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MG MGF Technical - Changing rear break disks and pads.
This weekend I'm going to attempt to change the disk and pads on the MGF. I have searched thorugh the archive and the fronts seem easy - pretty much a standard method required (that's tempted fate:-). However, I've never had a car before which has had disks on the back - so this will be a first. Is changing the disks and pads on the back any more difficult than the front; because of the handbrake? Any tips? Any special tools required?
I've ordered some "greenstuff" pads; any idea where I should get my disks from? Is it worth spending the 99UKP on the Brown and Gammon ones (I don't fancy 275UKP for Mike Satur's version)? If I buy standard disks are the Halfords ones OK?
|For "break" read brake - it's late and it has been a heavy weekend ;-)|
|No different to changing the pads and discs on the front. I took some piccies whilst Rog kindly replaced my front discs- description found in the DIY section of http://www.mgf.4mg.com|
I say no different- this is true with one proviso. Whereas with the front pads you lever the pistons back into the caliper with a suitable screwdriver used as a lever, with the rear calipers, the pistons need to be screwed into the caliper as the pistons are threaded. Not too difficult- is used an old screw driver to get the pistons to rotate inward.
Just one thing to be aware of- the brake fluid level as you push the pistons into the caliper. As you are displacing fluid into the master cylinder resevoir from the caliper, the resevoir can overflow, stripping paint from the bodywork in the process...
|I found that one of the "spanners" from my angle grinder fitted the bill as a "pin" spanner to screw in the rear pistons.|
One of the grinders attachment nuts is round and flat, but has 4 (~3mm from memory) holes in it - its a cheap and cheerful Wicks 4.5" one...
Thanks for your help. I'll make sure I take some different sized screwdrivers with me when I go to the father-in-law's garage.
I called in at Halfords today to get some prices for brake disks. The fronts are 29.99GBP per courner but they don't have a listing on their computer for the back disks. Does anyone have a Halfords part number for the rear disks? I'm sure I've read somewhere in the archive that a Metro GTi's (FRONT or REAR)??? disks can be used on the MGF's rear! Is this true?
P.S. Also ordered a K&N filter today. Looks as though they are pretty simple to fit. Why didn't I order one a year ago? :-)))
|Was thinking of replacing the back disc due to uneven wearing of the brake pads. However I'm re-thinking this as the disc seems to be only available from the dealer, hence no part number at Halfords, the dealers have quoted me £72. I personally think that it is rather excessive for a disc but there does not seem to be any alternative, tried metro discs and although they fit and look similar, the actual depth to the disc(confusing) is more in the metro disc, this then caused the brakes to catch so not really worth trying. Although metro discs you can get for about £10 a lot more reasonable.|
rear brakes : F = Rover 800
front brakes : F = Metro GTi
|Just to clarify what comes from where.|
Front discs are the same as all Maestro and Montego with vented discs. They are also the same as Metro GTi 16V and this is the source for the calipers too. Pads are dimensionally the same but have a different material make up.
Rear brakes use specific discs, which may be the same castings as other cars, but have centre drilling to suit the very specific 95.4mm MGF wheel stud PCD.
Calipers are from post October 1991 Rover 800 as are the pads.
For alternative sources for discs I do suggest you try a motor factor rather than a High Street chain. A factor who knows his business will usually find suitable alternatives.
|I have been able to source some Mintex discs for £90 (two front and two back). They're from a motorfactors called Scotties in Tredegar (01495722323). So, shop around! Just ensure that they are a branded make.|
I'm having real trouble getting the rear brake caliper piston to screw in so that I can take the old pads off.
I am trying to do it without the piston retraction tool.
Is it right that the piston face has notches on the side next to the rubber gaiter? (It's difficult to view thru the caliper assembly)
To retract the piston I am also assuming that the piston needs to be turned clockwise. Is this correct?
Can someone please clarify? (A piccy might be too much to ask).
Can the job be done with a handful of screwdrivers?
I have also noticed that the rubber cap on the inner top surface of the caliper is damaged. What is the cap covering? Is it a bleed valve?
Sorry for all the questions. (Civil engineers no alot about roads but f-all about cars LOL).
|Don't bother... but see the archive also for more instructions.|
I've got currently only this picture to hands.
See the piston 'form' on the right side.
|There are two usual reasons for difficulty in piston retraction. One is a seized/semi seized piston. This is usually accompanied by a fully worn brake pad on one side and less worn on the other.|
The second reason for difficulty can be hydraulic pressure resistance. I have found that is it often an advantage to attach a bleed tube to the caliper bleed nipple and then loosen it. I then find that turning the pistin becomes much easier. Note that to avoid introducing air into the system I squeeze the piston in by hand and at the same time tighten the bleed nipple. The small movement of the piston is enough to expell fluid and tightening during this means you close the system off with only fluid inside.
On cars old enough to need a disc change the expelling of some fluid from the caliper is not a bad thing. If the fluid that comes out is anything other than a honey or biscuit colour then a fluid change is perhaps a good move!
REMEMBER to top up the master cylinder afterwards.
|>>Is it right that the piston face has notches on the side next to the rubber gaiter? (It's difficult to view thru the caliper assembly)<<|
Not on the side, but on its face. There is enough there to get purchase to rotate the piston into the caliper with a screw driver.
>>To retract the piston I am also assuming that the piston needs to be turned clockwise. Is this correct?<<
>>Can someone please clarify? (A piccy might be too much to ask).<<
I forgot to take pix when I did this. Next time, I promise!
>>Can the job be done with a handful of screwdrivers?<<
That's how I did it :o)
To help, I unscrewed the lid of the master cylinder- to reduce back pressure and enable me to monitor the levels in the resevoir. An overflow is a diaster for paint work.
This thread was discussed between 03/06/2001 and 13/06/2001
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