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Kerbside Care - Brakes

Kerbside Care - Brakes Published: 28th Mar 2014 - 0 Comments - Be the first, contribute now!

Kerbside Care  - Brakes
Kerbside Care  - Brakes
Kerbside Care  - Brakes
Kerbside Care  - Brakes
Kerbside Care  - Brakes
Kerbside Care  - Brakes
Kerbside Care  - Brakes
Kerbside Care  - Brakes
Kerbside Care  - Brakes
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Originality is one thing but on today’s cut-and-thrust roads you can’t have brakes that are second best on your classic. Here’s our top tips

You may think that your classic’s brakes are still performing perfectly okay after all those years – but when you have to brake hard to avoid that sharper stopping modern, bear in mind that in an emergency stop those old anchors are providing an incredible 4.5 tons of pressure to each front brake pad to their discs!

The trouble with most braking components is that because they might look okay, and pass the annual MoT brake test, all is well when it patently may not be. By law, a vehicle’s brakes only need to muster up some 50 per cent braking effi ciency (under 20 per cent for the handbrake) to satisfy an examiner – a figure no rightful car enthusiast would be satisfied with. Here’s some advice to put a stop to all that while your classic is laid up over the winter!

Basic checks

Let’s start with the bits that stop you – the brake linings, either by pad or a simple shoe
They should have a fair bit of ‘meat’ left on them; pads can wear down to 1/16th inch while shoe linings mustn’t wear below the rivets – if fi tted – and no less than 1/32nd of an inch for bonded types. That said, you’d simply be mad to let any lining material wear this low as its efficiency will have tailed off way before then.

  • Linings are particularly easy to inspect once the drum is removed (you may need to ‘back off’ the adjusters to aid removal) but disc pads should be removed to inspect the pads.
  • Check for breaks, cracking, any lumps missing, and face discolouration, suggesting they have overheated at some point. In contrast, look for glazing, especially on pads which have been almost too lightly used; this can be removed with normal emery paper.
  • If the callipers are working okay, the pads should have worn evenly, otherwise it points to a seized piston (unless it’s a single piston design where the pads are tapered anyway). This can be rectified by ‘working’ them with a lever, pry bar etc (don’t go mad here!) and cleaning up their exposed piston surfaces with a rag soaked in a brake cleaner.
  • Check the calliper seals for leaking. Similarly on drum brakes, peel back the wheel cylinder dust covers and look for weeps. On both, overhaul with new seals or renew them if you unearth any problems.
  • Discs self-adjust as do certain front drum brakes but on many drum brake designs, it is also done manually. Along with selfadjusting mechanisms, these can seize and give rise to a long brake pedal travel and so subsequent poor and uneven braking. Free them off (soak in penetrating oil) or if this fails renew the adjusters. If bad, sometimes a new back plate may be required.
  • A spongy brake pedal also points to a failing master cylinder; a good check is to press hard on the brake pedal and see if it slowly sinks to the fl oor. Also check for leaks, of course. It can be resealed if the bore is sound but it’s usually best to renew for safety’s sake.
  • Hoses need careful checking. Metal ones rust (copper replacements is the answer if you can afford it) while flexible hoses deteriorate, to the point where they can slightly ‘bellow’ if tired and so give a soft pedal feel making it feel as though air is in the system. Apart from normal replacements you can also opt for braided types which are worth fitting if you have a high performance classic.
  • Servos can play up, not only by failing to provide the normal assistance but can also cause the brakes to stick on. Upon start up, the pedal pressure should change and the pedal should move slightly. If you can fi nd a quiet road, turning off the engine and applying the brakes several times to exhaust the servo should result in a rock hard pedal that requires superman to operate!
  • Problems can often be related here to lack of maintenance. Ensure that the servo’s air fi lter is regularlychanged. Also, if the pedal pressure seems unduly high, check the pipe which runs from the servo to the engine – it can internally collapse and restrict engine vacuum.
  • Don’t neglect the handbrake, keep linkages etc clean, lubed.

All pumped up over brake bleeding?

Brake fluid absorbs moisture from the atmosphere and as a result needs to be periodically changed, although many enthusiasts who pamper their classics neglect to do – because in normal usage the brakes feel absolutely fi ne… However, use them hard or go on a long run and the heat generated will make the brake fl uid boil due to the water content meaning a loss of brakes just when you need them most. The time-honoured way of changing and bleeding a braking system is by using an old jam jar and a short bit of tubing to fi t over the bleed nipples. It still works well enough although it’s laborious and requires a helper to keep pumping the brake pedal to expel both the old fl uid and air present and top up the brake master cylinder. If you fancy splashing the cash, there’s a wide range of tools which can make the brake bleeding process both a lot easier as well as become a one man job. Alternatively you can have a local garage do it.

Brake fluid is classifi ed by its (American) DOT (Department of Transportation) number; 2,3,4 and 5.1. There is a DOT5 but this is a silicone-based fluid and the higher the DOT number, the superior its performance under high temperatures. You can upgrade however; DOT 5.1 instead of DOT 4 and 3, DOT 4 can also replace DOT 3 but they shouldn’t be mixed. A typical system holds some 600cc of fl uid so you’ll need I-litre of fluid – and on larger cars probably 1.5-litres.

Face values can tell you a lot

Pay close attention to the disc and drum faces because if not to acceptable standards they will cause uneven and rough braking that’s usually felt through the steering and a pulsating brake pedal. Moderate scoring and normal disc face wear is inevitable and old discs can easily resemble a 45rpm record, but it can’t be left excessively so. If you run a thumb nail across the surface area it should not feel unduly uneven and grooved. Look also for rusting areas on the disc face suggesting uneven pad contact.

Check both sides of the brake disc for wear not simply the outside face – this is often overlooked. Are the discs warped? A good quick test is to insert a six thou feeler gauge between disc face and pads and spin the disc slowly. If it slips in with ease, then the discs are out of true.

With drums, it’s much the same story, checking for rust and heavy grooving. Both discs and drums can be rejuvenated by having them professionally refaced by skimming although there’s only so much metal you can safely remove; on most ‘traditional’ classics wearing sold discs, like an MGB etc, it’s around 40 thousandths of an inch in total and ideally it should be split both sides of the disc so a braking imbalance is not introduced. Drum brakes can only take a light skim otherwise they have a tendency to become ‘oval’ in use. Fitting brand new discs and pads, or drums and linings can reap considerable rewards (see our fitting pic sequence elsewhere).

Disc conversion, is it for you?

Converting a classic to front disc brakes is both popular and mostly advisable for modern roads and can be done either by simply fi tting the brakes from a more upmarket, powerful model or by using a dedicated aftermarket kit. Because of the resultant higher braking pressures, a servo may have to be fi tted as well – speak to a marque specialist about this. If your vehicle is already disc braked, you can go a stage further and fi t a better set up from a more powerful variant such as Vitesse/GT6 brakes for a Herald/Spitfi re, for example as a cost-effective uprate yet using standard parts. This is particularly appealing to owners who prefer the feel of normal brake pads during normal driving.

Contrary to popular opinion, harder, sportier brake pads don’t make a vehicle stop faster; you need larger discs and calipers for that! Rather, they combat fade better during extreme braking. In other words, because they are made of harder friction materials you need to press the middle pedal with more force, meaning that under normal retardation efforts they aren’t as effective as standard linings. One exception we’ve found are EBC’s Green Stuff pad range which is a very good compromise of both characteristics. Do you need discs at all? A number of specialists dealing in 1950’s classics, such as MGs, feel that unless the vehicle is highly tuned, the improvements aren’t as great as you’d credit. Bob West says he has rally-spec MGAs still on drum brakes. New old stock linings may contain asbestos and by law, can’t be fi tted or sold by professionals so it’s up to the DIYer – but according to one autojumble parts seller, they not only stop better but don’t wear the drum brakes as much. You see plenty of sellers at autojumbles so it’s your call.



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