Time to hit the brakes!
Welcome to this week’s tech talk at Venom Motorsports!
Many customers have asked questions about their brakes. So in this week’s blog we are going to chat about typical brake systems found on our bikes.
Please click on our excellent “Brakes” video links below for more information.
Keep in mind that this information applies to all of our excellent Super Pocket Bikes, Dirt Bikes and ATVs!
Ok, onto this week’s topics;
Tim...Why are brakes so important?
Braking systems seldom enter our minds. We always ask how fast will that bike go?
However, no one has ever asked me...how fast does it stop?
Why? The only time most of us are concerned about the brakes...is when we need to come to a sudden stop...and the brakes do not work. Then at that very moment we are really interested in our brakes!
I had my learning experience about inertia while driving a dirt bike through a field when I was a young wart hog. Came upon a ditch, not fast enough to jump it, and my brakes did not work well enough to stop me in time. So, I got to eat some dirt that day...and learned a valuable lesson. Inertia means that a body at rest will remain at rest, or a body in motion will remain in motion unless acted on by an unbalanced force. Even though the dirt I was eating was trying to brake my motion, my own inertia still drove me forward, until the forces balanced each other and I came to a stop. Gotta love Physics!
So what was the lesson? Always, Always, Always check your brakes to ensure that they work properly before going out for a ride! Yes, that means both brakes front and rear. In an emergency situation one will not stop you fast enough, you need both front and back to be working well.
Tim...Why do some brakes systems use oil and other do not?
These days many bikes use braking systems that contain brake fluid, typically DOT 3 grade. This means that the whole of the braking system contains brake fluid to use the effects of hydraulics. Hydraulic systems are used to transfer force instantaneously within the hydraulic system. So as soon as you apply pressure to the brake lever the bike calipers grab the disc and the bike stops.
Prior to hydraulic systems, cable systems were the most common type of brake system found on bikes. This sort of system has been used on bicycles for ages. If we beef it up a bit with stronger components it works very well on our bikes and ATV’s. Cable systems work well but cannot match hydraulic brakes for pure stopping power. So typically you will see hydraulic brake systems used on larger bikes.
You may also find a hybrid system with cable on the front and hydraulic brake on the rear wheels of your bike. This is a wise system as it prevents the operator from applying too much front brake and not enough rear brake.
If you have too much front brake you are going to do a “Superman” right over the front handle bars. If you have far too much rear brake action, the rear wheel could lock up and skid you out.
So it’s very important to apply the stopping force as evenly as possible, too brake in a safe controlled manner.
Tim...How do non hydraulic, cable based braking systems work?
There is a very good chance that you have seen this sort of system on a bicycle in your younger days. The brakes are activated by pulling on the brake lever. This generates a tension in the brake cable which is transferred to the brake caliper...which in turn squeezes the brake pads onto the brake disk and stops the bike.
Having the correct tension in the brake cable is the key to proper operation.
The brake cable tension can be adjusted at the caliper by the tensioning adjustment nut.
This allows you to increase the tension as needed to get a good braking effect when pulling on the brake lever.
If the brake cable tension is to slack you will have to pull the handle almost all the way in to get any sort of braking action, not good...as we typically need to stop “NOW”.
So, always ensure that the brake tension is well adjusted. Next have a look at the brake pads. The brake pad acts on the brake disc to stop wheel rotation. If the pads are worn the contact area of the pad is reduced and your braking effect is reduced. It is the friction between the brake pad and brake disc that stops the bike. More brake pad contact area = better braking action. If the pads look thin and worn, replace them.
While inspecting the brake system it is always a good idea to check the alignment of the brake disc and caliper to ensure that the disc is not warped or that the caliper is not properly aligned.
To properly align the caliper, check to see that both sides of the caliper are parallel to the disc. This will ensure maximum contact between the brake pads and the brake disc.
Tim...How do hydraulic brake systems work?
The braking action between the caliper and disc is the same as a non hydraulic, cable based braking system.
The big difference between the two systems is that a cable based braking system uses a wire cable to transmit force. A hydraulic brake system uses brake fluid to transmit force from the brake lever to a piston in the master cylinder. The piston in the master cylinder then pushes on the hydraulic fluid in the system and generate a pressure. Liquids cannot be compressed, and this fact produces an increase in pressure within the hydraulic fluid that is transmitted throughout the whole of the hydraulic brake system.
This increase in pressure then pushes on the slave cylinder piston built into the caliper at the wheel to push the pistons forward. As the piston moves forward in the caliper cylinder it pushes the movable brake pad forward to make contact with the brake disc.
When the brake pad touches the disc, friction between the two surfaces creates resistance and stops the wheel from rotating.
Keep in mind that for a hydraulic system to function properly it must be full of hydraulic fluid and have no air in the system at all. If you do have air in the system your brakes will feel spongy or soft.
You can check the level of hydraulic fluid by taking the master cylinder cover off. Usually that only involves removing a couple of screws and gently lifting the top cover off. Be careful as the gaskets will be reused.
If the level is low simply fill it to the indicated fill line which is on the inside of the master cylinder fluid reservoir. Keep in mind that as your brake pads wear the level in the master cylinder will drop. So if your master cylinder is very low, check the brake pads first and replace if necessary...before simply adding more hydraulic brake fluid.
Should you get air into the system you will need to bleed it out. This process is easier with two people. One person will squeeze the brake lever and hold it under pressure, while the second person opens the bleeder valve a little and allows any air to flow out.
Once you have a solid steady stream of oil coming out of the bleeder valve all of the air has been purged from the system.
If you have any tech questions about our vehicles, please feel free to email them to...
Check out our blog next week as we look at bike electrical systems.
Checkout our braking systems video by clicking here
Till then, Enjoy the ride!
Technical Support Specialist
Venom Motorsports Canada