Disk or drum brakes ?

[Renze]

I need an unbiased opinion on brakes:

They told me that disk brakes, though having the weight advantage (lower weight, more payload) have little mass to dissipate the heat into.
This may result in exploding tires, especially on smaller sized brakes and 13" light duty axles.

At the company i work, we use 9 ton BPW axles for the heavy trailers. BPW is Europe's leading axle manufacturer, and they told me that disk brakes dont work under low deck trailers that get off the road from time to time to load or unload equipment on a construction site, because a disk brakes open construction makes it prone to dirt contamination. And that sand is very abrasive if it grinds between the pad and the disk.

Then i asked an independent brake manufacturer when i had them on the phone: Knorr sells brakes to various axle manufacturers. The Knorr guy told me that BPW is biased in their advice, because they produce their own drum brake, and buy a disk brake from a subcontractor, which means that they can earn more by selling their own drum brakes, and also because drum brakes have more wear parts to be replaced every few year....

Hmm... who should i believe ? Can anyone draw a clear line between the application areas of disk or drum brakes, or is it just not that easy ?

 

[AlanB]

Disc brakes are far superior, assuming you are running a hydraulic brake.

Disc's Worse in off-road conditions? As the latest funny qoute I saw said, is that guy smoking crack or what?

Go look at a current competition offroad machine and tell me how many drum brakes you find.

As too dissapating heat, you must be kidding, discs dissipate heat far better then a drum. A drum in effect, is one large heat sink floating out there. That dog don't hunt either.

Oh, and on edit, are there drum brakes "sealed" against dirt coming in. I have never seen any that are, and it is harder to get out as well.

 

[BTDT]

Disc setups have far fewer moving parts, are the only way anti-locks would work, and are far easier to service/work on.

 

[cp1969]

Disc setups have far fewer moving parts, are the only way anti-locks would work, and are far easier to service/work on.

My Ranger pickup has anti-skid brakes on the rear only, which happen to be drums. No anti-skid on the fronts and they are disks.

FWIW, the most heavily loaded vehicles (class 8 trucks) on the road use drum brakes. Probably not because there is anything inherently superior about drums other than they work better when using air brake systems. Disks require a LOT of operating pressure because they are not self-actuating like drums. Also, a parking brake is easier to incorporate into drums.

 

[DieselPower]

Go with the disc if you have the option. They have far superior clamping force when compared to drum brakes and are easier to work on with less moving parts. They do run hotter since they do not have as much metal to disipate the heat as a drum does. That's one reason you need high temperature grease on disc brake wheel bearings and not on drum brake wheel bearings.

cp1969 - Many Class 8 trucks can be purchased with air disc brakes but at a much higher price than drum. Disc brakes are getting much more common on Class 8 trailer brakes. One downfall of disc on a heavy truck is the repair expense. I can do a 4 wheel brake job including new drums on a drum brake trailer for what it would cost to do a 1 wheel brake job including a new disc on a disc brake trailer.

 

[Mickey_Fx]

If the disk are of the vented design, they will cool a lot better than drums as they work like a turbine fan when turning. Disk brakes work with almost zero clearence between the rotor and the friction pad. IMO much less likely to get dirt between friction and disk/drum surfaces. When brakes get hot, drums expand away from brake shoes and disks expand into the brake pad.

YMMV

 

[Joe1]

One advantage of disc brakes not mentioned is their superior stopping ability in wet weather. Because they do have closer contact between the pads and the discs, they tend to dry faster. Also, centrifugal force on we drum brakes throws the water into the drums whereas it throws the water off the discs.

High performance cars all have disc brakes.

The metro trains in use throughout the country almost all have disc brakes. This has been true on the Washington D.C. system since its inception in the early 1980's or late 1070's.

When Jim Hall in the early 1960's came out with the Chaparral race car with an automatic transmission, he used disc brakes (not that common on American race cars in those days). He said it was because the drum brakes could not handle the 1,100 degree temperatures generated by the car since it had little transmission braking due to being an automatic. As a side note, I believe the transmission was a modified Powerglide 2 speed, although I might be wrong on this.

cp1969's ranger has drums in the rear simply because it was cheaper to put on a truck in the compact size where profit margins were lower and anticipated stopping weights were also lower.

 

[kenmac]

I think you are talking about disc. for trailer brakes. If so, when I was checking around to swap out my electric drum brakes for hayraulic disc. I found out that the disc. on trailers don't have as much stopping power ( or apply as much pressure )as do hydraulic drum brakes & the best set up would be to have electric over hydraulic drum or disc. It's been a long time, but I believe I was told that some states ( depending on the weight of the trailer) require elec over hyd.

 

[Joe1]

I have a friend that just bought a 37' 5th wheel RV and specified disc brakes. They are hydraulic brakes with electrical connections from his truck to the trailer that activates a hydraulic system to work the brakes. He said they REALLY stop the trailer well. I don't know exactly how they work whether its a "pump" or if an electrical actuator pushes on the equivalent of a brake pedal/master cylinder system to active them. The latter I believe. I don't know how much that cost but he's happy with it so it wasn't too much for him.

 

[patrick_g]

I was trying to think of an advantage for drum brakes and finally did. They can be used to build a DIY forge or hibachi and discarded rotors can't. I did use discarded rotors to weld to the end of a pipe driven into the ground onto which I put a metal plate to hold a large A/C unit. The Mercedes Benz rotors spread the load well.

Pat

 

[RayH]

I guess Im in the minority because I think that properly adjusted drum brakes can stop a vehicle just as well if not better than disc brakes. Drum brakes dont work as well when they are wet, they are more expensive and labor intensive to maintain (so they arent adjusted correctly very often) and they are heavier but drum and shoes have more surface area further from the center of the hub.
The draw back of disc brakes are that they are effected by heat more than drums are. The reason disc brakes are slotted or drilled isnt so much to keep them from heating up, its to allow gases to escape from between the pads and disc. When disc brake get hot, they produce gas. That gas is trapped between the pads and disc which reduces the friction between the pads and disc, so hot disc brakes just dont stop you. Slots or holes in the discs allow gases to go someplace.

 

[kenmac]

I have a friend that just bought a 37' 5th wheel RV and specified disc brakes. They are hydraulic brakes with electrical connections from his truck to the trailer that activates a hydraulic system to work the brakes. He said they REALLY stop the trailer well. I don't know exactly how they work whether its a "pump" or if an electrical actuator pushes on the equivalent of a brake pedal/master cylinder system to active them. The latter I believe. I don't know how much that cost but he's happy with it so it wasn't too much for him.

This sounds something like the trailer place was explaining to me . Without this system they told me that hyd. disc. wasn't as good as electric drum brakes on trailer. For this reason , I didn't convert

 

[wushaw]

The initial cost of disk brakes or drum brakes on a trailer is a huge difference just because of the operating system being either elect/hyd or air/hyd.

If it's my trailer and it sits for long periods of time I would pick drum brakes.

I personally feel disk brakes on the back of a standard vehicle....especially a pickup truck is a complete waste of money and and you get a poor parking brake just barely capable of holding it's own weight on a hill let alone a trailer with any kind of weight hooked to it.
Any of y'all try it with 3/4 ton or one tons that have disk on the rear???

Oh yea my 05 Pete has drums all the way around and it has anti-skid on all four drums, big trucks have had it for years.

 

[patrick_g]

Brake fade from repetitive hard stops from high speeds seems to be much worse in drums than disks.

I'm really surprised to find so many people who think drums are superior. If you have brakes sized for the application either will work under average conditions but when conditions get extreme, sign me up for disks.

The reason disks may seem to be overkill on the back end of a pickup is because most folks don't carry anything in the pickup and even inferior drums will provide all the braking force you can use without locking them up. If you carry a decent load in the bed and or gooseneck or receiver hitch load then disks are NOT overkill.

Observation: Funny that the term OVERKILL would be used to describe a brake that someone thought to be inferior.

Pat

 

[wushaw]

I just don't see why they traded a working system with a good parking brake just to make the masses happy with disk and a PPoor parking brake.


I do agree disk brakes have better braking performance than drums, I just think that disk are not the best platform in "ALL" applications.

My Pete came with drums in ft. because it was speced that way, I didn't spec out the truck or I may have opted for disk up ft.

 

[Joe1]

Maybe the question to ask is since disc brakes reportedly cost more and all new automobiles and light trucks have at least front disc brakes and most have rear disc brakes, then why are the manufacturers (concerned with the bottom line) installing disc brakes if drums are as effective?

Personally, I would always go with 4 wheel disc brakes on a motor vehicle if they are available since they are less likely to fade and perform far better when wet. If drum brakes get thorougly soaked then you have no brakes, period, and have to drive with your foot on the brakes for half a block before they start to work again. Not so on disc brakes. While it may be more complicated on a trailer, the same performance factors exist, not withstanding the cost or complexity. Plus, there are no magnets to wear out on the disc brake set up.

If electric brakes controlled with magnets are so effective, then why were they never used on automobiles or trucks?

 

[patrick_g]

If electric brakes controlled with magnets are so effective, then why were they never used on automobiles or trucks?

Because there are simpler and better ways to do brakes on the towing vehicle. Putting combo hydraulic/electric brakes on a trailer costs a lot more than the "standard" electric trailer brakes and most folks don't want to pay the premium.

There is no engineering problem preventing electrically actuated hydraulic brakes on trailers, just buyer's pocketbooks. Electric trailer brakes are a GOOD economical solution but if you need EXTREME capability go electrically operated hydraulic with disks.

Pat

 

[wushaw]

Joe1,
I have a 1975 Airstream that I have owned for seven years, it has been towed twice in the last year and once in the previous three years to that, if you were to let a disk brake setup that long what do you think happens to the disk...rust sets in real bad.
Electric drum brakes will always have their place on a trailer.

 

[kenmac]

.
Electric drum brakes will always have their place on a trailer.



On my trailer they will. It cost toooo much to convert elec. over hyd. drum or elec. over hyd disc. That's why I kept elec. drums

 

[Joe1]

I agree with all of you that say electric brakes will always have a place on trailers. Except for cost and the rust issues disc brakes do provide better performance. I would imagine there is some degree of rust in the drums, not as much and not as noticable.

Bottom line I guess is if the guy that pays the freight is happy in a free market economy then the system is working.