AIR BRAKE CHAMBER KNOWLEDGE

[akbusguy2000]

Pictures would help a lot.

"Crossover?" - Think anti-compounding setup.

maybe.

tg

[Joe Camper]

I think our bus at 41000lb and only having parking brakes on the drives is just flat dangerous. I have a set of 16/24 I pulled off of the tag on a 95 XLV and the next time I get under it for anything requiring the same tools for any other reason I will be installing those maxis on the tag on ours. It is a pretty easy upgrade.

That also carries another benefit being. With another axle with parking brakes I can go down to the way more common and less expensive 30/30s on the drive axle if I so choose.

I have pulled 30/30s off of buses that originally came with 30/36s a handfull of times at minimum and when Wayne first started this thread the first thing that came to mind was I wonder if those are original equipment for that chassis or were they also downsized by a previous owner. You should check to see what the book says.

This can happen in 2 ways, 1 out of cost savings 45 bucks vs 175 and the other is ignorance cause to the untrained eye they do look similar

Can anyone say for sure that they know of ANY 3 axle bus chassis with maxis on the drives only came with 30/30s in that location from the factory?

[bevans6]

For people like me who are a little slow to pick up things, on spring brakes the rear section of the canister holds a big ornery spring which is held back by the spring diaphragm.  In a 30/36 chamber, the spring diaphragm is 36 square inches.  That means that it can hold back a stiffer spring than a 30 square inch diaphragm can, so it can generate more emergency/parking brake force.  A normal 30/30 canister has a spring that can generate around 60% of a full service brake application, so a 30/36 would be closer to maybe 80%.  These things have to be carefully judged - one thing you don't want is the spring brakes coming on while you are on a slippery road and locking your rear wheels.  It's not just a "more is better, Tim the Toolman Taylor" kind of deal.  But I do think Joe's point is very valid - 30/30's are pretty ubiquitous on a lot of things, and therefore cheaper and easier to get than 30/36's or 36/36's, and may be on there by mistake.

The other thing is that spring brakes often have a vent hose or tube for the spring brake chamber, since it it open to atmosphere you want to keep as much moisture out as you can.

Brian

[belfert]

Dina uses 36/36 chambers on the drive axle.  They cost about $150 each to replace which is a lot cheaper than the rotochambers on the tag and steer axles.

[dickegler]

Hi All, please remember SAFETY FIRST!

when I bought my bus, it just never stopped well.  it's heavy, about 40k, but I always had an uneasy feeling about braking force.

while replacing linings and drums, I discovered a previous unknowling mechanic has replaced the slack adjusters with wrong type, and replaced cans, but did not cut the rod to the proper length,  the geometry was completely wrong and DANGEROUS

after correcting the deficiencies it stopped much better, but still not up to  my standards,  I then replaced the 30/36 cans with the 36/36 cans on the drive axle.  now I'm very happy with the brake performance.

Long story short, there is lots of information on the web about getting the proper set-up on the cans and slacks.  remember at full brake application the push rod/slack adjuster should approach 90 degrees.  anything else degrades performance.

I wouldnt dream of hiring maintenance labor, but am fanatical about learning the proper procedures to remain safe.

dick egler

[Joe Camper]

Hello Dick.When are you going to come over to Georges and labor on my bus with him for nothing like he likes to do? He makes some very cool tools too. Its a blast.    Hope Fla was good this year. We need to get togeather again soon.

Yes safety first. Let me make a safe guess.

I will say that on Waydes 90 Setra either it DOES also have maxis(parking brakes) on the tag axle making the 30/30s the right parts OR someone has replaced the correct ones for the drive axle with a set of less expensive smaller and IMO inadequate 30/30 or its only a 2 axle bus sorry for not knowing that LOL

switch gears a bit........

Here is a small piece of something a fellow was asking me to help him with.

This is dangerous. Very dangerous. Dick combine the prior performance of your bus with something like this and then try to imagine a panic stop or cross town traffic.

IMO the air compressor on this bus is damaged goods now and possibly prone to failure too. Who knows how long this situation took to progress.

 and it is out there more than you would ever guess.

" When I got to the RV resort (Aztec RV Resort in Margate,FL) to check in at the office, I let the coach idle and when I came out the right rear was listing (10 minutes). I got in the coach to go to my lot and the air was just above 50psi and when I accelerated it came up. By the time I got backed in to my lot, the entire coach laid down on all sides evenly."

Poor old bus. Id a laid down too if Id been huffin and puffin trying to stay up like that.

 Anything under about 70 or 80 psi and those maxis were talkin about are no longer sufficiantly released and the brakes begin to drag.

[luvrbus]

You should never replace a smaller size chamber like a 30/30 with 30/36 without doing reinforcements to the brackets you can get away with it for a while but it will catch up with you some day

good luck

[edroelle]

Vehicle brake systems are designed with various considerations.   High on the list, is front to rear balance.   A perfect design would have all wheels start to skid at exactly the same time, under all loads, temperatures, and surfaces.   

Exaggerating, consider a massive rear brake, and a wimpy front brake.   The rears would skid and the front brakes would provide very little braking.   The vehicle deceleration rate would suffer and stopping distances would be much longer.

Be cautious before increasing a brake size, because it may negatively effect the balance and overall performance.

Ed Roelle
Flint, MI

[robertglines1]

Some responding have factory converted coaches designed for a certain gvw and braking to match. most of our coaches were seated and designed for a differant gvw. I myself have never reached that original gvw after conversion of the 89 seated coach.  Food for thought.  If you have passed that original designed brake. Then you might need to adjust .  Bob     

[thunderstruck]

Where did you get 30/36s for 130 bucks that is a good price on those

Or possibly that was for a "piggyback" and not the entire thing.

L&L Distributors Inc. in Pompano Bch,Fl. compleat unit. I think it was actually $137...