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TECH: CHASSIS SET-UP


By Chad de Alva
Motorcycle manufacturers have a tough job in that they need to make their bikes on the dealer’s floor work well for all of their potential customers. So whether you’re a 300 pound six-foot four-inch linebacker or a five-foot two 130 pound ninja, that shiny new bike you just took delivery of has to be able to ride okay when you load it up to take it home.  Many riders will drive to the local riding spot and grip it and rip it and call it a day.  But by not taking the time to get their bike set up to best fit themselves, these riders are leaving so much performance on the table.  Likewise, if you just picked up a new-to-you (used) bike, you’ll be in the same boat of leaving performance on the table if you don’t set it up to fit you as a unique individual.  Setting up a bike for a rider is known as chassis setup, and to learn exactly how to do it, I consulted the motorcycle savants at Konflict Motorsports.

Whether you’re working with a new bike or a new-to-you bike, the same things apply to setting your bike up for yourself.  By taking the time to make these adjustments and periodically rechecking them, you can be sure that you’re getting the most out of that big price tag on your new bike, or showing your buddy who you just bought a bike from, how much faster you are on it.  Depending on exactly who you are as a rider in terms of height and weight, the way a bike is set up when you take possession of it could actually be working against you, so you need to check your chassis to get the most enjoyment out of any bike.

The first thing to check is sag or the amount your bike’s rear suspension compresses under two conditions. The first condition is static sag, which is how much the suspension compresses when the bike is supporting its own weight on a level surface.  The second condition is rider sag, and that is how much the suspension compresses when the rider wearing all their riding gear is on the bike in the riding position.  You’ll note I said all their riding gear.  Take the time to get fully dressed for riding and load your pack up just like you’re about to head out on an actual ride when you’re setting rider sag. If you carry three liters of water when you ride, load three liters of water.  Do everything to make this measurement as accurate as possible for the best results.  While you’re fully costumed, take a minute and hop on a scale (it takes 30 seconds before you set off on a ride) to get your rider weight. Write your rider weight down someplace where you won’t lose it.
 
Each manufacture varies where exactly on their bikes rear sag is measured, so consult your manual to figure out how it’s done.  If your manual doesn’t have any information on how to measure sag, reach out to a quality suspension shop for directions and other bike-specific setup advice.  While you’re reading your manual to learn how to measure sag, look for any information on what spring rates match your rider weight.  Don’t be surprised if you need to change out your springs (fork and shock) to match your rider weight.  For example, I’m 170 pounds, but by the time I get fully suited up and throw on my admittedly very heavy backpack, I’ve picked up nearly 50 pounds, bringing my rider weight to 215-220 pounds.  So I need different springs than stock.
 
Once you know your rider weight and you have the correct spring on your bike, set your static and rider sag to the correct specs, which either came from your manual or suspension shop.
 
A tool that makes setting sag an easy process (and the easier something is, the more likely you are to do it.) is the Slacker made by Motool.  With this handy gadget, you can set your sag all by yourself, and there are no funky ruler-contraption-tools involved.  With the Slacker, you just measure and adjust if needed, and then go ride.  Springs are like any other mechanical component in that they will wear out over time, so make sure to check your sag periodically to make sure that you’re still within spec.
 
Adjusting sag will have a dramatic impact on the way that your bike handles, and this is something that you can use to your advantage to manipulate your bike’s chassis to make your bike handle a certain way.  By increasing the amount of rear sag that your bike has, you’ll slack out your bike’s head angle, meaning the front suspension will be further tilted away from vertical when the bike is viewed from the side.  This will increase the bike’s straight-line handling, which is ideal for go-fast situations like desert racing.  Conversely, if you like to play in the tight and technical places of the world where cornering is everything, decreasing the amount of rear sag in your bike will steepen that head angle (bringing it closer to 90 degrees / vertical) and make the bike more flickable and corner-able.  Your manual or suspension shop will again spec a range of sag, so start by playing with adjustments within that range.  It’s also important to make sure that you’re only making one change at a time while testing to make sure you can correctly determine the impact of a given change.  

With your sag set correctly, we can move to the front suspension to take a look at a few more things. First up, make sure that your fork legs are at the same height in your top triple clamp. If your forks do not have any kind of marks, pull out some calipers or a high-quality ruler for a quick measurement check.

Again, your manual or suspension shop will know the correct answer for how much of your fork legs should be sitting above your top triple clamp.  Adjusting how much fork leg is showing is also a way to manipulate head angle. Once you’ve determined where forks should sit in your bike’s triple clamps, make sure that you’re following the manual’s workflow for installing your front wheel.  Even doing something as simple as torquing pinch bolts in the wrong order can have a discernible impact on how your suspension performs. The manual is very helpful, so read it.
 
With your suspension set up correctly, it’s time to address the fit of your bike to you as a rider, and that means handlebars, seat, and footpegs.  Handlebars come in a number of different widths, sweeps, (amount of) rise, and bends, which means that there’s a bar out there that will feel like a million dollars in your hands.  Furthermore, how you have the handlebars clocked in your bar mounts will make a difference in how the bars feel while riding.  So a good first step is to play with bar clocking to see if you can get a good feel before you shell out for an aftermarket bar.  Throw your bike up on a stand and get in your riding position to see what kind of impact a clocking change makes.  Personally, I find that turning my bar ends up makes for better ergonomics for me, as I’m standing while riding nearly all the time.  I’m also a taller guy at 6’ 1”, so I do like to add a little bit of bar rise to my bikes, and it’s here that I need to point something out.  

Do not add massive bar risers to your bike.  If you’re adding bar risers to the point that your riding position has you straight-legged, you’re exposing yourself to some real potential for bad things happening.  The first one is that in the event of a crash, you’re more likely to snap a longer bar riser bolt than a short one, and I’ve heard too many stories of this happening to guys who conveniently don’t happen to have spare bolts with them when they go down in the middle of nowhere.  If that doesn’t sound fun, the second potential issue arises from bar risers causing you to ride with straight legs.  Doing this will negate all of the suspension in your legs, and this will only make you more likely to crash.  I don’t know about you, but I find it much harder to absorb surprise hits and stay on my bike when my legs are locked.  If you need to add rise, do it the right way and use a quality solution.  You can also use footpegs to help make your bike fit you better, which can reduce the amount of bar rise you would otherwise want to add.

Companies like Fastway (Pro Moto Billet) make quality footpegs that we’ve reviewed in Upshift Issue 29 and can be run in stock or low position to help you fit your bike better.  In addition to being able to adjust the level of grip these footpegs provide, the low position will gain you the equivalent of several millimeters of bar riser.  This low position also will cause your footpegs to move aft on the bike a bit, with the added benefit of giving riders with larger feet a better interface with their foot controls.  So before you install inches of bar riser, see what swapping to adjustable footpegs can do. You may find that they’re exactly the change you’re looking for.

Last up is the bike’s seat, and where it’s placing your body on the bike when you’re sitting on it.  The factory seat that your bike comes with may feel less comfortable than a 2x4, but it puts your bum in the right spot – so make sure that any aftermarket seat you’re looking at doesn’t move your body to some place it shouldn’t go that would negatively impact your bike’s handling.  Going with a quality aftermarket seat like one from Seat Concepts is a good move, as Seat Concepts factors in rider position to all of the seats that they make.  If you’re a short person, a low seat can help you get your feet to the ground, which will add confidence.  Conversely, a tall seat can help you save energy while riding by reducing the distance you have to move to transition from sitting to standing.  Between your seat, footpegs, and your bars, you can dial your bike’s ergonomics in to make your bike fit you like a tailor-made glove.

Having your bike fit to you will pay off in a number of ways.  You’ll find you’re more comfortable on the bike, and thus more confident.  You’ll use less energy to hold yourself in the ideal riding position instead of being overly scrunched up or stretched out.  And perhaps most importantly, you’ll be able to ride longer and feel less fatigued at the end of your ride.   There’s no reason you should suffer on a bike that’s okay at fitting everyone.  Turn your bike into something that is fit to uniquely you and reap the benefits.

Motorcycle manufacturers have a hard task – they have to make their bikes work for all humans, and humans come in all shapes and sizes.  Some humans are short, and some are tall.  Other humans weigh a hundred, and something pounds ready to ride, and others weigh considerably more.  As riders, we’re leaving so much performance on the table by riding a bike that’s still set for everyone.  Take the time to get the right springs for your rider weight and set your sag following your bike’s manual.  Then take some time to get the ergonomics of your bike dialed-in to fit you.  Between your bars, footpegs, and seat, you can achieve a fit that will make your riding experience so much more enjoyable.  If you need more help understanding how these things work, consulting a knowledgeable race prep or suspension shop is a great resource to help you get the most out of your bike.
 
ORIGINALLY PUBLISHED IN UPSHIFT ISSUE 44, APRIL 2020 HERE>

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