I have the first year of 4 wheel disc brakes. For those who have owned both disc and drum rears...are there definate advantages to the discs? Pro's and con's??? Enough of a difference to look specifically for 2001.5 and newer? Limits your options a lot!

Edited June 4, 20168 yr by joecool911

Pads are easier to replace in disc haha.

 

I dunno if there is a real true difference in stopping power, it's still a heavy truck ya know ?

 

Drums can take more heat as they are heavier, but discs typically dissipate heat faster if they are not solid rotors.

drums retract more then disk and create less drag, but heat up faster, and i think don';t get the stopping power of a disk.

as for normal use of a truck, i don't think we could see the difference unless towing heavy ALOT!, drums are just fine.

My 96 had drums and it stopped just fine with and without the my trailer in tow. I do like the 4 wheel disc for the ease of brake jobs. Get an exhaust brake, that really eases up on the brake jobs. 

Just kinda long range planning for a 5 or 6 speed manual. Exhaust brake would then be a reality!

drum brakes can take a lot more abuse and offer more braking force when towing loads. Because they can take a lot of abuse they will overheat fast but not fail as fast as a disc brake would with same load. Why you dont see disc brakes on semi's.

 

With the combination of engine/exhaust braking while hauling/towing, either brakes will do fine.

12 hours ago, CUMMINSDIESELPWR said:

drum brakes can take a lot more abuse and offer more braking force when towing loads. Because they can take a lot of abuse they will overheat fast but not fail as fast as a disc brake would with same load. Why you don't see disc brakes on semi's.

 

With the combination of engine/exhaust braking while hauling/towing, either brakes will do fine.

 

 

Semis do run disc brakes.  Matter of fact the aerial ladder fire truck I drove bought new about 5 years before I retired had disc brakes.  My brother had to give up his 1.4 million mile rig and his company forced him into a new one so I will ask if his has discs or drums.

My 99 has rear drums.  I looked into putting a Disc upgrade kit on the rear end however the cost as well as lack of good emergency brake left me just upgrading the rear Cylinders to the 1-Ton Chevy ones ($8 apiece), replacing all hardware and new pads/drums last time I did the job.  Should last a good while and it gave me a good opportunity to teach my sons what a real brake job looks like!!

9 hours ago, Russ Roth said:

 

 

Semis do run disc brakes.  Matter of fact the aerial ladder fire truck I drove bought new about 5 years before I retired had disc brakes.  My brother had to give up his 1.4 million mile rig and his company forced him into a new one so I will ask if his has discs or drums.

i stand corrected

It would be my guess that discs are an option on otr trucks but old-school people will be hesitant to change until/unless they are proven safer, to last longer, are cheaper, or mandated by government. My $.02

Edited June 6, 20168 yr by Royal Squire

I suppose that in a case of loosing boost that the drum brakes would be easier to use due to much lower PSI required for drum vs disc? But then again, the rear pressure is probably compensated to allow for use of both types with one pedal...so maybe not.

On Sunday, June 05, 2016 at 11:32 PM, Russ Roth said:

 

 

Semis do run disc brakes.  Matter of fact the aerial ladder fire truck I drove bought new about 5 years before I retired had disc brakes.  My brother had to give up his 1.4 million mile rig and his company forced him into a new one so I will ask if his has discs or drums.

Unless I slept and technology passed me by, Their is not a single commercial semi truck in this country running disc brakes, its just not possible with the air operated systems with spring brake and s cam mechanisms. All commercial vehicles are built and inspected by federal dot standards.

 

3 hours ago, 01cummins4ever said:

Unless I slept and technology passed me by, Their is not a single commercial semi truck in this country running disc brakes, its just not possible with the air operated systems with spring brake and s cam mechanisms. All commercial vehicles are built and inspected by federal dot standards.

 

http://www.truckinginfo.com/channel/aftermarket/news/story/2013/07/meritor-projects-slow-steady-growth-for-nafta-market-air-disc-brakes.aspx

10% in the US and 90% in Europe are disc.

Interesting? I wonder how many of the 10% are tractor trailer or straight trucks, 

On our trucks Don't we get about 80% stopping power from the front disk?

Just a F.Y.I when I started trucking in the 80s you could get front disc brakes from most OTR manufactures. Unlike our trucks a big rigs carries most of its weight over the rear so most of the braking is from the rear. Not that you can do this any more but we would remove the front brakes on some of our trucks to save weight and reduce maintenance but we very seldom uncoupled from our trailers.  

35 minutes ago, Nekkedbob said:

Not that you can do this any more but we would remove the front brakes on some of our trucks to save weight and reduce maintenance but we very seldom uncoupled from our trailers.

 

I'm sure you'd heavily fined now by a DOT inspector if your caught removing front brake system today.

17 hours ago, 01cummins4ever said:

Unless I slept and technology passed me by, Their is not a single commercial semi truck in this country running disc brakes, its just not possible with the air operated systems with spring brake and s cam mechanisms. All commercial vehicles are built and inspected by federal dot standards.

 

 

 

 

Technology has passed you by then.  I texted my brother yesterday AM and he called right back since he was waiting to get unloaded.  His 2015 Mack has discs on the front steer and drive axles and drum on the tag axle which I think the company put on.  They do come from the factory too but it is cheaper for them to put them on in their own shops.  I forgot to ask him about the new trailer he is pulling to see what it is running for brakes.  He did say the set up does not look the same as an S cam but the fire truck I drove did look and adjust like S cams.  Not sure now how they work in either case since I retired in late '99 and the truck was new about '94 or '95. 

 

Drum brakes can offer more braking power because of the shoe contact surface area, whereas discs offer less weight, better heat dissipation, and better feel.  There's a reason as disc brakes are improved, the calipers/pads sizes are increased.  The problem is the larger the calipers/pads get, the more heat they generate in that area and thus the overall rotor size must be increased to offset.  For example, Air plane disc brakes can have multiple discs like motorcycle clutch system.  Pretty interesting design too.

 

In regards to drums brakes..... If you've ever stomped on the brakes in a class 8 OTR truck, it can be quite impressive.

 

All that said, the 2nd gen rear axle disc brakes were seemingly not a great design and have notorious issues.  Probably more from road salts corrosion than not, but nonetheless the 2nd gen manual transmission 2500 truck brakes are the same as the 3500 truck brakes and are pretty strong.  Well.....at least mine are.

Edited June 10, 20168 yr by KATOOM

3 minutes ago, KATOOM said:

Drum brakes can offer more braking power because of the shoe contact surface area, whereas discs offer less weight, better heat dissipation, and better feel.  There's a reason as disc brakes are improved, the calipers/pads sizes are increased.  The problem is the larger the calipers/pads get, the more heat they generate in that area and thus the overall rotor size must be increased to offset.  For example, Air plane disc brakes can have multiple discs like motorcycle clutch system.  Pretty interesting design too.

 

In regards to drums brakes..... If you've ever stomped on the brakes in a class 8 OTR truck, it can be quite impressive.

 

All that said, the 2nd gen rear axle disc brakes were seemingly not a great design and have notorious issues.  Probably more from road salts corrosion than not, but nonetheless the 2nd gen manual transmission 2500 truck brakes are the same as the 3500 truck brakes and are pretty strong.  Well.....at least mine are.

Interesting you say that.... the rear disc on the 3rd gen AAM axle doesn't have much of a different design. If I recall, they are almost exactly the same. (We can swap them onto our 2nd gens)

I dont spend a ton of time in the 3rd gen sections so I couldn't say whether or not those rear discs are as problematic as the 2nd gen.  But I do understand that the calipers and rotors are not the same either.  I even think they increased the rotor size a little too but am not positive.  And in saying that, ANY changes made from year to year could have solved whatever the prior issues were.  Thats not to say ALL 2nd gen rear discs were junk either but merely pointing out they're nothing great.

 

In regards to aerospace brakes, here's a couple videos to show the POWER behind those braking systems.  Really cool.....

 

https://www.youtube.com/watch?v=_g6UswiRCF0&feature=youtu.be

 

https://www.youtube.com/watch?v=_g6UswiRCF0&feature=youtu.be

9 hours ago, Russ Roth said:

 

 

 

Technology has passed you by then.  I texted my brother yesterday AM and he called right back since he was waiting to get unloaded.  His 2015 Mack has discs on the front steer and drive axles and drum on the tag axle which I think the company put on.  They do come from the factory too but it is cheaper for them to put them on in their own shops.  I forgot to ask him about the new trailer he is pulling to see what it is running for brakes.  He did say the set up does not look the same as an S cam but the fire truck I drove did look and adjust like S cams.  Not sure now how they work in either case since I retired in late '99 and the truck was new about '94 or '95. 

 

Ha! guess that's what happens when you live in the back woods, I have been with the same company for 20 years and have never came across a truck with discs, I have even sat in on new truck spec. ordering, and discs don't even come up as an option. We run mostly freightliners, international and mack, where I work I mostly do all the oversize loads with my rig. I have had my Freightliner since 2001, and personally hope to keep it until I retire from here. I dont like all the electronics and emissions there putting on these trucks these days ( just like our pick up trucks)  For braking I believe mass friction is the best,, bigger drums and bigger shoes mean more friction area, but will also increase heat and take longer to cool, but with proper engine rpm and gearing, and use of jake brake, the brakes should see minimum use.