2001 E350 brakes

[raydav]

I have two E350s; one is a 1984 that I modified with a dual wheel rear and a 94 IDI turbo engine. It weighs 9K#. The other is a 2001 PSD. It weighs 12K#. It used to be a bus, is now RV.

Both have disk front brakes, and the same DANA 70, dual wheel rear. The 9K rear has drums and the 12K has disks. Every year one or both go up the eastern Sierra, and back down. One year, coming down in the 9K, I cracked both rotors. The rear brakes held up OK and I got down OK. I just installed the sixth set of pads on the 12K trying to get something that can get me down the mountain without fading. There are roads on which I will no longer take the 12K. One road where I really had to take the 12K I descended in low gear - not advisable for a 4R100 in a 12K vehicle. The 12K has a rear pad size that I would expect on a car. I don't know that I have any caliper options.

Brakes work by converting kinetic energy to heat energy. It takes a certain number of calories to take the car from cruising to stopped. That is why rockets that we sent to space got up there OK, but burnt up when they fell back down. Same thing in brakes. Temperature is heat per unit volume. Think of heat as "stuff". It is a lot like water. If you have some, it occupies space, you can separate it into many shaped pieces, and move it from place to place. But unlike water it can be compressed. The transformation from kinetic to heat energy takes place at the interface of the rotor and pad. A drum probably has a bit more volume than a rotor, and shoes have a lot more volume than a pad. Therefore, for the same braking force - same number of calories - a pad will be hotter than a shoe. And more prone to fade because of overheat. Attached is a pic of the two friction parts.

How to get effective braking for the 12K. 9K is 3/4 of 12K. I don't think that difference is enough to explain the difference in braking behavior. The 9K has firm brakes. If I press too hard the back brakes lock. The 12K brakes are mushy and weak. Driving in traffic requires very precise operation to keep up but not rear end the vehicle in front.

There is 500psi to the calipers both front and rear.

The shop manual says the anti-lock unit can cause soft brakes.

I could reroute the plumbing to bypass the anti-lock unit.

I have a hydro-boost assembly.

Drums are self energizing which requires less line pressure to get the same braking force.

I am seriously considering upgrading the 12K rear to drums.

Ideas???

TY
Ray

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[u2slow]

Drums tend to have better initial friction, but as the drum heats up, the diameter increases. They also dont shed heat as easily.

The lining on E350 disc is reduced for the parking brake. The E450 has better discs (D70hd or 80) but the housing flange is different so it doesnt direct-swap.

I have noticed that the housing flanges are similar going to 05+ F250/350 so those larger brakes could possibly swap. Not sure what rotor would work; you'd also need 17" wheels minimum.

 

[raydav]

The lining on E350 disc is reduced for the parking brake.

Ah yes, the parking brake. I am guessing a spring broke. I was on the other side of the country. I have since removed all the parking brake parts. I have a 4R100 with a drive shaft brake that I need to check/rebuild and install.

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17" wheels minimum.

No thank you.

 

[raydav]

Drums ....... dont shed heat as easily.

Are you sure? My 84 cracked both rotors but had no issues with the drums.

 

[u2slow]

Are you sure? My 84 cracked both rotors but had no issues with the drums.

In general, yes. Drums have more mass and its all enclosed. They fade, and the front discs have to work harder.

Ford rotors have been on the thin side for years. F-series finally got thicker rotors for '99.

 

[asmith]

While I cant help with your swapping question, Disc brakes absolutely shed heat better than drums. That is why all race cars and performance cars use them. They shed heat better and resist fade better. Drums take longer to heat up, but once they do they take a really long time to cool back down. And once heated up their braking performance is hurt much more.

As for your van, I am not sure what the problem is. normally your fronts are supposed to do most of the braking with the rear doing less. make sure the proportioning valve is working correctly. after that Try the best quality and thickest rotors you can find. maybe rig up an air vent to direct air over the brakes like Ferrari's and other high performance cars do?