Brake Disc Raplacement.

Tools Required To Change Brake Discs - in addition to those mentioned in the previous post.
17mm Socket
Small Hammer (always useful)
Pozi Drive Screwdriver - I'll come to this later in this post!
Brake Cleaner

Presuming that you've followed my above instructions in Post #1, you now need to do the following.

Locate the 2x 17mm bolts that secure the Carrier to the Hub and remove. They will be very tight and you may need to use the breaker bar rather than the ratchet to crack them undone.

With the bolts removed you can pull the carrier away from the brake disc and move it out of the way, please remember to be careful of the flexible brake pipe.

Now comes the tricky bit. You need to remove the two retaining screw on the front of the brake disc, they are usually a pain unless you have access to an Impact Driver (which I don't). You may be able to use a Pozi Screwdriver but what I do is use a combination of tools, a 1/4" Drive Ratchet with a 1/4" Socket, and I insert a PH.3 Screwdriver bit. This combination has proven to work quite well for me and on this occasion worked perfectly.

If you are struggling to remove these screws because of the disc rotating here's a little trick which I find useful:
Take one of the wheel nuts and put it onto the stud and tighten, now take your breaker bar and 19mm socket and wedge it against the floor as shown in the picture below, it will help you to hold the disc while you remove those disk retaining screws.

With the disc retaining screws removed you can set about trying to remove the disc. If you're lucky, it'll slide off without too much fuss, however the chances are that the disc will be corroded on. If the disc is being stubborn and you are throwing the old discs away you could try tapping the disc around with the hammer and see if that works (please remember that if you hit the disc too hard you risk causing damage to the wheel bearings). If the disc is still stuck on (like mine was) you'll need to draw the disc off using a couple of bolts. On the front of the disc you'll notice another two holes which are threaded, these can be used to insert two bolts and as you tighten the bolt (do each a little at a time) it will pull the disc away from the hub. I managed to find a couple of 13mm bolts that fitted perfectly.

Hopefully you'll now have removed the disc successfully and we can proceed to fitting the replacement disc.

Brand new discs have a coating of oil, this is to protect them from rusting while in storage, it's important that you remove this film of oil before fitting them. You can get Brake Cleaner which is designed for this job, give the disc a good clean on both sides.

Before fitting the disc it's a good idea to also clean the hub of any old grease, rust and dirt with some Emery tape (abrasive tape), this will ensure that the disc sits correctly when fitted.

Now apply a thin coating of Copper Grease to the hub, this will make future disc changes much easier. It's also a good idea not to go over the top with the copper grease otherwise it may find its way onto the disc.

Now you can slide the disc back onto the hub, being careful not to damage the wheel studs in the process. Once in place you can repace the 2x disc retaining screws, always a good idea to put a little Copper Grease onto the threads before inserting them, it will make life a little easier in the future.

The final job is to fit the Carrier back into place with the 2x 17mm bolts and the disk part of the guide is complete.

Now continue reading Post #3.

 

Pad Replacement Continued.

The most important thing to remember here is that preperation really is the key to a successful pad change!

First of all, start by locating the brake fluid reservoir and remove the cap, you may find it necessary to remove the electrical connection to allow the cap to undo. The connector has a clip either side, pull these outwards slightly and slide the connector off.

Now remove the brake fluid reservoir cap and wrap an old rag around the top to catch any possible spillages - brake fluid is very strong stuff and spillages must be kept to a minimum.

Now we need to push the Caliper Piston back into the Caliper to allow it to fit the new pads. This is best done using a G-Clamp, I use an old welding earth clamp. Note: Some cars may still have a Shim which was originally fitted to the Piston, remove this before attempting to push the piston back, it simply pulls off the Piston. I will show a picture of the Shim later in the guide incase you don't know what it looks like.

The piston will be quite hard to push back, do it slowly and gently until the Piston is flush with the Caliper.

Once the Piston has been pushed back you need to check your brake fluid reservoir level, you might find that it now has slightly too much in, if so you can simply remove a little from the top with a pipette or a syringe (mine was fine). Replace the brake fluid reservoir cap and if you removed the electrical connector, push it back onto the cap.

The next stage is to prepeare the Caliper and Carrier ready for the new pads, this is probably the most important stage.

The pads come into contact with several areas on the Caliper and Carrier, if these are not clean and greased it may result in premature or uneven brake pad wear.

The Carrier has a metal insert at the top and bottom where the edges of the brake pads rest. Clean these carefully removing any traces of old Copper grease with a rag and brighten them up with some Emery tape or Abrasive strip. Here's a picture which shows both after they've been cleaned up properly.

Now the Caliper also needs to be cleaned up a little, firstly the piston itself and if fitted, the Shim (don't worry if your car hasn't got the Shim). And also the two inner contact points circled where the outer pad is held by the Caliper.

The next step is to apply some grease to the Guide/slide Pins, this is vital as if they're not done they can cease and can cause some grief. The Guide pins are located at the top and bottom of the Carrier, remember the 12mm bolt that you removed at the start of the guide, that goes into the Guide Pin.
Start by doing the lower one first. Ease the tiny rubber boot off the Carrier and pull the Guide Pin out of the Carrier like so.

Give the Guide Pin a good clean with a rag to remove any old Grease, you can also do inside the hole one the Carrier with a rag wrapped around a small screwdriver or similar.

Now apply Grease to the Guide Pin. I use a "Heavy Lithium" Grease which does the job very well, you can use almost any grease and if you have none available then Copper Grease is better than nothing, although Copper Grease doesn't slide as well so use it as a last resort. Coat the Guide Pin with Grease like this (actually I've put a bit too much on there).

Continued on Post #4

 

Continued....

Now re-insert the Guide Pin, push the rubber boot over the Carrier and wipe off any excess Grease that has pushed out.

The upper Guide Pin still has the Caliper bolted to it but this is not too much of a probblem. The Guide Pin can still be removed as before with the Caliper in place, ease off the rubber boot and then slide the pin out with the Caliper attached. Clean the Guide Pin and hole, apply some Grease to the Guide Pin and re-insert.

Finally we can test fit the pads. The inner pad usually has a sticking out metal strip, this is a wear indicator and the outer pad does not.

Try test fitting the new pads in the Carrier, they should slide in without too much force. My inner pad was actually quite stiff and this may cause uneven pad wear. To sort this out you need to file the two edges of the pad where they some into contact with the Carrier until they slide in the Carrier nicely. Just a small amount at a time, do't go mental.

Once both pads will slip into the Carrier easily you can apply a thin layer of Copper Grase to the contact points on each pad. NOTE: Your original pads may of had a Shim attached to the rear of them, if so it would be advisable to attach them to your new pads if they weren't supplied with them. As with the Shim fitted to the Piston, it is not vital, just nice to keep if possible.
The Inner pad should have a layer of Copper Grease on both ends and also on the rear where it touches the Piston.

The Outer pad needs to have Copper Grease on both ends and also where it comes in contact with the Caliper.

Insert both pads into the Carrier and push them towards the disc.

Now the final task is to un-tie the Caliper from the suspension spring and gently swing it into place. If you've pushed the Piston back far enough it will clear the pads and sit into place easily. If it doesn't clear the pads you will need to push the Piston back into the Caliper a little further.
Once the Caliper is in position you may replace the 12mm bolt into the lower Guide pin and tighten.

Job Done.

Now all you need to do is apply a smear of copper grease to the rear mating face of your wheel, refit it and tighten the nuts as much as possible, remove the car from the axle stands and lower to the ground and just finish tightening the wheel nuts.

For those who have Torque wrenches and are wondering what the settings should be, here they are:
Brake Caliper Guide Pin Bolt 12mm: 32NM
Brake Disc retaining screws: 12NM
Carrier To Hub Fixing Bolts 17mm: 81NM
Wheel Nuts 19mm: 100NM

It's good practice to press the brake pedal several times to allow the Caliper to take up any slack from when you pushed the piston back. I believe that this can be done with the engine switched off but I do it with it off and then on just to make sure. If you do not do this, you may press the brake pedal to come to a halt and find yourself failing to stop.

Always change pads and discs in pairs, don't just change the passengerside and leave the driverside for another time, otherwise you'll find yourself veering towards a ditch. Also, always allow your new brakes time to "bed in" before using them violently/hard, this "bedding in" time will probably be written on the instructions that came with the parts, if not 200 miles should be sufficient.

This guide is my method, it works perfectly fine for me however, please be careful when doing any work to your brakes as they are the most vital safety feature on your car. If you wish to follow my guide I will not be held responsible if anything was to happen..... that said, I feel that this guide is quite good and problems shouldn't arise. If you are in any doubt of your capabilities please do not attempt this procedure.

Thank you for viewing,
Ian.

P.S: If this guide needs anything extra adding please let me know and I'll add it later. Hopefully it should be ok as it's taken bloody hours to complete.

 

Carrier To Hub Fixing Bolts 17mm: 81NM

Is this correct for both front and rear?

Haynes also only has one value, but the rears have smaller bolts so the torque should be lower...

 

Nice guide, thats almost exactly how i did mine :lol:

Quick tip, put some copper grease on the the disc retaining screws to make life easier if you ever need to take the disc off again!

 

Yeah I forgot to mention that, thanks for reminding me. I usually just dip all the bolts into the pot of Copper Grease before reassembling them, it's a natural reaction. :lol:

Glad that you like it.

 

I'm not allowed to give you anymore rep or I would.
Well done fella, very useful indeed and very well written.

 

:lol: Thank you for the nice comments and for trying to give me some rep. You'll have to spread your love around a little first mate.

Cheers,
Ian.

 

Great write up bad problems with my breaks seizing up today in fact had some serious speed wobble and lots of smoke when i stopped!! So will use this to grease them up.

 

That sounds nasty mate.

I'm not sure which ZS you've got mate but I would assume that your Calipers will be very similar to mine, if not identical. Just follow the pad replacement procedure (skip post #2) and you'll get on fine.

brilliant guide mate, some good info for those who don't work on cars for a living, though if the discs mounting screws do sieze or round off then the only thing left to do is drill them out, you can still mount he discs with out them because when you refit the road wheel the disc will be "clamped" in the correct position on the hub, i have had to do this a few times

Yep, I've seen others that have drilled the heads off the disc retaining screws before, left the screw in the hub and then just fitted the disk without them. It's sometimes possible to remove the remainder of the screw out of the hub once the disc has been removed. It's always best to use the disc retaining screws where possible.

Thank you for the nice comments, I'm glad that you like the guide and hopefully it'll help others over the coming years.

Thanks,
Ian.

 

brilliant guide mate, some good info for those who don't work on cars for a living, though if the discs mounting screws do sieze or round off then the only thing left to do is drill them out, you can still mount he discs with out them because when you refit the road wheel the disc will be "clamped" in the correct position on the hub, i have had to do this a few times

 

nice guide there, if i had not learnt how to do this when i changed my disks and pads just a couple of months back this would have been a great help

as it was i watched one get done then was told to do the other side myself.

Not sure if you want to add something about bleeding - tho technically without changing the calipers and open the bleed screw they should not need it...

 

Hi, thanks for the nice comments.

I'm not going to cover bleeding the brakes in this "How To" as I don't want to complicate it further. Bleeding is possibly something for the future. My next guide will be another brake one, changing rear discs and pads, although it's obviously very similar to this I'll do a quick guide on them too. :broon:

Cheers,
Ian.

 

Hi!
That's an excellent guide & the photos are stunning - the best support photos for a job ever, making it clear what bit is being worked on. Are you going to work for Haynes? ;-)
I would just add 3 comments, if you don't mind:
1. when it comes to handling the pads, someone less experienced would be well advised to remove their gloves or wash their hands
2. the copper grease shows up really well on the pad photos, making it look as if there is more there than is wise
3. just to stress that the upper slide/guide pin must be cleaned & greased as part of the job - I know you say it should, but it's good to stress it.
This guide must have taken you hours to do, but you should be proud, I am sure you have saved many bumps, incidents/accidents & probably even injuries - I have seen trade places being less thorough.

 

Thanks for the comments Bill, they're good points well made.

I must admit that a couple of those photos does show a lot of copper grease on the back of the pads, more than is required, when I did the guide and pics I was having to work quickly and just stuck plenty on for illustration purposes. :lol:

Also, as you quite rightly pointed out, it's important that you're extremely careful when handling the discs and pads not to get any grease onto the friction surface. I just managed to get plenty of grease on my bloody camera instead. :irked:

I've personnaly not had any problems with the upper guide pin but as can be seen in the guide, I always clean it, apply some grease and reinsert the guide pin. It takes a matter of seconds to do and shouldn't be forgotten about.

Hmm, should I get a job working for Haynes... I very much doubt that I have the skills to produce a Haynes manual yet, although I do try my best. The guide did take a few hours of my time but if it helps a couple of people save some money and be able to change the discs and pads correctly, it will be time well spent.

I don't pretend to be a mechanic, far from it, I spent parts of my childhood helping to repair HGVs and when I bought my first car I always wanted to do as much as possible myself. Doing my own repairs was sometimes a necessity and now I still do my own repairs just for the satisfaction and peace of mind that it brings. Working on cars is frustrating, time consuming, and at times irritating although once I've completed a job I feel a sense of acheivement. I might swear and curse while working away but I'm secretly enjoying myself. :lol:

Thanks,
Ian.

 

absolute brilliant guide i have never changed brake pads and discs on my mg zr 1.4 before. I have the haynes manual as well but didn't need to look at it once finished and tested and works brilliant thank you very much.

 

I'm glad that you liked it mate. The Haynes manuals are ok but I've found that they just don't give you the hints and tips which make the whole job much easier. Just remember to allow the brakes to
"bed in" a little before using them too hard. :broon:

very concise. we need more of these types of general maintenance threads!

bit lavish with the coper grease lol, its very hard wearing stuff. only need a fraction that you would use of normal grease.

Cheers Dean. I must admit that there's lots of copper grease in my pics but a normal smear wasn't picked up very well by the camera. At least it shows what needs to be done and from the reports that I'm getting back the guide is working well so far.

 

very concise. we need more of these types of general maintenance threads!

bit lavish with the coper grease lol, its very hard wearing stuff. only need a fraction that you would use of normal grease.

 

Hiya thats a great guide pretty much how i did mine on the 200, i was just wondering is it the same for the mg zs, someone mentioned something about needed a tool to wind somethig back? any ideas. thanks

 

The tool that you refer to is for the rear brake caliper piston. Instead of pushing the piston back with a clamp you need a tool to wind it back with. I've found that you can use a very very big flat screwdriver or anything similar to wind the piston back with.

The front brakes on a ZS are the same as these.

 

ok kool thanks for the help mate may have a look at that. thanks

 

Anytime, glad to be able to help.

 

Great guide and very thorough. The only thing I would add is if you have a bolt or nut (guide pin bolt etc) that looks like its going to give you trouble, a quick soak of penetrating fluid often gives good results. Just remember to give it time to soak in. Now that the weather is better I need to give my rear brakes a going over (MG ZS 120). I am getting a metal to metal sound when I brake and I am wondering if this is the "audiable wear indicator" you mentioned. Also the handbrake is bad and I'm hoping I dont have seized callipers. Are ZS's prone to this like the 600's or will it be a case of a bit of TLC. Thanks for the guide.

 

Hi, thanks for the constructive comments. Personnaly I've never had any seized bolts (or even stubborn bolts) while doing any brake rebuilds but, as you rightly say, if there's a tough bolt, give it a good spray with penetrating fluid. If the discs are being reused then always be extremely careful not to get any onto the disc.

The audiable wear indicator isn't fitted to all pads, just the OE ones. Some of the cheaper after market pads are supplied without the wear indicator. The audiable wear indicator usually produces a decent squeal when you apply the brakes to remind you to get them replaced. If you have a harsh metal to metal sound I suggest you get to them straightaway.

Again, I've not had any problems with the rear calipers with regards to the handbrake on either my 218iS or the MGF. I'm sure however that they could possibly seize if not maintained. The last time that I changed the rear brakes I stripped them down, replaced the discs and pads, then pumped the brake pedal a few times and then finally applied the handbrake to check that it was working ok. I also found it helpful if my GF worked the handbrake a little so then I was able to lubricate the mechanism on the caliper while in motion.

Hopefully once you've replaced the rear pads you'll have a better handbrake and then it may be a case of adjusting the handbrake slightly to compensate for a stretched handbrake cable. If you've got any problems post them up on here and I'll try and answer it as best I can.

Thanks,
Ian.

 

Hey HTR, no prob. Credit where credit is due. I did have a prob with the guide pin bolts on my 620 and they started rounding a bit. So a quick squirt of the ol 40 and out they came. I always give troublesome bolts a hit with a hammer as well as I have found this breaks any seal that has caused the seizure. I may do a 'How to' on the ZS+120 rears as there does'nt seem to be one and if it helps even one person out then good. I noticed you did what a lot of DIY'ers miss and that is remove the brake fluid resevoir cap. I doubt you could push or wind the pistons back if you did'nt. Anyhoo if it stays sunny and warm I'll get them done in the next couple of days.

 

I noticed you did what a lot of DIY'ers miss and that is remove the brake fluid resevoir cap. I doubt you could push or wind the pistons back if you did'nt.

:rofl: You may want top double check my guide then because I did remove it and take pics too on post #3

http://forums.mg-rover.org/showpost.php?p=2925950&postcount=3

 

i need to do my brakes on my zr i have the 262mm solid brakes, is this easy for a complete amatuer to do? or are thre any members in glasgow with good mechanical skills who are free sometime soon to do this for a small nominal fee lol
also can i put on vented discs or does it need to be the solid ones, can i put on grooved ones? ncheers

 

You cannot fit the vented discs unless you change the caliper and carriers too. The reason is that the vented discs are much wider than your standard solid discs.

The whole job is relatively easy and doesn't take too long to do if you have the correct tools. Are you planning on changing just the pads or are you doing the discs as well? Changing just the pads is easy and wont take you very long at all.

 

i need to change the discs as they are warped, well so the guy i national autcar told me and its £110 for them to fit and install the new ones, can you use groovd discs on the car then instead ? cheers

 

You could have drilled and grooved discs as long as they're not vented.

If you're no't afraid of using spanners and have a decent socket set give it a go. Once you've changed one side the other will be much easier to do and from then on you'll always be changing them yourself. However, if you're not confident, let a reputable garage fit them instead, brakes are the most important safety feature of your car.

 

yeah got decent socket set and am confident plus the pictures and guide here make it look easy, will give it a go tomorrow maybe, just need to get a decent set of discs and pads

 

Well if you run into any problems send me a pm and I'll try and repy asap.

 

just wanted to say a big thank you, this guide was world class! took me 2 hours, bit of effort, lots of black stuff and a little blood....for a complete newbie 2 this sort of thing! everything works and the break squeal has GONE

cheers m8

 

You're very welcome mate,I'm glad that you got through it ok, hopefully you didn't lose too much blood though. :lol:

Remember to allow the brakes time to bed in. :broon:

Regards,
Ian.

 

Great guide mate. Looking forward to your rear disc one.

Just one Q. What did you use to clean up your discs?

Cheers

 

Do you mean clean as in getting the oil off new discs or actually geting my old discs looking clean again?

 

How did you remove the rust and make them "shiny" (oooo shiny lol) again?

Cheers

 

How did you remove the rust and make them "shiny" (oooo shiny lol) again?

Cheers

Shiny? :lol:

I just gave them a good clean up using some fine emery tape as mine were covered in surface rust. You can actually have the brake discs skimmed but it's just as quick and easy to replace the discs.

Chers,
Ian.

 

thanks for this, i have to do all 4 discs on my ZS very soon. any tips on doing the back ones, is it much different?

 

My pleasure mate.

To change the rears it's fairly similar although instead of removing one guide pin bolt you'll need to remove both so that you can pull the caliper away from the pads and disc. Once removed change the disc, clean the caliper as you did with the front ones and then you'll need to wind the piston back. On the front caliper the piston can be pushed back with a clamp, the rear needs to be wound back with a special tool or a huge flat screwdriver or something similar that is at least an inch or so wide. I think that the piston needs winding clockwise but do it slowly and check as I'm not 100% sure off the top of my head. When you wind the piston back ensure that it lines up correctly, the inner pad has a small notch on the rear of the pad that sits within the groove on the piston. One final thing to remember, ensure that the vehicle is chocked up at the front and that the handbrake is off and once the job is complete, pump the foot brake several times before applying the handbrake.

Hope that helps mate, if you get stuck drop me a pm and I'll try and help you out but the basics are covered in the main guide, follow that and most of it also applies to doing the rears.
Ian.

P.S: Always remember to grease the guide pins especially as the rears can/do seize.

 

Hi, just wondering if you can give me more details on the method for pushing/winding the piston back on rear brakes on a ZR.

A few posts have said that it needs to be wound back rather than pushed like the fronts ones.

However, it also says you can buy a proper tool or just something big like a chisel of 1" + flat screwdriver. Just wondering how they will work if you say it needs to be wound in (clockwise?).

I used a big chisel or screwdriver for the fronts just to push back but cant understand how you wind something in with these. If you are using something like that, surely you are just using it to push it back?

Does this mean that if you just push back slowly, it will start to wind in itself?

Please advise.

Thanks in advance.

 

Firstly, the rear piston will not push back. It must be wound back using a specific tool or something which can be inserted into the grooves on the piston to rotate it. The proper tool looks like this........

.......and is manufactured by Laser Tools. http://www.lasertools.co.uk/item.aspx?cat=518&item=3480

The rear piston has a "+" on its face, this is where the tool locates and can then turn the piston. It's possible to turn the piston without the above tool using something like a very large flat screwdriver, a chisel, a piece of metal etc, anything that will fit into the groove will do the job. The piston is quite easy to wind back, not much presure is required to get it moving and wound back.

I'm not 100% whether or not it needs to be turned clockwise or anti-clockwise. I think that it's clockwise, either way you'll soon see the piston begining to move inwards or outwards. Before you start to wind the piston back, make a mental note of its position of the "+", the inner pad has a small lug on the rear which sits in the "+" groove on the piston. It's important that this lines up correctly when you refit the rear pads.

Overall the rear brakes are fairly easy to do, if you can follow the guide and change the front pads without any problems, you'll ba able to change the rears without too much trouble too. The process is very similar, keep everything clean, grease the guide pins, copper grease on the contact areas of the pads and refit.

As I posted earlier the only differences to the front brakes are that when removing the rear pads you'll need to remove the upper and lower guide pin bolts and pull the caliper away from the pads instead of just swivelling the caliper on the top bolt. The piston needs to be wound back, don't bother trying to push it. And finally remember to line up the groove on the piston to the small lug on the inner pad. Also when working on the rear brakes, ensure that the front wheels are adequately chocked to prevent the car moving and release the handbrake before you attempt to remove the pads. Once the rear brakes are reassembled, give the brake pedal several hard presses, take it for a short drive using the brakes and then apply the handbrake.... don't apply the handbrake first.

Welcome to the forum Stu and I hope that helps,
Ian.