JP is a master of many tricks. Working as a bike journalist, he's been testing, analysing and writing about on and off-road motorcycles for various UK magazines, both as a staffer and a freelance journalist, since the nineties. Testing everything from Valentino Rossi’s MotoGP bike through sportsbikes, commuter bikes and, of course many, many miles on adventure bikes. JP has also spent much of his life competing at up to International level in trials, enduro, extreme enduro, circuit racing and hillclimbing. He also instructs at the Off Road Skills motorcycle training school, coaching and encouraging people in the ways of riding adventure bikes. Also a fan of vegetables and sea products.
We all know how important brakes are to the job of riding a motorcycle. Pretty damn important. So the notion of maintaining them ourselves or understanding them better is naturally a daunting one to many. Not least because people are worried about messing them up by putting something back in the wrong way around or not tightening something up properly. It’s understandable.
Be inquisitive though, have a little confidence and you can have better understanding of how your brakes work, what to look for in terms of maintenance and potentially have a safer biking life.
Along with tyres and oil, brake pads are the next likely mechanical part you’ll need to worry about on an adventure trip of any length so let us help you with a guide to brakes. Next issue we’ll teach you how to change your pads but first things first, here’s how they work and what to look for…
Basically our brakes work as follows: a hydraulic braking system (which most modern bikes have been using for decades now and is the type most likely to be fitted to your bike) is a lever which you pull or stand on to squeeze oil inside a tube which pushes some pistons inside a caliper (at the other end of the tube) which push on some pads (inside the caliper) that squeeze a flat metal disc bolted to your wheels. It’s not complicated really but it does have parts which wear and degrade with time and so needs maintenance.
Generally speaking your brake pads, those things which grab a hold of the brake discs to slow you down when you operate that brake or foot lever, need keeping an eye on. They wear out naturally enough and so keeping an eye on them means you can do something before you arrive at a point where you have no brakes left.
Brake pads are constructed in two parts: a metal backing plate and a fibrous pad material. Each of these two parts can be made of different materials, especially the pad material itself.
In general the backing plate is the mechanical part which fixes the pad into the brake caliper which sits around the outside of the brake disc or rotor. The caliper is the means by which the lever you pull at the handlebar can apply pressure (usually hydraulic in an oil line) through small pistons, which in turn squeeze the pads and that fibrous material against the disc(s).
Pads generally speaking need replacing when they are getting below 2mm of pad material left. In the UK the law is 1.6mm and it can vary slightly depending on your national law, if indeed one exists. That measurement is taken at the most worn part of the pad.
It’s fair to say if you can hear a metal-on-metal, whales being murdered kind of sound when you brake, it might be time to change them. For the record, metal-to-metal contact between pad and disc is not good because there’s very little bite from the pad, heat builds up very quickly and it is very damaging to your brake disc or rotor.
You can inspect pad wear usually by looking down inside the caliper and seeing how much pad material is (or is not) left between the pad backing and the disc. On most pads you’ll also find a wear indicator – simply a groove or line through the pad material which, when worn down to no longer be visible, indicates you’re had your monies worth.
As an example the rear pads on BMW R1200GS has one pad thicker than the other because they wear at different rates
Like any maintenance it’s worth inspecting your pads regularly for problems, uneven wear, oil leaks etc. But if you’re planning a long trip somewhere, or are in the midst of one, then keeping tabs on how much pad material you have left is a must.
Bear in mind the wear indicator (or around that 1.6mm benchmark) is there for a reason – below it and the pad is likely not to operate as well, particularly it won’t disperse heat properly which in the worst case scenario can mean the pad material delaminating off the backing and a pad failure.
Another reason to replace pads earlier rather than later is the pistons inside the caliper naturally have to push out further the more the pad wears so by the time the pad is worn right down the pistons can be out a long way, getting covered in dirt and quite likely causing some sponginess at the brake lever for you.
Organic or sintered, a mixture of both? There’s a lot of science behind brake pad technology. Usually it boils down to cost versus wear-rate. Road race bike (steel disc) pads are designed to be tremendously strong, dissipate heat well but they don’t like sitting cold and unused for miles and then being asked to work all of a sudden. They can cost more and wear out quicker too. The flip-side is obviously a cheap, hard-wearing pad that has less feel and stopping power. You will find everything else in between. A lot of the science comes in the pad material itself, which is effectively like a load of different cake mixes.
Organic pads tend to be softer and therefore both wear quicker but have less wearing effect on your discs. They can have better feel too. Sintered pads usually disperse heat better and last better because they contain metals but can wear you discs quicker and sometimes have less feel.
Aftermarket versus OEM
Brake pads can be a contentious issue and certainly forums will tell you anything you want to hear/not hear on any given braking subject. None more so than whether to buy original equipment (OEM) or aftermarket pads.
To an extent the brake pads which are original equipment in a bike have been designed to suit that caliper, that disc on that bike ridden in a broad range of circumstances – therefore it is the best pad for you to buy as replacement. A particular part number for your model bike can often mean those pads are tailored to your bike far better than any aftermarket pad is going to be. As an example the rear pads on BMW’s R1200GS has one pad thicker than the other because they wear at different rates according to how the caliper applies the pressure. An aftermarket manufacturer may not be aware of this and you could well find you wear one side quicker than the other.
To an extent that is also not true. Bike manufacturers also have a habit of treating things with a broad brush and specifying the same pad material for different models on their production line, choosing a particular compound for their pads because it will cost them 0.2 Cents less across 40,000 units, or simply specifying a particular compound which suits their warranty implications of a bike (and therefore costs them less in servicing).
You can also say all of the above about aftermarket brake pad manufacturers who can be making one pad compound to suit many bikes just as easily as they can be working hard to tailor-make pads by hand to suit many bikes.
It’s also worth considering the fact that most of the brake pads manufacturers are actually branded parts made in just a few factories around the world. For example many aftermarket and OEM motorcycle pads are in fact made by Ferodo in Italy.
So don’t trust the forums, go with recommendations for sure but go with experience more so.
What to chose on a long trip?
On a typical bike clocking up 10,000miles for example you’ll probably find the rear pads won’t last as well but both front and rears are likely to get close to or hit the bone in that time. With so many modern bikes having linked brakes, despite the fact that we should all use the front brake more, you’ll likely wear out the rears over that distance and probably the front too – depending on how and where you ride.
Different riding styles wear pads out at different rates of course but it would be wiser to look at sintered pads as a fitment if you’re about to set off on a high mileage trip because they’ll last longer.
If you’re doing any kind of maintenance on your bike’s brake system you need to understand how that system works particularly on your bike. Complexity of braking systems varies quite a lot between simple on very old bikes to very complex depending on how new/old, whether they are linked and how the ABS system is configured. It’s difficult to offer specific advice because so many systems are different.
Which brake fluid to use is a huge discussion point for many of the more nerdy among us (as well as our friend and king of the mechanical nerds Evan Davies, who helped us put this feature together). Simply, DOT4 brake fluid is all you need to worry about. There are other ‘superior’ brake fluids, such as Dot 5.1 but DOT 4 is inside the vast majority of all braking systems on any bike. So you haven’t got to worry about cross-contamination if you’re replacing or topping up fluid levels. There’s also no fear the fluid is going to mess with the strength of the o-rings in the system either (different rated fluids can cause perishing or degrading of seals designed to be used with DOT4 fluids). And, importantly, DOT4 is very widely available from pretty much any type of garage in the world.
You should change or have your oil changed every two years at least, and that is a time based factor not mileage. A visual check never hurts so if your fluid is looking a bit dark or Tar-like it’s probably time for a change.
If you’re on a really long trip changing the fluid is something which needs to be factored in before you leave or during the trip. Brake fluid is hydroscopic, it’s thirsty and tries to absorb water from wherever it can. It seems physically impossible but water can get in over time. Particularly if you’re adventure riding in wet climates, through rivers a lot or such like the brake fluid will be trying hard to suck some of that water, albeit very, very tiny amounts, through the hoses, seals at the master cylinder and calipers – anywhere it can. That water degrades the performance of the brake fluid over time because the brake system is designed to work with DOT4 fluid, not a DOT4 and water mixture.
Disc or rotor wear
Another aspect to take notice and care of is the brake disc itself. The pad is part of the equation but, although it wears at a much slower rate, the disc needs checking too. Most bike brake discs have the lower wear limit written on them somewhere. You should also be able to tell for yourself if a disc is wearing down because you’ll be able to feel the unworn lip on the outer edge. You’ll feel grooves and it’ll feel thin if you run your fingers across the surface. You’ll also see when you fit new pads if the disc is worn. If there are daylight gaps behind the pad and the disc surface then something is wrong. It may also feel spongy initially.
Look also for uneven wear, or scoring of some sort, if stones have had an effect. If a disc has got too hot for some reason it can also warp, so you’ll feel a pulsing at the lever. Inspect around the holes on discs as well because they can crack if old/thin or if they’ve been overheated.
General ‘other’ items to check
Brake pads are also held in by pins, as a rule, and they need checking for wear which can occur over time and prevent the pads from moving as they should. Check the calipers which sit on a sliding pin themselves, often the rear. They can warp, become corroded or gummed-up with dirt. Those types of calipers should glide smoothly to allow the brake to work properly.
The pistons within the calipers should be crud-free and not seized in position too. Over time road and dirt gets baked on pistons, particularly those where pads haven’t been replaced very often and this can lead to the pistons sticking. Don’t be tempted to whack a screwdriver in there if they are seized by the way. Pistons are made of soft, thin metal and you’ll easily bend, score or break them, let alone damaging the pads too.
What do you do if your pads are knackered and you’re miles from anywhere?
It wouldn’t be the first time someone has found themselves caught miles from anywhere with a diminishing set of pads. Dirt, particularly wet sandy dirt, can get in and act literally like grinding paste eating away at brake pads in no time. So what can you do about it? Ride smart.
Best case scenario is you’ve spotted the problem good and early so you can adopt a different way of riding early on to minimize wear. If you think about how your pads work (another reason why you should get hands-on with your bike – to understand how it works better) that’ll help understand what you need to do to reduce pad wear.
Quite obviously if you use your brakes less the pad will wear less so riding more conservatively, using engine braking, shutting the throttle good and early to get yourself slowed down before you need to brake will help and reduce wear. That means looking ahead more and planning what’s coming rather than reacting like a city driver to everything in front of your nose. Use one brake more the other if they haven’t worn evenly will be a solution too.
You can get away with using worn pads, for a bit, within reason – and the truth is many people have done it. It will still work but clearly not as well. It’s a last resort, you shouldn’t use the brakes with any force and you should use the lever for as short-a-time as possible. The pad metal will likely wear quicker than the harder disc material, but going metal to metal will savage the brake disc badly.
As mentioned above, now we’ve covered the what to look for and how it works side of brakes we will move on in our next issue to cover in detail how to change brake pads.
We’ve gratefully used the knowledge of Evan Davies for this feature. Evan is a highly experienced motorcycle mechanic who’s remit includes many makes and models. Not least Ev’s a veteran Dakar Rally mechanic and technician in charge of the BMW Off Road Skills workshop. It would be hard to find of a more widely experienced adventure bike mechanic, certainly there aren’t too many busier ones.
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