Which is best?
We used to have four drums, then two of each, now many cars have discs all round.
I quite like drums because they last forever and don't deposit brake dust all over the wheels.
So you need greater braking performance at the front.
Wouldn't it be possible simply to fit larger drums at the front than at the rear?
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Discs are self adjusting, do you want to go back to 5,000 mile servicing to get the front brakes to work? I have yet to see a good auto adjuster.
Last edited by: Old Navy on Sat 8 Jan 11 at 13:11
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...Discs are self adjusting, do you want to go back to 5,000 mile servicing to get the front brakes to work?...
Fords had mechanical self-adjusters on its drum brakes, although we sometimes used to help them along a click or two at service time.
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Were these on the front drums? I have not had a car with auto adjusting front drums, and I have had a few, (not Fords).
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Many moons ago I had a car with drum brakes. One summer I drove through a dust storm and the dust got into some of the drums. It reduced the braking performance considerably. (In fact the braking became quite iffy ;-) I wouldn't want to take a step backwards in technology and have drum brakes again.
Last edited by: L'escargot on Sat 8 Jan 11 at 13:26
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iffy must be having a retro day, next it will be carburettors, and distributors with points. :-)
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...I wouldn't want to take a step backwards in technology and have drum brakes again...
Some of the weaknesses of drum brakes could probably be sorted by some development work.
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Honestly iffy.
Everyone had self-adjusters on drum brakes in the later applications. Front drums were generally bigger than back ones, just as discs are.
You only have to drive a drum braked car past its first youth to understand why they are a thing of the past. The self-adjusters simply don't work all that well. With drums, if you were really motoring, you quite often had to hit the brake pedal twice, the first time to even up all the shoes, the second time to do the braking. You got used to the sort of little wriggle cars gave during this process.
Disc brakes don't need adjusters. They are intrinsically self-adjusting, and the way they work renders them much less prone to brake fade in high-speed stops. They are cheaper than drums too because much, much simpler in construction. It's a win-win situation.
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...Honestly iffy...
It's only a discussion point, not a battle of wits.
In answer to ON above, I can't recall if Fords had self-adjusters on all four drums, although I can only recall manually adjusting the rears.
We might have done that partly to improve the handbrake - it was all a long time ago.
Shoes needed changing regularly, but it was almost unheard of to change a drum.
Seems to me new pads now means new discs as well, which must be more expensive.
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>> It's only a discussion point, not a battle of wits.
Heaven forfend that I would risk a battle of wits with you iffy. But even as a discussion point we have seen all this before either here or in the other place.
Modern manufacturing methods and materials might make drum brakes work better than they used to (and as pointed out, well designed and expensively made ones worked better than cheapo). They might even make the mechanical brake servo that Rolls-Royce stole from Hispano-Suiza and fitted to all its cars until the late fifties work better.
But why have Heath Robinson and expensive when you can have simpler, better and cheaper? Even Rolls-Royce succumbed to the vacuum servo in the end. Same thing with drums and discs.
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....But even as a discussion point we have seen all this before either here or in the other place...
AC, as a former journalist you will know there are no new stories.
Only names, dates, ages, people and places change.
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I doubt drums would 'last forever' now - the same materials factors would apply to them as to discs (i.e. no asbestos).
Disc operation is faster with very little movement of fluid required - more suited perhaps to ABS/ESP control. They are more compact. They are usually less prone to overheat/fade but that could be dealt with.
I don't get brake dust on my wheels, as I avoid needless braking. Now over 90,000 on the same pads.
Drums can be good of course. I occasionally get a ride in a 1928 Lagonda 2 litre and the brakes are amazing. The drums are quite big though, which is obviously the trick.
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IIRC a couple of manufacturers reverted to front drums in an effort to improve economy.
The theory being the slight drag caused by pad to disc contact could be bettered by shoes being adjusted so there was no contact when the brakes weren't applied.
I wonder what changed?
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>> I wonder what changed?
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Probably smart clever dick young designers who didn't know that drums on the front are crap because they have never driven a car with them.
Last edited by: VxFan on Sat 8 Jan 11 at 16:48
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>> The theory being the slight drag caused by pad to disc contact ..........
Dunlop used to have a pad retraction system but it was found to be unnecessary. Axial runout of the discs knocks the pads off the discs when the pedal is released.
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...I doubt drums would 'last forever' now - the same materials factors would apply to them as to discs (i.e. no asbestos)....
Fair point, although I wonder if the semi-sealed nature of drum make the shoes last longer.
And there's probably a larger area of friction material in a drum brake.
...the brakes are amazing...the drums are quite big though, which is obviously the trick...
So maybe a modern car with big drums at the front could be made to work quite well.
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>> So maybe a modern car with big drums at the front could be made to
>> work quite well.
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Modern cars are much heavier with all the crash resistance and extra kit fitted so would need huge front drums to be of any use. Even a drum braked original (real) mini which weighed next to nothing was a bit iffy to stop from speed (50+ mph). :-)
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the new type material used in drum brakes means they do indeed last a very long time if adjusted correctly and not dragging
the downsides of the asbestos free material is the drums do wear much quicker giving rise to a lip which can make some car drums difficult to remove also these new materials seem much more susceptible to glazing i find
with regards drum brakes on the front of vehicles unless you know what you are doing is very easy to over adjust one side and then you get grabbing brakes on that side which can be very unpleasant
so long as you have free pistons etc on a disc set up then equal balanced brakes is much simpler to attain
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I think drums might be too big for some modern wheels and to get the perfomance some of them had to be "finned" to improve the drum/ brake cooling. See pictures here
tinyurl.com/2w6hck6
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...See pictures here...
Nice.
Some of those finned drums really look the part, which is another factor in the debate, even though many people will say it should not be.
I see the likes of Lola and Morgan are mentioned, which suggests drum brakes and performance cars are not mutually exclusive.
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>> I think drums might be too big for some modern wheels
Put me in mind of the ultimately disastrous 1955 Le Mans 24hr. The Jaguars had the advantage of disc brakes. The Mercedes 300SLRs had enormous inboard drums, probably because they were too big for the wheels. Notwithstanding those, they still needed an air brake to get on terms under braking for the end of the straights.
en.wikipedia.org/wiki/1955_Le_Mans_disaster
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Every time I think of drums, it reminds me of the constant nightmares I had with the self adjusters on the rear drums of my mk2 Cavalier SRi.
The basic principle was a strut with a ratchet mechanism on it, which engaged with an arm attached to one of the shoes. Once the shoe moved past a certain point, the arm was supposed to turn the ratchet on the strut, winding it out slightly and thereby adjusting the rest position of the shoe.
Never, in the 2 years I had that car, did I ever get the infernal setup to work properly. At every service, I used to have to take the drum off, wind the strut out until I couldn't get the drum back on, back it off one "click" and then refit the drum. A complete and utter pain in the rectum. I'd then feel the braking efficiency slowly die off, and the handbrake travel increase as the miles wore on
I remember many times disassembling the entire shoe and spring mechanism and painstakingly cleaning and reassembling it following the Haynes photo and diagram to the letter, but it never did any good.
Last edited by: DP on Sat 8 Jan 11 at 16:46
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Another disadvantage with drums is that they get waterlogged, something that doesn't happen with discs.
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>> Another disadvantage with drums is that they get waterlogged, something that doesn't happen with discs.
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It can, it is wise to check your brakes before you need to slow after a wet fast stint without using them. I almost learned that one the hard way many years ago.
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...The basic principle was a strut with a ratchet mechanism on it...
The Ford system was much the same and worked about as well.
From memory, it was possible to wind it up a couple of clicks from the rear of the back plate.
The job could be done with the wheel on, but was much easier on a wheel free ramp.
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Why do they still use drums on the rear on cheaper cars? I assume it is because of the hand brake?
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Handbrakes can work on disks, my Focus handbrake operated through the pads. My current car has a brake drum and shoes in the center of the rear disks for the handbrake.
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Which I assume costs quiet a bit more than drums, which answers my question :).
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Probably all pick ups still use drum brakes at the rear, nothing wrong with them for that application.
Not sure i'd want front drums any more either, given the lack of proper dismantle inspect servicing in many cases there could be all sorts of things going wrong inside unseen, shoes down to the rivets for years.
If rear drums are getting worn or have a problem with leaking cylinders then the problem shows itself through lack of handbrake.
Cost isn't a problem really for either system, today i've replaced the rear discs and pads on my daughters new to her Civic for the princely sum of £55 for good quality aftermarket parts, pretty certain they were the originals.
Last edited by: gordonbennet on Sat 8 Jan 11 at 17:47
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Rear drum brakes - properly designed can be easily inspected. On the Yaris, the drums are held on by the wheel bolts , so jack up, remove wheel , pull off drum. Inspect.Replace drum, wheels.
5 min job.
Of course Peugeot on the 106 used, the axle bearing retaining nut to hold on the drum.. so you had to remove the oil seal, and the nut.. . Typically French.
And Ford on Fiestas used 4 bolts..
I had drums on front brakes. Apart from adjustment.. unsprung weight was an issue. As was fade..
Anyone had fade on a disk? On a drum , smoke, smells and nothing happens.. On a steep hill terrifying..
Last edited by: madf on Sat 8 Jan 11 at 18:19
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>> Anyone had fade on a disk? On a drum , smoke, smells and nothing happens..
>> On a steep hill terrifying..
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Yes.... Mk3 Fiesta, cheap pads from Euros... coming down a steep hill in High Wycombe, with a t-junction at the bottom......
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>> Probably all pick ups still use drum brakes at the rear, nothing wrong with them
>> for that application.
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Mine has 'em at both ends, and until two years ago it didn't have a servo. Perfectly capable of passing an MOT, but going down a hill with a full load of firewood on board was a truly butt-clenching experience!
One major drawback with drum brakes is the problems caused when a wheel cylinder leaks. It usually trashes the brake shoes before it gets noticed, sometimes resulting in an otherwise serviceable set of shoes being scrapped; yes I know you can clean them off but I've always erred on the side of caution.
My old Harley Sportster,a 1972 model, has drums both ends. It goes far better than it stops, trust me!
Another argument for discs is that they're self-adjusting, and therefore don't make cars so prone to pulling to one side. Getting them set up correctly can be a tedious and time-consuming task, ask anyone who's worked on old Land Rovers..
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>> Mine has 'em at both ends, and until two years ago it didn't have a
>> servo.
>> time-consuming task, ask anyone who's worked on old Land Rovers..
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Stopping wasn't high on the list in 1971 either, my 5.7 litre Mustang Boss had non servo'd drums all round too, made stopping from it's considerable turn of speed interesting.
Could have done without the reminder of series 2a LR hell HarleyM, the only way i could get the brakes to bleed was to remove all drums and use a lot of G clamps to pin all the slave cylinders in tight.
I'd still be bleeding them now if not.;)
Hilux's self adjusters work quite well, i do keep the brakes cleaned out and a touch of lubricant where needed though..oh and the drums look nice in black Hammerite as do the front calipers.
Agree with the leaky wheel cylinder problem, it's typical neglect..out of sight out of mind.
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Usually drum brakes are more than capable of locking the front axle. Purely in terms of stopping power they are more than adequate.
Where drum brakes suffer is in terms of their propensity to brake fade - especially if they are twin leading shoe brakes. So, the reason for specifying front disc brakes ISN'T power, it is stability, thermal stability.
For a number of very good reasons, most cars have an excess of braking on the front axle - even after fully accounting for forward weight transfer under braking. Any modifications which further increase the braking force from the front brakes actually reduce the braking efficiency and increase stopping distances.
Drum brakes on the rear axle of most modern cars are exactly the correct engineering specification. The easy provision of a safe, cheap handbrake is something that most disc installations cannot boast - handbrakes acting on discs are usually expensive and complex. As the braking requirements on the rear axle are lower than the static weight distribution of the car might suggest, thermal problems are not usually an issue.
There was a time when it was difficult to incorporate ABS in cars with drum brakes - owing to the different threshold pressures and application dynamics - but, that problem has long been fixed.
As I've written many times before, the specification of rear disc brakes on many cars is a simple triumph of marketing over good engineering, and most of the public swallow it all up.
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>> Where drum brakes suffer is in terms of their propensity to brake fade -
But also, I would politely remind you NC, indeed primarily since most people even in those days didn't court brake fade and perhaps never experienced it, a tendency when only slightly worn to dart hither or yon on initial brake application. I am talking about front drums here of course.
Discs are marvellous after that. Even in fairly poor condition there's none of that skittish twitching under braking.
My second car, a Citroen Light 15, had very good brakes with big finned front drums. So did the R Type Bentley when the servo was working properly. It worked off a clutch on the side of the gearbox and was no small matter to fettle. Pure Heath Robinson.
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The transition to discs wasn't such a step forward at the time, unless you had a car equipped with servo assistance, despite the dire chevron warning sticker on the back of some ''Disc Brakes''.
My Mk2 Cortina had unservoed discs and took a lot of pedal pressure to stop, ended up fitting a remote servo (might have been from a Landcrab but can't be sure), that gave it the finishing touch.
Twin leading shoed drums had by design an inbuilt assistance as the shoes bit, and needed no further assistance...prayer didn't have any effect on the Mustang's fade.
70's Trannies (the van) had drums all round as i recall, the fronts never got adjusted enough to account for fast wear.
I used to carry a 9/16 ring spanner for adjusting up truck and trailer drum brakes, job was simple though, you could pull the operating arm and adjust till the movement was just right by feel without lifting the wheel, that would have been handy on cars.
Like cars out of adjustment it only took a few seconds driving to realise they needed doing.
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>>I used to carry a 9/16 ring spanner...
I used to be surprised how much difference there was between drivers. My father employed one driver in particular who was very heavy on the brakes - taking up the slack adjusters on one axle or another every week, and new linings would seldom last more than a few months. Expensive!
The self servo of the twin leading shoe brakes was a bit of a double edged sword though. Yes, it initially reduced pedal effort, but, as the brake heated up, and the brake linings faded, not only did you lose braking effort, but, you also lost servo action!
Yes, darting hither and yon, drum brakes did need more and better maintenance than disc brakes, and that alone would probably discount them from consideration as a modern vehicle's front brakes.
Last edited by: Number_Cruncher on Sat 8 Jan 11 at 23:55
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Leaving Lands End fully loaded with potatoes, I could never get past Oakhampton without having to use that 9/16 spanner!
Pat
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>> Every time I think of drums, it reminds me of the constant nightmares I had
>> with the self adjusters on the rear drums of my mk2 Cavalier SRi.
>> The basic principle was a strut with a ratchet mechanism on it, which engaged with
>> an arm attached to one of the shoes. Once the shoe moved past a certain
>> point, the arm was supposed to turn the ratchet on the strut, winding it out
>> slightly and thereby adjusting the rest position of the shoe.
>> Never, in the 2 years I had that car, did I ever get the infernal
>> setup to work properly.
It's OK DP, it wasn't you - they simply didn't work!
They could be adjusted up through the bolt holes in the drum/hub though.
Very early mk2s had manual adjustment, with two bolt heads on the backplate to turn. Adjusting these up with the car on a wheel free ramp was a very quick job!
The good thing about the Vauxhall self adjusters is that they failed in a benign way, and they would simply drift out of adjustment. Ford self adjusters, on the other hand, could suddenly slip. Awful design IMO.
I thought SWMBO's rear shoes needed replacing on her Astra. At 78,000 miles, they were beginning to grate a bit. When I took the drums off, I found the linings still in very good shape, and a quick once over with emery paper was all that was required. At this rate, I wouldn't be surprised to find the linings will last over 100,000 miles.
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I've just gone back to drums all round, having aquired a nice Series II LandRover as a toy.
The brakes seem perfectly adequate for the vehicle's performance. They need a bit more pedal pressure, not being servo, but stop quite decently and in a straight line.
I once had a LWB LandRover with a V8 conversion. The brakes were bigger than on the SWB, and were servo-assisted, but I don't remember them seeming inadequate even for the exiting performance. The most dangerous feature was the cart spring suspension on unexpected road ruts and pot holes.
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Tell us more Cliff.... SWB/LWB, engine, colour, project or all done??
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its also a fashion thing
toyota prius is the same car worldwide except...
in USA it is sold with rear drums and in Europe it is sold with rear discs, purely down to what the punters want
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>> Tell us more Cliff.... SWB/LWB, engine, colour, project or all done??
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SWB Series IIa petrol 2.25 marine blue full tilt.
I bought it in really nice condition to use as it is without further work.
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Excellent... the IIa SWB petrol was probably the model I'd have again of all the LRs I've owned. I'b be a bit of a wimp with the tilt though and fit a hardtop.
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The tilt is a bit warmer in winter, surprisingly, and quieter. Also fun in summer - it gets the children's "really cool" accolade.
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>> It's OK DP, it wasn't you - they simply didn't work!
I dread to think how many afternoons I wasted unnecessarily stripping and rebuilding the rear brakes on this car.
The problem seemed to be that the pawl on the end of the arm didn't engage properly with the ratchet. Or rather, it didn't stay engaged. Most of the time when I took the drum off, it was a couple of mill clear of the ratchet teeth, meaning it was never going to operate it, even if the rest of the mechanism was doing as it should.
I agree though, the failure was very benign and gradual over time.
One thing I do recall fondly about the drum era is that handbrakes seemed much more effective, at least when everything was working properly. But discs get my vote simply because they are maintenance free, and they allow me to check friction material wear, and braking surface condition with a simple glance. I also don't miss having to manhandle those heavy springs into place with pliers, and the "Piiiiiiiiing.....where did that go?" hassles that always accompanied reassembly of drum brakes, at least in my amateur experience ;-)
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i always find vauxhalls to have good adjusters so i must be blinkered to the past,its always fords i have problems with when the ratchets wear out you adjust everything up put the drum on pull the handbrake and you hear it jump off
the most dangerous springs for locating shoes in my opinion were the ones on a mk4 cortina as my long nosed pliers pulled off one turned round in mid air as i fell backwards and stabbed me deep in the face right next to an eyeball
happy times.not
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DP
reassuring to read of your experience (and NCs comments). I remember exactly the same thing happening with the rear brakes of a Chevette circ 1978. Later on in its life I remember entrusting a rear shoe change/adjustment to a mobile cowboy - he changed one of the self adjusters - only for me to find that he had fitted the wrong handed one on one side which meant that that side only ever worked for its first few applications having adjusted itself 'off'.
Vauxhall must have promoted that designer to work on the later Cavaliers.:)
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>> I also don't miss having to manhandle those heavy springs into place with pliers, and the "Piiiiiiiiing.....where did that go?" hassles that always accompanied reassembly of drum brakes, at least in my amateur experience ;-)
Heh heh.
For sheer wounding, bruising, polluting punishment, drum brakes have no equal in my experience. Left a lot of skin there.
And the damn things are so important! The juxtaposition of brake dust, road dirt, rust, grease and dirty old brake fluid sometimes containing small fragments of worn or perished old seals, with clean new hydraulic seals and clean new brake fluid, to an amateur mechanic perhaps working out of doors in an urban gutter, was always a source of persistent anxiety too.
For some time past no one has bothered with new seals in drum brakes. New cylinders are fairly cheap, obviously better and much easier to install than to dismantle to replace the seals. But there was a time when just changing the seals was a frequent option. It was quite a lot cheaper of course.
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Yes, drum brakes do need a bit more "knack" than quite a lot of other jobs on cars.
The odd simple special tool is also helpful. One of the best I used was an old flat bladed screwdriver - about 6 inches long and with a qaurter inch wide blade, and a small vee groove ground in the middle of the span of the blade. This enabled you to put springs on and off without having to try to grip them with pliers, mole grips etc.
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Anyone ever succeeded in doing a handbrake turn in something equipped with rear discs?
It took me years to master Fiat's self-adjusters. A pair of sliding washers of brake-shoe-type material, clamped by a spring either side of a slot in the shoe. It had a top-hat thing through the centre of it that was a very loose fit over a pin. The washers were usually in pieces as they were brittle and easily broken and whoever had been in there before couldn't be bothered to replace them. Two-a-penny from the Fiat main dealer.
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>> Anyone ever succeeded in doing a handbrake turn in something equipped with rear discs?
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Not as such. I could lock my Focus rear wheels (disc brakes) with the handbrake though.
Last edited by: Old Navy on Mon 10 Jan 11 at 20:45
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>> Anyone ever succeeded in doing a handbrake turn in something equipped with rear discs?
Even more difficult in a Citroën equipped with a front disc handbrake (when it worked, that is!).
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Discs or drums? - Old Navy
