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Author Topic: Broken brake drum  (Read 2805 times)
Sam 4106
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« on: March 06, 2013, 05:55:26 PM »

Can a brake drum be broken by over tightening the lug nuts? I had new steer tires put on the bus Monday, and today when I was under the front greasing and planing to adjust the brakes, I noticed a broken drum. The guy that put the tires on my aluminum wheels also spun the impact socket against the wheel. Apparently he never heard of a plastic shield to prevent wheel damage. I noticed the damage when I was letting air out of the tires. They were inflated to 120 PSI. Rode like a lumber wagon on the way home. Everything considered, I wish I had installed the tires myself. Hindsight. I called the shop manager to tell him of the damaged wheels, and he responded that he would get 2 wheels coming. Hopefully he follows through on that. I don't want to drive the bus back to the tire shop until I get a new brake drum installed. I hope I can get a drum locally.

Thanks for any advise, Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
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« Reply #1 on: March 06, 2013, 06:01:15 PM »

Would you quantify broken? I assume cracked...
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« Reply #2 on: March 06, 2013, 06:06:45 PM »

Sam, you will not break a drum with over tightening the lug nuts a wheel yes
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Sam 4106
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« Reply #3 on: March 06, 2013, 06:19:21 PM »

John,

I called the drum broken because there is about an 1/8 crack from the inner edge all the way to the wheel. I won't remove the wheel  until the shop manager comes to my shop to look at the damaged wheels. I don't want any doubt that his guy caused the damage.

Clifford, thanks for the info that over tightening the lug nuts won't crack a drum.

Thanks for the quick responses, Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
Sam 4106
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« Reply #4 on: March 07, 2013, 05:23:57 AM »

I have a '76 MCI 8. In order to try to get a new front brake drum locally, I think it would be useful to know the brand of the axle. I've looked in both the parts and maintenance manuals but can't find that information. I found that the rear axle is Rockwell, can I assume the front is also Rockwell?

Thanks, Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
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« Reply #5 on: March 07, 2013, 06:10:17 AM »

Sam,on the drum dig around and you will find a Webb number any truck place can match it for you,Nicks Truck Parts 1-877-428-9683 are good at matching with measurements I buy Eagle drums there for around 100 bucks each and most of the time it's free shipping fwiw and DuraBrake is a good resource also

good luck
« Last Edit: March 07, 2013, 06:55:58 AM by luvrbus » Logged

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TomC
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« Reply #6 on: March 07, 2013, 07:14:53 AM »

When buying a new drum, there are two different types of drums. One is a cast drum. They are one piece cast iron and should have some sort of balancing weight on them-these are the cheapest. Second is the cast iron with steel insert. Meritor makes these under the name of Steelite, and also there is Centrifuse. These have a cast iron outside with a steel insert where the brake pads rub against. Advantage to these-these are the best drums-they can get 3-5 lining changes (compared to replacing the cast iron drum at most every lining change [course this isn't that important to us]), they are lighter since steel is much stronger then cast iron, they are more resistant to heat cracking. Disadvantage-more expensive.

We carry the normal truck drum (16.5x7) for $85.00. A Centrifuse drum will be roughly twice that. I have 14.5 x 7 fronts-that will be more expensive then the truck drums. Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #7 on: March 07, 2013, 07:57:33 AM »

Sam

C&J in Minneapolis has a big inventory of brake drums. Call JD there and they'll hook you up.

Rick
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Sam 4106
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« Reply #8 on: March 07, 2013, 05:58:22 PM »

I removed the cracked drum and found the Webb number, 64004. It is 14.50" X 5". The new one will be here tomorrow. That number must be the best one that Tom described since it cost $222 plus $20 shipping. There is just over 5/8" of lining on the shoes so I will probably not live long enough to wear them out. I measured the cracked drum, as best I could, and it was still very close to 14.5" so the shoes should fit the new drum OK. All but one of the screws that hold the drum to the hub came out easily. The difficult one I had to give a few raps with a hammer and punch to get it out. so I don't think that drum had been on too long.

Thank you Clifford, Tom, and Rick for your timely advise, Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
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« Reply #9 on: March 08, 2013, 04:03:37 AM »

Hi Sam, how did you make out with your wheels?
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Sam 4106
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« Reply #10 on: March 08, 2013, 08:26:04 AM »

Hi Busn-Gramps,

The tire shop is taking responsibility for the damage and replacing my wheels. I will try to get back to the shop after I get the new brake drum installed. I had considered just picking up the new wheels and changing the tires myself. But, the shop manager wants me to bring the bus to their shop so they can remount and balance the tires for me. I will be very satisfied if they can do the work without further damage. I have an idea that someone, other than the guy that damaged my wheels, will be doing the work this time.

Wish me luck, Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
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« Reply #11 on: March 08, 2013, 03:12:28 PM »

I have to admire that shop manager, so many others make it as hard as possible to get proper work redone.
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Sam 4106
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« Reply #12 on: March 11, 2013, 06:03:16 PM »

I have the new brake drum partly on, but it is being difficult. The 2 drums have the same part number, they measure the same as the flange on the hub, and I have wire brushed and lubricated the flange. Still going on really hard by tightening all ten lug nuts against the drum, by hand with a 3/4" drive socket. Is something wrong, or should the drum fit the flange that tight? I can use my 1" impact if I have to, but I don't want to break the drum or hub flange. Any advise will be appreciated.

Thanks, Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
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« Reply #13 on: March 11, 2013, 07:20:07 PM »

Sam,

Don't tighten them any further until you either get an answer from someone with experience doing this same job here on the board or wait until morning and call JD or Curt, They'll tell you in two seconds whether thats normal or not. Good catching up with you on the phone the other day old friend and we look forward to seeing you and Char this spring/summer.

Take care and give us a call if you need anything,

Rick

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« Reply #14 on: March 11, 2013, 08:21:30 PM »

Drum should go on with a snug fit, not real tight, this could be the cause of the other one cracking. Does the drum and hub have small holes for the flat head screws? If the drum is a nice fit with the studs, you could relieve the center hole hole a little if you can do it fairly evenly. Are your coach wheels hub or stud piloted? You could remove the other front wheel and measure that hub od and drum hole id to be sure your drum is correct before you do anything to it. Oh, and make sure the brakes aren't rubbing/dragging. Did you back them off completely before attempting to install new drum? Was the other drum cut with oversize shoes installed? can you still rotate the wheel while trying to seat the drum?
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Sam 4106
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« Reply #15 on: March 12, 2013, 01:38:11 AM »

Rick and Chessie,

Thanks for your input. I think you are right about the reason for the drum cracking. The drum has the small holes for the flat head screws. Stud piloted. I took the drum back off and found that it is peeling metal off the hub flange for about 1" at every stud. I had only managed to force the drum onto the flange about 3/32". So I think the inner nut on the studs were over tightened when they were installed. I think the studs were changed when the PO had aluminum wheels put on. There is nothing wrong with the drum, the problem is the hub.  The drum fits easily over the brake shoes and the hub spins freely. I did back the brakes completely off to remove the cracked drum and the cracked drum is still the original size of 14.5," as best I can measure it, so I think the shoes are standard too. I will try filing the hub flange by each stud and try to put the drum back on. There will still be plenty of surface between studs to center the drum and the tapered, slotted screws will also help to center the drum. If that doesn't work, I'll have the flange turned so it is concentric, or look for a different hub.

I often lay awake at night pondering a problem and often arrive at a workable solution. But, input from others is valuable in broadening my thought process. This is a case where reading your input got me to thinking in a new direction. Your input is very appreciated.

Thanks, Sam
« Last Edit: March 12, 2013, 01:50:02 AM by Sam 4106 » Logged

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« Reply #16 on: March 12, 2013, 06:14:26 AM »

I have only removed a front drum.  It required a few few raps with a hammer to break the rust loose.  It slid back on quite easily by hand.  Is it possible that your old drum was the wrong part number and that is why it cracked?
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Jim Keefauver/1985 Wanderlodge PT36/6V92TA/MT654CR/East Tn.
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« Reply #17 on: March 12, 2013, 07:46:37 AM »

Could it be that someone has installed the wrong hub (hub piloted) on your bus?  The difference between hub bores on the wheel is 8.669" for hub pilot and 8.722" for stud pilot.  I'm guessing that the drum bores would be the same.
« Last Edit: March 12, 2013, 07:54:42 AM by Len Silva » Logged


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Sam 4106
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« Reply #18 on: March 12, 2013, 09:53:24 AM »

Jim, thanks for the info on how easily the drum should slide on.

Len, you could be right that the front hubs are hub piloted with stud piloted studs. Both the drive and tag axles had hub piloted hubs with hub piloted studs and nuts, but with stud piloted wheels when we got the bus. That allowed the wheels to be off center in any direction and the ride was not smooth as a result. Those were changed to stud piloted hubs and studs from an MCI 9 that a friend was parting out. Since the front axle has stud piloted studs I didn't change those hubs. Even if the front hubs were originally hub piloted they still work as stud piloted with stud piloted studs. The flange that the hub piloted wheels ride on is not the problem. As you point out the hole in a stud piloted wheel is larger than that of a hub piloted wheel. The problem I have is that the outside of the hub flange that the inside ledge of the drum sits on is enlarged at every stud location. The bore of the drum inside the stud holes doesn't rest on the hub flange, there is at least a 1/2" clearance there. Nor are the stud holes in the drum tight fitting, some clearance there too. I hope I have explained the situation adequately, if not ask more questions.

I appreciate all the thoughts that have been offered. Thanks, Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
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« Reply #19 on: March 12, 2013, 09:42:11 PM »

Jim, thanks for the info on how easily the drum should slide on.

Len, you could be right that the front hubs are hub piloted with stud piloted studs. Both the drive and tag axles had hub piloted hubs with hub piloted studs and nuts, but with stud piloted wheels when we got the bus. That allowed the wheels to be off center in any direction and the ride was not smooth as a result. Those were changed to stud piloted hubs and studs from an MCI 9 that a friend was parting out. Since the front axle has stud piloted studs I didn't change those hubs. Even if the front hubs were originally hub piloted they still work as stud piloted with stud piloted studs. The flange that the hub piloted wheels ride on is not the problem. As you point out the hole in a stud piloted wheel is larger than that of a hub piloted wheel. The problem I have is that the outside of the hub flange that the inside ledge of the drum sits on is enlarged at every stud location. The bore of the drum inside the stud holes doesn't rest on the hub flange, there is at least a 1/2" clearance there. Nor are the stud holes in the drum tight fitting, some clearance there too. I hope I have explained the situation adequately, if not ask more questions.

I appreciate all the thoughts that have been offered. Thanks, Sam

Sam,

Are the stud retainer nuts installed correctly and with a proper flat washer? The correct nut is a locking nut. One end is rounded. If they were installed backwards without a washer, it would probably bulge the hub flange as you have mentioned. I was thinking the hub is aluminum, but it's been a few years since I had mine off.

craig

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Craig Shepard
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Sam 4106
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« Reply #20 on: March 13, 2013, 08:17:38 AM »

Hi Craig,

I just went to the shop to see if the nuts are locking, the washers are there, and are installed correctly. They are. I have no idea if the hubs are the right ones for an MC 8, but the ones currently on the bus are cast iron.

I know it is possible to distort cast iron by over tightening bolts because when my brother was helping me change the manual transmission in our 4106 he overtightened the bolts holding the flywheel to the crankshaft. When I installed the new pilot bearing it would not turn freely so I had to put on the flywheel that I got with the transmission. I can't fault my brother because he was in the early stage of Alzheimer's disease and had already lost some of his former capability. He had been a good mechanic his whole adult life and was always willing to help me with projects. He lost his life to Alzheimer's 2 years ago.

I will update when I learn if filing or grinding off the high spots works. Thanks for your thoughts. Sam 
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Sam 4106
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« Reply #21 on: March 13, 2013, 03:50:33 PM »

I used my Dremel tool and a small grinding wheel to slowly take off the high spots of the hub flange. It took five tries but the drum finally slid into place using the five slotted screws to nudge it on. I did the final tightening with the lug nuts before I put the wheel back on and torqued it on. I will have to readjust the brakes after the shoes conform to the new drum. I left them a little loose initially.

Thanks everyone for your help, Sam
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« Reply #22 on: March 17, 2013, 05:09:04 AM »

Sam, I'm kind of concerned about your studs. If the backing nuts were overtightened to the point that it distorted the cast iron hubs, then surely the studs have been stretched which will result in weakened studs that could break. I'm not sure I believe that it's possible to distort the cast hub before the stud breaks, but obviously something is causing the distortion.
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Craig Shepard
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Sam 4106
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« Reply #23 on: March 17, 2013, 12:23:27 PM »

Craig,

Thanks for bringing that to my attention. I had not previously considered that, but I don't think I will change the studs at this time. If there is a problem with them and they do start to fail, I doubt that they will all fail at the same time. If one ever breaks, then I will replace them. There are so many things on a bus that have the potential for catastrophic failure that we live with every day, I am not going to worry about something that is unlikely to fail catastrophically.

Good luck, Sam
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« Reply #24 on: March 17, 2013, 12:42:07 PM »

Without any wheel installed, run a lug nut all the way down the stud by hand.  It should spin on easily and without any change in resistance.  If it starts to bind up anywhere along the stud, that's an indication it may have been stretched.
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« Reply #25 on: March 17, 2013, 03:48:50 PM »

"If there is a problem with them and they do start to fail, I doubt that they will all fail at the same time. If one ever breaks, then I will replace them"
A number of years ago I was getting my 4106 ready for a trip from Vancouver, Canada to California for a race. I had the bus in for service and apparently the tech told me I had 2 broken studs on driver's side rear duals.  I was quite new to buses and I'm sure I thought that even though 2 were broken that left 8 good ones.
Anyway, we were travelling down the I-5 and had just decended from the Sykyous Pass from Oregon to California and I notice a vibration. My son was travelling with me and he suggested I speed up to see if it would go away.  I sped up to 75mph and then returned to 55. A few moments later all hell broke loose as both rear wheels came off the bus and it ground to a halt dragging the left rear. One wheel hit the side of a car with a man and his son in it. Luckily the wheel and car were going the same direction so only minor damage. I remember vividly seeing the second wheel go spinning past me from the fast lane where I stooped to the right lane and into the ditch and a field 1/4 mile away. The cops came and a wrecker hauled the bus to Yrecka where I was able to get it a week later.
When I got home from the trip I mentioned to the mechanic what had happened and he said "I told you that you had 2 broken studs". As I mentioned earlier I am sure my thoughts were that "I still had 8 good one left".

Regards

Fred
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Sam 4106
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« Reply #26 on: March 17, 2013, 06:46:03 PM »

Len,

Your method is reasonable for the wheel end of the studs, but the end through the hub flange is what caused the distortion. I had the lug nuts on and off 5 times, grinding a little off the hub flange until the brake drum would go fully on. The lug nuts didn't ever bind. The tires that were on the aluminum wheels, when we got the bus, were dated 2003, so I think that is when the longer studs were put on. I have no way to verify that because the guy that converted the bus is dead and his widow, that we bought the bus from, knows very little about the bus. The bus was his project. We got a picture book with the bus and there are no pictures with the aluminum wheels showing. No broken studs in nearly 10 years, but I will watch them closely.

Fred,

Thanks for sharing your experience. It I see a broken stud I will have all of them replaced.

Thank you both for your thoughts, Sam
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
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