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Driving around the other day, I was surprised to note just how many modern cars still have rear drum brakes. This is the 21st century, surely discs all round should be the norm? Why persist with such antiquated brake technology? Are drums that much cheaper to fit than discs that there’s still a cost incentive for manufacturers to use them?
I should declare an interest at this point – I hate working on drum brakes. I had to do the rears on my 1993 Jeep Grand Cherokee a while back, and I ended up cursing whoever invented drums and whoever at Chrysler decided that the first Grand Cherokees only needed discs on the front…
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Combination of existing technology (easier to use existing dies and molds rather than design a new system) and cost. Also for most smaller cars and some trucks rear drums are more than adequate for stopping power. Personally I am not a huge fan of drum brakes, they tend to get neglected and therefore don’t really do their job.
I have a car with disc brakes all around and in the inside of the rear rotors there is a drum brake for use as the emergency brake. If the maker is going to do that then maybe they figure, on the cheaper lines anyway, why not just use a drum brake and save the expense.
I think you could make a very drivable car without rear brakes at all. The rears don’t do much. What you would have to do is figure out how to route the emergency brake mechanism to the front.
In a lot of cases drum brakes are better than disc brakes. For instance trucks and bigger cars should have rear drum brakes, But smaller cars do better with disc brakes. Drum brakes last longer on the rear than discs do. I deal with problems with disc brakes more often than drum brakes. They aren’t hard to work on but you do have to understand how and why they work, To me the hardest part is setting them up right.
Some things work just fine and do not need to be messed with. Like the wheel, round is good so we do not need hexagonal/square/triangle etc…
BTW Dunebasher I bet you would have had fits if you had to deal with front drum brakes like lots of cars had back in the day, if they weren’t set up right the car would pull when braking.
[quote=”barneyb” post=80516]I have a car with disc brakes all around and in the inside of the rear rotors there is a drum brake for use as the emergency brake. If the maker is going to do that then maybe they figure, on the cheaper lines anyway, why not just use a drum brake and save the expense.
I think you could make a very drivable car without rear brakes at all. The rears don’t do much. What you would have to do is figure out how to route the emergency brake mechanism to the front.[/quote]
Actually the rears do alot, more toward stability than raw braking power. If you only had front brakes, when you went to stop you have a situation where the suspension “bunches” up, your actual wheel base would get shorter as the front wheels are dragged towards the rear and the rear wheels are pushed toward the front by inertia. Having rear brakes allows for the rear wheels to “pull” back and maintain a proper wheel base and stability. Plus it also helps reduce oversteer, where the rear wants to “break away” having rear brakes makes the rear wheels stabilize and maintain position better.
The change in wheel base is interesting but I’m not convinced whatever change that might be would be significant. And, as to lessening the threat of under steer I think the result would be the opposite. In a heavy breaking situation there’s not much weight on the rear wheels and splitting that traction between braking and handling, well, there is less traction that can be dealt to handling.
Anyway, I wasn’t contending that a car with no rear brakes would be as good or better than four brakes but only that it would be very drivable. Rear brakes do contribute something.
Disc brakes came to the public the same time as front wheel drive and getting the disc/drum combination then in general use to work right on vehicles with 60% of their weight on the front axles gave engineers fits for awhile. I can remember seeing those little hatchbacks spin out. The fronts always have to be the first to lock on a non abs car, better the rear brakes don’t lock at all. If the rear brakes are first to lock the back wants to pass the front in an emergency situation. And realizing the rears have very little weight on them due to weight transfer during heavy braking, well, as I say, the rears don’t do much.
My car has an independent channel for each wheel brake all ran by a computer with two “G” sensors and a steering angle sensor. So, much has changed. When I stop in a panic situation I’m more worried about the driver behind me than the vehicle that just pulled out in front of me.
Correct me if I’m wrong, but lower cost… A drum brake also can serve as a parking brake, so you’re getting two for one. All modern cars with drum brakes are compact class (“cheaper” cars), and these cost saving measures add up.
The exception being those “loaded” Korean cars; Hyundai Elantra gets standard 4-way disc brakes.
🙂 Drum brakes are still the most cost effective and efficient form of stopping any vehicle. Braking has improved dramatically of the decades, as most of you do not remember having four wheel drum brakes. Better brake pad or shoe technology has improved an old design to be efficient and safe. Most instances of disc bakes being applied to the rear has been with sports cars. The excessive speed and build up of heat related to braking makes rear discs more efficient than drum brakes. In most other cases, the application of rear disc brakes in normal cars are for customer appeal and for looks. The braking ability is almost the same for both types in most regular application of braking. Drum brakes have been around for more than a hundred years and are still used and will be used in the future. No other item works as efficiently for the cost as do drum brakes. The perception of disc brakes being superior in normal use is the results of exposure of racing and the ease of repair that a disc brake imparts. The complexity of the drum brake is the Achilles heel of it’s use, but it is still as efficient at stopping as a disc brake.
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