Looking at most smaller cars i can see the rear brakes are Drum type
while at the front of the car are Disk type.
I cannot think Drums are that much cheaper to manufacture than Disc
type and i thought are less effective than Disc type. So why do
manufacturers choose to make the rear brakes Drums rather than Discs ?
Looking at most smaller cars i can see the rear brakes are Drum type
while at the front of the car are Disk type.
I cannot think Drums are that much cheaper to manufacture than Disc type
and i thought are less effective than Disc type. So why do manufacturers choose to make the rear brakes Drums rather than Discs ?
The rear remained drum because less braking is required. They are also considered safer, because if the handbrake is applied when the drums are
hot, as the drums cool down they contract and tighten the grip on the
shoes. Discs do the opposite, and tend to release the handbrake as they
cool down - but despite this, most cars now have discs on the rear (presumably because of their better braking action).
Looking at most smaller cars i can see the rear brakes are Drum type
while at the front of the car are Disk type.
I cannot think Drums are that much cheaper to manufacture than Disc type
and i thought are less effective than Disc type. So why do manufacturers choose to make the rear brakes Drums rather than Discs ?
On 23/11/2021 10:06, Ian Jackson wrote:
The rear remained drum because less braking is required. They are also considered safer, because if the handbrake is applied when the drums are hot, as the drums cool down they contract and tighten the grip on the shoes. Discs do the opposite, and tend to release the handbrake as they cool down - but despite this, most cars now have discs on the rear (presumably because of their better braking action).
Its a nice theory, but in reality the considerable length of the
handbrake cable will most likely have an almost constant tension to compensate for it ?
Trying to think how many cars have a true disc handrake. Isn't a drum handrake inside the rear disc the most common? Or is that just German cars?
But a drum also has a self servo action. If the car tries to move, it actually increases the braking effort. Not so with discs.
In article <sp7s18$983$1@dont-email.me>,
Abandoned_Trolley <fred@fred-smith.co.uk> wrote:
On 23/11/2021 10:06, Ian Jackson wrote:
The rear remained drum because less braking is required. They are also
considered safer, because if the handbrake is applied when the drums are >>> hot, as the drums cool down they contract and tighten the grip on the
shoes. Discs do the opposite, and tend to release the handbrake as they
cool down - but despite this, most cars now have discs on the rear
(presumably because of their better braking action).
Its a nice theory, but in reality the considerable length of the
handbrake cable will most likely have an almost constant tension to
compensate for it ?
Trying to think how many cars have a true disc handrake. Isn't a drum handrake inside the rear disc the most common? Or is that just German cars?
But a drum also has a self servo action. If the car tries to move, it actually increases the braking effort. Not so with discs.
On 14/12/2021 15:14, Dave Plowman (News) wrote:
In article <sp7s18$983$1@dont-email.me>,
Abandoned_Trolley <fred@fred-smith.co.uk> wrote:
On 23/11/2021 10:06, Ian Jackson wrote:
The rear remained drum because less braking is required. They are also >>>> considered safer, because if the handbrake is applied when the drums
are
hot, as the drums cool down they contract and tighten the grip on the
shoes. Discs do the opposite, and tend to release the handbrake as they >>>> cool down - but despite this, most cars now have discs on the rear
(presumably because of their better braking action).
Its a nice theory, but in reality the considerable length of the
handbrake cable will most likely have an almost constant tension to
compensate for it ?
Trying to think how many cars have a true disc handrake. Isn't a drum
handrake inside the rear disc the most common? Or is that just German
cars?
But a drum also has a self servo action. If the car tries to move, it
actually increases the braking effort. Not so with discs.
Conversely there is little braking when going backwards down a steep
hill, especially without the engine running.
Trying to think how many cars have a true disc handrake. Isn't a drum handrake inside the rear disc the most common? Or is that just German cars?
Trying to think how many cars have a true disc handrake. Isn't a drum handrake inside the rear disc the most common? Or is that just German cars?
But a drum also has a self servo action. If the car tries to move, it actually increases the braking effort. Not so with discs.
My 1966 Mark 2 Jaguar, along with all E types, S type / 420 / Mark 10
etc and all XJ saloons up to the mid 80s were fitted with a seperate mechanical handbrake caliper and pads with its own self adjusting
mechanism.
I seem to recall something similar on a 1967 Rover 2000 as well ? - it certainly had inboard rear discs which were a pain to maintain
Back in the days when brake pads were less abrasive than they are now
(they were allowed to use asbestos), the discs would often last the life
of the car which led to another problem - if the handbrake was never
used when the vehicle was in motion then the vanishingly small amout of
wear on the pads would mean that the self adjust mechanism would seize
up before you ever got to the first tooth on the ratchet :-\
Trying to think how many cars have a true disc handrake. Isn't a drum handrake inside the rear disc the most common? Or is that just German cars?
But a drum also has a self servo action. If the car tries to move, it actually increases the braking effort. Not so with discs.
Conversely there is little braking when going backwards down a steep
hill, especially without the engine running.
For front drums, maybe - with two leading shoes, which become trailing
shoes in reverse.
But rear drums usually have one leading and one trailing shoe - so
they're equally effective in both directions.
If you applied this on a slope, the vehicle would move quite a few
inches while it wound up the transmission.
motion, the vehicle would rock violently backwards and forwards.
In article <sp7s18$983$1@dont-email.me>,
Abandoned_Trolley <fred@fred-smith.co.uk> wrote:
On 23/11/2021 10:06, Ian Jackson wrote:
The rear remained drum because less braking is required. They are also
considered safer, because if the handbrake is applied when the drums are >>> hot, as the drums cool down they contract and tighten the grip on the
shoes. Discs do the opposite, and tend to release the handbrake as they
cool down - but despite this, most cars now have discs on the rear
(presumably because of their better braking action).
Its a nice theory, but in reality the considerable length of the
handbrake cable will most likely have an almost constant tension to
compensate for it ?
Trying to think how many cars have a true disc handrake. Isn't a drum handrake inside the rear disc the most common? Or is that just German cars?
But a drum also has a self servo action. If the car tries to move, it actually increases the braking effort. Not so with discs.
On 14/12/2021 15:14, Dave Plowman (News) wrote:
Trying to think how many cars have a true disc handrake. Isn't a drum
handrake inside the rear disc the most common? Or is that just German
cars?
No, it's not just German cars. Both my Volvo V70s (2 different vintages)
had this system - as does my Hyundai Tucson. You get the best of both
worlds with this system.
In article <spai0g$p9k$1@dont-email.me>,
Fredxx <fredxx@nospam.invalid> wrote:
Trying to think how many cars have a true disc handrake. Isn't a drum
handrake inside the rear disc the most common? Or is that just German cars? >>>
But a drum also has a self servo action. If the car tries to move, it
actually increases the braking effort. Not so with discs.
Conversely there is little braking when going backwards down a steep
hill, especially without the engine running.
Eh? No servo with any handbrake I've ever seen.
And a drum handbrake is
one leading, one trailing shoe. So you get the same self servo action forwards or backwards.
You're likely thinking of twin leading shoe front brakes which require
less effort going forwards than backwards.
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