Advanced Driving Hub

fungus wrote:AIUI, a drum has a larger contact area, and therefor more friction is produced which should result in more power. But this results in more heat being produced, which has an adverse effect on braking, therefor, drums are less efficient except as hand brakes.

Nigel.

Ah, so I see...

I wonder if someone has come up with a disc brake where you've got 4 pads acting on the same disc, on opposite ends of the axle...?

fungus wrote:
AIUI, a drum has a larger contact area, and therefor more friction is produced which should result in more power. But this results in more heat being produced, which has an adverse effect on braking, therefor, drums are less efficient except as hand brakes.

Nigel.

You only have to google a bit to find this is true. Look for the drum brakes on past racing motorcycles and cars and the complexity of trying to make them perform better.
Heat dissipation is the name of the game.
Then look for the disc brakes on large aircraft.

TheInsanity1234 wrote:

fungus wrote:AIUI, a drum has a larger contact area, and therefor more friction is produced which should result in more power. But this results in more heat being produced, which has an adverse effect on braking, therefor, drums are less efficient except as hand brakes.

Nigel.

Ah, so I see...

I wonder if someone has come up with a disc brake where you've got 4 pads acting on the same disc, on opposite ends of the axle...?

IIAC, some discs have a small drum on the rear hub for the handbrake.

Nigel.

michael769 wrote:

TripleS wrote:I don't know if this is a factor that actually affects many models, but I seem to recall a time when the Citroen Xantia was said to suffer from this problem.

The Xantia's had a different problem, where the handbrake operated the front disc brakes.

The problem was that if the discs were hot enough then when they cooled and contracted the brake could let go.

It happened on the Saab models that had front wheel hand brakes as well, though they were a more robust design.
The device used to confound MOT inspectors and I always reminded them as to which wheels were braked.
It was very handy though on slippery services and a pretty powerful brake.

Fiat Chrysler to recall 1.1m vehicles
http://www.bbc.co.uk/news/business-36117557

Bumblebee16 wrote:Fiat Chrysler to recall 1.1m vehicles
http://www.bbc.co.uk/news/business-36117557

Sounds like another "fix" for thick americans.
"Fiat Chrysler said it would update the vehicles to automatically prevent them from moving, even if the driver fails to put the vehicle in park. The company did not say when the fix would become available to owners."

Mind you, isn't "not moving" normal state for a Fiat?

Just like the "accelerator/brake override" problem which means you can't left foot brake in most modern cars any more

jont- wrote:Just like the "accelerator/brake override" problem which means you can't left foot brake in most modern cars any more

Indeed. Most of us are quite capable of using the controls correctly without needing technology to tell us.

WhoseGeneration wrote:

fungus wrote:
AIUI, a drum has a larger contact area, and therefor more friction is produced which should result in more power. But this results in more heat being produced, which has an adverse effect on braking, therefor, drums are less efficient except as hand brakes.

Nigel.

You only have to google a bit to find this is true. Look for the drum brakes on past racing motorcycles and cars and the complexity of trying to make them perform better.
Heat dissipation is the name of the game.
Then look for the disc brakes on large aircraft.

Isn't the clue in the 'drum' bit, as far as heat dissipation goes, cooling fins/air ducts or not?

Silk wrote:

jont- wrote:Just like the "accelerator/brake override" problem which means you can't left foot brake in most modern cars any more

Indeed. Most of us are quite capable of using the controls correctly without needing technology to tell us.

Indeed, and some of us jolly well do not want technology imposing constraints on our use of the controls.

Incidentally, I don't see how technology can determine that only the right foot can be used for braking. How would that be done - a mini video camera in the footwell from which the computer system can see that the 'wrong' foot is being used for braking?

What I have heard is that some cars will not allow simultaneous use of the accelerator and brake pedals, which means that the 'heel and toe' technique can not be used.

LFB also uses simultaneous brake and throttle, otherwise there'd be no point in it. However cars can detect it by working out which sequence the pedals are used in, so some will allow HnT without allowing LFB.