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This article was first published in 2004.
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Start talking brake upgrades and it’s easy to also start
talking lots of money and complexity. For example, going to bigger discs and
calipers could easily involve you buying and fitting larger diameter wheels, a
different master cylinder and different brake bias valve. Hmmmm – that’s fine,
but only if you’re happy spending a lot! But there’s an easier solution - try
upgraded quality discs, pads and fluid.
It’s all stuff that you can do at home, you get to keep your original wheels,
and it doesn’t need fancy tools or complex procedures. Best of all, all the
factory systems like ABS and EBD (electronic brake distribution) will keep
working happily and your insurance company shouldn’t turn a hair.
And the results? Less fade, more bite and a more progressive pedal. Sounds
good to us!
The First Steps
But before even thinking of upgrading brakes, they’s a couple of things you
should first consider.
Brakes can work only as well as the grip of the tyres on the road allows them
to: if the wheels are hopping in the air when braking over bumps (because the
shock absorbers – dampers – are stuffed), then a brake upgrade will be
worthless. Same with tyres – if the tyres have little grip, you can’t expect a
brake upgrade to make a helluva lot of difference. It sounds boring but it makes
sense – make sure that the suspension and tyres are up to scratch before
bothering to invest in a brake upgrade.
And if you think that suspension can’t make much difference to braking, check
out the story we did back in 2000 – No Float.
Going from stuffed suspension to new resulted in the braking distance of a BMW
318i falling from 16.6 metres to 15.4 metres from 80 km/h ... without any change
to the braking hardware! Those distances were recorded on a smooth track – throw
in a rough road and the difference could only increase...
Once you’ve considered the health of the suspension and the quality of the
tyres, it’s time to inspect the brakes. Jack up the car and place it on
jack-stands, then remove the wheels.
Brake Inspection
On disc systems there are three key areas to look at – how much meat is left
on the pads, the condition of the discs, and the general condition of the
calipers and hoses.
There should be at least 1-3mm of pad material left across the whole face of
the pad – in some cases, pad wear is asymmetrical so make sure that you use a
torch to inspect as much of the pad as possible. Note that while the texts say
1mm, this should be regarded as the absolute minimum and in many cases, pad
replacement should occur prior to this thickness being reached.
There are three aspects to look out for when inspecting discs.
Firstly, the discs shouldn’t be heavily scored or cracked. That is, the discs
surface should be shiny and flat, not badly scratched by the pads.
Secondly, the disc shouldn’t be thinner than the minimum recommended
thickness. The discs get thinner through two processes – wear, and being
periodically machined. If the disc has been machined a few times, and then is
worn thinner by the action of the pads, it may be at or below minimum legal
thickness. Some discs have their minimum stamped on them while with others
you’ll need to consult a brake discs catalog (eg www.dba.com.au)
to see what the spec is. You can easily measure the disc thickness with a
measuring caliper.
Finally, you should have a look at ‘run-out’, that is, see if the discs are
warped. This is most easily checked by turning the hub by hand – if the disc
resists being turned at just one part of the rotation because the pads rub at
this spot, it may be warped.
Here you’re looking mostly for brake fluid leaks, frayed hoses and the like.
A braking system should have no leaks at all and the hoses and lines should be
in good condition. If you have problems in these areas, we suggest that you take
the car to a brake shop to have the calipers overhauled and the hoses replaced.
Decisions, Decisions
What you decide to do depends quite a lot on what you’ve just found in your
inspection.
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Note that if you’ve discovered that the discs are below minimum thickness, or
the pads are at their wear minimum, or the discs are badly scored or have lots
of run-out, you have no option – at minimum,
maintenance is required.
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Normally, discs that are scored or have run-out problems are machined, which
both smooths the faces and also ‘trues’ them. However, another option is to take
the opportunity to replace the discs with a higher performance design. Same with
the pads, too – if they’re well down in material, you don’t just need to buy
stock replacements but instead you can upgrade. That way, the cost of the
performance increase is lessened – because you were already going to have to
spend maintenance money anyway.
Brake work is always done in pairs on the one axle – so you’d have both front
discs machined, or replace the front pads, for example. But you don’t need to do
all four wheels at the one time – so if you’re on a budget, keep this in mind.
Another thing to consider is how common your car is. If it’s a high priced
European exotic, for example, it’s quite likely that aftermarket upgrade brake
pads won’t be available off the shelf (in Australia, at least!). Instead it
might take a two or three weeks to get the right pads in – time when you don’t
want your car off the road. Another hassle can be with grey market Japanese
imports, where the dilemma is in deciding exactly what pads and discs fit the
car. (It’s seldom a problem sourcing the components in the end, but it can take
some time to work out what actually fits.) This is why inspection,
decision-making and ordering should occur before you have the whole brake system
in pieces.
In the case of the car on which we were working – a Japanese grey market
import Toyota Prius – the decision-making needed to take into account these
factors:
Scored front discs...
...that proved to be well under legal thickness and very rusty...
...and front pads well down.
But the back was a completely different story, because we’d recently upgraded
from the original drums to Corolla discs and matching calipers. These were in
much better condition, but since the front needed a complete upgrade, why not do
the back at the same time?
And finally there was the brake fluid. Nearly all brake fluid is hygroscopic
- that is, it tends to absorb moisture from the air. The more moisture that it
has absorbed, the lower its boiling point. That’s why brake fluid should be
replaced every two years or so... and why in the case of this import which came
without service records, fluid replacement was a must.
So what do we have on the shopping list? New discs front and back, new disc
pads front and back, and new brake fluid.
Picking Parts
The sky’s the limit when it comes to picking replacement brake parts – even
those that will fit straight in all the original spots. The discs can be
standard (ie a normal replacement), grooved (sometimes called slotted) or
drilled (the ones that look like mice have been nibbling holes). Pads can be
standard, grading all the way up to full-race.
As with all car modifications, it pays to be conservative when picking
upgrade parts. Race-style pads won’t work very well when they’re cold (ie the
required pedal pressure will be higher than normal in suburban driving) and this
type of pad can also be noisy. Drilled discs are more likely to crack than
undrilled discs, although this normally only happens when they’re worked very
hard. Some combinations of discs and pads will also result in warped discs, and
the higher the performance of both these parts, the quicker that they’ll wear
out. (Remember, discs and pads are both designed to wear – and the softer they
are, the better the braking and the quicker they’ll be abraded away!)
Discs and pads specified as a ‘street level’ or ‘towing’ upgrade will have
the least everyday downsides while still providing a noticeable improvement over
stock.
In the case of the Toyota we went for EBC Kevlar
‘black’ pads that cost AUD$79.20 for the fronts and AUD$59.40 for the rears.
Originally we had intended to use DBA Longlife slotted rotors but they proved
not to be available for this car. Instead, we sourced RDA replacement rotors
with custom machined slots. These cost AUD$187 a pair (front) and AUD$198 a pair
(back).
The brake fluid we selected was Castrol Response, a premium fluid.
So, that’s all the parts in hand – now, what about fitting them?
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Next: installing the discs and
pads
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