gm 4106 brake question

4106-123 · November 11, 2007, 01:51:52 PM

just got back from hour drive in the bus and have some question about the brakes. ive only driven it 3 hours from on the purchase trip back home and then today. i put new shoes and chambers on the front and the po had a receipt for the back brakes being redone, any way as i was making stops i was trying to gage the stopping distance and i would mash the brakes pretty hard and it would stop ok but never gave that good hard stop like cars do im used to the more you press on the pedal the faster it stops. should you be able to lock the wheels with the brakes? they just dont feel right to me but ive never driven a coach before so i dont have any thing to compare it to. ive driven some of the bigger ryder box trucks with air brakes and they stop really well. how does one tell if the brakes are working as they are supposed to. when i put the brakes on the front i adjusted the slack adjuster one side but i havent done the other. they are new shoes so i would think the chamber would have plenty of throw, this has me really concerned! any imput or sugestion would be grateful thanks george

TomC · November 11, 2007, 03:53:18 PM

If the brakes are cold and you mash the pedal all the way to the floor, it should skid the tires. If not, may need to be adjusted. Do you know how to adjust the brakes? Good Luck, TomC

Don4107 · November 11, 2007, 04:01:58 PM

Don't understand why you would only adjust one side.

A slack adjuster has a 'mile' of adjustment. You may have zero brake on that side. If increasing the pressure on the brake petal is not increasing braking action then your brake chambers may be at max throw. Not good!!! If you put new shoes on did they match the arc of the drums?

I would find someone qualified to work on brakes that will show you how to inspect and adjust brakes. There is more to it than cranking on the adjuster. One thing that should be included in any brake adjustment is a test drive and a check of drum temps. To tight is not good either.

Having spent many hours herding trucks around grain fields, the last thing we wanted was a tight brake setting fires, so we ran them on the 'loose' side. Just tight enough to hold with a full load on good slope. I have the habit of popping the parking brakes while still rolling a bit. If they don't hit with good authority, time to see why not.

Good luck

4106-123 · November 11, 2007, 04:31:12 PM

i just didnt get around to adjust the one side i measured the front drums a 14.5 inches and the guy at mohawk manufacturing gave me the correct shoes. the side adjusted felt warm after a stop half way thru the drive today so i may have one side a little a little tight. i would think adjusting the slack adjuster so the wheel wont turn then backing off until it rottates frely would be the correct way to adjust them? the front wheel bearing seals were leaking so i replaced every thing. i was thinking of using the icc brake at a slow speed to check how the back brakes are working?i have a suspicion some thing is going on with the rear brakes

Don4107 · November 11, 2007, 06:10:22 PM

Could also be that the warm side was working ie helping to stop you and if the other was cold it may not be braking at all. Did you check the rear drums? Temp of course depends on how many brake applications over a given amount of time.

Always a good idea to hold the new shoe against the drum to check for proper fit before installing. If the drums have been turned one or more times they may not match up well. All things considered, the expense and work involved, new drums can be cheap.

Tony LEE · November 12, 2007, 12:02:25 AM

With car hydraulic brakes the only limit to the amount of pressure is how hard you can push on the pedal. With air brakes the maximum pressure is whatever the brake pressure regulator is set at - no matter how hard you press.

I've seen information on relative breaking performance for various heavy vehicles and it was stated that buses are set up so as not to be able to skid the tyres. Perhaps it is because of the relatively long wheelbase where locking the back wheels up would result in a lot of sideways skidding compared to shorter wheelbase trucks and prime-movers.

4106-123 · November 12, 2007, 03:53:15 PM

today i aired the bus up and flipped the icc brake switch and when to the back of the bus and i could hear air dumping out around the back wheels? i guess i need to pull the rears off and look at whats going on any hint on jacking up the rear of the bus? thanks george

gomer · November 12, 2007, 05:53:31 PM

George: first thing you do is BLOCK the bus up when air is built up. leave the park brake OFF if you can if not scotch the wheels in the front and rear. DO NOT DO ANYTHING UNLESS YOU HAVE SECURED THE COACH.
WE have lost several busnuts because of the bus not being blocked solid. now! shut down engine and apply parking brake. Run to the rear and listen to which side the air is coming from. Let the air go down to 0. Jack up the axle just to get the wheels off the ground. My thoughts are the dd3 brake chambers need rebuilt and parts are a lot cheaper than a rebuilt dd3. Luke has the diaphrams, which takes 2 for each rear wheel. most times you dont have to remove the wheels if you can crawl under the coach. if the diaphrams are bad replace both sides to be safe. take the slack adjusters and turn them all the way LOOSE and then remove the clevis pin onthe chamber, remove the chamber and mark it so the air lines will re-align up and remove the bands and clean the chamber and replace diaphrams and reverse installation WHEW I am done

roadrunnertex · November 13, 2007, 06:45:23 AM

If I read a previous above post right it's where the 4106 owner flips the ICC park brake valve on?

Correct?
OK! I do not think this coach has the DD3 rear brake chambers.But just standard brake chambers with one hose going to each chamber.
But hey! I have been wrong before with these old buses who knows who or what has been done to them in previous years.

jlv