Brake Upgrades

 In Brakes, Wheels, Suspension And Steering, MGA-MGB, Midget

When do you need to upgrade your brakes?

For normal – even exuberant – road use, the standard brakes are fine, especially if fitted with uprated pads and linings. My key reference point here is rally use – I always rallied on standard discs, calipers and drums (but with well uprated linings) and never remotely had a problem in stopping power. (Odd bit of smokey, but no fade – though wear at the rear was a problem) Another MGBGT owner here competed in the New Zealand Targa rally for 8 years on an identical set-up and also never had a problem. Both of us were very competitive, so the brakes had a hammering.

Racing on fast circuits certainly does require more from the brakes, so upgrades are definitely needed.

For the road, I usually observe that if you are wondering whether to uprate, then forget it – if you drive that hard, you won’t have a licence for long!

If your main concern is about coping with the odd emergency stop on public highways, read no further – the standard brakes will cope with this with plenty to spare.   The best investment you can make to achieve this outcome is to ensure you have quality tyres fitted as in these circumstances the grip of the tyres is the weakest link.

Notwithstanding the above, if you are still keen to upgrade your brakes, there are a number of options for doing so – it usually comes down to the money!

What is involved in an upgrade?

There are a number of options for doing so – it usually comes down to the money!

The three basic methods of brake upgrade are:

  • Brake booster/servo
  • Improved linings
  • Upgraded rotors/drums/callipers etc.

(You shouldn’t need to change your master cylinder – it should perform well with any upgrade of the rest of the system. )

In deciding which of these to undertake, you need to consider which of the three factors (there are only three) which affect braking capacity is limiting braking performance:

  • The grip of the tyres on the road
  • The frictional grip of the brakes themselves
  • The capacity of the brakes to dissipate heat

Of these, the most common limiting factor is the grip of the tyres.   Most brakes are powerful enough to cause wheel lock-up so the second factor is seldom the limiting one. (Though modern cars differ a bit – see below)

The third factor, heat dissipation, comes into play when repeated heavy application of the brakes are made – such as when racing, driving hard on twisty roads, or on long downhill roads.  High temperature causes the frictional grip to reduce.   Under arduous conditions this becomes the limiting factor.

Brake balance

Before you start, you also need to understand that the most critical aspect of upgrading brakes is to retain the optimum front/rear balance.   You could spend thousands on better brakes, yet be no further ahead (or even worse off!) if one end of the car locks up well before the other has reached full braking effort, as this limits the total amount of effort you can apply and still have control.   If doing any more than fitting a booster, critically check this aspect and be prepared to rectify it through such means as changes in wheel cyl size or adjustable front/rear bias controls (mechanical or hydraulic).

Brake boosters were optional on the MGB and not available ex-factory on the Midget or MGA. They do not increase maximum braking power (as the grip of the tyres on the road is unchanged), but they do reduce the effort needed by the driver to apply the brakes.  This means that for any given amount of pedal pressure the car will stop harder …. but the maximum deceleration is still the same as it’s the tyres which are the limiting factor.

On an MGB the brakes have enough capacity without a booster to lock the wheels anyway, and even in my own B with dual master cyl’s and competition linings (both of which require extra effort) and no booster, I still have to take care to avoid lock up under heavy braking with sticky tyres.

The big advantage of, and main reason for, fitting a booster these days is that most other cars have them, and when swapping between cars which require vastly different pedal efforts it can be very strange and disconcerting – notwithstanding that the brakes stop just as well with enough extra push on the pedal.   I remember almost ending up in the creek down the road after getting back in the B following a period of driving my brother’s Falcon which had very boosted brakes!

This is especially an issue for small women (as Bronwyn finds) as they can lack the oomph behind the pedal of an unboosted car they are not used to.  A booster can be very useful in such situations.

Ironically, modern cars have become dependent on boosters, as they have reduced mechanical advantage in the hydraulics on the assumption that the booster will be there to make up for them.  If the booster is not working on one of these, the pedal pressure needed is so high you almost need to use both feet on the pedal!   Yet the limiting factor remains the grip of the tyres on the road.

Lining upgrades allow the brakes to operate at much higher temperatures before encountering problems.

For fast road spec cars, lining upgrades are usually enough and certainly worth trying as a first step – but be prepared to go further if you are a hard charger into the corners.

As noted above, for the MGB the standard brakes are up to normal, even fast, road driving so it’s only if into competition that the linings/rotors need upgrading.

Having said that, not all linings are the same, and some “standard” linings are sub-standard.   If your brakes get excessively smelly, or the pedal effort increases as the brakes work harder, then a lining upgrade is worth considering.

For the Midget, or earlier MG’s with front drum brakes, a lining upgrade is definitely useful if you like twisty downhill bits of road.

Disc rotor etc upgrades.

As noted above, lining upgrades allow the brakes to operate at higher temperatures.   Disc or drum upgrades reduce the temperature the brakes run at.   There are a number of ways of doing this:

  • Increasing the mass of the disc allows it to soak up more heat – but can’t dump it any faster.
  • Ventilating the discs allow them to dump the heat faster.
  • For drums, incorporating fins will help dump heat faster. (The simple way to upgrade drums is of course to change to discs!)

Again, my rally experience indicates to me that rotor or drum upgrades for an MGB or disc braked MGA aren’t really necessary for the road.   Midgets or drum braked cars driven vigorously may be worth thinking about if you have tried uprated linings and found them wanting.

For sprints, hillclimbs etc,  the requirements are no more arduous than fast road work – perhaps less so.

Circuit racing is significantly different.   The speeds are higher and on most circuits at least once per lap there is a high speed approach to a tight corner.   If your car is seriously quick, you’ll need brakes to match.

The simplest disc upgrade involves fitting the MGBV8 disc rotors at the front, which are quite a bit thicker. To accommodate the thicker rotors, a spacer needs to be inserted between the two halves of the caliper to spread them apart….. with the appropriate seals of course. (The original factory V8 calipers are very difficult and very expensive to get.)

As a next step or as an alternative, either the V8 or standard MGB discs can be drilled to help cooling.

Next step is to fit 4 pot calipers at the front, The Austin Princess has 4 pot units which are a direct fit – nice & simple except they ere getting a bit hard to find.

From there, there are vented discs available in kit form including callipers & mountings. Price for these (full kit for the two front wheels) is up to $2500 NZD (depending on type).

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