a question about mini-maxes...? ANy one have good info on them?

zubzub · February 13, 2009, 01:11:35 PM

A recent thread opened my eyes to the possibility of a quick change over to spring brakes for my 4104. The brake mounts for my 4104 are aluminum ( I think) so I was not looking forward to changing the mounting points so as to fit 30/30s back there. If anyone knows about the mini maxes I would be very grateful...
The questions I have:

Are they as strong as the 30s? I have read a few threads that say they bolt right in, but...DO they have the same throw/strength as the 30s (or the stock cans if their throw/strength is shorter)?

RJ · February 13, 2009, 02:06:12 PM

Zub -

Mini-Max brakes have been off the market for over 15 years, IIRC they were pulled after the company that manufactured them got involved in some liability lawsuits and lost.

The mounting brackets for the OEM brake pots are steel, not aluminum, on your 4104.

Hope you can weld, because it's virtually impossible to find a professional welder who will move the brackets - liability issues.

DD3 cans will fit on your '04 as is, with the additional plumbing necessary, albeit lots more expensive than spring brake cans.

FWIW & HTH. . .

gus · February 13, 2009, 02:56:33 PM

Zub,

My 4104 came with spring brakes when I bought it in '05 and I was told they were new. They looked new and it appeared that my complete brake system had been replaced.

My understanding is that there are two sizes of spring brakes and only the smaller ones will fit an '04.

I have never looked at them closely so don't know exactly what I have.

I might be able to get a photo in a day or two but right now I can't get under the bus.

They work great.

uncle ned · February 13, 2009, 03:34:44 PM

On one of my 04's #172 the brackets are aluminum on the newer one they are steel. both have spring brakes.

Just get the right ones and it is not to big of a job to replace.

also get rid of the johnson bar parking brake, and cover up the air hole in the floor.

uncle ned
"huggy bear"

JackConrad · February 13, 2009, 03:52:14 PM

Brake cans are listed as a 12, 16, 24, 30, etc. The number is the square inches of the rubber diaphragm surface area. This number times brake application pressure (PSI) is the amount of pressure that is applied to the slack adjuster. The larger the number, the more pressure that is applied when braking. This is also used to control relative amount of braking force per axle, largest on drive axle, smaller on front axle and even smaller on tag axle to prevent locking up the tag wheel.
A 30/30 DD3 would have more emergency braking pressure than a 24/24 DD3. 2 numbers are used on drive axle brakes, one number is service diaphragm and the other number is emergency/parking brake diaphragm. I don't remember which number is which (I think the first number is emergency/parking and the second is service brake), but I have seen 24/30 spring brakes. Jack

zubzub · February 14, 2009, 07:16:59 AM

Quote from: uncle ned on February 13, 2009, 03:34:44 PM

On one of my 04's #172 the brackets are aluminum on the newer one they are steel. both have spring brakes.

Just get the right ones and it is not to big of a job to replace.

also get rid of the johnson bar parking brake, and cover up the air hole in the floor.

uncle ned
"huggy bear"

I guess what I am looking at is what the cans that can be installed without mods are. I will need to get under there and take some measurements, but I was hoping to hear that there is a strong enough spring brake that will fit. There are definatly 2 schools on this as I have heard there is not way to install spring brakes without welding on a new support. On steel that would already be a challenge and I checked the book and on mine the suspension arm is aluminum. Is there any chance Uncle Ned knows the # for his spring brake?

Len Silva · February 14, 2009, 08:00:20 AM

There is no problem installing spring brakes on a 4104. It's the 4106 that starts having a space issue. There is no reason to go to mini-max or DD3. Just plain old NAPA 30-30's will work fine. You just need the added plumbing for the park brake. Schematics are available at Bendix

Sojourner · February 14, 2009, 08:22:19 AM

Gus and Uncle Ned...could you if you can or will post a photo or two of the spring can set-up for us (or me)?
Like at to the list of bus's brake system.

Thank you so much, Gerald

RJ · February 14, 2009, 10:11:10 AM

Quote from: Len Silva on February 14, 2009, 08:00:20 AM

There is no problem installing spring brakes on a 4104. It's the 4106 that starts having a space issue.

Len -

I'm curious about your comment that the '06 has space issues compared to the '04 for spring brakes. Especially since the undercarriage construction and dimensions of the two models are virtually identical. (I know the '04 uses air beams and the '06 rolling lobe bellows, but that, and the different off-set to the rear axle pumpkin, are the only major differences in the rear axle area, TTBOMK.)

Please clarify. . .

Len Silva · February 14, 2009, 10:21:18 AM

Never having been under a 4106, I can't tell you the difference. I do know for sure that standard spring brakes will fit a 4104 without interference.

gm4106 · February 14, 2009, 02:07:06 PM

I'm curious about this too. Maybe Uncle Ned or Gus could get some pictures for us. If not to much trouble
thanks guys

zubzub · February 15, 2009, 08:15:22 AM

Len, if what you say is correct you have made my weekend! I always presumed that as the 4106 was so much like the '04 the rear would be the same, but then I have only recently learnt the '06 doesn't have air beams. Spring brakes have been my #1 mod (with jakes #2) for my 4104. I have always worked the brakes and suspension first on my old rides, and left the body work last as I don't care so much about looks as the safety, Guess I'll pick up a 30/30 and see if it fits and then Bob's your Uncle.

Len Silva · February 15, 2009, 08:55:04 AM

Check it out here:

http://www.coachinfo.com/Manuals/Coach/GMC/4104.html

PD4104 Spring Brake Conversion Procedure Guide for installing spring brake chambers and update to the E-Model brake foot valve on the PD 4104. Comes with air system diagram and parts information.

zubzub · February 16, 2009, 06:28:41 AM

Hi Len, before I put down my $ on this do you know if I need this? Seems with a little research I should be able to install spring brakes and the air lines to control. The air valve has me ? as well. Need to see what I have, I'm guessing that mine has already been replaced once as it is very responsive and tight as a drum (by which I mean no leaking not tight to operate).

Len Silva · February 16, 2009, 09:18:44 AM

My guess is that if you are comfortable figuring it out yourself, you don't need the coach info stuff. Your treadle is probably fine. You can find the plumbing diagrams for spring brakes all over, most notably the Bendix Air Brake Handbook. You can download it here: http://www.bendix.com/EN-US/SERVICE/LIBRARY/Pages/Home.aspx