How electric dirt bike brakes work
Most electric dirt bikes, including the Surron LBX, are equipped with hydraulic disc brakes. Hydraulic disc brakes work by pulling the brake lever on the handlebars and using the principles of hydraulics, pressure is transferred through liquid in a tube to pistons. These pistons exert a force on the brake pad which contacts a rotor attached to the wheel. This action applies a stopping force to the wheel, bringing your Surron to a halt. It is an identical system to what you would find on most modern mountain bikes.
Within this seemingly simple system, there are a few weak areas. The main concern is heat. Whenever friction is created, such as between the pads and the rotor, heat will occur. Heat weakens the brake system, and it could even boil the fluid. Heat gives a feeling of ‘brake fade’. There are also so many variables when looking at your brake system. What type of lever is best? What about brake pads? The type of fluid used? Let’s first look at what comes on the stock Surron LBX, and why brake upgrades are one of the most common mods.
First, let’s quickly recap the components of the brake system:
The master cylinder is mounted on the handlebar and contains the brake lever. It produces the pressure on the fluid in the brake lines. There are two independent separate brake systems on the Surron LBX, mounted on each side of the handlebars. One system is for the front brake and the other is for the rear. Unlike gas-powered dirtbikes, the Surron LBX uses hand brakes instead of a rear foot brake.
Brake lines connect the master cylinder to the caliper, also known as the slave cylinder. They are routed from the brake levers separately to the front and to the rear brakes.
Brake fluid can be any liquid that won’t compress. However, most liquids have low boiling point, evaporation, and compressibility limitations. The standard fluid is a choice between DOT fluid or mineral oil. Each has pros and cons; do not mix the types and only use the fluid your brake system has been designed for, as the components will corrode with the wrong type.
For the LBX specifically, DOT fluid is personally recommended and used by the GritShift team; it is a glycol-ether-based fluid. DOT stands for Department of Transport – meaning it is closely controlled and classified according to its performance properties, mainly its boiling point. DOT fluid has the advantage that it is hygroscopic; it absorbs any water that may be present in the lines. Dot 5 has a boiling point of 500°F (260°C), and DOT 5.1 has a boiling point of 518°F (270°C). An interesting point to remember is that DOT 5 fluid is not hygroscopic. Instead, it doesn’t absorb any water, and it is silicone-based. DOT 5 is unique and cannot be mixed with any other DOT fluid.
You may be looking at these temperatures and thinking that’s hot! But have you seen the red glow from the disks on race cars? And it’s not just the speed that could heat up the brakes – and fluid; it could also be repeated use over a long descent. If you’re on the brakes often, they will heat up, and the last thing you need is to loose the brakes entirely, which is what could happen. That would ruin your day! This is why choosing the correct setup is so important.
Mineral Oil isn’t as controlled, so stick to the recommended brands from the brake manufacturer. Unlike the DOT fluid, mineral oil doesn’t absorb water. This means a longer time between a brake service than the DOT fluid brake system. However, water is heavier than mineral oil, allowing it to sink to the bottom of the lines, and be the liquid closest to the brake pads. This also means it will be the first to heat up when under use. Water has a much lower boiling point than Mineral oil, creating a weakness, which is why we recommend DOT fluid.
Calipers, also known as the slave cylinder, are at each wheel and house the brake pads and pistons. Depending on the design, there might be one piston on either side of the rotor or more. Some calipers only have pistons on one side, others on both sides of the rotor. It is essential to note it’s not the number of pistons that determines stopping ability, it’s the surface area contact with the rotor. There are also various designs for the construction of the calipers. Some are one piece; others are two piece with a bridge that joins each side.
Pads are what cause the friction on the rotor. There are many different types of pads.
Organic: made from materials such as rubber, glass, or Kevlar. They are a softer compound, and therefore quieter. However, they wear down faster, particularly in mud and gritty textures.
Semi-metallic: like organic, but with some metal content. This helps with heat dissipation and lengthens the life of the pad.
Ceramic: Great for heat dissipation and longer lasting. A top-of-the-line pad.
Sintered: Made from hardened metallic ingredients. Good heat dissipation lasts a long time, but it takes longer to bed in and has a slight lag when the brakes are applied, as the best friction comes from warm components.
The Rotor is the part that stops the Surron, it is what is connected to the wheel. The larger the rotor, the more stopping force. There are a few different mainstream rotor designs, but all must run true with constant thickness and be able to dissipate the heat as quickly as possible.
What type of brakes are on the Surron?
Currently, on the Surron X, you’ll find an opposed four-piston hydraulic system with Metallic Brake Pads and a 203mm rotor. It is designed for mineral oil brake fluid. The stock brakes are more like mountain bike brakes rather than dirt bike brakes. This is for two reasons. Firstly, the overall weight of the Surron is roughly half the weight of a gas-powered dirt bike, so, thanks to physics, a smaller stopping force would need to be applied. Secondly, as the e-moto is so light, any increase in component weight will be very noticeable. There are some flaws in the Surron braking system, which the GritShift team has found when putting their Surrons to the test. As the Surron is heavier than a mountain bike, the brakes need to stop a heavier momentum, causing more friction and more heat. The stock system also uses mineral oil with a lower boiling point, so is easily susceptible to brake fade.
How do I know if my brakes need replacing?
This is a two-part answer. The first is about whether they are adequate. Secondly, what can fail and why? If you have brakes that are made for pulling up 30 lbs instead of 120 lbs, they’re not going to do the job very well. The biggest issue is heat dissipation. When I ride, I like to know what performance I’ll be getting from my brakes. Even at the end of a session on the track where you’re pushing it to the edge, I rely on that stopping power! But when you get heat that builds up in the system, it behaves differently. It could be subtle or a quick decline in stopping power. Brake fade, or more specifically, pad fade is when the pads literally start melting. Depending on the type, it may be the metal particles or the compound that holds it together. Either way, the melting properties give the pad a slight lubrication. Something you really don’t want! It shows up as your brakes just not giving you the stopping power you’re expecting, even when pulling hard on the lever. Troubles can also start if the fluid in the lines starts boiling. Boiling liquid produces gases, which are compressible. This will give you a spongy effect on the levers. Of course, you can get bubbles in the lines from other ways – such as a cut in the line or incorrect fluid replacement, but that is another issue that leads to bleeding your brake lines. It is really surprising how quickly the fluid can heat up to very high temperatures. It makes sense on a downhill run, with a large amount of stopping at the bottom, but it can also heat up very quickly with many uses such as on a tight technical trail.
Heat also causes other issues, such as warping your rotors. You could imagine what this would do when applying brakes. They just won’t work the same!
Other rotor troubles can start if your brake pads aren’t properly aligned. If one of the pads is touching the rotor surface unintentionally, you’ll be creating unnecessary drag, but also unnecessary heat. Without realizing it, you could be heating your brakes to a high level before actually using them.
As you can see, heat is a brake system’s worst nightmare. With the additional weight of an electric dirt bike, you need a system that will withstand the heat! I was going to ‘break’ this down (pardon the pun!) into two sections – a beginner or cheaper mod and a mod for those who push their Surrons to the limit and beyond, but I’m going to stick with just one option, which I’ll explain here:
Different Options for Different Riding Styles
GritShift’s R&D pro, Rusty said ‘For brakes I recommend ditching the complete stock system and going to a Hayes or Hope brake setup. These two setups utilize DOT fluid instead of mineral fluid…. I do this with all my bikes. We (the GritShift team) tried all sorts of combos of different fluids, different pads, etc., on the stock setup, and there is no difference, really. It feels better but still boils over way too fast.’
So, what does this mean? Basically, replace the stock system with a setup like Hayes Dominion A4 Brake kit. The Hayes kit from GritShift makes life easy, no bleeding of the brake lines or anything messy. It comes to you at the perfect length to place straight onto your Surron. The kit even has the brake pads installed and a spare backup set of pads. It doesn’t get much easier than that. The Hayes system also uses DOT 5.1 fluid in a four-piston design, eliminating the low boiling point issue. It has a strong Kevlar hose and works across all temperatures. This is something that the GritShift team can attest to. They push their e-motos to the very limit.
If you are a beginner or a weekend warrior, you might be thinking that replacing the brake system might be an overkill. But can you recognize brake fade quickly enough to do something about it? Upgrading the power is always well talked about, but it’s just as important to be able to stop! Although we would all love to say we’re pros, there’s a good chance that we don’t get to go for a ride as much as we would like. It could be weeks between rides for myself – life gets in the way! And that means my skills aren’t up to my usual standard like when I’m riding every day. That’s even more reason to have good-quality brakes that I can rely on.
On the other hand, if you’re jumping the triples and carving up the berms on a regular basis, you’ll also need top-notch brakes. There’s a good chance you’ll be pushing the Surron closer to its limits, creating more heat in your brakes. Yes, you’ll probably notice the fade quicker and respond quicker, but do you really want to let it interfere with your ride?!
Do you change the rotor? I would recommend changing the brake system first then see how your rotor holds up. All rotors will show signs of wear after a few heat soaks. If you notice it starts to warp, change it then. Save some money initially! When the time comes to change the rotor, check out the Warp 9 floating disc. Floating rotors are awesome because they are great at dissipating heat quickly and are lightweight. Just be sure to pick up the adapter at the same time, so your new shiny rotor fits your stock Surron LBX.
The question always remains on size. The bigger the better? Well, yes, up to a point. The greater diameter allows greater cooling. But at some stage, it just won’t fit on your e-moto! Adapters are great, but once again, only go so big. If you upgrade the complete front end to a MX style, that comes complete with a MX style brake system. The other side of the question is weight. Actual weight, and applied sciencey forces. Spinning a larger circle of metal creates a gyroscopic force. It’s not as much as your wheels create, but it is another force that could affect stability. (If you’re not up to speed on gyroscopic forces, just think of how your balance is on a stationary e-moto vs a moving one – that’s gyroscopic forces helping!)
How to change the brake system on a Surron LBX
(This guide is not exhaustive; it is to give you an idea of what to expect if you are going to tackle changing the brakes yourself)
Remove the stock lever and unbolt the rear caliper.
Remove the brake line from the frame (This may involve removing some components to get to the brake line.)
Rethread the new line through the frame. (This also may involve removing some components to replace the brake line – or if you kept them off from the first step, to replace the parts)
Mount the new rear caliper, ensuring it is centered on the rotor.
When to make the changes to your brake system.
Surron brakes not working like you’d expect? Time to change! Whether it’s a spongy feel or you’re pulling the brake lever as hard as you can and your wheels are still turning, it’s time for some work in the garage! Like I’ve recommended before, always ride your stock Surron first. Find out what it feels like. Then you’ll know if you’re happy with things as they are, or know if any upgrade is actually an upgrade.
If you still have a stock brake system on your Surron, consider changing it to something more robust. If you’ve already done an upgrade, it might be time for some maintenance. You should be replacing your brake fluid every year as a minimum to avoid that spongy feeling. Side note, only buy small quantities of brake fluid as its shelf life is very short once opened. It is also very corrosive, so be sure to handle it appropriately and store it safely away from children.
What is the maintenance on the Surron brakes?
If you’re the proud owner of a pre-loved Surron LBX, I would suggest reading this paragraph also, unless you can 100% say when the last maintenance was completed within a respectable timeframe, and are happy with the outcome. Most brakes will require you to change the fluid every year or two, depending on use. Even if your Surron has been sitting in the garage over winter, I personally would be changing the fluid in the lines, or riding very cautiously. If condensation has accumulated in the lines, the fluid will not be effective and you might be in for a nasty surprise with a fast-approaching corner.
When you pull the brake levers and don’t get that firm bite, also look at your brake pads. They probably will need replacing. If you’re getting a shudder as you brake, it could be that the rotor has warped. That will also need replacing. There are plenty of online tutorials to guide you if you have a little mechanical knowledge. Otherwise, you can take your Surron to a reputable mechanic to complete the work. Riding an e-moto is no different from gas-powered dirt bikes or mountain bikes, or your car for that matter – brakes need regular servicing. Look after them, and they’ll look after you.