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MG MGF Technical - Front brake discs 25,500 miles

Hi

Just had my MGF1.8i in for a service and 2nd MOT and was told the front brake dics needed replaced. The car has done only 25.5K miles all at sensible speeds !

The dealer said the discs were rusting and that is why they needed changed. I think it is crap that they need replaced with this low mileage on the car. Anyone else had a similar issue. As for the dealer (Shields Rover - Glasgow) they did not want to know even although it has been bought and serviced there. Never again !
David Law

Hi David,

You having problems with shields also. My car has been in several times and they still haven't sorted the problem out. My F was in for 3 days last week sorting out little things, they managed to fix one, the throttle body.

I do think replacement disks at 25K is out of order.

I shall be contacting them tomorrow to complain.

Regards
Sandy

V361 MEC
Sandy Grant

Front discs replaced by Dealer at 4,500 miles so 25.5K
doesn't seem too bad...
Dealer tells me that there was a problem with the Discs
on the Early Cars.
My Discs weren't Rusty, just Warped.
Mark.
MARK PERKS

In these days of the almighty profit, money saved on production costs haunts owners later. Most modern cars have discs which no longer have linings to protect against rust. If your car has covered a low milage, it may well fall victim to this ( my family's Pug 106 had new discs at 12,000 miles due to this.)
Perhaps all that can be done is a good blast down some quiet back roads.
Andy Bourne

probably rusty through lack of use ;-)
I got through a set of discs on a 420 in 12500 miles of heavy-ish use, and also remember that asbestos-free pads have dictated softer material for discs which therefore wears faster, so 25k is not unreasonable in any circumstances IMO..
David Smith

Just a silly question from a non-F, non-MOT regulated driver, but why does rust on the non contact portions of a large hunk of iron matter? If there's rust on the contact areas, either the brakes don't work or are not being used, so the disc is not the problem.
George B.

I have seen discs which have failed the MOT on a friends Pug 106 due to rust. After taking the wheel off everything seamed okay but after looking on the back of the disc the reason was most obvious the disc was rusty and badly pitted.

Beforen getting anywork done ask the dealer to show you the problem.

Tom
Tom Randell

I am getting the idea that Disc Replacement is becoming a modern car scam!

If discs fail because they have a few 'pits' in them I am dreading the day my bike is due its MOT as the front discs have bloody great holes in them.

I don't know the legal situation on discs but as I understood it they should be changed if they are badly worn or warped, as one of our other 'posters' says a bit of rust aint going to do any harm and on the braking face the rust is soon worn away.

Surely the best test of the discs is a rolling road brake test!

Ted
Ted Newman

I agree with David- 25k miles is probably not completely unreasonable. My F's discs were changed at about 40k miles, which includes plenty of city work and a few jaunts onto the track. I find it hard to quibble about such essential safety items: if brake performance is badly affected by pitting reducing the brake contact area then so be it. But I think I would want to see the evidence first!!!

Interesting point regarding cross drilled brakes Ted. My Triumph Spitty has these too. Perhaps the random pattern of corrosion is deemed dangerous because of the possiblity of grabbing? Rog I am sure will have better insight into this issue.

Light surface corrosion is no problem- as Ted says it rapidly gets removed after a couple of applications of the stop pedal.

Rob
Rob Bell

The discs on the F are exactly the same as appeared with the 2.0 litre Montego in 1984. This car, with incidentally very similar weight to the F, has a very heavy front weight bias so a massive proprottion of braking effort is done by the fronts. Even so the incidence of dick wear was not severe, even if the brakes were not that effective.

During the late '80's brake pad material went through an enforced change to non asbestos types. The initial change involved considerable noise during braking which has largely been solved, but a continuing downside is the much higher metaic content of the pads which is far more abrasive to the disc, forshortneing service change points. Driver inputs then alter this point considerably!

Now add the MGF set up which has a much more open wheel design and no backplate, all in the cause of improved braking and trying to achieve a good braking performance without the need to tool up for a more suitable 260mm disc size. (240mm standard) This is fine for most 'normal' aplications which involve a degree of reasonably firm or harder use. The relatively smaller size also allows for greater heat generation.

Now the general design usually leads owners to find the shortcomings of the brake design and move to higher performance brake pads such as EBC green stuff. These increase disc wear, sometimes considerably (doesn't it Rob?!), and you end up changing discs because of serious scoring of the disc.

Corrosion on discs is a clear indication of infrequent and very light use. Traffic driving can allow this to happen as urban speed braking for a light brake user means next to no heat and frocition generated so corrosion on what is a virgin steel surface gets hold quickly. This builds up over time rather than miles and almost always affects the inner face of the disc first.

A pad acting on a surface that has anything other than just surface corrosion will show significantly reduced braking performance, sometimes very signifcantly reduced, because with a corroded surface that surface is uneven and so you end up with areas that the pad never contacts, no contact means no braking!! The other aspect is that the pad also wears unevenly which adds to the reduced contact area. To top it all corrosion involves expansion of that area of corroded metal and not only are the heat transfer properties cr*p, but lumps of corrosion will break off and lead to uneven and poorer still braking.

All that said if the cars service interval reflects it's age as about 2 years old, then the concept of corrosion having reach the point of excess and needing a disc change seems somewhat unlikely. Only in a slat laden atmosphere should corrosion accelerate to that level, as witnessed by specific salt tests done on many metalic car components.

To add weight to this is the simple fact that rear brakes do even less work and these are by far the most common ones to fail due to disc surface corrosion. If the fronts have needed a change then I am pretty damn sure that the rears should be in a worse state. Why no comment about these I wonder?

The end test has to be one of brake performance. Clearly excessive corrosion or other damage cuases significant problems and can be a reason for an MOT failure. But otherwise it is a matter of measured braking performance and here there are clearly defined limits in terms of actual stoping power and balance.

Rog

Roger Parker

Interesting read Rog :o)

The MGF's smaller discs (which therefore has more rapid heat build up) plays into the hands of those who want to use harder pads that need more heat to work- it may, therefore, be possible to use EBC red stuff pads on an F successfully for road use, but I haven't tried it so I can't recommend it!!!

>>Now the general design usually leads owners to find the shortcomings of the brake design and move to higher performance brake pads such as EBC Green Stuff. These increase disc wear, sometimes considerably (doesn't it Rob?!), and you end up changing discs because of serious scoring of the disc.<<

In defence of EBC pads, they weren't the culprit of the disc damage I had- and boy, were those discs badly grooved. No, the the problem arose when I fitted replacement Mintex 1177 pads (the ultra-hard, high metal content motorsport pads). For some reason the pads friction surface had broken up causing extensive damage to the discs. You think that 25k miles is a bad rate of wear David? My discs were toast within 200 miles of fitting these pads!!! New discs (thanks Rog) and new Mintex pads, and problem solved. Some minor grooving on the disc surfaces, but nothing to be worried about. Phew. The performance of these pads are phenomenal, but not everyone is prepared to put up with the high rates of disc wear (I should be lucky to see 20k miles- at which time both pads AND discs will need replacing).

I am not complaining! :o)

Rob

BTW the EBC pads did have some rather worrying wear characteristics- I am not sure whether these are peculiar to my car. The rear Black stuff pads were down to the metal backing plate within 10k miles. Fortunately, the Green stuff material is now available for the rear calipers- and worth upgrading to if you are already an EBC pad user. The Green stuff front pads still had plenty of material on them- good for another 10-12k miles I'd guess, but the friction block itself appears to be relatively fragile: parts of the friction material had clearly broken off, reducing the pad's surface area. Putting this into perspective, the braking performance was still excellent, but the apparant damaged caused me to raise an eyebrow!
If anyone else has cause to look at their EBC pads, I'd be interested to hear whether this is a common feature of these pads.
Rob Bell

What are you guys on !! Do you left foot brake - all the time. My Montego 2.0 est had 178,000 on th clock when I got rid of it and it only had pad changes at 65,000 and pad and disc changes at 142,000 with lots of time spent towing. My present vehicles , a primera ( yes I know but it is built in Britain ) has just had a pad change at 44,000 and that only because my son was using it away from home for 2 months. My metro GTi has 38,000 on without anywork to the brakes. I don't hang about either as I am self employed and road time is unpaid.
Graham Robson

Graham,

It reflects your driving conditions rather than style which gives you abnormally low wear rates. As a matter of interst what was the disc thickness at the change point? 5000 miles for pads and 10,000 miles for discs was an accepted wear rate on our old fleet of patrol Montego's, of which there were several hundred over the years, and this with Rover's supervised set up and spec for this particular application. The old SD1 brakes even with the vented discs and 4 pot calipers that were later standard on the Vitesse were sometimes changed twice a month because of their inadequacy leading to warping and glazing.

For more normal use in the same traffic conditions the average is a little better with around 35 to 40K being the norm before normal expected wear due to normal pad to disc contact actually removed metal and reduced the contact area to below the minimum thickness, which incidentally is 20mm. 60 to 70k being quite exceptional for even the softest of drivers, and then corroded discs are often seen.

The above change points are done by following the guidlines set by Rover and Girling. It is very possible to keep running discs that are well below the minimum thickness and with little repeated brake applications required the system will function quite normally.

The rate of wear for pads is another matter to ensure change before the minimum sthickness point is reched ideally since with a thinner disc and thinned pads the caliper pistons have to extend further and I have seen a number of occasions when they stick because they are able to attain slight skewed angles.

Rog
Roger Parker

Roger

I don't wan't to be controversial, well I do really, but could the frequency of pad and disc changes on the patrol cars be related to the latest police report on standards of driving.
My montego discs could have taken a skim instead of being replaced, but it was done at the same time as front wheel bearings in a day between jobs and it was quicker to replace. Incidentally the Engine was never touch in the 178,000 miles apart from 2 temp sensors and a stepping motor clean. It did object for a while after I had put Kart 2 stroke mix in the tank but it sorted itself out eventually.
My work at the time I had the montego was IT rollouts all over th UK and involved motorway, cross country and town driving so it covered the whole spectrum.
I put the longlevity down to anticipation on the road, always trying to be in the right place at the right time,
and the fact that I try, wherever possible, when I am going to be parked up for sometime and it has been wet, to apply my brakes before I stop to get some heat into them to try and dry them off. I don't know for sure whether this helps but its a bit like not walking under ladders, a habit you get into.

Anyway all the best to everyone for Xmas and safe driving in the New Year

Graham
Graham Robson

All interesting stuff. I'm interested in what you have to say Rob about the EBC pads. I have green stuff on. i put them on for a track day. i bedded them in for 500 miles before and then obviously gave them a hammering on the day. resulting in my wheels looking like they had been painted black. he car slowed well but i was on the gears alot so i don't know how much was down to the pads.

Now however i am not particularly impressed with the brake performance. The feel is terrible and i get the impression i have to pile on a lot of pressure onto the brake pedal to slow down. They do work and i guess they work well, they just down feel good. I wouldn't be suprised if there is some kind of damage to either discs or pads - who knows. i want something better though.

Is there any chance of anybody getting hold of some mintex 1177 for me?

Another question i have, is there any reason why i should get a dealer to change my discs/pads or will any garage be good enough. the reason being i am fed up of stupidly high costs of dealers. and are the discs that B&G sell any good?

Matt

Track days certainly are very hard on components- if the wheels weren't black afterwards, I'd be amazed! The last track day I did, I still had the EBC pads on the car- and yes, the wheels were black too. I had EBC blacks on the rear- appropriately named as it turns out, as the rear wheels were several shades darker than the fronts!!! ;o)

Brake feel is an interesting subject. Have you got standard brake hoses Matt, or braided replacements? I think that there are two causes of the MGF's slightly spongy, rather lifeless brakes- beyond the usual causes of poorly bleed or contaminated brake fluid. The first are the brake hoses. With age, the walls of the hose become more compliant. Stainless braided hoses erradicate this particular problem. The other cause is rather less apparant: the mounts for the brake servo. It is mounted on the most flexible part of the front bulkhead. Again, an age thing, there is more and more movement of the servo that detracts from the brake's feel. A solution here is to fit a strong auxillary servo bracket- something that is available from Brown and Gammons. Remedy these two things, and the difference in the brakes is like comparing chalk and cheese. Simple fixes that are well worth while.

Regarding Mintex pads... They cost over 80 quid a pair- so are SIGNIFICANTLY more expensive than EBCs. Additionally, the discs need replacing far more frequently. Are they worth it? Ask me in a few months time when I've competed some sprints with them!! These pads are available to anyone with an MSA licence from MG Rover sport. They closed recently to move their operation to Longbridge. I haven't yet heard that they've re-opened? I do not know if they can be sorced from else where.

I think I would change the hoses and fit the servo bracket first, and then re-appraise.

Rob

Rob Bell

Matt,
if it's any help I too have used EBC greenstuff (on my Monty turbo) for a track day at C/Combe. Cooked the brakes in 4 laps - my fault really as the pads were well worn to start with. Fitted a set of 1177s bought from Merlin Motorsport in the paddock and transformed the braking. Completed the sprint season with them and they are still in the car in everyday use. Sure Merlin could supply F pads too. Mine were about 55 IIRC.
Brake disc and pad changes are a doddle with a jack and basic tools - get someone to show you first time round, and save so much money you can afford the pads !
Hope this helps
David Smith

Are the 280mm discs worth the extra money?
Nathan Carnie

280mm worth it? from my MS brakes experience...

YES ! YES ! YES ! YES ! YES ! YES ! YES !

Also make sure your seatbelt is fitted all the time, you might get surprised how quick you stop :-)
Dirk

Graham, no controversy as the brake issues go back to even the Mark 2 Jags of the late '60's. These were true performance cars capable of 130mph plus in 3.8 form. Subsequent cars like the Triumph PI's and even Cortinas had dreadful brakes. The only difference with time has been the development of friction materials that have a much wider performance envelope and now they can provide much better braking rather than complete fade out. The downside is severe wear rates.

BTW the Monty mileage is still a little low, I know of several cars running brilliantly with well in excess of 200k mies and another that was up to about 330k miles and still running well. Odd that these are regarded as such unreliable cars that the private hire people use so many and clock huge mileages!!

Overall you will have to take much of the credit for achieving the life from the brakes that you get.

On the subject of 280mm discs, yes they are worth it!

Rog
Roger Parker


Mintex 1177s are not available for the 'F through normal retailers - Merlins at CC included. :-(
They could do me 1166s but would have to order them.

As Rob says, the only correct way of getting them for the 'F is through Rover Motorsport.
I do not know why this situation arose, but I hope it changes to allow anyone to get them.

I don't have braided hoses (but might by my next sprint!) but I do have the master cylinder
bracket. It has improved the feel of the brakes on my car. It's scary to see how much
the bulkhead moves when you stand on the brakes!

P.
Paul Nothard

I have also been told by Rover that the brakes on my car are "in a very bad state." The discs do have some wear visible - but does this really affect braking performance - the contact area is not reduced by this wear. Anyway I think I'll go for larger 280mm front discs when they really do need replacing. Is there any difference between the larger discs from Mike Satur or PAW or HJW motorsport - apart from about 180.
Nathan Carnie

Mintex used to have an open door policy of supplying any of their product ranges on demand. I used to take advantage of this over many years, but some years ago they had a rethink following some problems. I experienced one aspect of these in the supply of several bad sets of the old Mintex 171 pads. The report that came back following the complaint and return of three sets was that the materials had degraded following periods of bad storage.

Not my problem, but one which was exagerated by their open door system. What had happened was that the 171's I was using, for the V8 which with 145mph potential benefitted from decent brakes, were a rarely ordered item and the supplier system meant that I had the pads from a dealer who was further up the pecking order and not direct from the factory at Cleckheaton. These had been in store for some time and had taken on water, hence they broke up soon after fitting.

Following this, and probably due to other complaints like mine, the dealer system was reorganised. The arrival of a wider and more sensitive range of friction materials also meant that some specs were really completely unsuitable for road use. The upshot was and is that for the competition range only a very limited number of outlets exist and this way thay can control that the pads supplied are correctly matched for the job in hand and not the 'wide boy' who simply wants them to add to his bar room specification list. Problem is that it makes it more difficult for those who genuinely have a need.

It is worth a visit to www.mintex.co.uk and have a browse around the site. The pad selection catalogue is especially useful. On the competition side it doesn't offer any direct suppliers, but there is a dealer listing and I am sure some of these would be able to supply. Rovers sporting arm, MG Motorsport, which incidentally is still closed for the transfer to Longbridge, (Which is going well according to the chap in charge) should not be the only outlet for these as the pads are the same pattern for all Rover Metro's from 1990.

Of interest a quote from the Mintex site re competition pads will be of interest, and confirms their view.

"This family of materials has been developed from our involvement in motorsport. The first material M1144 is mainly used for fast road use and is primarily targeted at hot hatch drivers. The other three materials M1155, M1166 and M1177 are specifically for circuit and rally competition use only."

Rog
Roger Parker

This thread was discussed between 20/12/2000 and 23/12/2000

MG MGF Technical index

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