How to Establish Baseline Settings Before Tuning A Dirt Bike's Suspension
This article on establishing the baseline settings on a dirt bike is primarily targeted towards those with dirt bikes built from about 1986 to present, (since these have the greatest amount of adjustability), so if your steed was built after 1986 (which applies to most people reading this), you're in luck as you'll be getting hooked up with pretty much everything you need to know to get a dirt bike back to a baseline setting and handling better, and if you ride a vintage style bike, there's info here that should help you as well.
You'll find this article especially helpful If you've been trying to get a motocross style dirt bike's suspension and handling characteristics dialed in, and you've been twisting clickers, changing fork height and messing with the sag so much that you really don't know where everything is set at presently (or you just don't want to admit it), now would be a good time to start over and get all your baseline settings established.
The manufacturers of off-road motorcycles and suspension components perform extensive testing to establish a baseline setting for their motorcycles and components so they will perform and handle as optimally as possible for the widest range of riders, so it's safe to assume that the manufacturers baseline settings are an excellent starting point when tuning the handling characteristics of a motorcycle, as these settings are often reached after extensive R&D and testing.
Furthermore, establishing a baseline setting usually only requires a factory service manual specific to the motorcycle being tuned, along with some basic tools to include a flat blade screwdriver, a few T-Handles, a torque wrench, a hammer and punch, a sag scale (or metric tape measure) and a high quality low pressure tire gauge.
Topics Regarding Motorcycle Baseline Settings to Enhance the Handling Performance of a Dirt Bike
If you're interested in zeroing in on a specific section, the links below will take you directly to the topic you may be most interested in, although for the best results, I recommend reading this page from top to bottom and following all of the steps as they are outlined, setting clickers to the values listed in an OEM Service Manual Specific to the Motorcycle
The acceptable baseline settings that are given throughout this article are only intended to give you a rough starting point, and are not the most idealistic baseline settings for any particular motorcycle.
Also, it is very important to remember that when making changes, to always make the same changes to both fork legs or rear shocks together.
Before Getting Started, It's Important to know that...
Free Setup Logs
If you're going to be making changes to a dirt bike's suspension, chassis or engine in an effort to fine tune the performance of the motorcycle, be sure to record the changes as they are made on either the: Advanced Setup Log or Basic Setup Log, both of which are free and available for download, use and distribution.
This article will help you with establishing a baseline setting on a stock / OEM suspension that you can work off of and If you ride a vintage style motorcycle, following the steps outlined in this article can prove to enhance the performance characteristics of an older style dirt bike with remarkable results as well.
Having a dirt bike setup properly for an individual rider is one of the most important things someone can do to enhance their experience while on a motocross track, off-road course, weekend on the trails, or while attacking the freestyle motocross (FMX) hits at your favorite compound.
By starting with the basics, which are commonly referred to as the baseline settings and that cover the suspension's compression clickers, rebound clickers, spring sag, fork tube height (fork overlap), along with getting all of the other available motorcycle controls dialed in, you can experience a remarkable difference in the handling of a motorcycle.
It's all too often that people send their suspension off for a re-valve or other magical rework when they could have greatly benefited from just getting their suspension, chassis and controls dialed in to as close to optimum as possible for their riding style, abilities and stature beforehand.
With the availability of technology that comes stock on current motorcycles, setting a modern motocross style dirt bike up for a riders height, weight, riding style, and taking into consideration the individual riders ability, an optimal setup can frequently be reached with just optimizing the motorcycle's available external adjustments, and all without sending your suspension off for any fancy, expensive re-valve loaded with internal anodized parts you might not have needed.
Lastly, setting and tuning of your suspension and motorcycle ergonomics is not a "set & forget" one time job either, as the motorcycle setup will change from one track to the next, as well as needing your input from a screwdriver or T-handle to adjust for terrain and conditions from one outing to the next.
Bottom line here is that the best thing you could do for your bike (and yourself) if you're interested in getting your dirt bike to handle better than it is, is to follow the steps outlined below before you start unbolting suspension pieces and boxing them up for a trip to a suspension shop for a possibly unnecessary modification, which you may even be able to muster yourself with the help of Race Tech's Motorcycle Suspension Bible
If a motorcycle's suspension components have been modified, the baseline values in a factory service manual specific to the motorcycle will no longer apply. In this event, you'll need to contact the suspension builder that modified the suspension for a recommended baseline setting to base your adjustments / settings off of.
If you bought a used dirt bike that it appears the suspension was previously modified on, you may want to contact the previous owner (if possible) and ask them what weight and skill level of rider the suspension was set up for, including any information on who performed the modification(s), although if contacting a previous owner is not feasible, you may consider sending the suspension components to a reputable suspension builder to have the suspension returned to an OEM spec, or have it valved and sprung for the intended riding style, as well as the weight and skill level of the rider.
Proper Dirt Bike Maintenance has to come First
Before you even bother with baseline settings, or any other setups, It's crucial that you ensure the motorcycle is in a good solid and sound condition.
Once you've taken care of the basic maintenance surrounding the motorcycle and it's suspension, before working on bringing the motorcycle to a baseline setting to work from, you may also want to consider changing the oil in the forks and shock(s) as is detailed in the Race Tech Motorcycle Suspension Bible, as changing the oil in suspension components is an excellent maintenance task that should be performed periodically, and is very well detailed in the Race Tech Motorcycle Suspension Bible.
There are lots of dirt bike suspension outfits running around that will gladly re-valve your suspension for you but if you just start with fresh oil and with everything working properly, then get the baseline settings established and work off of those, you may be surprised at how well a dirt bike can perform in stock trim and which is probably just the way you've always wanted and intended for it to.
Getting the basic baseline settings dialed in as discussed below after you've got the controls adjusted to where the bike fits it's rider is free performance that most anyone can do themselves, and can have a tremendous effect on the motorcycle's handling.
How to Get the Fork's Dialed In
Oil Levels & Valving In Regard to Baseline Settings:
Unless the suspension has been modified prior such as oil level and / or valving adjustments having been performed, or the fork seals have lost fluid (at which point the fork seals would need replaced and the oil changed then set to the factory level), the oil levels and internal valving shouldn't elicit any concern if only working to obtain a baseline setting to work from.
Fork Height / Fork Tube Overlap
When setting up the forks, getting the fork height / fork tube overlap back to a baseline setting is an excellent place to begin.
If you don't know where your forks are currently set at, or if you don't understand why your front end is pushing (e.g. Not turning when the handlebars are turned, and rather just sort of plowing through a turn or washing out with you fighting the bike for control), or if the dirt bike is head shaking (e.g. Giving violent tank slappers), or knifing into a turn (e.g. Cutting in too sharply / over reacting to input) when you attempt to make a turn, setting your fork height / fork tube overlap can prove an excellent starting point towards establishing the baseline settings.
When making changes to your fork tube height / overlap, do not try to "Eye-ball" it and instead, use a precision machinist steel rule at a minimum to measure the fork tube height / overlap, although use of the depth measurement function on a vernier caliper is the best method, just be sure that if you do make changes to the fork leg height, that you ensure that the forks are not binding and that you re-torque the triple clamp pinch bolts to the manufacturers recommended torque as can be found in a factory service manual specific to the motorcycle you are working on.
On most modern motorcycles with inverted forks aka "upside down" or "USD" forks, there will generally be a line etched into the fork slider which is the point that the manufacturer recommends for a starting point for fork height. Before continuing, it is recommended that the forks be brought back to this point while ensuring that the forks are not in a bind when the pinch bolts are re-tightened.
Once you have a baseline setting established for your fork height / overlap, here are a few tuning tips regarding fork height that may help.
If you want greater high speed stability (less head shake) If your motorcycle's turning seems to be responding too sharply (e.g. The front end knifes in) or you're experiencing head shake elsewhere such as between jumps and other high speed sections, you can lower the fork tubes in the triple clamps to correct some of this, but only make small changes when lowering your forks in the triple clamps and keep in mind that the lower the fork tubes are in the clamps, the less responsive the turning abilities of the motorcycle will seem.
If you need greater or quicker turning abilities (and you're not experiencing head shake) If you're experiencing problems with the motorcycle's turning (e.g. The front end pushes "The front end washes out"), raising the forks in the triple clamps will correct some of this but only make small changes when raising the forks in the clamps, and be cautious of head shake when doing so, since raising the forks will steepen the steering angle of the motorcycle which can influence a head shake condition that's especially scary at high speeds when things get hairy with handlebars that are hard to hold on to.
Before Getting into Compression and Rebound Damping Adjustments on the Forks, Make sure you know whether you're working with "Twin Chamber" or "Cartridge" Forks
On a Twin Chamber fork, the externally adjustable low speed compression damping adjuster will be the center screw on the top of each fork leg, with the exception being the Showa Separate Function Forks (SFF) which only has the compression damping on the left side, as the externally adjustable preload adjuster is on the right leg.
When looking at the top of the fork on a Twin Chamber fork, you should see the marking "comp" near the center screw with a rebound adjustment at the bottom of each fork leg labeled "reb" or "TEN", (again with the exception of the Showa Separate Function Forks (SFF) only having rebound damping on 1 side.)
Conversely, on a Cartridge fork, you'll find the rebound adjuster at the top of each fork leg, while the compression damping adjuster will be at the bottom of each fork leg, both of which are opposite of how they are positioned on a Twin Chamber fork.
Low Speed Fork Compression Damping
As the label "Comp" implies, the fork's compression damping adjustment is for making very fine adjustments to how quickly the forks compress when the front wheel is traveling over rough terrain, or when absorbing hard hits, as well as when landing from jumps.
While referring to an OEM Service Manual specific to the motorcycle you're working with that the forks have not been internally modified on, it is recommended that you set the low speed compression damping circuit to the baseline setting as will be described in the book.
Remember, When setting the compression damping on the forks, The adjustment at the top of the fork leg on a Twin Chamber fork is compression, and on a Cartridge Fork, the compression adjuster is at the bottom. Also, the number of clicks listed in an OEM Service Manual will be clicks from full hard which means that you turn the adjuster clockwise until it seats lightly, then turn the adjuster out the specified number of "clicks" being certain to set the number of clicks on both forks simultaneously unless working with a Showa SFF (Separate Function Forks), Marzocchi or other cartridge forks which have rebound in one leg, and compression in the other.
If a factory service manual is not immediately available, setting your externally adjustable low speed compression damping to 10 clicks out from lightly bottomed is a pretty close baseline setting that should work well as a starting point for a wide range of riders.
What About High Speed Damping?
Adjustment of the fork's compression or rebound damping circuits can be altered either internally or externally, but since this article is primarily about obtaining baseline settings of the motorcycle, only external low speed compression and rebound damping adjustment is covered here.
Should you have an interest in learning more about Damping and Valving, Be sure to check out Race Tech's Suspension Bible as this has a wealth of information on internal compression and rebound damping adjustments and modifications and how they are another aspect of fine tuning, as modification of these circuits is what "Re-Valving" is and is not regarded as baseline settings.
Fork Rebound Damping
As the term "Rebound" implies, or "TEN" (Short for Tension, NOT TEN) as it may be labeled, the fork's rebound adjustment is for making fine adjustments to how quickly the fork extends after being compressed such as when landing from a jump, absorbing a hard hit such as a G-Out, or when traveling over rough or irregular terrain, and the rebound DOES have a direct influence on the front tire's contact with the terrain.
Remember this about forks... Rebound damping adjustment on Twin Chamber forks is at the bottom of each fork leg (with the exception of the Showa Separate Function Forks (SFF) which only have damping adjustment on 1 side) and rebound damping adjustment on Cartridge forks is at the top of each fork leg, otherwise adjustment of the rebound damping is the same principle as compression damping adjustment as you will turn the adjuster in fully until lightly bottomed, then back the adjuster out the specified number of clicks as can be found in a Factory Service Manual specific to the motorcycle you are working on, although if a factory service manual is not currently available, turning the rebound adjuster out 10 clicks from lightly bottomed can be a comfortable baseline setting to work from.
How to Measure and Set the Suspension Sag / AKA "Race Sag"
Having the race sag set properly is one of the best things anyone can do for the handling characteristics of a dirt bike, yet it's a commonly neglected adjustment...
Some riders wonder why all the talk about sag is and seem to think this is a set & forget type of thing but constant adjustment of your sag from a baseline setting is critical to the optimum performance of a motorcycle.
Having the sag set properly is important for numerous reasons and can affect the way that a motorcycle handles from the steering, and the way the rear end reacts to chop or braking bumps to the way the bike leaves the face of a jump, or it's high speed stability, so staying on top of the race sag is highly recommended.
When Making a Rear Sag Adjustment...
If you just have this thing against beating on the rear shock's preload rings with a hammer and punch every time you need to make a small adjustment of the rear sag, you may want to consider getting a trick for your rear shock.
Before setting either the front or rear sag, you need to ensure that the rear suspension is in good shape and not binding or suffering from any slop, For this, there's an excellent article on Servicing the Rear Suspension that may reveal some needle bearings that are beyond needing lubrication.
When setting either the front or rear race sag, it is best to do so after a short session of riding the dirt bike in the elements that it will be used in such as after any available practice, as this will allow the suspension to get warmed up, thereby ensuring all the parts are moving freely and reducing any chances of "Stiction” affecting your measurement.
Additionally, when measuring or adjusting the sag, be sure the bike has the same amount of fuel as it would normally have for a race or practice session, ensure that the rider is in full gear, and if you are preparing the bike for a mud race, and if there is mud accumulated from the warm up ride or practice session, leave the mud intact, as this will be additional sprung weight which can affect the measurement when measuring or setting the sag.
Taking the Measurements and Setting the Race Sag
Since sag measurements are not usually discussed in a factory service manual, the steps below should provide you with all the information you will need to obtain an accurate sag measurement, just remember that when taking a measurement of the suspension sag, it is imperative that the same point is consistently referenced both when measured on the stand and in a compressed state.
When measuring the rear suspension... You may find it useful to make a small mark on the rear fender with a sharpie marker so the same point can be easily located and referenced each time the sag is measured or adjusted, as this will help with obtaining consistent measurements in the future.
When measuring the front suspension... You'll likely find it will be best to measure from the axle lug to the bottom of the triple clamp, as these points are easiest to get a reliable, accurate and consistent measurement from and a tape measure works the best for this.
Note: Considering the importance of achieving an ideal reading, and in an effort to avoid any stiction ("Stiction" = Sticking caused by the natural friction created during the movement of the shock shaft / piston in the shock body, or the fork tube moving within the fork slider) of the suspension which could alter a reading and cause your race sag's baseline setting to be inaccurate, it's important to roll the bike and bounce the suspension before taking a measurement as mentioned next.
Before taking a compressed measurement with the rider on board, it's best to roll the bike fore & aft while the rider aggressively bounces the suspension which can also be accomplished best by the rider riding the bike around briefly while bouncing the suspension while in motion, and then allow the bike to come to a stop without ANY application of either the front or rear brakes or any other influence in stopping, then with the rider in the normal riding or racing position that is the most comfortable and natural while simulating an attack position, take the compressed measurement.
The ideal targets you are looking for when setting the sag are as follows:
Up front... A good starting point for a baseline setting on the sag for the front suspension when compressed is around 35-50mm, which should be obtainable through internal shimming by using from about 5mm to no more than 15mm worth of washers stacked under the fork springs, or can also be done by adjusting the spring preload externally as can be done on the Showa SFF (Separate Function Forks) although if an acceptable sag baseline setting is not easily achievable without offsetting the static sag, heavier or lighter spring(s) will be needed.
And on the Rear... A good starting point for a baseline setting on the sag for the rear suspension when compressed is around 90-105mm, which is adjustable by adding or removing preload to or from the rear shock by adjusting the position of the shock collars and / or by installing an although if an acceptable sag baseline setting is not easily achievable without offsetting the static sag a heavier or lighter spring will be needed.
Begin by placing the bike on a stand so both wheels are elevated and off the ground with the front and rear suspension fully extended.
Using a metric tape measure, or one of the trick aftermarket sag measuring tools, measure the extended distances of both the front and rear suspension and note these measurements in the appropriate fields in either the Advanced Setup Log or the Basic Setup Log, both of which are excellent, free downloadable log sheets that have appropriate fields for this.
Here's a Trick Tool for Measuring the Sag by Yourself
If you want something trick that you can show off to your buddies, you may want to consider purchasing one of these trick Sag Measuring Tools, as these allow you to take a measurement of the suspension when the suspension is compressed without needing any assistance (which can be rather convenient for doing the sag by yourself).
With the fully extended measurements noted, pull the bike off the stand and have the rider climb aboard the bike and bounce the suspension as mentioned above, then take a measurement of both the front and rear suspension at the exact same locations that you took the measurement from with the bike on the stand.
Once a measurement is obtained with the rider on board and you have a pretty good idea of how much of a change is needed, have the rider dismount the motorcycle and then place the bike back on the stand so the wheels are elevated.
Once the weight of the motorcycle is off the springs, adjust the front sag by either adding preload to the fork spring via the external adjuster found on the Showa Separate Function Forks (SFF), or by placing shims under the fork springs on a conventional style fork, Twin Chamber or Cartridge fork, but be sure to recheck the race sag and unladen / static sag as discussed below before sending the rider out, and refer to a Factory Service Manual or Race Tech's Suspension Bible for disassembly of the forks if necessary.
When adjusting the rear sag, do so with the rear wheel elevated by adjusting the spring preload on the shock by turning the preload rings, or even by dialing in the the sag by using an .
Don't forget that once a change has been made to be sure to repeat the procedures outlined on bouncing the suspension and rolling the bike so as to avoid any stiction from causing an inaccurate measurement, then readjust as necessary to obtain the baseline setting you're after.
Once you've reached the sag measurement(s) that you feel are ideal and a good baseline setting or starting point, place the dirt bike back on the same level ground that you used for measuring the compressed sag when the rider was aboard and compress the suspension again vigorously by hand, then grab the rear fender and lift up on the rear of the motorcycle effectively "topping out" the suspension, then quickly let go while holding the handlebars with one hand to balance the bike and allow the motorcycle to sag under it's own weight
At this point, take a measurement using the same points of reference as before to reveal the rear shock's unladen sag.
The ideal unladen sag for the rear shock while or after measuring and adjusting the rear sag using the same conditions such as fuel level and any mud accumulation (if applicable) should be 15 to 25mm. If you're unable to achieve an unladen sag of 15-25mm after setting the sag, be sure to see the next section on determining whether you need a heavier or lighter spring for your or the riders weight.
Determining whether a Heavier or Lighter Spring is Needed
After setting the rear sag as detailed above, if you're left with an unladen sag measurement of less than 15mm, the rear spring is too soft for your or the riders weight and conversely, if the unladen sag is more than 25mm, this would indicate that the spring is too stiff for your or the riders weight.
If the examples given above regarding unladen sag have left you scratching your head in disbelief, the following should make sense:
Why You'll Need A Stiffer Spring If there is not much unladen sag left (less than 15mm) after setting the rider sag, this means that you have the preload cranked down so tight on the spring that it is holding the bike up too high in the rear, and the motorcycle needs a stiffer spring in order to get the rider sag and unladen sag balanced.
Why You'll Need A Softer Spring If there is more than 25mm of unladen sag after setting the rider sag, this means that the spring likely has almost no preload (or not enough) and the motorcycle needs a softer spring to achieve a balanced rider sag and unladen sag measurement.
How to Get the Rear Shock(s) Damping Circuits Dialed In
Getting the baseline settings for the rear shock absorber(s) dialed in can be done externally and doing so can have remarkable results as to how the motorcycle handles if the adjustments are out of whack.
On rear shock absorbers with externally adjustable compression damping there may be two externally adjustable compression damping circuits on your particular model.
The low speed compression damping circuit will be the most inner of two adjusters, as the high speed compression adjuster is usually the outer part of the low speed compression adjuster and has wrench flats machined into it for adjustment via an open end wrench, unless working with an Öhlins Shock in which case, some models may have separate knobs placed side by side for external adjustment of low and high speed compression circuits.
Rear Shock Low Speed Compression Damping
The rear shock's low speed compression damping circuit is most active when landing from jumps, charging through widely spaced whoops and bottoming out.
To determine the manufacturers recommended baseline setting for low speed compression damping, it will be necessary to refer to a Factory Service Manual specific to the dirt bike or shock absorber that you're working with to obtain the manufacturer's recommended baseline setting. If a factory service manual is not readily available, you can likely set the low speed compression damping at 10 clicks out from lightly bottomed, as this is a good baseline setting to work from and then fine tune this circuit from there.
Rear Shock High Speed Compression Damping
High speed compression damping is a damping circuit that is not available on all rear shocks, but on those that are equipped with high speed compression damping, the rear shock's high speed compression damping circuit is most active in high speed wheel movement sections such as square edged chop, braking bumps, roots or rocks, and can be tuned by adjustment of the knob with wrench flats that is external of the low speed compression damping adjustment, or with the separate external high speed compression adjuster found on some Öhlin's shocks.
To determine the factory recommended baseline setting for the rear shock's high speed compression damping circuit it is necessary to refer to a Factory Service Manual specific to the motorcycle you are tuning, although if a factory service manual is not readily available, a good baseline setting for the high speed compression damping circuit is 1-1/4 – 1-1/2 turns out from lightly bottomed.
(Note: The high speed compression damping adjuster on OEM style shock's with high speed compression adjustability is generally adjusted in quarter turns and does not have detents, so there will likely not be any "clicks" noticed during the adjustment of the high speed compression damping circuit.)
Rear Shock Rebound Damping
The rebound damping is what controls the rate at which the rear shock extends after being compressed and the rear shock absorber(s) rebound damping can be adjusted and brought to a baseline setting or fine tuned thereafter on shock(s) equipped with adjustable rebound damping.
To adjust the rebound damping of a rear shock, there will be an adjustment on the shock clevis near the bottom of the shock. To determine the factory recommended baseline setting for the rear shock's rebound damping it will be necessary to refer to a Service Manual specific to the motorcycle you are working on tuning, although if a factory service manual is not readily available, a good baseline setting for the rebound damping is 10 clicks out from lightly bottomed.
Obtaining a baseline setting for tire pressures according to different types of terrain is another factor that needs attention when going from one track or riding area to the next, and this is also true for changes in terrain or weather and the table listed below can give you a pretty good idea of a baseline setting to start with regarding tire pressures but be sure to use a quality low pressure, tire pressure gauge when making changes to tire pressures as the quality tire pressure gauges that are available have a bleeder function for making incremental changes to the tire pressure as well as they are much more accurate than conventional tire pressure gauges.