Why do I need rear disks?

avantra

Helping another mate find a car and he commented that many of the cars small or large from the last 6 -7 years got brake disks all round, and it made me wonder why?


Surely the drums and pads system for the back is a better and cheaper solution for the conditions in northern Europe?!, after all they are sealed systems which require very little maintenance at a very long intervals while disks are exposed and attract rust if you don't use them as hard.

waynedance

Not much in it price wise but I much prefer discs. Better stopping power hence why modern cars have them.

I think it is easier to change rear pads then shoes.

Gloomendoom

I have 1950's Land Lover with drum brakes all round. I also have an early 1970's Range Rover with discs all round.

The Rover Rover brakes need a lot less maintenance and stops better than the drum braked Land Rover, particularly when the brakes are wet.

I have a modern car with discs all round for the main service brakes and, like the Range Rover, drums for the parking brake. It's only the parking brakes that need regular adjustment and maintenance.

The other reason modern cars, even small ones, tend to have discs is that they are easier to control with the ABS and stability gadgets that are now de rigueur.

worried_jim

Surely anything that helps you stop quicker is a good thing?

SailorSam

I've got an 05 Fiesta, i'm sure there's drums on the back. I thought they were all like that.
Discs are much easier to change.

colino

You don't need discs on the rear at all. Most of the braking effort is on the front, it just comes down to cost of manufacture and speed (and frequency) of servicing.

poppasmurf_bewdley

The difference between discs and drums is like the difference between steam engines and the modern Pendelino tilting train.

Drums were invented back in the 1910's if not earlier and are real stone age technology. Discs work far more efficiently, and are much easier to maintain, ie self adjusting and easy to replace.

Stigy

Drum/shoe setups do have more stopping power for short periods of time, but under heavy or continual braking they overheat and so fade etc (due to the enclosed space inside the drum). It stands to reason really, as there's much more surface area covered with shoes than there are with drums.

On the rear though, as only 25% of the braking is done at the rear, brake fade is less common, hence why a lot of smaller cars still have this setup at the rear, and you wont find any modern cars with drums at the front. Cost wise discs are cheaper than drums, and pads are around the same price as shoes (most of the time!). Also, although you need a tool (or are good with a screw driver!) to wind the rear caliper pistons back, discs/pads are far easier to replace than shoes. Also, they're easier to service and check wear etc than drums and shoes. They also look nicer through the wheels than drums do

Until quite recently, HGVs/larger buses still had drums at the front.

The reason very old cars often feel like they have no braking power at all, is more often than not, not the drum/shoe setup, but the fact that they are non-servo assisted, where as all modern cars over the last thirty odd years have had power assistance (hydraulics and servos) to aid braking power.

Notmyrealname

avantra wrote: »

Helping another mate find a car and he commented that many of the cars small or large from the last 6 -7 years got brake disks all round, and it made me wonder why?


Surely the drums and pads system is a better and cheaper solution for the conditions in northern Europe?!, after all they are sealed systems which require very little maintenance at a very long intervals while disks are exposed and attract rust if you don't use them as hard.

They are not sealed systems at all. Where do you get that idea from?

Rear discs don't rust if you drive the car. Rear drums need MORE maintenance than disc brake systems. Drums are more likely to have completely worn out brake shoes than a disc system is worn out pads .

GolfBravo

avantra wrote: »

Helping another mate find a car and he commented that many of the cars small or large from the last 6 -7 years got brake disks all round, and it made me wonder why?

Surely the drums and pads system is a better and cheaper solution for the conditions in northern Europe?!

The only reason for manufacturers to persist with rear drum brakes is lower cost. They are not better than disc brakes, they are in fact much much worse.

I used to work for a major global car manufacturer for years, and rear drum brakes was one of the favourite ways to cut car manufacturing cost. For a car like Vauxhall Corsa the manufacturer's incremental cost to go from drum brakes to discs is around €12 per car (so just above £10).

You may think that £10 is not much, so why would a car manufacturer bother with saving £10? Because they can get away with it - rear drum brakes are only just good enough, and most people buying small and budget cars don't care about brakes. They don't care about brakes, sound deadening, metal panel thickness, alternator size, shock absorber quality, etc. People don't care about these things because they can't touch/smell/see them - so with the money saved car companies add equipment that gives better perceived value: cup holders, vanity mirrors, etc.

Drum brakes are just useless. They need to be constantly adjusted (the self adjusters simply don't work), they don't work well in wet and cold conditions (hardly any braking and then suddenly lock up, so ABS kicks in all the time), make front brakes work harder/wear out faster, etc.

poppasmurf_bewdley

GolfBravo wrote: »

The only reason for manufacturers to persist with rear drum brakes is lower cost. They are not better than disc brakes, they are in fact much much worse.

I used to work for a major global car manufacturer for years, and rear drum brakes was one of the favourite ways to cut car manufacturing cost. For a car like Vauxhall Corsa the manufacturer's incremental cost to go from drum brakes to discs is around €12 per car (so just above £10).

You may think that £10 is not much, so why would a car manufacturer bother with saving £10? Because they can get away with it - rear drum brakes are only just good enough, and most people buying small and budget cars don't care about brakes. They don't care about brakes, sound deadening, metal panel thickness, alternator size, shock absorber quality, etc. People don't care about these things because they can't touch/smell/see them - so with the money saved car companies add equipment that gives better perceived value: cup holders, vanity mirrors, etc.

Drum brakes are just useless. They need to be constantly adjusted (the self adjusters simply don't work), they don't work well in wet and cold conditions (hardly any braking and then suddenly lock up, so ABS kicks in all the time), make front brakes work harder/wear out faster, etc.

And there's me thinking the reason a car manufacturer would save a meagre £10 per car on brakes was because £10 saved over half a million cars equals £5million in their pockets!