Kenworth makes Bendix front air disc brakes standard

[kscarbel]

Fleet Owner / December 9, 2013

Kenworth is making Bendix front air disc brakes standard on all Class 8 tractors and trucks.

According to Kenworth, the Bendix ADB22X air disc brakes have a two-pin floating caliper design that provides a more stringent overall dimension accuracy and consistent force distribution. The design also significantly reduces brake fade with no degradation of stopping power, Bendix said.

“We’ve offered Bendix air disc brakes as an option on our Class 8 trucks previously. Customers appreciate their superior performance, car-like feel, ease of maintenance, and light weight design, while they also exceed the federal government’s RSD (reduced stopping distance) requirements,” said Kurt Swihart, Kenworth marketing director. “These benefits are so compelling that Kenworth decided to make air disc brakes standard on Kenworth Class 8 trucks. For additional weight savings, the air disc brakes also come standard with an aluminum hub and splined disc rotor assembly.”

[1958 F.W.D.]

We have air discs all the way around on the last two firetrucks we bought- a 1989 Simon-Duplex chassis and a 2007 Spartan Chassis. What a world of difference, I would never have anything but discs on a firetruck ever again.

[kscarbel]

Fire apparatus in year 2013 should be equipped with disc brakes front and rear (and independent front suspension), and all class 8 heavy trucks should have disc brakes on the steer axle.

[j_martell]

I would love discs.....just gotta find a way to convince the boss man. Anyone have a ball park number to convert an triaxle from drums to discs? i realize there are lots of variables, just a rough estimate will suffice for the time being........

[fullfuel01]

Might be ok for firetruck. But i don't see any trouble at all with drum brake. They've been installed on million of trucks and are still very relianle.Disc brake might bing you to a complete stop in a shorter time but that will just lead to shorter distance when following another vehicle. Just about the same with the air ride suspension. 'I can drive faster on that bumpy road and it still ride ok!' My opinion but am I totally wrong?

[1958 F.W.D.]

NFPA (The National Fire Protection Association) are the adopted standards of many Fire Departments throughout the United States. Although not law, nor are they mandated to be adopted in any fashion, the NFPA standards are the recognized authority for everything from tactical firefighting methods and procedures to equipment purchases such as hose and apparatus, NFPA standards are regularly cited in court cases and legal fights everywhere and are the first source of "how it should be done" that Attorneys go to.

NFPA 1901 "The Standard for Automotive Fire Apparatus" (most recent edition which I believe is 2012) does not require discs all the way around at this time, just on the steer axle.

We chose to go all the way around in 1989 with the Duplex chassis which was a tremendous improvement. I think that was Meritor brakes. In 2007 on the Spartan Chassis we went discs all the way around again with Rockwell if I remember correctly. This truck also has independent front suspension and let me tell you it's about the nicest damned riding and braking pumper I have ever driven in 25 years- and I have driven a bunch of rigs.

[KECorbin22]

Disc brakes have been standard in Europe for 20 plus years. I was under the impression that all 2015 Class 8 tractors and trailers are required to have all disc brakes. Our Company is already gearing up to service them. The biggest problem we have is doing DOT inspections, You got to pull all wheels off to measure the brake pad linings. By the way there is no longer any core charge on brake shoes, hence no rebuilding them.

[kscarbel]

Might be ok for firetruck. But i don't see any trouble at all with drum brake. They've been installed on million of trucks and are still very relianle.Disc brake might bing you to a complete stop in a shorter time but that will just lead to shorter distance when following another vehicle. Just about the same with the air ride suspension. 'I can drive faster on that bumpy road and it still ride ok!' My opinion but am I totally wrong?

The new FMVSS 121 braking regulations that took effect for highway vehicles on August 1st of this year raised the bar for brake performance (Now the US is catching up with the European braking requirements).

For example, a tractor-trailer traveling at 60 mph must come to a complete stop in 250 feet, versus the old standard of 355 feet (a 30% reduction of truck stopping distance). Disc brakes on the front, complimented by an engine brake or retarder, allow trucks to meet the new requirements.

[2stacksuperdog]

I agree with fullfuel. Why fix if not broke. Good for fire trucks but not the public in my opinion. The shorter stopping time just means to a new steering wheel holder "ooh, i can drive faster and follow cars closer now!" and didn't they try disc brakes before and they failed in the market?

[jakebrake86]

Just something to make what we're running now ''obsolete." Anybody know what a replacement rotor and shoes would cost? I can't imagine them being cheaper to service than drums. Maybe I'm wrong?

[j hancock]

I know that drums get over heated but just think of the bitching by the driver's about warped rotors and vibration under braking.

More time in the shop...

[kscarbel]

Change is not always good (e.g. foreign truckmaker Volvo owning the American icon Mack), but the change to disc brakes is good. Speaking of the short pad life of the B.F. Goodrich disc brakes of many, many years ago (1978) in North America has no relevance with today's situation.

Disc brakes are now a mature technology that's been proven in Europe where trucks run at much higher GCWs than the US. Every reason that your car or light truck at least has disc brakes on the steer axle if not also on the rear is why most heavy trucks soon will as well.

• Vastly superior braking performance
• Weight savings over drum brakes for greater payloads and profitability (while larger "enhanced" drum systems add weight)
• Faster brake maintenance
• Numerous brake inspection and maintenance benefits

What's not to like?

http://www.foundationbrakes.com/media/documents/airdiscbrakes/awhitepapercaseforairdiscbrakes.pdf

http://www.mpgseries.com/pdfs/Air_Disc_Brakes_For_Tractors_and_Trailers.pdf

[gearhead204]

we had a rd with disc brakes 15 yr. ago brakes seemed ok until you needed parts. ended up converting to shoes and drums. never ran it in the winter thou don't know how they will get along with calcium chloride, I'd suspect a lot of stuck calipers. maybe nightmares like "p" shoes sezing on the anchor pins

[1958 F.W.D.]

Granted- I have never run something big with discs across country or to deliver freight.....But I have run a boatload of fire apparatus- everything from pumpers to ladder trucks (straight frame) and tractor-drawn tillers, weighing damn near 80K..........I have driven big trucks for maintenance purposes and some other nefarious purposes (no comment) and I have to say that there is a tremendous difference in performance between disc and drums....again stressing I have not driven anything other that fire apparatus with them, I find it hard to believe that discs are not being more widely accepted. I couldn't imagine going back to drums on firetrucks.

[Joe Ditchkus]

I am not familiar with disc brakes on class 8 trucks but in a DOT roadside inspection how would they determine lining left on pad or if rotor is in compliance? Self inspection would entail removal of wheels a lot of work. As gearhead said calcium chloride cause more maintaince problems on disc than drum brakes. Joe D.

[Joe Ditchkus]

I forgot to add that on public service vehicles maintaince costs are absorbed easier than vehicles in private fleet where maintaince costs are closly monitored.I am not saying cost is no object with public service vehicles but the few I have dealt with had more free reign. Joe D.

[BGarofalo]

We got a few new tractors with disc brakes all around. The problem is we had to buy new spare rims for all the new trucks. The rims have to have more air flow so they have five holes instead of the standard 2 hole rim. Had a course on servicing them and the trainer said "don't worry if you see the rotors cherry red hot while breaking, its normal!"

They are much easier to work on but I can see rotors are going to have shorter life span than drums.

[BC Mack]

We run 300 buses on disc brakes on all 4 corners, about 30,000lb gross with autotrans and retarders.

are they better or cheaper than drum brakes???.... well, the jury is still out... here is some rough math.

downtime per axle pad change is about 3hrs... we do that 3 times a year on 80,000km/50,000miles per year... about $250 for pads.... 21mm new, off before 3mm.

rotor changes are at 37mm, new is 45mm, no machining done or needed during life... about $300 each.. about every two years. Unable to measure for annual govt inspection, so wheels off if it hasn't been done very recently.

calipers... we replace boots on EVERY pad change... if adjuster fails test or boot is burned the caliper is replaced, IIRC $1600 new, no exchange... company policy... there are remans out there but we won't buy them.

our calipers electronically read the pad thickness on the dash... you can also check pad thickness by protusion of a guide pin... same as on the big jets actually.. so that is how dot can check lining wear...

biggest problem we have is the calipers, we get inbalance across the axle and when it gets more than 3mm difference we take it off the road and tear down everything..

heat.... being a lowfloor bus, poor airflow, 36/36 maxi clamps it hard.... and practically no visual on the brake, can't see anything move with the wheels on... and the heat is cooking wheel bearings in rear as they are grease not oil... ZF axle.

never had any serious reports of brake fade, and we do 110kph on freeways as well as city stop/start... I drive them and have found them to be smooth and not jerky..

one opinion...

bosses say nothing when asked... we got them with the bus so big learning curve when new..

HTH

BC Mack