When news that the Empulse R would be available before the Empulse, I was pretty excited. This news was that last justification that I needed in order to spend the extra money on the R version. The R offers up some carbon fiber bodywork, fully adjustable suspsension, and (I think) a different motor. Of that list, it’s primarily the suspension that I was most excited about.
A lot of sportbikes come with fully adjustable suspension, but the Empulse belongs to that weird segment filled by street fighters and sporty standards. It sources Marzocchi forks and a Sachs shock in an OEM variety that is devoid of any kind of identifying marks. I had my concerns about the whether or not the extra adjustability would be of any consequence. Add to that some initial reports from the earlier owners that the suspension on the R was just too firm and would have to be replaced with something aftermarket. My heart definitely sunk a little as I waited for my bike to come in.
When I received my Empulse R, I didn’t know what to think. I was still in the break-in period, but it did seem really harsh. Did I just get suckered? Short answer is No. The Empulse R is undersprung for my weight (180 lbs. with full gear), but is otherwise phenomenal for stock suspension. Hopefully this blog post will help owners get the most out of the suspension on their Empulse R.
Where to Start
I’ve been doing a lot of research into suspension setup. In the past, I’ve taken my racebikes to a chassis/suspension shop. Their work was superb, but I learned next to nothing. The Empulse is my first sportbike since I gave up spirited riding on the street years ago. I do still have gas street bikes, but I’m more of a touring guy now.
I had a lot to learn about motorcycle suspension. As I read more, the more that I realized that suspension tuning information is out there, but it’s never in one complete place. You have to read a bunch of half truths from several different sources. Finally I found once source that really clicked with me:
Sean Onipede put together a great guide that does a few things that I found to be very important:
- Provides an order to follow when setting up your suspension.
- Details the key responsibility for each setting.
The first point is pretty critical. Just like a race track is a series of corners that must be linked together successfully, your suspension works in related stages to get you through the micro-steps of every corner. It steepens the front-end for turn in, relaxes the front end at the apex, settles the rear end for traction when rolling on the throttle, and it keeps the bike on line while powering out of the corner.
This moves right into the second point. In order to setup the suspension for each of those stages, you have to know which setting affect the bike through each of those stages. Typically people describe symptoms and then offer up one or two adjustments to correct those symptoms. The problem is, the description of these systems with “soft” terms that may have no meaning to most readers.
I can’t compete with the quality of Sean’s guide or even with all of the other random good information on the Internet, and so the rest of this guide is mostly just tips on how to make the adjustments to your Empulse R.
What You’ll Need
Most of the measuring is for calculating static sag. It’s easier with a helper, but I didn’t have one so I devised a scheme to set the sag myself. The above shows the tools that you need to adjust and measure your suspension without a helper. Here’s a break-down:
- Wooden Dowel
- Zip Tie
- Telescoping Magnetic Retriever or Car Antenna (or a helper)
- Metric Ruler
- Bungies (or a helper)
- Flathead Screwdriver
- Spanner for 3/8″ Socket Driver
- 3/8″ Socket Driver with 1″ extension
- 7/8″ Wrench (22mm might fit best)
Sag goes by different terms and there are different ways to measure it. I’m going to stick with the Racetech terms and methods as outlined here:
First you need to measure full extension. Then you measure free sag (bike without rider) and static sag (bike with rider). For the two sag measurements, you’ll want to take two measurements for each. The first measurement is taken when the suspension is allowed to compress and settle to a stop. The second measurement is taken when the suspension is allowed to rise and settle to a stop after you’ve compressed it down and released. You take the average of these two measurements as a way to compensate for “stiction” (sticky friction).
It difficult to take these measurements without help, but the following descriptions illustrate a way to take the measurements by yourself for extension, free sag, and static sag.
The first thing to do is to put a zip tight on your right front lower fork leg.
To measure the extension, put the bike on the side stand with the bar turned all of the way to the left. From the right side of the bike, push up on the right handlebar until the front wheel is barely off of the ground. Then slide the zip tie up and measure from the top of the zip tie to the bottom of the silver fork leg.
To measure free sag, you’ll balance the bike straight up and down allowing it to settle on the way down or on the way up depending on which of the two measurements you’re taking. Once it settles, carefully reach down and slide the zip tie up. Then carefully put the bike on the side stand and take the measurement from the top of the zip tie to the bottom of the silver fork leg.
To measure the static sag, you’ll balance the bike with you on top of it wearing all of your gear. This is easiest next to a wall on your left side. You’ll want to hold the bars and center your weight over the bike in a natural riding position as it settles. I do this by leaning just slightly with my left elbow against the wall. Then slowly move down with your right hand and push the zip tie up. Stiction is your friend here, because it will prevent the fork from compressing as you slowly lean over the front more. Carefully get off of the bike and measure the zip tie again.
Free sag equals the full extension reading minus the free sag reading. And likewise, static sag is the full extension reading minus the static sag reading. Racetech recommends 30-35mm of static sag for street applications and 25-30mm of static sag for race applications. I run my Empulse R at 33mm of front static sag.
Now that you can measure static sag on the front, we’ll discuss setting it. You set sag by changing front preload. Preload is set by using a 7/8″ wrench on the red adjusters on top of each fork. I didn’t have a large enough metric wrench, but I suspect a 22mm is the perfect size. The imperial wrench did just fine since it doesn’t take much torque. My static sag was originally 38mm, and three full revolutions (tightening) added enough preload to bring me to 33mm of static sag.
What Does Preload Do?
Adding preload to a spring compresses it slightly, making it stiffer. Springs have a spring contant k. The force a spring exerts is determined by Hooke’s law where F = kx. Force equals the spring constant times the displacement of the spring which is a distance measurement. The more you compress a spring, the more force it exerts. By adding some preload, you change that displacement making it exert more force. If it exerts more force, then it will sag less. This is because the bike has a certain amount of weight that the springs must counteract with spring force. The system is balanced when the springs exert the proper amount of force. If the springs have a low spring constant, then the springs will compress (sag) until the force is right.
Why is sag important then? Keith Code explains static sag really well in his Twist of the Wrist book. Suspension is really designed to work well in that middle third of travel. In the initial third of travel, the spring force is too low. The middle third is just right. The last third is too stiff. Sounds a little Goldilocksian at first, but it makes sense on some level. So by setting your static sag to just less than 1/3 of the shocks travel means that when you’re cranked over in a corner, the cornering forces will compress the suspension right into the magical middle third of travel. Of course, if you go through corners fast, there’s going to be more compression. This is when you have to ask yourself how fast you want to go through corners. If you set you bike up with less static sag, it’s going to feel like crap if you pull into a parking lot through that dip in the concrete too slowly. If you pull through there going 35mph, it’s going to feel like magic.
How much preload is too much then? I can’t really answer that, but I do know that by adding preload you’re reducing the amount of travel available to the spring. If the fork or shock is designed to utilize all of a spring’s travel then this is bad news. Regardless, it’s best to start with the correct spring rate and use a small amount of preload. The rationale behind this is that by adding preload to your spring, it’s like placing a shorter, stiffer spring in there that will get stiffer sooner as the wheel moves through its travel. You really want a spring that changes its force more slowly.
I’m not sure about the dimensions of the fork and shock on the Empulse R, but I plan to at least pull my shock and get some detailed measurements of the spring and the shock without the spring.
Rear static sag is probably more crucial than front static sag for most riders, because you’re going to feel it right in your spine. If you’re the kind of rider that trailbrakes really hard into corners, then I’d say the the front end is as important or more. When I first received my Empulse R, I was astonished at how firm the rear-end was…or so I thought. I would run over bumps in the road that would chatter my teeth. This is the point where I was really doing some soul searching about my decision to get the R.
Luckily I sorted out this method for measuring sag without a helper and I got some measurements. My rear static sag was a whopping 51.5mm. I was basically riding so far down in the travel that I was getting into that nasty last third of travel.
To measure my rear extension without a helper, I devised a scheme that provided the same benefit of using the zip tie. I bungied a telescoping magnetic retriever to the swingarm right over the rear axle.
Then I bungied a wooden down under the seat just above and slightly forward of the rear axle.
Then with the bike on the side stand, I pull up until the rear wheel was just off of the ground, and with one hand I extended the magnetic retriever until it hit the wooden dowel and then I move the retriever to the side just slightly so that I could lower the rear wheel without fear of compressing the retriever. Lastly I take the measurement from the top of the retriever to the middle of the rear axle.
Measuring free sag and static sag is much the same as before with the front, with the only real difficulty coming when you are on the bike and trying to reach back to extend the retriever carefully for the static sag measurements. There’s not as much stiction in the rear shock, so you’ll be doing a bit of a balancing act here.
Adding rear preload is a little more complicated. It’s done by loosening the lock collar and then tightening the newly released adjusting collar. The collars are two large nuts with notches. They’re located on the shock body at the top/front of the spring.
To measure how much preload you’re adding, people typically measure the length of threads showing above the collars. For my Empulse R, there was 8mm of threads showing from the factory. To loosen the lock collar and then to adjust the preload collar, you’ll want to use the spanner with the 3/8″ driver and 1″ extension. They sell normal flat spanner wrenches for this, but the collars are right behind the subframe on the Empulse and so it’s hard to get to.
You can also use a hammer and punch to loosen the lock collar, but I highly recommend against using it to tighten the adjusting collar since the numerous revolutions will bugger up the notches. Using the spanner to add preload can get difficult, and I found it best to attack it from the left side making sure that the spanner tooth is a notch correctly and that the spanner body is lined up and resting squarely on the collar. Lastly avoid any twisting motions when twisting the 3/8″ driver. The spring and lower collar will likely rotate too. That’s OK.
The whole process of adding preload will be much simpler if you can remove as much spring force as possible. I do this by keeping the bike on the side stand and then placing a scissor jack under the frame so that the rear wheel barely comes off the ground.
The procedure for setting rear sag is to add/remove some preload and then measure again. Once you hit your target then tighten the lock collar against the adjusting collar. Racetech recommends 28-37mm of rear static sag for street use and 23-32mm for the track. I ended up adding 10mm of preload for a total of 18mm in order to get my rear sag to 35mm. It feels phenomenal! I’m really impressed with how planted it is in nearly any corner I’ve encountered on the street. It’s a bit harsh for the low speed corners, but that was to be expected. I did end up adding a lot of preload, and so I’m in the middle of trying to determine what spring rate to choose for my new spring.
The good news is that you’ve now finished the most critical adjustments to your bike’s suspension. The bad news is that the remaining settings are much less of a science than they are an exercise of personal preference. That preference is determined through lots of trial and error experiments as you ride through a chosen set of roads/corners the same way…again and again.
I’ve made several attempts to tweak my damping, but it’s really hard to come up with repeatable experiments on the street. For instance, in order to set your front compression dampening correctly for a corner, you need to hit a very late brake marker. I tend to brake early on the street and so it really doesn’t matter how quickly my front compresses. And as for setting up front rebound, the Empulse doesn’t have the bite in the corners that a V-Twin does and so you’re not likely to jack the front end up when rolling on the throttle. That leaves suspension packing as the likely only factor that you can use to judge your front damping setting and I don’t really know what suspension packing feels like. The rear is just about as difficult on the street with the exception of rear rebound. That’s usually easier to set up because it’s easy to get the rear end to chatter in corner exits under power.
Anyhow, I’m going to leave this up to you as a very long-term project. The critical thing you you need to know is the following:
- How to adjust all four damping settings.
- The range of each setting.
- The original factory settings.
Three of the adjusters are free spinning (measured in degrees) and one has detents (measured in clicks). 0° and 0 clicks means fully open (fully counter clockwise).
Front compression damping is a flathead screw adjustment at the bottom of each fork leg. It has about 1080° of adjustment and is set from the factory at 360° or 33.3%.
Front rebound damping is a flathead screw adjustment on top of each fork leg. It has about 1260° of adjustment and it is set fromt he factory with 495° or 39.39%.
Rear compression damping is a black knob on top of the remote reservoir for the rear shock. It has 45 clicks of adjustment and is set from the factory with 28 clicks or 62.22%.
Rear rebound damping is a flathead screw adjuster on the lower clevis of the rear shock. It has 990° of adjustment and is set from the factory with 450° or 45.45%.
I still haven’t dialed in my damping settings, but I don’t know if I will move far from stock until I get a trackday under my belt. As for static sag, I feel like I’m there. I might add a little static sag to the front since the bike has a more upright riding position due to the standard bars. I am getting a new rear spring, but I still need to get some critical measurements of my shock and rear spring (including stock spring rate) before I can order one. Stay tuned (pun intended).