Pimple’s broke brakes
The previous owner of Pimple, the RSP Mini Cooper, did very little maintenance. The brake discs in particular looked pretty grim, so I planned to replace them along with fitting new pads when the suspension cones were changed. However, when the pads came out, I knew I was probably going to have to cough up for a set of new calipers as well. That’s because there was only about 1mm left on the brake pads. I hadn’t bothered checking them because they were going to be replaced anyway, and the dreadful terminal squealing of metal brake pad bases on metal brake discs hadn’t happened yet, but it would have done in another month or two.
The big problem here is that by the time the pad material has all worn away, the steel pistons have been poking out maybe 10mm further into the weather and the wet, so they rust. If you change the pads on a Mini when they’re half worn, that will cost you £13 for a set of AP pads, rather than £200 for a pair of new calipers. Because you have to replace calipers in pairs to ensure even front braking.
On the righthand caliper, the pistons were gently pressed back into their cylinders with a woodworking clamp, and it still functioned okay, but the left one was seized. It had been working fine with almost no pad left because those parts of the pistons weren’t rusty, but even if the pistons could have been forced back into the caliper, the rusty surfaces would have ripped up the rubber seals within a day or two, and the brakes would have lost fluid and failed.
In addition, the previous owner had fitted fancy braided brake lines. Their securing attachment to the caliper was of poor quality monkeymetal, and it just rounded off rather than coming undone. So the hoses are scrap as well, although I would have binned them anyway. Braided lines are potentially dangerous, unless they’re fairly expensive and designed, marked and sold specifically for road use – with racing braided hoses, the stainless wire covering rubs at the plastic pipe it covers, and after a number of miles they leak or burst. Actual race cars don’t do enough miles to wear them out.
In practical terms, the only benefit of braided lines is that they look shiny and give a slightly harder brake pedal feel. Back goes Pimple to standard rubber hoses, 100% good enough. It’s worth replacing all the brake hoses, as the rear ones are usually 30 years old like the front ones, and we’re going to have to bleed the system anyway. The bleeding of the system is no bad thing: brake fluid should be replaced every few years anyway, as it hygroscopically collects water and rusts out anything steel in the system. As we have seen.
The calipers’ cylinder surfaces looked fine, so it was a rebuild with four new pistons and seals. In order to hone and polish the cylinder walls, we also split the calipers which means they need a new set of square-section sealing rings to put them back together again.
I ordered new rear wheel
“Brake fluid hygroscopically collects water and rusts out anything steel in the system”
cylinders as well, because they were bound to be rusty too, and new bleed nipples for the calipers because the old ones will otherwise snap off: that’s one of the karmic rules, like the one about hand-packing grease into bearings always making the phone ring.
Nowadays I keep the old brake cylinders if they’re original, because of the poor quality of the now ubiquitous Chinese replacement parts. These are so cheap they’re almost free, but that’s not a bargain if they’re porous or just don’t work. A Vancouver acquaintance recently sold his MG repair business of 25 years, partly because of the stress of having to pay for recovering freshly repaired cars on a distressingly frequent basis because the new parts had failed on the customer’s way home or within a few days. So I retain old rusty BL cylinders just in case – they can be sleeved in bearing bronze. This isn’t cheap, but they will last for 100 years rather than 100 minutes.
Previous Owner had also fitted racing Alfin fin- cooled brake drums to the back of the car, although it was usually either parked in a storage shed or used for shopping and going to car shows. Cooled rear drums would be useful if you wanted to do lots of handbrake turns. As it happens I do want to keep my rear brakes cool for doing handbrake turns when I use the Mini Marcos for slalom, so the Alfins went into the Marcos stash and the new rear drums destined for the Marcos ended up on Pimple.
As ever, when you start opening stuff up on a neglected car you find unpleasant surprises, but at least with a Mini the consequences are usually cheap. The balljoints were all knackered, dry and stiff, and the bump stops had collapsed.
Although that was because they were being used as the car’s suspension, because the 1990 rubber suspension cones had collapsed and then fossilised. The new cones were actually quite disappointing, as the suspension merely improved from a trolley jack ride to a go kart ride. I do have a set of the new soft Mini suspension cones, but again they’re being saved for the Marcos, which only weighs 1000lbs, and on which the ride is brutal. The new not-seized balljoints lightened the steering up nicely, though.
The new brakes don’t feel much sharper than the old ones, but those were actually working effectively although they were on the last few millimetres of pad. I’m probably using less pedal pressure for the same retardation. There’s a definite improvement in the ride height, which is up a good few inches. And the standard new- cone ride height means I can now use the full extent of the steering rack, lock to lock, without the front tyres scraping on the wheelarches.