FIX THOSE BRAKES
WE HAD A LOOK at brake f luid back in issue 406 and this time I reckon we should look at the hardware. Checking out disc pads is easy – you can generally grab a torch and sight along the disc. As for drums, there’s no way round it, you’re going to have to pop off the wheel and the brake cover. As a general rule you don’t want anything less than 2mm of material.
When it comes to disc brakes on older cars, most people are up to speed on the basic technolog y. For your old Ford, Holden or Valiant, you’re working with PBR or Girlock or similar, with a master cylinder under the bonnet, a vacuum booster, with a simple caliper and disc at the other end.
Let’s say you’ve got access to the caliper to change the pads and give it a general check-over. When you go to push back the pistons, a proper pushback tool is ideal, but a G clamp or similar used with care is just fine. Inspect it thoroughly and give it a gentle clean out. What you’re looking for is any sign of f luid leaks. If there are, it’s rebuild time. This isn’t necessarily a huge job, but you need to be sure you’re using the correct and good quality components. Remember your life might depend on it!
There are some very good change-over and rebuild services out there (such as Power Brakes, which featured in last issue – Ed.) who can do it for you quickly and it generally doesn’t cost a bomb. It’s always worth considering as a precautionary measure, particularly on a restoration. It makes the whole assembly job easier and cleaner, and you know what you’re starting with.
It’s easy to accidentally pop the piston out of its cylinder and getting it back just requires a little patience. They’re a tight fit and need to be wiggled back into place. What you don’t want to do is force it and damage the working surfaces.
Popping the pads in is very simple. Hopefully you’ve taken note of how they were installed when you pulled them out – including any retaining bolts or clips. And here’s a key tip: don’t forget to pump the brake pedal once it’s all together again to get your normal pedal feel back. There’s nothing worse than taking off and finding no pressure in the lines !
Just be aware that some later model cars have a screw-back rather than push-back system for the rear pistons. If that’s the case, it’s best to have the right tool. A set of multigrips will do at a pinch, but you risk doing damage. One easy way to check whether it’s screwback is look for a handbrake lever on the back of the caliper.
Older solid discs are generally designed to be machined to refresh them if they need it, but only to a certain point. Generally, the minimum acceptable thickness is stamped on them. If you’re near the minimum, shout yourself a new set – they’re not worth the gamble.
With later systems, particularly European cars, you’ll notice the black brake dust that seems to get liberally spread over the wheels – that’s a fair indicator you’re dealing with a set-up where the disc is designed to wear quickly along with the pads. The performance and feel is terrific but, instead of machining them, you’re generally dealing with a disposable item and they’re priced that way – often a third of the cost of a more ‘traditional’ part.
If you’re working with multi-piston systems, just be aware you need to be able to push back all the pistons at once and that’s where having the right tool is a big help.
Drums are a little more labour-intensive to work on – or at least to get access. Once you’re in there, you’re looking for: no leaks from the wheel cylinder, good thickness on the shoes and drum itself, and even wear.
If the drums are squealing it’s often because they didn’t radial grind the shoes and match them to the drum, so the wear is uneven and you’re working a smaller area. People used to do all sorts of things to stop the noise, such as springs around the outside to stop the harmonics, but basically it’s a matter of setting the brake up correctly.
If you’re out there restoring a car with a drum brake rear end, it’s critical you get the right-sized wheel cylinder and match the shoe to the drum. Drums and shoes can be reconditioned/relined, but it’s a professional job.
Now here’s my final bit of advice: don’t be a cheapskate. Brake components have come down a lot in price over the years and this is one area where I really won’t take a chance – too many lives at stake. So if I’m not using original equipment, I’ll go for known brands such as EBC, Bendix, PBR, Lucas/Girling and so-on.