Brake disc change on my 2010 is250 SEL Auto on 18” rims.
I checked my caliper slide pins at the beginning of the month and found my brake pads were all a bit worn down so changed the pads to my new set of Pagid pads that I had bought in advance.
Whilst doing this I couldn’t help but notice the actual discs were also really quite worn. The fronts (which do most of the work) were really quite badly worn with a very noticeable deep lip at the outer edge. So I made a few notes and checked a few diameters and thicknesses while it was all exposed and pressed on with the pin check and pad change. Pretty sure that would be a MOT fail come November, when it's due!
Having established the sizes I ordered up a complete set of discs. Check your specific types as there are a few variations of disc … not just diameter, some are solid discs too. My model has vented discs front and back. The fronts are 296mm dia and 28mm thick. The rears are 310mm dia and 18mm thick.
The set I purchased were Mintex at a very good price of £108 for the whole set delivered. Having seen how shoddy the old discs looked I thought I’d do a bit or prep work on them before fitting. I had some spray cans of silver and a black hammerite to hand so put them to good use. Probably turn out to be pointless but heck they'll look good for a while!!!
All the pad contact areas and the shoe contact point on the rear discs were masked up…. but deliberately just a little under-sized. I figured the pads would cut back the very outer margins of the 'inner' and 'outer' to re-reveal the silver of the disc, thereby keeping a tidy looking disc. They can look quite shabby when the rusty surface gets a grip on everything outside the contact area. Having masked up the contact points I marked the relevant circles with a felt pen and the trimmed with a Stanley knife. This was made easy by using a 10” turntable with a piece of cardboard over to protect it. Then the inside faces were sprayed silver and the outside faces in black, again making using use of the improvised turntable. I should have left these for about 5 weeks to fully cure but other commitments and an imminent trip to the Picos de Europa and various Rioja valley bodegas' have put paid to that! They got 2 weeks.
Then it was on to fitting …. I worked off the jack .... not for some I'll grant. The other three wheels were chocked for safety. All the slide pins have rubber boots fitted so be careful with easing them off when removing slide pins.
Front Discs. Loosen the wheel nuts a tad before raising the wheel. Apply the parking brake. Raise the bonnet and remove the brake fluid reservoir lid and put an old towel or similar under the resvoir … just in case you get absent minded later!! I then removed a small amount of brake fluid, about two table spoons, with a syringe to another clean pot. Then remove the wheel and put to one side. I chose to gently squeeze the caliper just enough to slacken the pad grip. There are two caliper pin bolts to remove (14mm socket or spanner) and if you need to prevent the pin moving you’ll need a 17mm spanner. Then remove the caliper and rest it on an old towel on the suspension… just be wary of the hydraulic pipe. You don’t want to stretch or kink it. Some folk opt to hang it up with a bent wire or similar….up to you.
I then use a G clamp and a piece of wood to squeeze, gently, the caliper piston back into its housing. The new disc and pads will be thicker than your original set so you need that piston pushed back or it will not fit over the pads at re-assembly. Pushing the piston back will raise the fluid level in the reservoir … that’s why you need to remove some. Keep an eye on the level each time you push a piston back.
Remove the pads and put to one side. Then you’ll need a 17mm socket to remove the bolts that hold the caliper carrier in place. It’s likely the front disc will now be loose and easy to remove …. mine were. If it is stuck fast you’ll need a couple of 8mm bolts to wind into the 2 threaded holes to push the disc off the hub.
Here's an internet pic, credit to original uploader, to give an idea of using the 8mm bolts to crack off the disc from the hub.
The arrows point to the threaded holes.
Give the hub a bit of a clean up with a wire brush and apply a little anti-seize copper grease to the contact face of the hub…it will help with disc removal next time. Then fit the new disc onto the hub. I used the wheel nuts to pull the disc securely onto the hub and visually checked it was spinning without any wobble.
Front disc, carrier and pads fitted
Then refit the carrier and refit the pads being mindful of the shims. I use a little copper grease on the shims and have not had any squeal in 6 years. Some prefer to use Ceratec grease. The choice is yours. I checked the slide pins and then refitted the caliper and bolted down securely. Then refit the wheel, start the car and prime the brakes with a couple of presses on the brake pedal. On to the next!
old front discs
Rear Discs. Slightly different process here. Loosen the wheel nuts before raising the wheel. Do not apply the parking brake and put the shifter into Neutral (not P). If you don’t do this you won’t be able to turn the hub and the brake will hold the disc to the hub preventing removal.
Remove the wheel and put to one side. Next remove the guide pin retainer spring…fitted vertically between the two pins and slide out the pins. A pair of long-nose pliers do this nicely. There is an anti-squeal spring associated with the lower pin… so note how it locates for reassembly. Gentle squeeze on the caliper may be necessary to free up the pads. Then remove the pads. Then undo the upper caliper pin, I think it was 17mm socket, and remove it completely. The caliper should now rotate towards the rear of the car…its pivot point is the lower slide pin. This lower pin is fixed. Wiggle the caliper backwards and put aside in a secure place on that old piece of towel. Again, careful with that hydraulic pipe!
There is a rubber grommet fixed in the disc … this covers a hole for adjusting the parking brake. Remove it and keep it for placement into your new disc. Now remove the old disc. Mine were ‘frozen’ solid (both sides) and would not budge. So it’s time to use those 8mm bolts again! A snick and a snack and it’s loose enough to remove. Now clean the parking brake shoes and parts with brake cleaner. You will be able now to see the adjuster for the footbrake and how it works. These shoes are only used for parking so are highly unlikely to be worn. But you may need to adjust the shoe to the new hub. If you turn the cog wheel you’ll see the pads move in and out. When the disc is fitted that circular access hole allows for a screwdriver to enter and engage with that cogged adjuster.
Once again, give the hub a bit of a clean up with a wire brush and apply a little anti-seize copper grease to the contact face of the hub…it will help with disc removal next time. Then fit the new disc onto the hub. Again I used the wheel nuts to pull the disc securely onto the hub and visually checked it was spinning without any wobble. So, back to that access hole again and screw up the adjuster until the disc is locked, then undo it about 6 teeth and check the parking brake operation - it should go down 7 clicks or so to engage securely.
Again, you will need to push that caliper piston right back to get it to fit the width of disc and pads. Keep an eye on that fluid reservoir each time you push a piston back. You don’t want that brake oil oozing all over the place!! Grease (red rubber grease) the slide pins and refit the caliper securing the upper slide pin Refit the pads with a liitle copper grease on the shims and fit the upper guide pin to hold the pads in place. Position the anti-squeal spring and slide the guide pin through both pads and the coils of the anti-squeal spring and push the tags back into the centre holes of the pads. Then refit the retaining spring. Wipe off any mucky bits resulting from the refit and ensure the brake contact area is clean. Then refit the wheel, start the car and prime the brakes with a couple of presses on the brake pedal.
I then took the car for a gentle low speed drive 20-40mph and gently bedded the brakes onto the discs for about 15 mins. I’m not sure if this is critical but it felt the right thing to do …. I recall my Dad used to do that! After a cuppa had a longer 30 minute drive at gently increasing speed with braking (when nowt was around...pretty easy in Dorset!!) and all feels good.
Front and Back all refitted and bedding in nicely!
It’s not a particularly challenging task, if you’re up to a bit of spannering. Just take your time and be methodical. Take pics of any unfamiliar parts and how they assemble to refer back to. In total, with a few cups of tea and the odd slice of cake and one ear on the football scores, it was nearly 4 hours start to finish.
Total parts cost was around £150 ....better than the £700+ quoted by u know who!!
Credit to Newbie and Johnatg for doing this in the past. Your guides gave me the encouragement to have a bash at something I knew couldn't be that difficult.