Brake conversion: Drum to disc, and the DD3's to spring

[John316]

I had another curiosity question.

I wonder what it would take to get our front and tag axle brakes to disc? The kicker is we don't have anti-lock brakes. I wonder how that would be to install anti-lock?

Also, I don't anticipate having a hard time putting the spring brakes on. We have plenty of room on that axle. It will mostly be getting the new relay set, and figuring out my parts.

Speaking of parts, does anybody have tips on how to get the parts? I could get pretty lost with that.

Thanks for you help.

God bless,

John

[robertglines1]

brake rotors 350 each-drums on sale at auto wheel & rim 65 (I know they are for semi)but used as example for comparison..antilock need wheel sensors ,brakevalves,computer and rear differential with sensors if you go for drive also.

[bevans6]

You can have anti-lock drum brakes too, I believe all new trailers have them.  There is an amber tell-tale light at the drivers side rear of trailers that tells the driver the anti0lock system is active.  Honestly, this is a place I wouldn't go.  It's one thing to do maintenance on the vehicle yourself, another step to change to spring brakes, but when you start to completely re-engineer the entire braking system, I think it's a step too far.  In my view, even changing to spring brakes, if you do it right, needs a really fundamental upgrade to full dual tanks, the application valve, the push/pull valve setup, the whole schmear, and I would be well daunted by that, totally regardless of any regulatory or legal issues that might arise.

Brian

[bevans6]

Actually, speaking of curiosity, I wondered why anyone would feel a need to change from DD3 to spring brakes?  In my view, the DD3 system I have (1980, I think earlier systems were a little different) is superior to a spring brake system in many respects, and I wouldn't think I would want to change.  Compared to costs for modern truck brake parts I don't regard the current prices for DD3 cans (I see them at $550 each for new) as being outrageous, not when I spent close to $1300 last year for new rear disc's on my Dodge pickup.  They are only expensive when you compare them to spring brake cans at $100 each.

I think the reason the DD3 went away is down to costs (they ARE more expensive, it is true), simplicity and ease of maintenance in fleets, and being a little more fool-proof in operation, and not because spring brakes are inherently superior.

Brian

[TomC]

Personally-I would change to conventional spring brakes-they are simple and cheap to repair/replace.  As for adding anti lock brakes-forget it-it would cost in the thousands.  Just having the wires made to exact lengths for each wheel end would be in the hundreds.  Anti lock brakes will not shorten your stopping distance-only prevent wheel lock up.  And if you're an attentive driver, you should never need the use of anti lock brakes (in 1.3 million miles of truck driving and over 500,000 miles of car driving I've NEVER rear ended anyone).  Course in snowy and icy conditions, they are helpful.

When I first started my truck project, I called Meritor for a conversion kit to discs, and they didn't have them. About the only way to swap out to discs (and you should do all wheels, not just the steer and tag) would be to get a wrecked bus and transfer all parts to your bus-BIG time job.

Thee most significant improvement you can do to your braking system is to use brand new linings (new brake drums would be good too).  There are about a dozen different brake linings you can choose from with each being for a specific use.  For instance: semi metallic linings for transits-they work better the hotter they get; hard lining for heavy haul; normal "gray" lining for everyday use; linings for dirty/dusty environments, etc.  When I was driving, I used a lining that worked when cold and had moderately hot resistance.  This is the lining I would suggest since we don't drive that much, and the softer lining will grab better-but has a shorter life.  On my truck, with the use of Jake brakes, my linings would last 300,000 miles between brake jobs.

Transit buses have the largest brakes, then highway buses, then big rig trucks (but they have alot more brakes).  Save yourself ALOT of work and headaches-don't attempt installing anti lock brakes, and keep your drum brakes-just change out the drums and use the corrrect lining-you'll be happy with the results.

Good Luck, TomC

[luvrbus]

John, I went on a service call for a friend on a H-45 that had the Krorr disc brakes and that is one fine system easy to work on the way you use your bus and the weight I would check into it.
Check with Wayne he is installing a disc brake system on his new Eagle.
The way I see those on some buses is disc brakes on the front and drivers with drum on the tags also the VanHool used a non anti lock system with the discs on some models
Brian likes the DD3 brakes reading from reading his post me I would not walk across the street for a set if you have the room go for the springs, you use your bus it doesn't set for 11 months a year you knock a DD3 off or it fails in a small town in Idaho you are dead in the water for a week with springs any Napa store can have one overnight the DD3 are old technology time for a change I for one was glad when Bendix dropped the DD3 line 

good luck

[bevans6]

What I'm looking for is understanding why the DD3 is worse than the spring brake, other than the cost and the availability.  what I like about the DD3 setup is that if  you lose air pressure in your primary system, you don't just get automatic lockup of the drives, you get several controlled applications from the emergency tank.  What I don't like about the DD3 is that after you use up your emergency air you can't set any parking or emergency brake, although they do auto-apply at 40 psi in the emergency tank.  so what I don't understand is did they  do away with the DD3 because it was more expensive, too complicated, not reliable or because it was proven to be inferior, like drive shaft strap parking brakes were?

Just looking to increase my fund of information, not pre-judging the result!       I do kind of like the modern spring brake systems with dual tanks, I think that is a really good idea. 

Brian

[belfert]

MCI makes conversion kits for some models to go from drum to disk brakes.  Price is around $10,000 if I recall correctly.  I suspect these are for E series and up if the D series still had D3s.  I am surprised that a 1995 bus still has DD3s.  My 1995 Dina has spring brakes along with ABS on the tag axle only. 

[buswarrior]

DD3 was abandoned primarily due to $upply and demand.

There was no inferior/superior aspect to the decision. Both spring brakes and DD3 do the same job by way of different methods and both are acceptable to regulators.

Not enough market, not enough sales, not enough customers, meaning only one: MCI, and their hapless coach owners, who had no choice due to axle/suspension geometry.

You may note that the decision to give up coincided with the bulk of the coaches so equipped leaving the original purchasing front line fleets.

And disc brakes have been here for a decade and a half now, further eroding the future limited market for the DD3 component.

Call MCI, they very likely have a kit to do the swap, just for folks in your position.

As for swapping Drum for Disc, why bother? The D model stops very nicely. When did you inspect/change the linings last? Age of your brake valving? Have you done an air pressure check to be sure you are getting the squeeze at the chambers that the treadle valve is calling for, especially for the rears? Relay valves are the devil. These are tests that the Europeans do routinely. North Americans should be scared as to what might be going wrong under there. Brake action does not mean you are getting proper pressures delivered to the brake chambers.

And the costs involved with a sticking/seized caliper... can't ignore your preventive maintenance schedule on these components.

As for ABS, why bother? Lots of money and work, and no, it works like CRAP in the snow, and even worse on bumpy and rutted frozen icy parking lots. The coach simply won't stop, ABS cycles like mad and you keep rolling along. A locked wheel will stop against the next few ruts.

Wet roads, yes, it helps a driver who foolishly tries to brake hard and steer at the same time.

But, remember what happens to coaches that try to swerve....

Winter in the northern climates is a fine, and annual, skid school. Steering control, under all road conditions, is easily restored by modulating the brake pedal, against the inexperienced intuition to push down harder on it, when it doesn't stop or turn as you'd like.

ABS is no friend of mine.

happy coaching!
buswarrior

[zubzub]

ABS is no friend of mine.

happy coaching!
buswarrior

Or mine. They only work on uniformly wet roads when you need to brake and steer at the same time....as BW said they really suck on ice and snow, i find them dangerous .

[belfert]

I've never had ABS on a large vehicle nor really driven a large vehicle on icy or snowy roads.

I personally find ABS to be a godsend on cars, pickups, SUVs, and the like.  This might be because most of my driving life I have had vehicles with ABS.  The first few vehicles I drove didn't have ABS so I do have plenty of experience with pumping brakes in winter weather.

ABS is not a substitute for slowing down in bad weather nor a replacement for cautious driving in bad weather.  Too many people think that 4 wheel drive, ABS, and stability/traction control mean they can drive recklessly on slippery roads.

[John316]

Thanks for the insight, folks.

What you all said makes a lot of sense. Good sense.

I agree about the ABS system. I think I could do it, but it would take a monumental amount of time and money (anybody want to donate? )? I just don't think it would be worth it. And I agree, we have driven in a lot of winter weather and haven't needed it at all. So much has to do with speed/how careful you drive. You can't help the idiot drivers (in the four wheel drive F150's ), but you can watch out for them. I also agree with the ABS not being good in most winter weather. When I am sliding in my truck, and ABS is pulsing, I find myself just standing on the brakes harder to get just a little more stopping power. I haven't had a problem without ABS. I wonder if I can pull the fuse on the ABS in my truck?

I also agree, the disc's probably don't make sense. That is just too much time and money to invest in that.

I do think that I will try to install the spring brakes. Simply because they are so available.

BW, you are right. I should check those things. The bus really does stop well, but I think it could stop better. I haven't driven another bus, so I don't have any comparison. We always drive with the jakes on. If we are in traffic we have the retarder on, and we can stop on a dime then.

We rebuilt the brakes two years ago (60K ago), and they still are going strong. I do think next time I might go with a softer pad.

Thanks for all of you help.

God bless,

John

[luvrbus]

John, just don't ever drive a bus with ABS disc brakes and you will be fine ,  if you do ever drive one that will be on the top of your gota have list lol truly amazing how easy one stops with the small brake pods Prevost uses a 24/24 on the drivers and 16/16 on the tag and steers



good luck

[John316]

Awww, Clifford. Come on. I had just convinced myself I didn't need them .

Well I guess it is back on the sometime list. I will start by seeing if MCI has a kit for the disc. I don't think I could do the ABS. However, in thinking about it, maybe on the steer and tag ABS wouldn't be too bad. I will just stay off of the Prevosts for now. Maybe next bus

Thanks.

God bless,

John

[belfert]

A PDF brochure about the conversion kit is at http://www.mcicoach.com/literatureAssets/drum2Disc.pdf.  The brochure says the kit is for the D4500 so it might not work for the DL3.

MCI's online parts store doesn't list a price for the kit.  It just shows out of stock with a price of $0.00.