17" disc brakes

[PiecePilot]

Anybody have any experience with 17" disc brakes on their units?

We are specing a new Sutphen 100' platform and brake options are S-cam drums, disc front with S-cam rears or all wheel Bendix disc brakes with quick change pads.

Our current Engines and ladder run 16" disc fronts and we've had some problems with overheating brakes, cracked rotors, short pad life, etc.

One problem area for all discs has always been parked holding power on hills, has Bendix made any improvement?

The new unit will be tandem axle quint, 70K GVW, Detroit 60, Jake brake... any thoughts about brakes?

[chiefengineer11]

Disc brakes

We have an '89 Duplex/Quality with Rockwell Duramax ADB-1560 disc brakes on both axles. They have performed very well for us. They stop straight, true and fast, even when they're wet, and without locking up. We put new pads on 3 years ago and will be doing front pads later this week. The rear rotors were fine. I don't know what the fronts look like, but I don't have any reason the think that there's a problem. I will grant you that pads do wear faster than shoes, but that's probably because they have fewer square inches of braking material.

We like disc brakes so much that we've spec'd the Meritor 17" EX-225 brakes on our new Spartan/Toyne (see "Toyne Wins" on Page 6 or 7 of this forum) on both axles. Many builders want to give you disc brakes on the front but balk at putting them on the drive axle. Other than price, I don't know the logic for that. Several years ago when we were talking to HME, their guy flat refused to put disc brakes on the drive. He would put them on the steer axle, but only reluctantly. Maybe someone else will come in with some thoughts on that point.

The only time we had a problem with the parking brake not holding was when the automatic slack adjusters failed to adjust. It takes considerably less of an out-of-adjustment condition to cause that to happen on that type of disc brake. The newer ones don't use slack adjusters.

In defense of the drum brake people, I do remember being in a well known shop in Manasquan, N.J. getting an ambulance worked on. They were removing the disc brake system from an engine and replacing it with drum brakes. I think that the engine belonged to a company from not far away from there. The shop manager told me that the company complained that it took too long to stop. I can't imagine what the problem was unless they were just too small. Our experience is just the opposite.

Point to be aware of: DOT's proposed braking standards are going to shorten allowable stopping distances considerably. I don't think that a Final Rule has been issued yet, but it's coming. In order to meet the standard, either disc brakes or larger drum brakes will be needed.

Stay safe out there, everyone goes home!

[lvwrench]

just started

We are just getting into the 17" discs and only have two new units with them on so have not had a real trial period to judge by yet. You might give thought to putting the 17" discs on the front and the cast Qplus shoes for the rear axle. Try going to the Arvin Meritor web for a search of brakes. I did look once and found a larger brake shoe but it required a change to the backing platre and rims used.

[Chauffeur6]

We've got 17" front disc with rear drums on our 80K GVW tandem axle quint, S60 w/Jake and it stops surprisingly well for the beast it is.

[Engine305]

Disc Brakes

We put 4 wheel discs on the Enforcer Rear Mount Rescue Pumper being built at Pierce. The only issue i have is also how is the Park Brake going to hold over time
Tak 4 w 17" on front and 17' on rear

[Rescue101]

CE11,It's already happening.Look to see drums increasing by at least an inch or two and rotors to gain about the same. Instead of the old 6.5xX you'll now have 7.5 or 8 by X.Intead of 16 or 17" rotors you'll probably see 18 to 19".We've always specced the biggest rears we could get,and it pays off in reduced maintainence.Like any new system,I suspect there will be a few issues until they get the systems matched.Time will tell. T.C.

[chiefengineer11]

Your're rignt, TC, in order to meet the proposed stopping distances, changes have to occur. Europe has been running primarily discs for some years. The trucking industry here is looking to larger drum brakes because they want to avoid the move to discs. 17" disc is as large as I've seen so far. I haven't heard of any move to get bigger - yet. I'll check with some of my TMC sources on that.

But we're running out of space behind the wheels. Are we going to see a return to 24.5" wheels (formerly 22" tube type)? Maybe. But to keep trucks from getting too tall, we'll need some serious low profile tires. As you say, time will tell.

Stay safe out there, everyone goes home!