| Author | Message | ||
| george bruton (Tazman632000)
Registered Member Username: Tazman632000 Post Number: 33 Registered: 2-2007 Posted From: 65.184.69.36 Rating: N/A |
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 | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 290 Registered: 8-2006 Posted From: 76.168.69.233 Rating: N/A |
A couple of thoughts: If it doesn't pull to one side while stopping, the fronts are ok. The rear drums and shoes are essentially twice the size of the fronts, and do twice the work. A quick easy test is to pull the parking knob at about 5 mph. The bus should stop fairly quickly. If it just "glides" to a stop, look at the rears. BLOCK IT UP SECURELY AT THE JACKING POINTS WITH GOOD BLOCKING MATERIAL, before going under, or between tires and fenders! It sounds to me like it should stop better than it does. Well adjusted brakes shouldn't have more than about 3/4" travel... Look at the rear drums for signs of oil leakage. Do you have about 120 lbs of reservoir pressure? HTH, George | ||
| george bruton (Tazman632000)
Registered Member Username: Tazman632000 Post Number: 34 Registered: 2-2007 Posted From: 65.184.69.36 Rating: N/A |
yes i have 120 psi on the tank my 4106 has the icc brake valve its a lever you flip to apply the emergency brakes | ||
| Larry D Baker (Lbaker4106)
Registered Member Username: Lbaker4106 Post Number: 71 Registered: 5-2005 Posted From: 207.69.137.24 Rating: N/A |
I had the same condition on my 4106 and found the rear brakes needed adjusting. Adjusted the brakes and now I have to be careful how hard I push the brake petal. | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 291 Registered: 8-2006 Posted From: 76.168.69.233 Rating: N/A |
George, You should also have a parking brake knob, which you pull to apply, or a manual parking handle. DO NOT count on the ICC lever to hold the bus while parked, because the brakes will release as soon as the air leaks off. The ICC lever applies the rear brakes only, (if I remember correctly) so it would be a good test of the rears also. You should get an abrupt stop from 5 mph or so with it, again, if you don't, look at the rears. George | ||
| george bruton (Tazman632000)
Registered Member Username: Tazman632000 Post Number: 35 Registered: 2-2007 Posted From: 65.184.69.36 Rating: N/A |
mine has a manual lever its the lever is out right now as im working on the front floor area. does the lever apply the rear service brakes or a drive shaft brake? | ||
| Nathan S. Cornell (Gampyn8)
Registered Member Username: Gampyn8 Post Number: 4 Registered: 10-2007 Posted From: 66.82.9.57 Rating: N/A |
You may also want to check to see if new brake drums were installed. New shoes and new chambers are good but if the drums are wore(grooves or ridges in them)they will not work as well either. New drums are not installed every time new shoes are. Slack adjusters should be turned in until tight then back off 1/4 turn. You also need to make sure the locks work on the slack adjusters or they will not stay adjusted. This is assuming you have cam brakes and not the wedge style. | ||
| Dan West (Utahclaimjumper)
Registered Member Username: Utahclaimjumper Post Number: 73 Registered: 1-2005 Posted From: 208.66.38.115 Rating: N/A |
George, the lever applies brakeing to a drum thats mounted on the pinion shaft of the rear end.>>>Dan | ||
| george bruton (Tazman632000)
Registered Member Username: Tazman632000 Post Number: 36 Registered: 2-2007 Posted From: 65.184.69.36 Rating: N/A |
THE DRUMS Were in good shape no groves and i checked the slack adjusters. 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 | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1144 Registered: 5-2001 Posted From: 65.74.67.83 Rating: |
George, you have an air leak; there is a good chance it is serious. You don't need to take the wheels off to find the air leak; a rear pot, hose, tubing or valve is probably the culprit. Once the coach is blocked so that it can't settle down on you while you're under it, your ears and a pistol grip spray bottle with soapy water are the tools of choice. Your bus will never behave like a car; it wasn't designed to. It also won't behave like a rental truck because the truck brakes are designed to work with twice their empty weight. The coach will be near it's loaded weight if it has already been converted. Even if it hasn't, it will be 2/3 of it's loaded weight when empty. There have been many reports that the treadle valve on an intercity bus was designed to apply a reduced force to the brakes when used normally to avoid throwing passengers around from panic stops. If you want to know if the treadle valve is applying all the available air pressure to the brakes, it can be measured by connecting a gauge to the treadle valve. We have installed a dual needle gauge so that we can see the application pressure anytime that we use our brakes. If the brakes are adjusted properly, the angle of the slack adjuster gives the best mechanical advantage; as they become out of adjustment, the advantage is gradually lost. To find out if they are adjusted, set the Johnson bar hand brake with air up but engine off. Have someone sit in the driver's seat. You get near each wheel so that you can look under with a flashlight and see the opposite wheel slack adjuster. When you can see the adjuster, tell the person helping you to step on the brake treadle. You will see the slack adjuster rod move. Normal travel is around an inch. Normal pots have a little less than three inches of travel. If you heat the drums up while coming down a grade, they will expand. When they do, you will have more travel at the rod. If your brakes are out of adjustment, and you come down a long grade, it is entirely possible to have the travel increase to the pot's limit. If that happens, the brakes will start fading. This is why the brakes must be kept in adjustment. It's also part of the reason they are so easy to adjust. I hope this discussion helps put you on the right track. Good luck. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 292 Registered: 8-2006 Posted From: 76.168.69.233 Rating: N/A |
George, As you can see, Tom just got my vote! You may be able to find your leak thru the engine room, but whatever you do, DON'T GO UNDER AN AIRED UP BUS, OR BETWEEN THE TIRES AND FENDERS, without blocking it properly at the jacking points. There was a fatality caused by this a month ago. Don't let the bus roll away either!! George | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1318 Registered: 12-2000 Posted From: 67.181.166.160 Rating: N/A |
George MC-6 - It's quite rare to find a push/pull emergency/parking brake on a 4106. The 4106 was the first GMC parlor coach to offer DD3 brakes as an option. Very few operators chose them, preferring to "stick with what we know". Some conversion folk have changed over to spring brakes (Tom's one), but that also requires that you know how to weld, because there just isn't room behind the rear baggage bin bulkhead and the axle. The mounts for the brake pots have to be cut off and re-welded in a different position to squeeze spring brake cans in there. George B - Tom's given you excellent advice! I, too, suspect an air leak, possibly a blown diaphragm in one of the rear brake cans. However, it is possible that you will only have an air leak with the ICC valve in the "on" position, in which case that's a different problem. But before you start jacking the coach up and spending $$ fixing things, surf over to the "Articles of Interest" section of this BBS and check out the "Pre-Trip Inspection." In that you'll find an air brake check procedure, something that should help you work through this. IBME that most busnuts, unless they've been trained, have no clue about this very important SAFETY procedure. And sadly, very few of those who have been trained actually use it regularly. . . Obviously the brakes should be adjusted properly, - any possibility you can get the coach over a pit? That makes it very easy to do. BTW, on a two-axle coach such as yours, 60% of the braking is done by the rear axle. FWIW & HTH. . .  | ||
| William Sloan (Ole_timer)
Registered Member Username: Ole_timer Post Number: 10 Registered: 9-2006 Posted From: 71.82.100.232 Rating: N/A |
George If new chambers were just installed ,the rod adjustment to the slack adjusters may not be right and you won`t get all of the braking power.When the brakes are applied the rod and the slack adjuster arm should form a 90 degree angle.If the brakes are adjusted and you don`t have 90 degrees pull the pin on the clevis and loosen the lock nut and turn the clevis in or out as needed.Readjust the brakes as needed. Good Luck Ole Bill | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 294 Registered: 8-2006 Posted From: 76.168.69.233 Rating: N/A |
RJ, Please read the first line of my first post of 11/12, as it does mention "manual parking handle." As the ICC valve puts reservoir pressure directly into the rear diaphragms, thru a tee with the treadle valve, I think the leak will be there with a foot application also... Bill, I know what you are getting at, but changing the clevis position on the rod doesn't change the relation of the rod to the slack adjuster. The rod to the adjuster arm angle varies (and worsens) as the brakes go out of adjustment. FWIW, George | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1319 Registered: 12-2000 Posted From: 67.181.166.160 Rating: N/A |
George MC-6 - Oops, missed that! My comments were based on your first post dated 11/11. Thanks for catching me being asleep at the keyboard. Will be interesting to see what he finds as the saga continues. . . | ||
| george bruton (Tazman632000)
Registered Member Username: Tazman632000 Post Number: 37 Registered: 2-2007 Posted From: 65.184.69.36 Rating: N/A |
ok i can hear the air leaking with the brake pedal applied. i also flipped the icc valve while ai was moving the bus around the yard and the brakes seem to lock harder than using the brake pedal? | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1145 Registered: 5-2001 Posted From: 65.74.67.83 Rating: N/A |
George, the treadle has no effect once you throw the ICC lever because ALL available air is applied to the rear cans and nowhere else. That's if nothing has been modified. Thowing the ICC lever is the equivalent of stomping on the treadle valve, but with only 2/3 of your brakes. Good luck. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska | ||
| William Sloan (Ole_timer)
Registered Member Username: Ole_timer Post Number: 11 Registered: 9-2006 Posted From: 71.82.100.34 Rating: N/A |
Hi George Todd Your are right,the rod does not change the angle,but the location of the clevis or yoke as GM calls it will change the angle of the slack adjuster arm.GM calls for no less than 90 degrees with the brake applied. If the arm goes to less than 90 degrees you loose a lot of leverage.If the rod is too long and interferes with the slack adjuster arm where it goes through the clevis it has to be cut off. I had to do that when I put Mini-Max on My 04. Good Luck Ole Bill | ||
| george bruton (Tazman632000)
Registered Member Username: Tazman632000 Post Number: 39 Registered: 2-2007 Posted From: 65.184.69.36 Rating: N/A |
i guess i need to word my post different i just used the icc valve as i was moving aroung the yard as soon as i flipped the switch it would come to abrupt stop then i tied to compare it with just the treadle and the icc lever off seemed to stop better with just turning the icc valve on than using the brake treadle | ||
| RJ Long (Rjlong)
Registered Member Username: Rjlong Post Number: 1320 Registered: 12-2000 Posted From: 67.181.166.160 Rating: N/A |
George B - I think it would be well worth your time to read this long thread regarding brakes. Be sure to follow the various links to additional info, too. Here's the first post in the thread: http://www.busconversions.com/bbs/index.php?topic=1489.msg12432#msg12432 FWIW & HTH. . . |
