Air brake cans.

[johns4104s]

The air brake cans on my MCI 9 steer and tag axles are quite small. On changing drums shoes and anything else necessary I was considering also the changing the brake diaphragm cans. When I changed the cans on my 4104 I used larger ones, when I had finished the 04 would stop on a dime. Is it possible if they dont catch on the wheels to install the  larger cans on the MCI 9 steer and tags? Any negatives to doing this?

Thanks

John

[bevans6]

The size of the brake can has a direct effect on the braking force applied to the tire.  It has been balanced by the engineers to ensure that each tire is getting the appropriate amount of braking for performance, and most importantly to ensure that the tires don't lock up prematurely.  This is based on anticipated load factors, weight transfer under braking, road conditions, etc.  Locking the front tires leads to total loss of steering control, locking the rear brakes leads to loss of control while the rear end of the bus tries to make a break for it (pun) and pass the front end of the bus.  With race cars, we set things so the fronts lock first by a very slight degree, that being something that is more directly controllable than having the rears lock first.

So bottom line, unless you you have quite radically changed the load balance and over-all load on your bus, which is unlikely but you could have your water tanks behind the front bumper, I suppose, you shouldn't change the can size.  Most buses and trucks seem to have 30's on the drive, 20's on the steer and probably 20's or smaller on the tags.  I wouldn't vary from what the engineers put on.

BTW the lever arm length of the slack adjusters has an equally great effect on braking force.  If you change the slacks out, make sure you get new ones with the push rod attachment hole the same distance from the pivot as the ones you are replacing.  This is absolutely critical on the steer axle, that has to be matched side to side.  That's also why the applied angle of the slack adjuster is critical side to side, it must be the same.

Brian

[Tom Y]

John, The DD3 has a 30 sq in area.  Your front should be  24 sq in, not sure of your tag.  Tom Y

[JackConrad]

Putting a larger can on your tag axle may result in the tag wheels to lock up.  Jack

[buswarrior]

NEVER TRUST the previous owner to have installed the correct parts.

Confirm that you are properly equipped before considering changes.

happy coaching!
buswarrior