Go Back   Team-BHP > Under the Hood > Technical Stuff


Reply
 
Thread Tools Search this Thread
Old 18th February 2007, 12:07   #1
BHPian
 
abhaybakshi's Avatar
 
Join Date: Jan 2007
Location: Pune
Posts: 177
Thanked: 71 Times
Question Why drums in rear and discs in front ?

A small query...why Indian car manufacturers provide drums at rear tyres and discs in front ?

Why can't they provide discs on all four ?? or is there any other reason ?
(I guess cost)
abhaybakshi is offline   Reply With Quote
Old 18th February 2007, 15:03   #2
Team-BHP Support
 
Zappo's Avatar
 
Join Date: Oct 2005
Location: Hyderabad
Posts: 5,653
Thanked: 2,013 Times
Default

Well, actually cost is a big reason for this setup. However having said that this setup is mostly adequate for most of the everyday use cars. Anyhow most of the modern cars drive the front wheels. The rear wheels are only pulled. So if the front wheels have a good braking setup (perforated/ventilated discs) this proves adequate along with a good drum setup at the rear.

Read the edmunds article on the same.
Zappo is offline   (1) Thanks Reply With Quote
Old 18th February 2007, 16:53   #3
Distinguished - BHPian
 
CrAzY dRiVeR's Avatar
 
Join Date: Jun 2006
Location: Bangalore / TVM
Posts: 8,974
Thanked: 16,772 Times
Default

Also, on braking... The main component of vehicle weight acts on the front wheels, and only a small component of it acts on the rear wheels

In simpler words, weight gets concentrated towards front due to the inertia of the vehicle

So... We need better braking at the front...

Even in cases where both discs are provided, the front brakes will be a disc of bigger dia, than the rear ones...
CrAzY dRiVeR is offline   Reply With Quote
Old 18th February 2007, 19:37   #4
Team-BHP Support
 
theMAG's Avatar
 
Join Date: May 2006
Location: Long Island, NY
Posts: 7,036
Thanked: 1,473 Times
Default

Cost. C+/D segments and above have discs all-around.
theMAG is offline   Reply With Quote
Old 18th February 2007, 20:05   #5
Distinguished - BHPian
 
condor's Avatar
 
Join Date: Jun 2006
Location: Speed-brkr City
Posts: 10,752
Thanked: 4,345 Times
Default

Quote:
Originally Posted by Zappo View Post
Anyhow most of the modern cars drive the front wheels. The rear wheels are only pulled.
Zappo, are you sure about this? If I were to extend this logic, then RWD vehicles would have discs at the rear and drums at the front.

The same edmunds article gives a good explaination to Abhay's question: "Combined with the fact that between 60 and 90 percent of a vehicle's stopping power comes from the front wheels, it's clear that a well-designed, modern drum brake is all that's required for most rear wheel brake duty"

Last edited by condor : 18th February 2007 at 20:07.
condor is offline   (1) Thanks Reply With Quote
Old 18th February 2007, 22:49   #6
Team-BHP Support
 
Zappo's Avatar
 
Join Date: Oct 2005
Location: Hyderabad
Posts: 5,653
Thanked: 2,013 Times
Default

Hmmm... but why is it that 60 to 90% of the stopping power comes from the front? Probably one of the reasons is that if the "driven" wheels are stopped adequately the rear wheels which anyhow do not have a power of their own are easier to stop. Of course another big reason could be the inertia thing. With the engine and other components being there at the front the inertia starts generating from the front. That is where you need the max stopping power, as pointed out by CD.

Last edited by Zappo : 18th February 2007 at 22:50.
Zappo is offline   Reply With Quote
Old 18th February 2007, 23:25   #7
BHPian
 
sharathjeppu's Avatar
 
Join Date: Apr 2006
Location: Bangalore
Posts: 156
Thanked: 3 Times
Default

Does the ABS work differently if the rear has a disc brake vis-a-vis a drum brake? I was always curious about this.
sharathjeppu is offline   Reply With Quote
Old 19th February 2007, 00:49   #8
Senior - BHPian
 
revtech's Avatar
 
Join Date: Nov 2004
Location: Bombay
Posts: 1,988
Thanked: 35 Times
Default

i guess it would work the same way.intention being to prevent locking.
revtech is offline   Reply With Quote
Old 19th February 2007, 01:11   #9
Team-BHP Support
 
Rehaan's Avatar
 
Join Date: Feb 2004
Location: Bombay
Posts: 22,381
Thanked: 22,610 Times
Default

Quote:
Originally Posted by sharathjeppu View Post
Does the ABS work differently if the rear has a disc brake vis-a-vis a drum brake? I was always curious about this.
I seem to be under the impression that it is not possible to have 4-wheel ABS if you have drums at the rear..... (true?)

cya
R
Rehaan is offline   Reply With Quote
Old 19th February 2007, 01:58   #10
BHPian
 
Join Date: Jan 2007
Location: bangalore
Posts: 227
Thanked: Once
Default

ALSO helps the vehicle in deparment of the mechanicaly operated handbrake. Modern(er) 4-disc brake cars come with drums co-existing with the rear discs.
Desert fox is offline   Reply With Quote
Old 19th February 2007, 02:10   #11
Senior - BHPian
 
rocksterraghu's Avatar
 
Join Date: Feb 2007
Location: Bangalore
Posts: 1,202
Thanked: 65 Times
Default

Now it's time for me to express my opinions and understandings.

* Think about it this way, on a RWD, if you pull the hand brakes while the car is still in motion, would it still spin the car? That should answer one question. Having the car in motion and applying harder brakes on the rear wheels is never a good idea, regardless of the type of vehicle.

* Regarding ABS, it shouldn't really matter. The ABS just lets the wheel rotate when there is a slippery surface where the chances of the car sliding are higher when they're not rotated. So, what technology is involved to stop the wheels from rotating is out of question.

Disagree with me? Please go ahead and correct me.
rocksterraghu is online now   Reply With Quote
Old 19th February 2007, 08:43   #12
Distinguished - BHPian
 
condor's Avatar
 
Join Date: Jun 2006
Location: Speed-brkr City
Posts: 10,752
Thanked: 4,345 Times
Default

Zappo, more than driven wheels, doesnt it make more sense when we consider the direction of motion? The inertia is also in the direction of motion, and it's more effective to stop it there than holding the vehicle back, from the rear end.
condor is offline   Reply With Quote
Old 19th February 2007, 10:32   #13
BHPian
 
WhiteKnight's Avatar
 
Join Date: Mar 2006
Location: Bangalore
Posts: 828
Thanked: 73 Times
Default

Quote:
Originally Posted by condor View Post
doesnt it make more sense when we consider the direction of motion? The inertia is also in the direction of motion, and it's more effective to stop it there than holding the vehicle back, from the rear end.
Spot on!! Add to it the weight trasfer. In case of deceleration, weight is transfered to the front, meaning less grip at rear. So a brake biased to rear would only help locking up the rear.
WhiteKnight is offline   Reply With Quote
Old 19th February 2007, 11:08   #14
Team-BHP Support
 
Vid6639's Avatar
 
Join Date: Jul 2006
Location: Bangalore
Posts: 14,471
Thanked: 19,385 Times
Default

Exactly whiteknight it's due to the weight transfer.

Try going in reverse and pull the handbrake, you will notice the brakes will not lock. Why? because the weight transfer goes to the rear giving more inertia and the brakes need more force to stop the car.

it does not make difference whether RWD or FWD or even if the car's front engined or rear engined.

Even in a rear engined RWD the braking force will be more for the fronts than the rears.
Vid6639 is offline   Reply With Quote
Old 20th February 2007, 00:08   #15
Senior - BHPian
 
adya33's Avatar
 
Join Date: Apr 2005
Location: Pune
Posts: 1,838
Thanked: 91 Times
Default

Quote:
Originally Posted by Rehaan View Post
I seem to be under the impression that it is not possible to have 4-wheel ABS if you have drums at the rear..... (true?)

cya
R
Yup. Incase of cars with rear drum breaks the ABS module is only connected to front wheels.

Also having disc breaks to all 4 wheels without ABS is a suicide. The car will lockup more often than car with drums in rear.
This is the reason all cars with disc breaks all around come with ABS.

Last edited by adya33 : 20th February 2007 at 00:13.
adya33 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Paint for disc brake pads & rear brake drums VC12 Modifications & Accessories 8 25th October 2011 17:18
Swift - Wheel Discs and Brake Pad problems ravi23 Technical Stuff 25 18th August 2010 15:07
130 bhp, VVT-i, Airbags, climate control and all round discs..here she is. nitroxx Test-Drives & Initial Ownership Reports 49 19th October 2009 12:00
Plan to have 40 GB of songs and 100 GB videos without discs shreyasma In-Car Entertainment 16 30th May 2008 13:36
Rear Discs on Zen arjab Modifications & Accessories 6 16th March 2005 10:06


All times are GMT +5.5. The time now is 15:46.

Copyright 2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks