Desmo-Brian
05-26-2008, 02:08 PM
Ok, many guys have different ways of measuring sag. This is how we do it. They way we do it is going to measure overall sag...
Rider sag is anywhere between 25mm and 45mm. That's pretty big in terms of a guideline, but each rider is different and what and where you ride will dictate what numbers you will use.
For this exercise, I like between 30-35mm up front and 32-37mm in the rear... This is more track prep than street prep and you'd want a little more for street use considering the duties a street bike performs...
Tools you need:
-17mm T handle or a socket with a longer extension to adjust spring tension. Your bike may be different, but most are 17mm...
-Zip tye for the front fork. This helps with measuring accurately.
-Rear fork tool. Most street machines require what they call a spanner wrench. The Penske we have and use is a round stock bar with a slight bend in it.
-Tape that reads in MM as it is referred to use MM vs. inches, etc...
-Two buddies and yourself as the rider.
Front sag:
First, you need to wrap a zip tye on the front fork. Make it tight. Don't worry, it'll move under load and won't bind your fork. Trust me. Too loose and you get poor readings as to where the exact place of travel is...
Once you have the zip tye on, get your two buddies.
Role for each person:
Person (A): Rider. The one who will sit on the bike
Person (B): One who measures the distance. Get someone who can read the tape measure accurately.
Person (C): Just helps to hold the bike...
Now, before you measure, the Rider needs to have all their gear on for an accurate reading. I also prefer the bike to have been ridden at least one session to get the fork and shock fluid moving and warmed up a tad. Helps getting a better and more accurate reading. If it is cold, the oil is cold and doesn't allow the suspension to move as free...
So, once geared up, the Rider and Person C each take a bar and lift the front of the bike until the wheel is completely off the ground. Person B will then take the zip tye and push it to meet with the dust seal. Most bikes have upside down forks, but if you have traditional forks, you do the same thing - push it to meet the dust seal. See figure A....
Figure A: Push zip tye to dust seal with wheel off the ground and suspension unloaded:
http://img218.imageshack.us/img218/1762/frontziptyena5.th.jpg (http://img218.imageshack.us/my.php?image=frontziptyena5.jpg)
Now, GEBTLY rest the bike down onto the ground and straight up and down. The Rider will hand the bike to Person C and Person C will hold the bike by the upper fairing stay while straddling the front wheel. Person C CANNOT hold the wheel with their legs or knees. They must also not push down on the upper or allow the suspension to be restricted. Person C's job is to simply hold the bike straight up and down while the Rider climbs on.
The rider needs to get on smoothly and not bounce the suspension when they climb on. Rider then needs to get into the tucked position as if they were ripping down a back straight away...
Once the Rider has been into position (only takes a few seconds), they then must GENTLY climb off the bike taking great care to not push down or bounce the forks or front end. Rider and Person C will each again take a bar and lift the bike so the front wheel is off the ground. While off the ground, Person B will measure from the dust seal to the edge of the zip tye that was up against that dust seal. The number you read is the sag. In this case, it is a hair over 35mm. See Figure B...
Figure B: Measure the distance while the front wheel is off the ground from the dust seal to the edge of the zip tye. This is your sag reading...
http://img218.imageshack.us/img218/1426/frontrideheight1xd3.th.jpg (http://img218.imageshack.us/my.php?image=frontrideheight1xd3.jpg)
Again, I prefer 32-35mm so, we're pretty close here. To get closer to 32mm, I would need to get that 17MM T Handle and turn in the front pre-load adjusters. Turning in or clockwise stiffens the front up and will reduce the sag number. Loosening or turning counter clock wise will soften the front and increase the sag number...
The final stage on the front is to note your zip tye position. The zip tye shows the amount of total travel when you come off the track. I prefer about 1/4" left from the zip tye to 100% bottomed out. That allows for a bit more room should need be and it also shows I have the forks working at almost their entire range of motion.
Rebound and compression help in these overall, but that again is rider preference and a whole other thread...
Rear sag measurement:
Rear sag is also done via completely unloading the rear shock and measuring. So, there are a few things you need:
-Spanner wrench or shock tool to add or subtract spring tension via the spring adjustment collar on the shock. Some are like the Penske and smooth with small holes for a special tool while others 9most common) are with what appears to be teeth and are a threaded collar requiring some type of spanner wrench to adjust.
-Two buddies like needed for the front.
-Measuring tape that reads in MM.
-Blue tape or masking tape and a pen...
Ok, if you did the front, the rear is pretty much the same. The following people have key roles:
Person (A): Rider. The one who will sit on the bike
Person (B): One who measures the distance. Get someone who can read the tape measure accurately.
Person (C): Just helps to hold the bike...
Again I prefer 32-37MM sag in the rear depending on the track, etc. This is going to be different for each rider and each application....
So, to begin, Person C needs to find a solid point on the subframe to measure from and a spot on the swingarm to measure to for total distance. Some people use the rear axle hole which works, but on my bike, that means pulling from the tail section which is NOT secure as the subframe itself. You want to pull from a secure and solid spot that will not move under the weight of the rider or could be moved if any pressure placed on it like a tail section could be...
Also, try and make your measurement as straight a line as possible. Reason being is that it will help to tell proper sag as opposed to a steep angle say from the passenger pegs to the rear axle hole... In Figure C, I show where we pull and measure to on my bike.
Note in Figure C that I use painter's tape to make a mark where I place the measuring tape against to have an accurate reading every time I measure... Consistency...
Figure C: Shows as straight a line as I can get and pulling from the subframe which is MUCH more solid than from my tail section. The painter's tape allows me to mark a line that allows me to hit the same spot each and every time for more accurate readings...
http://img501.imageshack.us/img501/6581/dsc00661wx4.th.jpg (http://img501.imageshack.us/my.php?image=dsc00661wx4.jpg)
So, to measure this sag from the rear, Rider and Person C need to lift the bike so the rear is completely off the ground. If you have a kick stand, it is strong enough to lift up and support the weight on it. However, it makes it tough to get a reading as you have to work on the exhaust side. In my case, no kick stand so, Rider and Person C grab hold of the foot pegs or subframe and lift the rear off the ground. I get a total reading from my measuring points as seen in Figure C and write the total number down.
Then, each person rests the bike back on the ground. Person C then goes back to the front of the bike and JUST LIKE they did for measuring the front sag, they hold the bike via the upper fairing with care to not restrict the forks, etc. Rider then gently gets onto the bike and gets into the tucked position. As before, they should have their gear on to get a more accurate reading...
I usually have the Rider do a gentle bounce while sitting to make sure the suspension is set. While the Rider is on the bike, I then take my tape measure and place it on the same points as seen in Figure C. I then write down the number. That number should be close to 35mm when you tally the difference.
For example, if the original number was 205MM when fully unloaded and rear wheel off the ground, the measured number with the Rider on board should be 170MM. Figure D shows the example. The picture was taken w/o a rider so, it is totally an example...
Figure D: Shows how the tape measure is placed next to my mark and shows how I read the number. The number shown should be 35MM less than the number read at full extension of the shock while unloaded.
http://img167.imageshack.us/img167/7420/rearrideheightmarkpe2.th.jpg (http://img167.imageshack.us/my.php?image=rearrideheightmarkpe2.jpg)
Now, if you need to get MORE sag, you need to turn the threaded coupler clockwise. From the sprocket side of the bike, you would turn the coupler to the left...
If you need LESS sag, you would turn the coupler counter clock wise or to the right from the same side...
Hope that helps a few out there. Sag is VERY important to the performance of your machine. Especially you track day riders. Too often, most never check and they struggle with their bikes when if they would take about 15 minutes, they could easily enjoy it more and get more out of their machine...
Good luck!!
Rider sag is anywhere between 25mm and 45mm. That's pretty big in terms of a guideline, but each rider is different and what and where you ride will dictate what numbers you will use.
For this exercise, I like between 30-35mm up front and 32-37mm in the rear... This is more track prep than street prep and you'd want a little more for street use considering the duties a street bike performs...
Tools you need:
-17mm T handle or a socket with a longer extension to adjust spring tension. Your bike may be different, but most are 17mm...
-Zip tye for the front fork. This helps with measuring accurately.
-Rear fork tool. Most street machines require what they call a spanner wrench. The Penske we have and use is a round stock bar with a slight bend in it.
-Tape that reads in MM as it is referred to use MM vs. inches, etc...
-Two buddies and yourself as the rider.
Front sag:
First, you need to wrap a zip tye on the front fork. Make it tight. Don't worry, it'll move under load and won't bind your fork. Trust me. Too loose and you get poor readings as to where the exact place of travel is...
Once you have the zip tye on, get your two buddies.
Role for each person:
Person (A): Rider. The one who will sit on the bike
Person (B): One who measures the distance. Get someone who can read the tape measure accurately.
Person (C): Just helps to hold the bike...
Now, before you measure, the Rider needs to have all their gear on for an accurate reading. I also prefer the bike to have been ridden at least one session to get the fork and shock fluid moving and warmed up a tad. Helps getting a better and more accurate reading. If it is cold, the oil is cold and doesn't allow the suspension to move as free...
So, once geared up, the Rider and Person C each take a bar and lift the front of the bike until the wheel is completely off the ground. Person B will then take the zip tye and push it to meet with the dust seal. Most bikes have upside down forks, but if you have traditional forks, you do the same thing - push it to meet the dust seal. See figure A....
Figure A: Push zip tye to dust seal with wheel off the ground and suspension unloaded:
http://img218.imageshack.us/img218/1762/frontziptyena5.th.jpg (http://img218.imageshack.us/my.php?image=frontziptyena5.jpg)
Now, GEBTLY rest the bike down onto the ground and straight up and down. The Rider will hand the bike to Person C and Person C will hold the bike by the upper fairing stay while straddling the front wheel. Person C CANNOT hold the wheel with their legs or knees. They must also not push down on the upper or allow the suspension to be restricted. Person C's job is to simply hold the bike straight up and down while the Rider climbs on.
The rider needs to get on smoothly and not bounce the suspension when they climb on. Rider then needs to get into the tucked position as if they were ripping down a back straight away...
Once the Rider has been into position (only takes a few seconds), they then must GENTLY climb off the bike taking great care to not push down or bounce the forks or front end. Rider and Person C will each again take a bar and lift the bike so the front wheel is off the ground. While off the ground, Person B will measure from the dust seal to the edge of the zip tye that was up against that dust seal. The number you read is the sag. In this case, it is a hair over 35mm. See Figure B...
Figure B: Measure the distance while the front wheel is off the ground from the dust seal to the edge of the zip tye. This is your sag reading...
http://img218.imageshack.us/img218/1426/frontrideheight1xd3.th.jpg (http://img218.imageshack.us/my.php?image=frontrideheight1xd3.jpg)
Again, I prefer 32-35mm so, we're pretty close here. To get closer to 32mm, I would need to get that 17MM T Handle and turn in the front pre-load adjusters. Turning in or clockwise stiffens the front up and will reduce the sag number. Loosening or turning counter clock wise will soften the front and increase the sag number...
The final stage on the front is to note your zip tye position. The zip tye shows the amount of total travel when you come off the track. I prefer about 1/4" left from the zip tye to 100% bottomed out. That allows for a bit more room should need be and it also shows I have the forks working at almost their entire range of motion.
Rebound and compression help in these overall, but that again is rider preference and a whole other thread...
Rear sag measurement:
Rear sag is also done via completely unloading the rear shock and measuring. So, there are a few things you need:
-Spanner wrench or shock tool to add or subtract spring tension via the spring adjustment collar on the shock. Some are like the Penske and smooth with small holes for a special tool while others 9most common) are with what appears to be teeth and are a threaded collar requiring some type of spanner wrench to adjust.
-Two buddies like needed for the front.
-Measuring tape that reads in MM.
-Blue tape or masking tape and a pen...
Ok, if you did the front, the rear is pretty much the same. The following people have key roles:
Person (A): Rider. The one who will sit on the bike
Person (B): One who measures the distance. Get someone who can read the tape measure accurately.
Person (C): Just helps to hold the bike...
Again I prefer 32-37MM sag in the rear depending on the track, etc. This is going to be different for each rider and each application....
So, to begin, Person C needs to find a solid point on the subframe to measure from and a spot on the swingarm to measure to for total distance. Some people use the rear axle hole which works, but on my bike, that means pulling from the tail section which is NOT secure as the subframe itself. You want to pull from a secure and solid spot that will not move under the weight of the rider or could be moved if any pressure placed on it like a tail section could be...
Also, try and make your measurement as straight a line as possible. Reason being is that it will help to tell proper sag as opposed to a steep angle say from the passenger pegs to the rear axle hole... In Figure C, I show where we pull and measure to on my bike.
Note in Figure C that I use painter's tape to make a mark where I place the measuring tape against to have an accurate reading every time I measure... Consistency...
Figure C: Shows as straight a line as I can get and pulling from the subframe which is MUCH more solid than from my tail section. The painter's tape allows me to mark a line that allows me to hit the same spot each and every time for more accurate readings...
http://img501.imageshack.us/img501/6581/dsc00661wx4.th.jpg (http://img501.imageshack.us/my.php?image=dsc00661wx4.jpg)
So, to measure this sag from the rear, Rider and Person C need to lift the bike so the rear is completely off the ground. If you have a kick stand, it is strong enough to lift up and support the weight on it. However, it makes it tough to get a reading as you have to work on the exhaust side. In my case, no kick stand so, Rider and Person C grab hold of the foot pegs or subframe and lift the rear off the ground. I get a total reading from my measuring points as seen in Figure C and write the total number down.
Then, each person rests the bike back on the ground. Person C then goes back to the front of the bike and JUST LIKE they did for measuring the front sag, they hold the bike via the upper fairing with care to not restrict the forks, etc. Rider then gently gets onto the bike and gets into the tucked position. As before, they should have their gear on to get a more accurate reading...
I usually have the Rider do a gentle bounce while sitting to make sure the suspension is set. While the Rider is on the bike, I then take my tape measure and place it on the same points as seen in Figure C. I then write down the number. That number should be close to 35mm when you tally the difference.
For example, if the original number was 205MM when fully unloaded and rear wheel off the ground, the measured number with the Rider on board should be 170MM. Figure D shows the example. The picture was taken w/o a rider so, it is totally an example...
Figure D: Shows how the tape measure is placed next to my mark and shows how I read the number. The number shown should be 35MM less than the number read at full extension of the shock while unloaded.
http://img167.imageshack.us/img167/7420/rearrideheightmarkpe2.th.jpg (http://img167.imageshack.us/my.php?image=rearrideheightmarkpe2.jpg)
Now, if you need to get MORE sag, you need to turn the threaded coupler clockwise. From the sprocket side of the bike, you would turn the coupler to the left...
If you need LESS sag, you would turn the coupler counter clock wise or to the right from the same side...
Hope that helps a few out there. Sag is VERY important to the performance of your machine. Especially you track day riders. Too often, most never check and they struggle with their bikes when if they would take about 15 minutes, they could easily enjoy it more and get more out of their machine...
Good luck!!