The Slacker digital sag checker

//The Slacker digital sag checker

The Slacker digital sag checker

Measuring sag is the first task most discerning motorcyclists have in understanding what happens to their bike under its own weight and then with the rider on. That normally involves a minimum of two people so either you trust their math or you find someone your own weight to sit on the bike for you while you do the measuring.

Then you change settings and want to measure again to see where you are and what the change(s) manifested in sag so you can understand what a few turns of preload gives you in math and with that math, you can get an understanding of how the geometry of the motorcycle changed.

If you had a digital tool that allowed you to do it all by yourself, would that be a better option for you?

Do you prefer the tried and trusted tape measure and your own eye?

John Casebeer’s “Slacker” tool lets you do the task by yourself for street and dirt bikes with digital accuracy for static and rider sag measurements. I went down to Button Willow a day early to visit with John and use the tool. I did not use it beforehand nor did I do any reading or video watching on how to use the tool. I wanted to quite literally get hold of the box, open it and get to work. One of my key criteria for any product is ease of use, so from box opening to actually using the tool needed to be a couple of minutes not fifteen to twenty minutes.

I wasn’t disappointed at all.

Having opened the box, I put one of the adhesive hook holders on the tail and then placed the Slacker on the rear axle. I took the hook, pulled up the wire and placed it in the  holder. I set the unit to zero and at that point was ready to measure static/free sag and record data. Total time was less than 2 minutes. Easy to use is an understatement. Adding the remote display is as simple as plugging it in, securing it to the cockpit area via the velcro strap and then recording what you see.

Note that when you plug in the remote unit the Slacker will reset to zero so make this your next task as soon as the Slacker is mounted and at zero. Then there won’t be any confusion at all. Like any tool you have to know how to use it correctly and YOU must use the tool in the right way so that means focused concentration to get each task done correctly.

Static sag

Was as easy as pulling the subframe and forks up to make sure both were topped out taking the shock first and then the forks second. I repeated the exercise 4 times until I got a consistent reading which made sure I had completely topped the rear shock out, then the same with the forks. If this is less than proper for you, you can put jack stands under the foot pegs to make sure the rear wheel is off the ground and measure static sag that way and put the front end in the air with a triple tree pin stand to ensure full extension of the forks. Honor who you are and your criteria for acceptable data!



Letting the bike sit under it’s own weight each time would also give you very important information on stiction. Each time the weight was placed back on the shock the reading would change between 2-3mm showing me how much stiction I had (5mm is acceptable). That can throw off a reading measurement not to mention cause less than good suspension action, so invaluable data can be gathered here.


Rider sag:- solo and two up

I simply need to know where I am as a starting point so I never gear up. Sitting on the bike whether you hold the bars or sit upright will change the sag values. Note that you cannot see the Slacker digital display while sitting still and the remote unit becomes invaluable for you to use as you can see the data right in front of you.



  • If you have a remote preload adjuster, the next series of tasks is easy. If you have a ramp adjuster, that is slightly more difficult but you go notch by notch. If you have two lock rings, you will go .5 of a turn at a time for a maximum of 5 turns.
  • As you change the preload also make note of what happens to you free sag. Does it diminish to zero? If so, where do you lose all the free sag? If you get the right rider sag but you have no free sag, the spring is too soft. If you can’t get the rider sag and the free sag is almost the same, the spring is too stiff.


If you see a sag number that is way off, you can add or remove preload and then sit on the bike again to see how many turns of preload changed the sag number. If that is not enough data for you, leave the bike at resr with zero preload, zero the unit and then add preload in increments of 3 turns. How does the sag measurement change? repeat with three turns until you get to maximum with the preload adjuster. Given the digital read out, as you added preload was the math linear throughout or did it veer away from linear? Where did it change – at the beginning or towards the end of preload being added?

Once you have that range you can then sit on the bike and see what happens with the preload changes based on your weight from zero through 3 turns at a time to maximum. Does the prior no rider math relationship you discovered hold true with you on the bike? Again, the Slacker gives you that information instantly.

If you ride two up often, you can use the Slacker in exactly the same way to manage weight transfer very successfully so you both had a fun and safe time on the motorcycle. Settings will also tell you what your passenger prefers so you can record the settings to make sure there’s no guessing. If you add more weight for longer trips, set the tool up again to see what happened to sag and make the changes you need to keep the handling of the bike consistent.


Gear verses no gear

Run through the process in regular clothes and then fully suit up with everything on and run through the sag check again as done previously with preload. Does the math change with gear in terms of consistency or not? The Slacker can provide you with very interesting data in this regard.



Static sag via the Slacker can give you information on the pitch of the chassis with the bike at rest and with a rider or riders on the bike, showing how that pitch dynamically changes based on the current settings. While this may not seem important, one of the big issues we try to cope with is weight transfer, so knowledge about how the bike sits with no rider and then changes with 1 or 2 riders can clearly explain any handling issues that you may have.

Adding all the preload made my forks 6mm longer than no preload. That can explain why the bike is harder to turn or flat out won’t turn based on fork position. Similarly, you can gather the same data on the rear shock to see how that effects or affects your swing arm angle to understand why you run wide or your radius tightens on the throttle.


This tool does not simply measure sag – it does a huge amount more if you look at what the data can offer you and what you can use the tool for. On or off road, any rider can very quickly see what they are dealing with in all the above criteria and get to work to change their bike to rider significantly better.


I use it to make sure I have all the data points above sorted out before a race weekend to make sure my bike is perfect or if there is an issue, how to deal with it before or during a race. The Slacker brought me 3 Championships this year with AFM. What can it do for you?


Don’t be a Slacker, get one!


Video link:

By |2017-12-28T05:43:19+00:00November 25th, 2017|Categories: How-To|0 Comments

About the Author:

Journalist, published author, 1-1 coach and mentor, video presenter

Leave A Comment