Surron Suspension

Upgrade Your Sur Ron’s Suspension for Free: Tuning Tips From a Pro Racer

By Mark Kitaoka – 

When the GritShift staff asked me to write about suspension their suggested title was “Best Suspension Upgrades.” Anyone that knows me at all can attest that “Mark seldom if ever says ‘best of blah blah blah’ UNLESS he’s talking about donuts!” It’s true though I’m a real b*tch about donuts and light…. Best is relative and anyone who says something is ‘the best’ especially in an article title is just using click bait.

Read about The Secrets of a Pro Racer on his Go-To- Tires here

Mark Kitaoka Sur Ron ebike

The true best suspension upgrade for a Sur Ron is to understand how all the parts work based on your riding style. There are a few parts you can add that will really make a difference, but before you spend all that money it’s important to understand that the right adjustments will make or break your setup even if it’s bone stock. Let’s explore what those adjustments are and what parts I installed to improve my Sur Ron’s suspension and overall performance.

How I Learned About Suspension

Before going further I wanted to explain how I learned about suspension. My tuner was formerly the Crew Chief for Erion Racing and the largest Ohlins dealer in the world. He mapped my bike, Dyno’d it until it mapped correctly, and changed the dogbone on the rear linkage to allow me to get on the power much earlier while exiting corners. So when Dan said to me, “I believe it’s time for you to upgrade your bike to Ohlins forks and remote shock” I asked him if he was planning to install a new pool in his home or buy a new Porsche! I had both the forks and shock revalved for me by RaceTech so why do I need Ohlins stuff! After thinking about his advice I got out my well used credit card and bought both along with an Ohlins steering damper.

I went to Buttonwillow which was my least favorite track and thought “Wow they must have repaved this POS track because it’s so much smoother.” Nope it was the new legs on my bike. Amazing. Then during my training with a top AMA racer, his pit chief would adjust my suspension or sometimes ‘pretend’ to adjust it and have me ride my bike. I’d make two laps at speed, come into the pits and he would ask me ‘Well…?” Sometimes he would adjust something, sometimes not. Tricky bastard.

Dan and my trainers have forgotten more than I’ll ever hope to know about suspension, but I am so fortunate to have had their tutorage.

OEM Suspension Setup

In the beginning, I like anybody else would get a motorcycle and not really pay much attention to the suspension. I’d hold the front brake lever and bounce the forks up and down just to see if they worked. Same with the rear shock. Because all motor companies ship and adjust their bikes to what they consider ‘average’ for the market, the bikes are shipping to hit the average sweet spot for the Sur Ron Light Bee. In reality this doesn’t just apply to the SR but all motorcycles whether they are dirt or street focused.

I purchased my Sur Ron in 2018 and it arrived with the white RST Killah forks and Fast Ace rear shock. Both dampers had preload, compression and rebound damping adjustments. I understand that the later models switched to DNM or Volcano inverted forks with respective rear shocks. The Killah’s use a spring rather than air as the spring for the forks. When mine arrived the damping as well as the spring were adjusted completely ‘out’ meaning the softest spring and damping rates. The compression and rebound were set to the lowest (softest) setting. So before I go further, let me clarify these terms:

  • Spring rate for a fork or shock is determined by air pressure or rated spring weight
  • Compression is defined by how much resistance the fork/shock places as the fork/shock is compressed forcing oil through the shim stack(s)
  • Rebound is defined as how quickly or slowly the fork/shock returns to its original position
  • High speed compression adjusts for sharp or sudden compression of the shock/fork as when your wheel impacts something like a square edge at higher speeds. Think of hitting a curb at 20 miles an hour. Generally more expensive forks/shocks come with high speed compression damping

The dirty blue and black levers are the Ohlins TTX compression settings. The black lever is the high speed and the blue dial the low speed compression adjuster.

Sur Ron suspension Mark Kitaoka

Fast Ace shock compression damping knob (- is for LESS compression, + is for MORE compression damping)

Sur Ron Fast Ace adjustment

Fast Ace shock rebound adjusting knob (S is for LESS rebound, F is for MORE rebound damping. Think of S as Soft, F as Firm)

Sur Ron Fast Ace shock rebound adjusting knob

RST Killah Forks. Later models of the Killah forks came in black but have the exact same internals.

Early Sur Ron RST Killah forks

RST Fork Compression Damper Dial

RST Fork Compression Damper Dial

RST Fork Rebound Damper Dial located on the bottom of the right fork tube.

RST Fork Rebound Damper Dial

First Adjust the Suspension TO YOU

I too fell into the mindset at the beginning where I’d ask a more experienced or faster rider to ride my bike. “Hey Colin, can you ride my bike and give me your thoughts on how I should set it up?” Or “Wow I just read an internet article that the BEST way to set up my suspension is by balancing a used condom on my nose and if it falls off it means I have too much preload.” Or a favorite, “Wow So and So the world downhill champion and Redbull Rampage 2021 winner uses Fox 40 Boost forks, they must be the best!”

Colin doesn’t own my bike, a condom won’t make me a better rider (at least on a Sur Ron;-)) and unless you’re piloting a 33 pound downhill mountain bike Fox 40s or for that matter any other fork won’t make you a champ.

Setting Fork Preload

For your forks determine what type of spring is used; air or physical spring. The very first thing to do is to adjust your preload for your body weight, including gear you will be wearing. A general rule of thumb for preload is to adjust it so that the travel range while just sitting on the bike, in your riding gear with your feet on the pegs should be 20% of the total travel of the fork/shock. And keep in mind that the percentage is A GUIDE not a hard and fast rule. Some tuners recommend a 30% preload range. And IN GENERAL with both forks and shocks the compression damping adjusters are located on the top of the damper and rebound on the bottom. THERE ARE ALWAYS EXCEPTIONS.

Get a buddy to hold your handlebars and sit squarely on your bike. Or if you have something like a front wheel chock you can do this yourself. Be sure to take a measurement of where the top of the fork tube sits prior in relation to the stanchion prior to mounting your steed. Settle into the bike and don’t worry about bouncing a bit. Measure how far the fork stanchions go into the tubes and then dismount the bike. Example:

  • You measured the top of the fork stanchion to the top of the fork tube before mounting and it measured 10”. After mounting the bike the fork stanchions showed 8” to the tube.
  • 8/10=0.80 meaning you have 80% left of travel which translates to 20% preload. If that percentage is higher or lower that means you need to adjust your fork preload softer or harder. If you have air sprung forks you will need to have a fork/shock pump. If your forks use a spring you’ll need a wrench to adjust the spring’s tension.
Measuring Sur Ron suspension adjustment

In this example I’m showing inverted forks. Tube seal at the top so you measure from the seal to the stanchion travel measurement band for preload span.

This example is of forks that use a spring. In this example I’ve marked the compression screw adjuster so that I can keep track of how many turns I’ve done when adjusting compression.

Compression screw adjuster marked

Various pumps for air sprung forks. I had one for my full suspension mountain bike and one came with the Dorado Manitou forks.

Air fork suspension pumps

Read your owner’s manual (GASP!!!) to determine how much pressure in PSI or BAR that is recommended by the manufacturer for your weight. If you are under 20% reduce the pressure and if you are over 20% increase the pressure until you are in that range. AGAIN 20% IS A GUIDE NOT A HARD AND FAST RULE.

Like all things mechanical, forks and shocks have a ‘sweet range’ where their performance is optimal. Setting your preload properly puts your suspension into that sweet range. It’s what most people like to talk about when referring to preload percentage. But later I explain other reasons setting your preload is as important if not MORE important for getting your Sur Ron’s suspension to feel and perform as it should.

If your forks uses a spring there will be a hex adjustment on the leg of the fork that allows you to either reduce or increase the amount of tension on the spring. Adding tension will reduce preload percentage, reducing tension increases preload percentage.

I also set my compression and rebound damping to the middle setting to start. I focused on compression first going up one click or down one click over the same terrain and at the same speed to determine if the compression felt correct for how/where I was riding. I then did the same for rebound.

Once I am happy with the forks I focus on the rear shock. Some people use a stick and measuring tape to measure the rear shock preload travel, but I prefer to use the shock’s Bottom Out Bumper (BoB). All shocks have them. In this image my Fast Ace shock’s BoB is slid to the top of the shock’s plunger. I measure the shock’s plunger length between the shock body and the bottom of the spring before sitting on my bike. Once I’ve done that I dismount and measure the distance the BoB had moved from the top of the shock body and do the same calculation I did for the fork.

Sur Ron rear shock adjustment

The Ohlins BoB

Sur Ron Ohlins rear shock adjustment

I then set both the compression and rebound adjustments to the mid-level. I take the same route at the same speed to determine how the bike is handling and adjust the compression by one click up or down until I’m satisfied. I perform the same with rebound as with the forks.

Aim for Balance Between the Front and Rear

Now here’s the thing, suspension is an eco-system, not the kind involving insects and plants, but the front affects the rear and vice versa. So as you travel along the same route at the same speed, determine how your bike feels. IT SHOULD FEEL BALANCED BETWEEN THE FRONT AND REAR. What the hell does ‘balanced’ mean?! Well some riders like a more firm front, others a more firm rear (no pun intended) so the Best Balance is the balance that is right FOR YOU AND WHERE/HOW YOU RIDE. It’s easy to think you’re some bad ass fast as shit rider, but the reality is often far from that. So believing that setting up/buying the settings or gear fast pros use is just silly. Suspension can be adjusted as you ACTUALLY BECOME FASTER. That’s the beauty of adjustable anything. Adjust it to your abilities, terrain, etc. Getting into a vehicle after a 4-11 person just drove it and complaining that there’s no leg room is just plain lazy. It ADJUSTS just like your suspension so use those adjustments to your advantage.

What Happens if I Can’t Get My Fork/Shock Preload Tight Enough?

So what happens if you cannot adjust your preload to 20% meaning no matter how compressed you screw down the spring or the amount of air pressure you inject it just isn’t enough? This is where having a physical spring has an advantage. An inexpensive method is to insert a length of PVC into the fork tube that houses the spring. Mountain bike forks (which the Sur Ron uses) only have air or springs on one side. You would need to refer to your user’s manual to determine how to safely remove the spring cap and then estimate the diameter and length of PVC to use to give you enough extra length of the spring. Or you can just purchase a longer spring if one is offered. For air spring forks, you’d need to send the forks into the manufacturer for adjustment.

Here Is the Hardware I Run On My Sur Ron

I’m using a 502 pound spring on my Ohlins TTX. I weigh 187 in full riding gear.

Sur Ron Ohlins TTX

Because I purchased a 9.5” TTX I had a custom shock tower extender made to bring the rear ride height back to the OEM level since SR shocks are 10.5 inches eyelets center to center. Ohlins does make a 10.5” shock but the max spring rate they offer is too low for my weight. Remember these are mountain bike shocks! Here Gerard is measuring my bike for the extender.

Sur Ron electric bike suspension modifications

The shock tower extender made of billet aluminum. Sano! And no sorry he’s not interested in making more for others.

Custom Sur Ron billet aluminum rear shock mount

I have heard countless times riders complaining that their Sur Ron ‘bottoms out’ when jumping or going over rough terrain even though they’ve screwed down or inflated their spring load to the max. Like I said in the beginning SR made the suspension for a wide swath of people, not every single person. Weigh 220+ even before gearing up? Well… you can lose some weight or buy new stuff.

I personally prefer the screw type shock spring adjusters over the stepped type. Both the Ohlins and Fast Ace use this type of spring adjusters. It just makes for the ability for fine adjustments.

Ohlins spring adjustment
Sur Ron rear shock

In the advice I’ve just outlined straight line testing and refining is a basic step. Some have questions about why pre load is important. If you consider riding on a rigid bike, no suspension at all or suspension with NO preload what happens? Proper preload allows the bike to ‘float’ when depressions in surface are encountered by extending the wheel down to the depression. A tire that stays in contact with a surface allows the vehicle to remain stable and the transfer of weight is reduced due to suspension absorbing the depression as it extends the wheel down into the hole or rut. To put it another way consider this:

  1. Your tire hits a hole in the terrain and your wheels do NOT extend down to follow the hole
  2. The ENTIRE front end of the bike, not just the wheel follows the detent in the terrain pitching the bike and YOU forward
  3. As your rear tire follows it does the same thing upsetting the angle of the bike

By not having the preload set properly instead of the wheels/fork/shock dropping down to meet the indent and keeping the bike stable you are pitched.

To illustrate this further

  1. Take your dominant arm and lock it at the elbow
  2. Put your fist of the extend arm against a closed door
  3. With your other hand quickly open the door while you have some pressure on the extended arm
  4. Then do the same, but with your arm bent

See the difference? It’s the very same thing by having proper preload. You can extend your bent arm to maintain your balance when the door is quickly opened. The ‘preload’ of your bent arm is absorbing the depression of opening the door by having the ability to extend without your pitching forward and losing your balance. This is my own “Wax On/Wax Off” lesson. And if you don’t know WTF I’m talking about NVM.

Most believe that forks/shocks just absorb impacts in the terrain, but it does so much more. In a turn, how your suspension reacts to the terrain and the forces applied by braking, acceleration and neutral throttle determines how fast you will proceed through the turn. Adding bumps, off camber or other factors like loose dirt exacerbates the inability of your tires to remain in contact with the surface. To put it into simple terms, you slow down or lose control, in some cases both.

Suspension is a Black Art

Now let’s talk about damping, compression and rebound. After setting preload this is where suspension becomes almost an art form. I’m going to mention here that once you dial in your suspension, unless you are riding in identical situations each time you swing your leg over your bike adjusting your damping is something to consider. Do I do that each and every time I ride? Oh hell no, I’m not racing. Like all things, and you will hear this over and over from me, I set my bike up as a compromise to my riding. I set my damping in the mid-point of how/where I ride so that I’m not fiddling with the effing thing every time. Like I said, I’m not racing. Set your compression so that when you press on your forks or when you press down on your pegs you get the right amount of resistance so that it’s not a jarring motion.

Same with the rebound, you don’t want to set it so high that the suspension packs down and does not recover well when downward forces disappear, but not so fast as to pogo your bike as if no damping is being used. Single clicks either way, more firm, more soft is the black art. The magic happens when you have set up your suspension where BOTH the forks and shock are working in harmony and I’m not talking about them singing Kumbaya around a campfire.

No, going over whoops, jumps and chatter should feel balanced. Having the right spring rate means you don’t bottom out the suspension and the right combo of damping means you don’t feel JARRING CHATTER. I cannot tell you how to specifically set up your damping simply because I don’t know shit about how/where/what you ride, how much you ride or your skill level. Experiment with damping and it will pay off dearly. The concept of ride it how you got it is for fools, and back markers.

Buying New Stuff

Hey we all like to do it. Mentally we like to believe that the new stuff we got at a great deal or what others call “The Best” feels great and makes us either faster or cooler than others. The saying “The bullshit stops when the green flag drops” is true. Sure you can blame your gear if you want, but skill level trumps gear any day.

Sur Ron fork swap

I talked to people who ride well and had experience with several brands of forks before deciding on the Dorados. I prefer USD forks because they are more rigid at the triple clamps. And for those folks who like to think that absolute stiff forks are the best, think again. Flex is necessary in a fork which adds to the feel of the connection between your handlebars and the dirt. I rode my Sur Ron with the Killah forks for about 8 months before I felt that no amount of adjustment would give me the performance or feel I wanted. So I made the choice to purchase and install Dorados onto the bike.

After riding the bike with the new front legs it became apparent that the rear shock didn’t match the performance of the forks. Remember that eco system I talked about earlier? Off camber turns caused the bike to track like a dream at the front but the rear stepped out and slid. So I found a used Ohlins TTX to buy. Both front Dorados and rear Ohlins damping include high speed compression adjustments which is really sweet. On fire roads with lots of chatter or single track that are rocky hitting square edged objects is much less jarring than before but more importantly allows me to maintain control. And keeping contact with the surface meant I had much more control of the bike in sketchy situations.

Sur Ron Dorado forks

To Sum It Up

Suspension upgrades can be done with the forks you own. Or it can be done having your forks or shock revalved or resprung. And of course it can be accomplished by buying new stuff. But remember that in order for your suspension to work WELL for YOU be they newly purchased, rebuilt or what you have, they need to be adjusted correctly.

So to me the Best Suspension Upgrades is KNOWING how to adjust your suspension and doing it. A mind is a terrible thing to waste…

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