Mini Front Brake Disc Replacement

I’ve finally wrapped up all the servicing and repairs that needed doing on our Mini, if you haven’t seen the other videos I highly recommend checking them out in the cards above, but this was the last job. The front discs had just fallen below the minimum thickness, so it’s time to swap them out. In theory this should be an easy job, but in practice it took two of us almost a full day and even then we still did a bit of a bodge job on it that I’ll need to correct later.

Before you get to any of that though, you’ll need to jack up the car. You can do one side at a time, although since I was also doing an oil change I got both sides up on jack stands. I also used my DIY wooden ramps to help lift the car enough to get the large jack under the front leaving the jacking point free for the jackstands. You can then take the wheel off – you might want to crack the bolts loose before lifting the wheel off the ground – but once they are out the wheel should come right off. If it doesn’t, give the sidewall of the tyre a few smacks around the edge, if still not use a rubber mallet on the back side around the edge and that should definitely do it.

Before doing anything, it’s a good idea to give the area a brush down with a metal wire brush to get any dust and rust clear. Next, I’d highly recommend starting with the T50 M10 bolt that holds the disc to the hub. That’s for a few different reasons, first is having the caliper in place means you can slide a pry bar or screwdriver through the gap at the top to stop the disc from spinning, but the main reason is that if they’ve been on the car for a long time that bolt is likely seized to kingdom come.

We tried using a 3/8ths drive ratchet, then a ½ inch. Then the impact driver, then the proper impact. It. Didn’t. Budge. Trying full blast with the impact made it look like it skipped slightly, so we swapped to carefully using the breaker bar and it moved again. Success! Or so we thought… But no, the bolt snapped clean off. Luckily that bolt isn’t exactly essential nor is it in a terrible place to extract although as hard as I tried, as much as I drilled it out, it still wouldn’t get out of there. I’ve got a new set of bolt extractors on the way so I’ll get it sorted and reinstall new bolts shortly. Feel free to leave your tips for dealing with this sort of issue in the comments by the way, I’d love to hear them, although we likely tried everything you can suggest from a bit of heat with a butane torch (best I’ve got), penetrating fluid, using a punch to jolt it loose, using a punch to spin the snapped piece and probably more I’ve already forgotten.

Anyway, once that bolt is out, one way or another, you can then remove the caliper. You’ll need to pop off the metal wire clip from the front of the caliper first – don’t forget to reinstall that by the way or it’s an advisory on your MOT. Once that’s off you’ll also need to pop the plastic dust covers from the slide pins. The pins use a 7mm allen/hex, yes you will need to buy one because trust me whatever tool box you have won’t have that. You’ll have 4, 5, 6 and 8. Crack both loose and slide them backwards. You don’t have to take them all the way out, although it’s a good idea to so you can give them a clean then reapply some lube so they can slide freely.

With both slide pins out, lift the caliper off and use a bungee cord to hold it up and out of the way – as long as the brake line isn’t stressed it’s fine. You can then remove the caliper bracket bolts. These are tight, like really tight, so you’ll need either a breaker bar or a lot of grunting to get them free. With those out the bracket will come off as will the disc.

When fitting the new disc use some brake cleaner and clean towels to wipe off the oil they ship with – look how nasty the towel looks after one wipe! It’s really important to get that oil off so you don’t contaminate your brake pads and have less effective braking. Once they are clean though, stick them on the hub and if you didn’t snap the bolt you can install a new one now. Then reinstall the caliper bracket, the bolts get torqued to 110 Nm so like I said, tight.

The outer pad can then be placed on the bracket – if you are installing new pads as is generally recommended now is the time to do that, same for the rear pad that clips into the piston. Then press the caliper into place. It’s likely going to be a tight fit since the old disc (and pads if you’ve replaced them too) will be a fair bit thinner than your new ones, so you will want to open the brake fluid reservoir cap then press the piston backwards. Once the caliper fits over both pads and the disc you are all set and can tighten the slide pins to 30 Nm. Stick the dust covers back on, and reattach the wire clip on the outboard side of the caliper. It’s a pain and you might need two people to give you a hand but once it’s on that’s it. The wheel can go back on, with those bolts getting torqued to 120 Nm.

If you want to go the extra mile to bleed and flush your brake lines, before you stick the wheel on you can crack the bleed nipple loose and attach a bleeder kit and ideally have someone pump the pedal and hold it while you open the valve then close it and pump again, but if you are solo even my ‘one man’ kit does work fairly well. Just remember to add fresh DOT 4 fluid as you are draining the old nasty stuff.

Of course, repeat all that for the other side too. It’s important to keep it even so if you are replacing one side I highly highly recommend you do the other side too.