Rear disc brakes

Drum pros vs discs:
-They last much longer.
-They're better at keeping big chunks of crud out.
-The parking brake works better (newer disc brake designs seem to negate this?).

Drum cons vs discs:
-They have less heat dissipation ability.
-They have diminished performance at high temperatures from the expansion of the drum.
-They have less modulation ability which will hamper ESP, ABS, EBD (what makes the fancy MTS/ATRAC system work).
-Once crud gets in, it stays in.
-Once water gets in, it stays in longer, and must dry before they will work again.


Therefore, in the case of the Taco, the rear brakes will last a long long time, but if you find yourself towing/hauling often, loading your rig down with heavy goodies like armor and camping stuff, or drive hard on a regular basis, you may find that your front brakes will wear faster than usual because they have to pick up the slack.

Also, if you don't have a rear locker, your off-road ability may be affected. I don't know this for a fact, but if the drums don't modulate as well, the brake-lock differential might not work as well. Not that I think this part is a deal breaker since the OR and Pro trims are the only ones with MTS/ATRAC, and afaik they both have standard lockers. The basic traction control is already limited, so slightly worse modulation might not matter.

FYI, most over the road trucks have drum brakes for their lower operating costs. The only way they can get away with using drum brakes is because they also have engine braking. Without engine braking, they could not use drum brakes because they would overheat and fail. That is why "runaway truck ramps" exist.

 

It costs more to maintain drum brakes on a heavy commercial vehicle. Much more.

That same heavy commercial vehicle also has to be able to operate safely without an engine brake or intarder. Drum brakes will not just fail if those
Supplemental braking systems don’t exist.

 

This is actually because you can get massively stronger clamping forces with drum brakes in any given size form factor and they are more efficient at the size capable of fitting under a 24.5" wheel.

They also have zero engine braking because diesel. They have specialized systems (e.g. Jake Brake) that emulate engine braking similar to a gas engine but not all trucks have them. Rigs have had drum brakes literally forever and it's not generally a problem only having drums so long as the driver works the gears properly and isn't constantly on steep downward grades.

Runaway truck ramps exist for inexperienced drivers who miss shifts or overheat brakes and for trucks that have air (and thus, brake) failures.

 

I'm not a trucker, so I have to base that on what I read on the googly, but so far, you are the first and only person I've seen that thinks that.

”Air disc brakes cost more, so there isn’t a more cost-effective way to stop a truck than a drum brake,” says Joe Kay, director of engineering for brake systems at Meritor, which offers both types.

Also, trucks driving in the mountains WILL absolutely have brake failure if they didn't have engine brakes. Sure, on flat roads where the brakes only need to be used periodically, they will work just fine. On long grades, the brakes would overheat and fail if they were the only thing used to control the truck's speed.

 

I'm referring to any supplemental braking system as "engine braking." I'm aware that's not accurate, but that's what I'm used to saying. How the supplemental braking works is irrelevant to the discussion at hand.

 

It takes me bout 45 minutes to do a pad slap on a heavy axle. As long as the calipers are maintained, make sure they’re lubed and they slide good, and it’s done. Cost of pads and time.

Drum axle takes me 1/3 to 1/2 a day + shoes, rollers, springs, s cam bushings (maybe) and 2x hundred pound drums.

I understand how hills and brakes work lol. People have been trucking on those same hills well before jakes and intarders. Hills will certainly fuck up a persons day, especially if they don’t have supp. Braking system. But if a heavy vehicle can’t stop on its own service brakes, at its weight, with proper technique, it wouldn’t be allowed on the road. Jakes and intarders are supplementary, as per DOT

 

I'm pretty sure this is false. Discs that you can fit under those same wheels will have much higher clamping force. Actually, you don't technically have ANY clamping force in drums because they aren't clamping, but I'm not gonna nit pick semantics. The point is that disc brakes are absolutely superior at providing brake force. Heavy trucks have drums for the same reason my taco does. They will work most of the time, they last forever, and cost less.

Exactly my point. The drum brakes alone can not be the only thing slowing a truck on a grade because they will inevitably fail. Disc brakes will lose braking performance when overheated, but they will not lose contact with the braking surface entirely like drum brakes will.

I know. See my post above.


A bit of reading material that I was picking info from. There IS a little bit of info that seems to reinforce what @stun gun said about cost, and the gap may be narrowing in operating costs as more disc systems hit the road.
https://www.foundationbrakes.com/media/documents/airdiscbrakes/awhitepapercaseforairdiscbrakes.pdf
https://www.truckinginfo.com/155132/brake-trends-drums-vs-discs
https://auto.howstuffworks.com/auto-parts/brakes/brake-types/truck-brakes3.htm
https://www.fleetequipmentmag.com/what-know-air-disc-brakes-heavy-duty-trucks/

 

This all day long. I really don't know why people get so much heartburn on the drum brakes. If all the 3rd gens magically got discs overnight, I wonder how many people would notice before they took the wheel off and saw them.

 

"Clamping" applies in both directions and the ultimate force available in a drum brake system is significantly higher in similarly sized systems due to the lever design of the shoe and the massive friction surface (commonly 5-6" wide). The mechanical advantage is huge and you can't apply logic for light vehicles (e.g. more force) like you are to heavy trucks. Heavy trucks aren't designed to be driven like a passenger vehicle and their systems are designed to reflect that.

Where discs are advantageous is that they do fade less than drums. However, any brake trying to stop 35T is going to fade - the drums will do it just a little faster. The idea here is to use all the tools available to prevent that situation.

Where are you getting the idea that a shoe loses contact when overheated? The material has less friction and they're prone to glazing but these are not issues exclusive to drum brakes - they're a feature of the friction material. Drum brakes have been the only thing stopping many trucks for decades and most have not had issues. They absolutely do not fail like you are suggesting under any circumstance other than a mechanical failure.

This right here is exactly why the industry has moved to rear disc - ignorant buyers who demand things they don't understand.

 

That’s so many things these days.

 

Look at the race cars, brakes are critical. No drums, always disks, lighter, better heat dissipation, easier to work on.

 

Lol. Fascinating.

 

Good thing NASCAR doesn't race Peterbilts with 20T behind them.

 

Any recommendations on better drums if someone was inclined to change them out?

 

Finned drums.

 

Slotted drums.

 

Larger drums from a 1st gen Tundra... no idea how involved the swap is.

I'm looking to add discs to the rear of mine, and keep the drums.

 

Metal expands when heated. That expansion moves the drum away from the shoe. I'm not the one that came up with that idea. It's a scientific flaw in the design of drum brakes, and is the reason they fade so much faster and worse. Disc brakes fade as a result of what you said, but drum brakes have the addition of a physical change in the size of the drum.

 

I believe we can use 2010-2016 4Runner rear disc brakes for the 3rd generation Tacoma?

Used StopTech website as reference as to what components they use for conversion kits. Would be cheaper to build your own kit off a 4Runner... ?

 

Exactly how far do you think these drums expand? This is not a problem except on extremely poorly maintained, non-self-adjusting brakes and even then, the wear of the friction material and drum are more a concern than expansion.