and Rear
1. Measure the front of the bike as for measuring the static sag. This measurement E. Subtract E from A
and try to obtain 25-35mm on a race bike and 35-50mm on a road bike
2. Measure the rear of the bike using the same mark as previously. This is measurement F. Subtract F
from A and this is the rear loaded sag reading. Try and get between 20-25mm on a race bike and 30-
40mm on a road bike by adjusting the preload as before.
If you can't get in these ranges for BOTH Static and Loaded then you will need to change the spring for a
harder or softer one. Harder if you're outside the range and softer if you are inside the range. Now go and
ride and feel the difference!