Which type of motorcycle brakes
Disc brakes | Drum brakes | Twin leading shoe | Single leading shoe | Brake pads
There are two types of motorcycle brakes in common use. Drum brakes and disc brakes. Both have their advantages disadvantages.
Drum brakes date to the turn of the 20th century; around 1902 or thereabouts. They were first used on cars and then on motorcycles.
The prime advantages of drum brakes is that they offer a self-servo effect. In other words, when the brake shoes make contact with the inside of the drum, the shoes tend to grab a little and exert extra stopping force. Disc brakes have no self-servo effect. Also, drum brakes are more enclosed and are less likely to be affected by rain water or puddles—and they emit less environmentally unfriendly brake dust (the dust tends to be captured within the drum and can be wiped/swabbed away carefully during routine brake servicing).
Brake shoes used to be made from (dangerous) asbestos. Nowadays manufacturers use organic fibres bonded in resin.
Drum brakes are generally simple to maintain, but can be a little tricky to set-up for best performance, especially when twin-leading-shoes (TLS) are employed.
So what's a twin-leading-shoe (TLS) brake? Well, this design has two shoes that both lead/grab. Consequently, both shoes offer a self-servo effect and have more stopping power. A TLS brake also has two trailing shoes. A single-leading-shoe (SLS) brake, meanwhile, has one leading/grabbing shoe, and one trailing.
Imagine riding a motorcycle and suddenly putting down the sole of your boot. Friction will try to snatch away your foot and/or force it down harder on the tarmac. That's a self-servo effect, and it could be extreme. So care should be used. But if instead you drag the toe of your boot, that doesn't have the same self-servo effect. Your toe will bump along with far less risk of a sudden grab. It's the difference between a leading shoe and a trailing shoe.
Drum brakes are generally considered more "classic" or "traditional". They need more maintenance than disc brakes, and due to poor maintenance often develop an unfair reputation for weakness or inefficiency. Check our BSA/Triumph conical hub page.
Disc brakes arrived in the mid-1950s for cars, but took another decade or so to be fitted routinely to motorcycles. These are more effective than drums. Why? Because drums overheat quicker, and that leads to brake "fade", meaning a progressive loss of friction. Discs, meanwhile, are better cooled by the oncoming air, and so fade less. However, discs can be negatively affected by puddles and rain water that gets between the disc and pads thereby temporarily reducing friction. Usually a quick dab every once in a while (during the wet) keeps discs dry and effective.
Meanwhile, brake discs can also cause problems. The example to the left is from a T140 Triumph Bonneville. It's cast iron (which is good), but chromed (which is bad). Yes, cast iron can rust, but in regular use that isn't an issue.
But the chrome wears, and that leads to "snatchy" operation. Tip: de-chrome these discs, or buy plain cast iron.
Stainless steel disc can also be weak, and any disc can become badly scored/ploughed leading to reduced efficiency. Like drums, these need to be inspected regularly.
Discs tend to be fitted at the front. Drums tend to be fitted at the rear. Many classic bikers with post-1970s machines prefer a combination of disc and drums. Most modern bikes have discs front and back.
Ultimately discs are better brakes, technically speaking (and within certain criteria). But there is still a place for drum brakes—especially with regard to feel/feedback. Discs often suffer in this regard and can be more "on-off" as opposed to progressive.
Remember to look at our Motorcycle Workshop pages too. We have more helpful tech tips there.
Copyright Sump Publishing 2019. Terms and conditions