Air Disc verses Drum-brakes

[Truck Shop]

I wish I had a video camera to film a shoe change in our shop. With disc brakes wheel seal change outs doubled the time verses out board drum, But we use a wheel dolly for drum,
average time for me to change a wheel seal even with a Hendrickson Max air hub with drum brakes 35 minutes. Air disc 1 hour 30 minutes, it's all inboard-remove the tires, remove the caliper,
remove the air hub, install jack with hub stud adapter remove out board bearings and nut, remove hub then reverse and torque caliper to 500 ftlb torque on the mounting bolts. We went
backward 45 years, not forward.

 

[Truck Shop]

First job this morning at 5:30 a.m.. Tractor with 70,390 miles and right rear wheel seal leaking-2 hours. And this one has already had a rotor design change from the previous group of
tractors 1 1/2 years old. Also you folks are going to need a 1 3/16 torque adapter to loosen the bottom caliper bolts [No room for large ratchet head and socket} Note the fine shape
the surface is on that rotor and a new pad next to the inboard used pad for a comparison-nice huh.

 

[Truck Shop]

A few more

 

[Truck Shop]

And I had a standard, straight forward wheel seal to change on a trailer with drum brakes-30 minutes. Had it been disc-1.8 hours. Tractor has same basic set up except you have a axle to deal with.
Also the air cans for disc are $175.00-a standard 30-30 air chamber piggy back my cost $32.66 .

 

[funwithfuel]

3 steps backwards. So glad I'm not flat rate in the trucking industry anymore. That's a whole lotta extra BS for less efficient brakes. What a crying shame.

 

[DMiller]

I agree FWF, not my kinda game anymore. We had the Chesterfield MO Airport Maintenance account, they had a 15,000 gallon four axle foam truck that MSHP/DOT would grant a Non Licensed Oversize permit Once annually to bring to the shop for work. That got changed in a hurry to four times annually due to the Early Bendix Air Disc set up, NONE on steers just on two drive axles and ATE THEM ALIVE, less than 500 hours and they were completely used up. Bendix paid us in the third year to replace ALL with Air Drum set up. Rotors lasted MAYBY 16 weeks, AT A AIRPORT!!! Beast had a 8V92 on a Allison, pump was operated as a Drive Line component, either trans or pump, not both.

I am NOT sold on any OTR Air disc set ups. My late Father was in Military aviation, did not understand why never went to multi disc wet brakes as aircraft had, did not see such self destruction on those with seriously severe duty.

 

[funwithfuel]

Wet brakes do last forever, the downside is, "outta sight, outta mind." You don't see em, you don't pay attention till something happens then it's expensive and usually destroys critical pieces. Definitely not practical for on road use.

 

[John C.]

I've taken apart wheel loader axles with 40,000 hours on them and the disks and frictions only showed minimal wear. The problem come when someone thinks they are paying too much for oil and use substitutes or will work brands.

 

[Truck Shop]

Before the air disc came on the market a few years ago truck manufactures started installing 16.5 x 8 5/8 shoes #4711's with 3030 long stroke air chambers. Those were actually pretty
worthless for a up grade shoe over the standard 16.5 X 7" 4707 shoes. Biggest problem was the shoe block bed/plate would flex way more with the extra width and the shoes would
wear the center out of the brake block material. The drums would be convex with a big hump in the center full of hard spots. The standard 7" 4707 shoe actually lasts longer and the braking
was no different between the 8 5/8" and 7"wide shoes. We have found the Gorilla 23K shoes get about as good life as it's going to get for our use.

 

[Truck Shop]

One other note because of the new required stopping distance that was put forth trucks are not required to have disc brakes, and can still be ordered with drum brakes.
But the interesting side of that is because with the newer brake block material drum brakes are meeting the required stopping distance anyway. And the new block
material is becoming almost fade free.

 

[Birken Vogt]

Mike, I was just about to ask and I think you answered. Back when this nonsense came on the scene they told us discs were going to be necessary to meet increasing 121 standards. Or the extra wide drums or some weird stuff. But you are saying that it can still be done with standard 7" drums?

 

[Truck Shop]

There is no requirement that I have seen or found {and I have looked high and low} for such in regards to shoe replacement after the originals are worn out and need replacing.
I just went through a Stemco Wheel End and Brake re-certification seminar and I asked that very question. And the instructor only said as far as he knew that their was no
requirement to install only 8 5/8" shoes with 8 5/8" shoes. If you installed 7" in-place of the wider shoe your ok because the stopping distance is negligible. How ever you can
install the 7" shoe in the wider drum made for 8 5/8' shoes, but you need to look the drum over real well because it is probably worn with a convex {hump in the center} which
will cause lousy contact area between shoe and drum and ruin a set of new shoes. We change drums out every time we shoe my cost per drum averages $66.00. It stops like
new plus the DOT won't say a word about the condition of the brakes. DOT doesn't care how much shoe is in the drum what they are looking for is how close the wear limit
indicator built into the edge of the shoe lining is to the original edge of the drum surface. If it's close or even it could be defective equipment time with DOT.

 

[funwithfuel]

Had a carrier that would not allow us to replace any drum unless it was severely cracked. Grooves so deep you could place your fingers into. I adopted a new service program for when I replaced brakes for them . I would simply free the drum from the hub pilot with a 20 pound sledge. For some reason, they always needed drums.
If bean counters are going to drive policy, we just have to adapt the policy.
Of course this was back when disc was an expensive option on Paccar trucks. Q+ was the latest and greatest at the time.

 

[RZucker]

I've taken apart wheel loader axles with 40,000 hours on them and the disks and frictions only showed minimal wear. The problem come when someone thinks they are paying too much for oil and use substitutes or will work brands.

Had a customer with an older 644 JD loader that called me regarding no brakes. I drained the diffs and they were full of 90wt. That doesn't work... Gave the diffs a flush of kerosene and a fill of JD hydraulic fluid and they worked fine again.
2 weeks later I get a call that it has no brakes again. Checked it out and it was full of gear lube... WTF? Turned out the owner's 80 year old father saw me put hydraulic fluid in the diffs and just knew I was stupid (maybe I am) and changed the oil out as soon as I left.

 

[wornout wrench]

The last several companies that I worked for all had the same idea when it came to brakes relines.
Everything new. Simple.
The companies got decent pricing on parts, I think the shoes were about 80 and the drum was 100, spring kits were cheap.
All outboard drums so took nothing for time.
Trucks had good brakes, the Commercial vehicle inspectors were happy, the loads were moving so management was happy.
End of problem

 

[Truck Shop]

Two 4707 shoes $18.22=$36.44, drum $66.00, hardware kit $5.44, total per corner $107.88, all four corners $431.52.

 

[DMiller]

I always hated cheapskates on parts, got to a point I would give them the parts list and Suppliers I would use, they asked if could choose anyone else for price and I would explain could reassemble they could pay for estimate and take it elsewhere. NOT the way I would do the repairs. I also would not accept doing half now make the worn crap last awhile, they could drive that to another mechanic. Got really picky, got to where many would not come back until they could not get anyone else to scratch and patch either.

 

[John C.]

Way back just after the hippie age I had a fleet of four old Ford dump trucks built in the late sixties with 3208 engines and two stick 5 and 4 transmissions. Now these rigs never left town. They went out on about 5 miles total of city streets, maybe 2 miles of county road and the rest was on gravel roads. Brakes were done when I noticed the noise when they drove by my shop or someone saw the smoke coming from inside the duals. The owners in those days didn't know any other way but to scrimp and save anyway possible on parts. That always gave me nightmares of a runaway dump truck coming down the hill into the back of a car full of women and kids at the stop sign at the bottom. When I moved on I figured I would never again take any crap from an owner about top flight repairs on brakes and steering. Thankfully, I ended up back at a dealership keeping my hands in big iron from then on.

 

[DMiller]

Inspected a worn slick and sick Corn Queen for a buddy a short time ago. Turned out to be an old county truck with maintenance records so was taken some care of. Cab was shot, salt cancer had full hold of it and I explained to him this would be a no buy unless he was interested in a cab buy and likely have to change the dump box in a year or less. 2001 7500 Workstar, no floor pans left, doors rotting heavily. He bought it anyway, has had five body shops look at it to estimate sheet metal repairs, None would touch it. He is now mad at me for not telling him was junk, go figure.

 

[funwithfuel]

You can't make everyone happy, but it's easy to make everyone mad.