Braking 101: How Do Motorcycle Brakes Work?

Brakes are probably the most important part of your bike next to the engine. You need them to offer the best performance they can and be confident that they will not fail you when you need them most. In this article we will aim to explain how the braking system on your motorcycle works.

What are the best brakes for you and your bike? What’s the difference between sintered and organic brake pads? Does it really matter? What the hell is a floating disc?! We are going to take a look at the elements of your braking system and hopefully give a guide to help you make the right choice for your needs.

Piston to piston: Pascal’s Law

First off let’s look at how your brakes work. Generally speaking most modern brakes are hydraulic and based on the same principal. This is Pascal’s law, which states that “a pressure change anywhere in a confined incompressible fluid is transmitted through the fluid such that the same change occurs everywhere.” In layman’s terms this means that if you apply pressure to one end of a piston, the same amount of force will be generated through the brake fluid to a second piston at the other end of the enclosed area.

 

Still following? This is how your brakes work. You have one piston in your master cylinder which puts pressure on the brake fluid that is contained inside your brake lines. Since the fluid can’t be compressed further it forces the second piston, attached to your caliper, outwards against the brake pads. The same amount of force you applied to the first piston is transferred through the fluid to the second one. That’s why if you only pull the lever gently you brake gently as it transfers the same amount of force you apply to it. Brake harder and you’ll feel the braking system working harder.

Now the above only applies to hydraulic brakes. Drum brakes are mechanical. With a mechanical system, when the pedal or lever is compressed it pulls on a cam inside the brake housing, turning it and forcing the brake shoes against the inside of the wheel hub. Drum brakes are an older form of braking and tend to feature on classic motorcycles and cheaper, smaller capacity modern machines.

Drum vs Disc

When you are choosing your bike what brakes it has is a factor in your decision. Motorcycles and scooters generally have two options, drum brakes or disc brakes. Both have their own benefits and drawbacks. First, let’s look at how these work.

Drums:

Consisting of a solid case around your wheel hub containing two brake shoes facing outwards. When they have engaged a cam inside turns, pushing the shoes out onto the inside of the hub. This causes friction that slows the rotation of the wheels. When you release the brake, springs pull the shoes back into their original position.

Discs:  

These consist of a metal disc that is fixed to the wheel with a caliper mounted on it. The disc spins with the wheel while the caliper stays stationary. Inside the caliper are a set of brake pads –  two individual pads that sit either side of the disc. When you engage your brakes the two pads are pushed out from the caliper against both sides of the disc. This applies friction to slow the wheel down.

So what are the perks and the downfalls of the two types?

Disc Pro:

• Better performance
• ventilated options available for better heat dispersal
• Less prone to brake fade
• Can be used in conjunction with ABS

Disc Con:

• More expensive than drums
• Regular fluid changes are recommended
• Time-consuming to fix/replace

Drum Pro:

• Cheaper to produce
• Easy to fix or replace
• Cheaper replacement parts

Drum Con:

• More susceptible to brake fade
• Lower performance
• Generates brake dust (unhealthy!)
• Enclosed – so heat does not disperse as easily

A lot of older bikes will have discs on the front and drum brakes on the rear. Most of your braking is done on the front so this takes a lot of the stress whilst the rear is there just for the occasional bit of extra stopping power or slow speed control, so the worries of brake fade are essentially removed as they are not used enough to heat up that much. Nearly all modern bikes feature disc brakes front and rear as standard. Scooters and small capacity bikes often still have a drum on the rear. Drums are a lot cheaper and as a rule scooters are cheaper than motorcycles.

Visit our website to see the complete range of brake discs we stock.

A Brief History of Braking

 

Early production motorcycles such as this BSA had drum brakes on the front and rear – at the time, engine capacities were not as big as they are today, and speeds were not as high, so these did the job just fine.

MV Agusta was the first company to offer disc brakes on a production motorcycle in 1965 – as you can see in this image, these are solid discs (with a single pot cable-actuated caliper).

Honda was the first company to offer discs on the front and rear, with the CB750 in 1975.

Modern motorcycles tend to be a lot larger in capacity than those produced 50 years ago, and so the brakes are a lot bigger to handle all the stopping power they require. You’ll often see ‘twin pot’ calipers, as opposed to the early single pots on the early MV and Hondas. Most discs these days will also be ventilated and/or wavy.

Brake pad types

Organic pads:

These are generally made of a mixture of rubber, glass and an Aramid compound. It’s important to note that these days organic pads do not feature asbestos. Asbestos is great for absorbing and dissipating heat but has that unfortunate downside of being extremely hazardous to your health! Organic pads are all-rounders – they work as well as sintered in most conditions and are ECO-friendly. Due to their composition, these pads do not last as long as their metallic counterparts but they cause less wear on your discs. These are a good choice for smaller capacity bikes and offer smooth consistent braking. Organic brakes work better at lower speeds as they can’t heat up as much as sintered pads – perfect for the daily commute and short distance riding where braking is less extreme.

Sintered pads:

Also called metallic pads, sintered pads are made from a much harder compound than the organics. This means you get more stopping power at high speeds so they are perfect for faster sports bikes and racing. Normally made from metal particles fused together at high temperature. Since they are made of a harder compound they cause more wear on your brake discs. Sintered pads are more effective than organic at higher speeds as they can handle much higher temperatures, so they can be pushed a lot harder before you experience any fade.

You can view our full range of EBC pads on our website

Which disc is best?

So you have decided what pads you are going to have but now what about discs? There are a few things that you need to take into account when buying discs. The style of the disc is important – options include solid, drilled, wavy or floating, as well as combinations of these options. You are also going to have to think about what material the disc is made from. First, let’s look at the style.

Solid Discs:

These are exactly what they say. These discs are made from one solid piece of sheet steel or stainless steel. Solid discs are cheaper than other styles and can start to warp over time. Normally they are only between 4-6mm thick, this also contributes to how much they will warp. Solid discs are an older design, and nearly all modern bikes will come with at least drilled discs. If you have a classic motorcycle, you may want solid discs to stick with the vintage styling.

 

It doesn’t get much simpler than a solid disc

Drilled Discs:

These are basically solid discs that have had a pattern drilled into them. This has some great advantages to it. It enables more heat to be dispersed at high speeds without reducing the overall surface area of the disc. You can also get wavy drilled discs which disperse even more heat than the normal solids and wavy discs making them good for high-speed riding.

An example of a drilled Rezo Brake Disc

Wavy Discs:

These are essentially solid discs that have a pattern around the edge. Wavy discs were first developed for use off-road, before eventually making their way into road and race use. There are not really any performance improvements from them but they look nice and also disperse heat better than solid discs because of the extra material around the edges – they have a greater surface area than solid discs. Wavy discs tend to wear out pads faster than solid discs.

 

A Wavy Rezo Disc – notice the bobbins, making this a floater too!

Floating Discs:

A lot of modern motorcycles come with wavy discs, which “float” on bobbins rather than being fixed directly to the wheel. This let the discs move around with the wheel and stay centred in the caliper. It also stops warping and reduces the amount of heat that is transferred to the wheel hub. The centre section is normally made from aluminium whilst the outside is steel. When the disc heats up it will expand in all directions at once whilst sitting on the bearings. Solid discs are mounted directly to the wheel and when they expand they are pulled in just one direction, increasing the risk of warping. Floating discs can expand evenly and thus are less susceptible to warping.

Materials

When it comes to materials, nearly all brake discs are made of SUS 410 stainless steel. It is good at resisting corrosion and can even be hardened using induction techniques to increase its durability. If you are looking for something purely for the track there are carbon fibre alternatives but these are no good for road use as they need to be very hot to work well.

Brake shoe types

Brake shoes come in two forms – either organic (the same as brake pads) or grooved. The organics work exactly the same as the pad version, they wear out faster but are less damaging for the surfaces they work against. Grooved shoes will normally be found on off-road bikes and ATV’s but can be installed on road bikes as well, the grooves basically funnel dirt, water and other debris away from your pads so braking performance is not affected. When brake shoes were first used some mechanics would just saw these patterns into the shoes! Manufacturers do not recommend that you do this now and use high-pressure water jets to make the grooves.

Brake lines and fluid

Your brake lines make up part of the sealed system that allows pressure to be transferred from the lever to the caliper. It is important that your lines are sealed and even more importantly don’t have any air in them! If you have ever had spongy brakes this is caused by air or water getting into the hose which affects the pressure that the fluid transfers between your master cylinder and brake calipers.

Types of Lines

You have a couple of options when it comes to brake lines, these being stainless steel braided hoses and rubber hoses. Most Motorcycles come with rubber lines as standard and braided is considered a performance upgrade. The advantages of upgrading to steel lines is that they reduce bulging in your lines and are more resistant to becoming damaged or punctured. But what is bulging and why is that a problem? Well, bulging occurs in your lines when you apply the brake since it is pressurised the whole system will expand when you use it, reducing your stopping power. Braided lines help reduce the effect this can have on your stopping power as they do not flex and bulge with pressure. Rubber hoses are recommended to be replaced every ten years, whereas braided hoses are a one time upgrade. Once fitted, they should never need to be replaced.

We sell a wide range of HEL Performance brake lines that we make to order in house. You can purchase them on our website here. 

 

Now we are coming to an integral part of your brakes, the fluid! Without fluid your brakes would simply not work at all. Fluid comes in a few forms: DOT 3, DOT 4, DOT 5 and DOT 5.1, DOT 3 is an older fluid and is not used as standard anymore. The most common you will find is DOT 4 or DOT 5.1. 3,4 and 5.1 are all glycol-based fluids whereas DOT 5 is silicone-based. Let’s run through the differences between these types.

Glycol:

This is a hydroscopic fluid so it takes on water from the atmosphere which can lead to it becoming corrosive to your seals, hoses and pistons. The extra liquid will also lower the boiling point of your fluid which can lead to brake fading and reduces the stopping power of your vehicle. It is also famous for destroying your paintwork if spilt, so always be sure to cover your bike surfaces before doing anything involving it!

Silicone:

DOT 5 is silicone-based fluid. It does have a lot of advantages over glycol-based fluids – it is hydrophobic so actual repels other fluids rather than absorbing them, so it does not degrade over time. It is also non-damaging to your paintwork. However it is really expensive, has a lower viscosity and compressibility so does not have the stopping power of glycol fluid. It was originally designed for military use so vehicles can sit for long periods of time without the need to change the brake fluid. It was standard for Harley Davidson until 2006 when they switched to DOT 4.

Brake fluid boiling points

Different fluids have different wet and dry boiling points:

DOT 3: Dry 205C, Wet 140C DOT 4: Dry 230C, Wet 155C DOT 5: Dry 260C, Wet 180C DOT 5.1: Dry 260C, Wet 180C

Dry boiling point is the temperature the fluid will boil at when brand new without any extra moisture in it, while the wet boiling point is after 1 year of use. Most manufacturers recommend that you change your brake fluid and bleed your brakes every two years. This is a fairly simple job that you can do at home with a handful of tools.

 

You can see our full range of brake fluids here.

If you are unsure of the fluid your motorcycle needs, most bikes will say on top of the master cylinder which type is required and if it does not, get in touch with us and we will do our best to help you out.

Symptoms of poor braking:

Spongy feeling

This is usually symptomatic of air or water in your brake lines – as discussed, the brake fluid in your lines will degrade over time, and it is recommended to change it periodically to give the best braking performance. This can also be caused by brake fade – if you have been braking hard, or for an extended period of time. Your brake pads/shoes might also be worn and require changing. If you regularly brake hard, you need to be careful that you don’t glaze your pads, as this will reduce braking performance. Glazed pads are easy to identify by the shiny surface of the braking material.

A shuddering as you pull the brake lever

This would indicate warping in your discs or an issue with your brake caliper. It is definitely worth getting this checked out at a garage if you are unsure!

Squeaking when you apply the brakes

This usually applies to drum brakes – normally if weather conditions are damp, or you have a build-up of brake dust in your drums they will squeak. This won’t cause any issues, it is just irritating! This can be improved by roughing up the surfaces of your brake shoes and cleaning the drum. Be careful not to breathe in any brake dust!

That’s it!

So that’s is our guide to brakes, hopefully, you have found this helpful and will now have a bit more of an insight into how your brakes work and what you are looking for when it comes to your bike. If you need any further help you can always contact us at [email protected].

You can also see our full range of braking parts on our website – www.motorcyclepartswarehouse.co.uk. We have an extensive range of EBC brake pads and shoes, Rezo Discs and Hel hoses.

You can see our range by clicking here.