How to - Setting sag...

[Moto-Brian]

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 ©: 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:

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...

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 ©: 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...

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.

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!!

[Disclaimer]

Nice writeup Liz.

Although this information seems a little dated, I found these articles to be pretty informative and helpful regarding suspension setups:

http://www.sportrider.com/tech/motorcycle_suspension/index.html

[NinjaNick]

Thanks Lizard, I will be printing this and using for reference.

[NinjaNick]

*BUMP*

I read someone asking about sag in another thread. Free bump.

[Angrish]

*BUMP*

I read someone asking about sag in another thread. Free bump.

I asked about dirtbike sag .

[NinjaNick]

OK...Lizard...

When we first started we marked a point on the subframe and the swingarm and measured. We then lifted the whole rear off the ground and measured, then when we sat the bike back down it only made 1mm difference! It had NO travel really I guess stock! We needed to go from 235mm to 202mm. The sag ended up being 218 stock. So I had stock sag at the rear of 17mm. WAY STIFF. So we spent a long time moving the adjuster, actually about 30-45mins with stopping and measuring accounted for in that time frame. Well after all that adjusting we only made it down to 211mm!! So now I got 24mm sag! We were trying to get down to 202mm for a sag of 33mm, but the sag wasn't moving anymore it seemed. We got pissed and was like,"wtf!?".

My buddy wanted to see what you would say about that and wanted me to ask you,"Why is it doing that? What is going on?" You ever had this happen before?

[Moto-Brian]

OK...Lizard...

When we first started we marked a point on the subframe and the swingarm and measured. We then lifted the whole rear off the ground and measured, then when we sat the bike back down it only made 1mm difference! It had NO travel really I guess stock! We needed to go from 235mm to 202mm. The sag ended up being 218 stock. So I had stock sag at the rear of 17mm. WAY STIFF. So we spent a long time moving the adjuster, actually about 30-45mins with stopping and measuring accounted for in that time frame. Well after all that adjusting we only made it down to 211mm!! So now I got 24mm sag! We were trying to get down to 202mm for a sag of 33mm, but the sag wasn't moving anymore it seemed. We got pissed and was like,"wtf!?".

My buddy wanted to see what you would say about that and wanted me to ask you,"Why is it doing that? What is going on?" You ever had this happen before?

Try going out and riding the bike say, 30 minutes or so. Getting the fluid moving and warm will help to get accurate sag numbers. Also, it wouldn't hurt to shoot some WD40 onto the threads to help them allow for the collar to be rotated easier. I need more info so, I will look at a ZX14 tomorrow at a shop and see what I am looking at...

[Moto-Brian]

I asked about dirtbike sag .

MX sag is the same principle. You go with a different amount of sag, but overall, the measuring steps are the same... Also, you can use the zip tye method on an MX bike. I do... Mostly for Supermoto, but I also used it in MX...

[InyaAzz]

A suspension change on my bike made it handle like a totally new beast. I'm about 240+ with gear on. BIG difference.

[NinjaNick]

Thanks Lizard. Yeah, we bought a motion pro spanner and it didn't work, so I found out there is a special tool for the 14 from drag specialties that will supposedly move it easily. I'm ordering one.

I did notice this past weekend handling was MUCH better. Toe sliders were on the ground and I just saw this week that it took some of my shift lever rubber off a bit. I just need want to get it very accurate. I think with a better tool it will move more and I will try the WD40 on it too.

[NinjaNick]

I can't wait to pop mid-ohio's cherry with a 14. If not this year I will next year for sure and maybe you can give me some pointers.

[Moto-Brian]

I can't wait to pop mid-ohio's cherry with a 14. If not this year I will next year for sure and maybe you can give me some pointers.

Love to. Just give me a heads up. I usually am there pretty often, but I miss some so... If I know your dates, I can try and be there.

I look at a 14 today at a shop and I'll let you know what I see that may help...

[Moto-Brian]

Nick-

Ok, the damn shock is a battle to get to, no? Jesus... Also, there's not much thread left stock to loosen the damn thing much, either.

However, I suspect that there should be more than enough to get it softer. You simply break loose the top collar (I am sure you know this, but in case...) and spin it up enough to never be an issue while you adjust the spring tension...

On rider's left, you'd turn the collar away from you or from the rear tire side, you'd push it away from you. Make sense? That's loosening the collar. I'd mark the collar before you did this and do three complete turns. That got me pretty damn close to 30mm and had a lot left over. Now, this ZX14 may have had some adjustment done to it as it was used, but I got her softer. It was pretty damn stiff...

Now, the issue here is that it may be stiff for a reason. Maybe it is because you usually run two up on a bike like that or run bags, etc. Not sure. If it gets wallowy, go more towards 25mm and try that. I cannot imagine it needs to be 25mm sag, but I've been way wrong before...

Good luck.

[NinjaNick]

Thanks Lizard! Where did you go to get to play around with the shock? haha

Anyways, 3 full turns huh? Interesting. Yeah it was stiff as hell stock!

Ok, what is your definition of "wallowy"? So we understand eachother.

Also, what did you use to get the bottom collar moving? Was it easy?

[Moto-Brian]

Thanks Lizard! Where did you go to get to play around with the shock? haha

Anyways, 3 full turns huh? Interesting. Yeah it was stiff as hell stock!

Ok, what is your definition of "wallowy"? So we understand eachother.

Also, what did you use to get the bottom collar moving? Was it easy?

I messed with one at a dealership I went to Thursday.

Wallowy to me is the way it seems to be very slow to react. It also will feel too plush and like a cadillac instead of a Porsche... You want stiff and want good feedback....

I used a screw driver and a dead blow hammer. Kinda made some marks, but overall, not a big issue. Again, I'd recommend spraying down with WD40 and wiping off and then turning. Would make it easier I suspect... The top collar came off really easy (came loose) and the bottom one turned fairly well...

Again, it took three full turns to get me at 30 mm for my weight (190lbs)...