Why do new cars have drum brakes???

[Shannow]

When I was at uni, one of the guys that I studied with had completed a christmas break engineering stint with Mitsubishi Oz.

He had seen the tenders that were called for the braking system on the Mitsubishi Magna.

They put out a tender for 4 wheel disks. the company he was placed with put in two complying offers, for all wheel disks, and one non compliant for disk/drum...lower cost, but same performance as the lower cost 4 wheel disks.

Mitsubishi returned with wanting the cost of the disk/drum, but with 4 wheel disks.

Brake company won the order, by meeting the needs of their customer, offering 4 wheel disks, at the price of disk drum.

Mitsubishi got to advertise that they were the first family car with 4 wheel disks as standard, even 'though they could have offered better braking for the price.

They produced their last car last week.

BTW, my first car was 4 wheel non power assist drums...amazing brake performance in wet weather.

 

[mechtech2]

Maybe the reason we see rear discs being so problematic is because they are used with less force than the front discs. About 1/4 -1/3 as much. Rust, warp, seize.
They seem to respond to heavy use to keep them clean and operating properly. Racing or hard use takes care of this automatically.

 

[Jim Spahr]

I think disc front/ drum rear is the best set up for a street car. Why? The front wheels do about 80% of the braking and the rears do only 20 %. So have the disc up front to provide the best braking and have the drums in the back to keep costs low and to provide an easy way to support a good 'emergency brake' system. I have a car with 4 wheel disc and the rear calipers tend to rust up and 'freexe' in position. Watch those two caliper pins and replace if they become rusty. They also don't provide a strong emergency brake.

 

[JohnBrowning]

beryllium is too high risk for airport use...It has even been outlayed in F1! That stuff will destroy your lungs!

 

[crw]

I'm surprised that nobody has mentioned the disk/drum combo on GM trucks... at least my 2000 Suburban. The rears are disk, but there is also a mini drum in the middle! The little drum brake is for the emergency/parking brake.

 

[Kestas]

Thanks John - it's been 23 years since I've been involved in that technology.

CRW, the drum-in-hat design has been around for a while. I believe that design gives rather wimpy performance and is prone to corrosion problems when compared with a full drum design for the rears.

 

[Jim Spahr]

The rear Drum inside the disc that GM and maybe others offer to give us 4 wheel disc and still have a rear emergency brake system is a poor compromise! Why? It is heavy so the disc weight advantage is lost, it is expensive, the rear caliper pins tend to rust and freeze the caliper, and the emergency brake provided is not as strong as the good old drum brake based E/B system. The disc front/ drum rear is efficient and lower cost and provides the best emergency brake operation- the best of both worlds.

 

[ikeepmychevytoo]

Older Eu Fords were also having a separate friction surface for the hand-brake albeit all drum. In 80's MB is like this with hat for the disc and drum for the hand-brake. Disadvantage of theese was if a kid to use hand-brake for turns etc. daddy could notice it assuredly, may be within a month.

 

[astraelraen]

Noone has mentioned 4 wheel disc looks much cooler than drums?

Especially with the advent of using of real rims on 95% of cars in the last few years, rather than steelies + hubcaps.

Its not so cool looking to have your 1995 whatever with nice shiny chrome 18's and low profile tires and have nasty rear drums showing to the world

 

[Kestas]

Don't the ricers have a product on the market where you can bolt on a slotted rotor-looking thing on the inside of the rim so it looks like you have disc brakes?... how ghetto!

 

[BuickGN]

Originally Posted By: astraelraen
Noone has mentioned 4 wheel disc looks much cooler than drums?

Especially with the advent of using of real rims on 95% of cars in the last few years, rather than steelies + hubcaps.

Its not so cool looking to have your 1995 whatever with nice shiny chrome 18's and low profile tires and have nasty rear drums showing to the world

I painted the drums black on my GN early on to make them less noticable. Even though they were aluminum and I didn't have to worry about rust, they still looked bad.

 

[gomes512]

Originally Posted By: Kestas


CRW, the drum-in-hat design has been around for a while. I believe that design gives rather wimpy performance and is prone to corrosion problems when compared with a full drum design for the rears.


Agreed, the parking brake mechanisms in my rear disc Jeep rust almost completely to the point of breaking everytime the rear rotors need replacing. I end up paying an additional 20 for new hardware and another 20 for new parking brake pads.