amphi : What's up with my brakes????

What's up with my brakes????
Post by amphi on May 18, 2006, 10:42am

They make this loud deep screeching sound --- like a semi – during moderate to heavy breaking. My truck is very heavy --- nearly 9,000 lbs with the fire equipment and a full load of water (260 gal). It has a vacuum assist break booster and will stop on a dime. You've heard of coming to a screeching halt --- well this does that --- not tires but brake noise. Really loud very deep squeal. Any ideas?

I have pulled all four drums and nothing seems wrong other than worn lining. Not worn completely out but getting pretty close. The thinnest has about 50 to 60 thousands before contacting the rivets. No oil or fluid leaking on the brakes. Drums look good – maybe a little out of round but all four are smooth and shiny.

I marked each drum and put it back in its original location. I can see by the maintenance records the FD has had these off --- I doubt if they put them back as original. What is the reason for this? Why can't they be rotated or moved about?

The shoes on all four wheels are installed with the small (short) shoe to the front. Is this correct?

Does anyone recognize the brake booster pictured? Record show hydro-vac #379776

Here are some pictures.

http://landru.myhome.net/sivart/rfront.jpg
Right front


http://landru.myhome.net/sivart/lrear.jpg
Left rear


http://landru.myhome.net/sivart/drum.jpg
All look like this


http://landru.myhome.net/sivart/booster.jpg
Brake booster


Thanks for any replies
Gary

Re: What's up with my brakes????
Post by socal715 on May 18, 2006, 10:44am

Looks fine to me... but im not a huge drum brake guy... your rig weighs 9000#'s? and it actually stops with stock brakes? (only kidding)

Re: What's up with my brakes????
Post by amphi on May 18, 2006, 11:18am

Yep!!

Weighed in at 6,745 lbs with me and a half tank of fuel added 260 gals of water at 8.345 lbs per gal. Total 6,745 + 2,169.7 = 8,914.7 lbs



http://landru.myhome.net/sivart/Laoded.jpg
Taken yesterday 05-17-2006 Fully loaded.

See the little sag between the bed and cab.

Re: What's up with my brakes????
Post by socal715 on May 18, 2006, 11:27am

Wow... it barely sagged. I don't think my truck will even move when i load it up tonight to go camping.. probably only weigh in @ 500-600lbs

Re: What's up with my brakes????
Post by brute4c on May 18, 2006, 11:54am

The drums are "indexed" with the hubs for purposes of balance and straightness...

A while back Barrman took his off in order to facilitate turning his drums. He found that each one was off a little in relation to the others and would make turning a drum with one hub have a different true center than it would have if it were installed to a different hub...in other words, each drumand hub needed to stay with each other and stay indexed as they were on the hub...he can explain it better when he has time I am sure...


As far as your booster, never played with one like that so I cant say too much there...I know that a conventional, between the master and firewall, type will give a pedal that is as hard as a rock when they go bad...that may be no help at all to you though.


Ever put a light coat of grease on the back edge of the shoes where they rub on the drum when they are moving? This helps get rid of squeaks and such...the shoe can basically vibrate on the backing plate as the forces are working on it...pushing in with the fluid, trying to be ripped out by the rotation...

Re: What's up with my brakes????
Post by amphi on May 18, 2006, 12:04pm


Quote: <TABLE class=bordercolor cellSpacing=1 width="90%"><TBODY><TR><TD width="100%"><TABLE class=quote cellSpacing=0 cellPadding=2 width="100%"><TBODY><TR><TD width="100%">Ever put a light coat of grease on the back edge of the shoes where they rub on the drum when they are moving? This helps get rid of squeaks and such...the shoe can basically vibrate on the backing plate as the forces are working on it...pushing in with the fluid, trying to be ripped out by the rotation...</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>

Are you talking about where they contact the back-plate? If so I didn't do it but will.

My noise is definitely shoe to drum squeal or growl. I do get some surging.

Re: What's up with my brakes????
Post by brute4c on May 18, 2006, 12:19pm

Yep...a little grease on the backing plat n the area that the shoes hit when they move...obviously not a lot, but some lube to keep them moving freely...

Might have a combo thing going on here....remember this is a guess...

If the shoes are worn to the thin end AND he brak springs arent completely up to snuff, possible that the ccombination of these is letting the shoes "bounce" off the drum as it goes around...not really bouncing as in leaving the surface and coming back to it but losing some of the pressure that should be exerted steadily due to the springs being old and being extended more due to the shoe wear....

Make any sense?

This is a guess, this is only a guess...do not pass go, do not collect $200...

Re: What's up with my brakes????
Post by amphi on May 18, 2006, 12:28pm

Sounds reasonable!! Gotta go --- I'll be back to check this thread later.
Thanks
Gary

Re: What's up with my brakes????
Post by kaiser715 on May 18, 2006, 12:40pm

Ummm, so what if you've mixed the drums up...any way to get them matched up again?

How do they line'em up in the first place????

Re: What's up with my brakes????
Post by drvnkaiserdaily on May 18, 2006, 12:52pm

I have found as the lining on the pad gets thin,it will allow the metal part of the shoe to contact the lip at the back of the braking surface of the drum(inside edge of drum sometimes gets a lip just past where the pad wears) that ridge sticking up from the drum can contact the shoe just past the outer edge of the lining and cause the metallic sound you have described

Re: What's up with my brakes????
Post by thetroublemaster on May 18, 2006, 1:59pm

A squeal is a high speed vibration or chatter. Super suggestions above. Can you see any evidence of the brake shoe frame contacting the drum like DKD mentions above? I would doubt you are getting the squeal from the shoe lining and drum. I always lube the raised pads on the backing plate. You could try replacing the brake shoes. Use quality material. I would not turn the drums at this point. They look OK plus they are rare. I scuff them up with some 36 grit and stop easy for a few days. Never had a problem with that method. If you do what I just mentioned, don't glaze the shoes by stopping to hard with all that weight. Stop very easy for about a week. I just did this on my CJ and the brakes work very well.

So... What they said...LOL

Re: What's up with my brakes????
Post by elwenil on May 18, 2006, 2:18pm

Another point on the grease on the shoes is to use the correct grease. Wheel bearing grease will turn watery and run off if it gets too hot. For this reason there is a special high temp grease used for this.

Re: What's up with my brakes????
Post by barrman on May 18, 2006, 3:02pm

I have a spare set of axles. I am also an auto tech teacher. I had my students take each corner of the spares apart, clean them, put one hub on the brake lathe and turn all 4 extra drums. I then swaped out everything hub, shoes, backing plate, bearing, seals, nuts, wheel cylinders one corner a day on my then daily driven M715. The more corners I changed out, the more my neck hurt from the surge. So, once I got all 4 swapped out. I took each hub and drum, put them on the brake lathe and figured out which of the three possible positions had the least amount of run out. I then stamped the hub and drum so I would be able to find it again and turned the drums to smooth. I now have no surge.

I did however get a very bad squeal from both back brakes when I was done. I could only stop it by backing off the adjusting screw one click at a time, drive it, listen and keep on backing off until each one was not making as much heat. Therefore, I personally feel your squeal is a result of the load you have and maybe one or two of your brakes being adjusted a little bit tighter than the others.

Remember, drum brakes are not self adjusting and only move as far as the fluid pulse lets them on the first pump. Try pumping the brakes once or even twice the next time you hear the noise. If the noise is gone after a pump or two. Then you have at least one corner not adjusted right and not contributing to your stopping power. You take away 25% of your braking surface when you are already at max gross load and it makes a huge difference.

Re: What's up with my brakes????
Post by robertcowan on May 18, 2006, 4:21pm

THEM BRAKE DRUMS HAVE BEEN BLUE HOT. you can see it in the pix. what you,ve done is cristalize your brake shoes. they,ll do it from now on till you change the shoes. thats why semi,s do it because they get em too hot at times like on long down grades or panic stops loaded heavy.
bob

Re: What's up with my brakes????
Post by robertcowan on May 18, 2006, 4:22pm

kevlar linnings help some too.
bob

Re: What's up with my brakes????
Post by brute4c on May 18, 2006, 4:35pm

Thanks for the info Tim....I wish my brakes had been treated to your level of workmanship BEFORE the fire...

Re: What's up with my brakes????
Post by 919maint on May 18, 2006, 8:49pm

I had a booster like that once on a Chevy Grain/Farm truck. It works like any of the old 1950's large truck ones, that boost using Vac. Works great when they work.

Re: What's up with my brakes????
Post by amphi on May 18, 2006, 11:17pm


Quote: <TABLE class=bordercolor cellSpacing=1 width="90%"><TBODY><TR><TD width="100%"><TABLE class=quote cellSpacing=0 cellPadding=2 width="100%"><TBODY><TR><TD width="100%">Ummm, so what if you've mixed the drums up...any way to get them matched up again?

How do they line'em up in the first place????</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>

Kaiser: I am wondering the same thing? I just think the FD mixed them up or at least didn't keep them aligned as original.



Quote: <TABLE class=bordercolor cellSpacing=1 width="90%"><TBODY><TR><TD width="100%"><TABLE class=quote cellSpacing=0 cellPadding=2 width="100%"><TBODY><TR><TD width="100%">I have found as the lining on the pad gets thin,it will allow the metal part of the shoe to contact the lip at the back of the braking surface of the drum(inside edge of drum sometimes gets a lip just past where the pad wears) that ridge sticking up from the drum can contact the shoe just past the outer edge of the lining and cause the metallic sound you have described</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>

drvn: Didn't see any evidence of rubbing at the top of the shoes but have to admit I didn't look at the bottom --- could be hitting there. I'll check later. Thanks


Quote: <TABLE class=bordercolor cellSpacing=1 width="90%"><TBODY><TR><TD width="100%"><TABLE class=quote cellSpacing=0 cellPadding=2 width="100%"><TBODY><TR><TD width="100%">A squeal is a high speed vibration or chatter. Super suggestions above. Can you see any evidence of the brake shoe frame contacting the drum like DKD mentions above? I would doubt you are getting the squeal from the shoe lining and drum. I always lube the raised pads on the backing plate. You could try replacing the brake shoes. Use quality material. I would not turn the drums at this point. They look OK plus they are rare. I scuff them up with some 36 grit and stop easy for a few days. Never had a problem with that method. If you do what I just mentioned, don't glaze the shoes by stopping to hard with all that weight. Stop very easy for about a week. I just did this on my CJ and the brakes work very well.

So... What they said...LOL</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>

thetroublemaster : This low-pitched sound happens at slow speed just before coming to a hard stop. It doesn't sound like metal to metal (no grinding) just a deep squeal. You are right --- I wont have the drums turned but since this is a 4x4 and I can spin the two wheels on one side a time I might try the sticky-backed sandpaper trick on old shoes to true them up a bit. Ever done this?

I definitely will replace the lining with good stuff and follow your advice. Thanks



Quote: <TABLE class=bordercolor cellSpacing=1 width="90%"><TBODY><TR><TD width="100%"><TABLE class=quote cellSpacing=0 cellPadding=2 width="100%"><TBODY><TR><TD width="100%">Another point on the grease on the shoes is to use the correct grease. Wheel bearing grease will turn watery and run off if it gets too hot. For this reason there is a special high temp grease used for this. </TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>

elwenil : Will do. Thanks


Quote: <TABLE class=bordercolor cellSpacing=1 width="90%"><TBODY><TR><TD width="100%"><TABLE class=quote cellSpacing=0 cellPadding=2 width="100%"><TBODY><TR><TD width="100%">So, once I got all 4 swapped out. I took each hub and drum, put them on the brake lathe and figured out which of the three possible positions had the least amount of run out. I then stamped the hub and drum so I would be able to find it again and turned the drums to smooth. I now have no surge.</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>

barrman: My pea brain is not quite absorbing this!! Did you grab the inside of the hub for center (bearing surface)? Did you turn the drums while mounted to the hubs with the three countersunk screws? Do you think maybe this means the hubs are machined this way at the factory?


Quote: <TABLE class=bordercolor cellSpacing=1 width="90%"><TBODY><TR><TD width="100%"><TABLE class=quote cellSpacing=0 cellPadding=2 width="100%"><TBODY><TR><TD width="100%">I did however get a very bad squeal from both back brakes when I was done. I could only stop it by backing off the adjusting screw one click at a time, drive it, listen and keep on backing off until each one was not making as much heat. Therefore, I personally feel your squeal is a result of the load you have and maybe one or two of your brakes being adjusted a little bit tighter than the others.</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>



Quote: <TABLE class=bordercolor cellSpacing=1 width="90%"><TBODY><TR><TD width="100%"><TABLE class=quote cellSpacing=0 cellPadding=2 width="100%"><TBODY><TR><TD width="100%">Remember, drum brakes are not self adjusting and only move as far as the fluid pulse lets them on the first pump. Try pumping the brakes once or even twice the next time you hear the noise. If the noise is gone after a pump or two. Then you have at least one corner not adjusted right and not contributing to your stopping power. You take away 25% of your braking surface when you are already at max gross load and it makes a huge difference. </TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>

barman: Great idea I will do this first!!! The sound seems to be from the rear and they are worn a little more than the front. Will give it a go. Thanks




Quote: <TABLE class=bordercolor cellSpacing=1 width="90%"><TBODY><TR><TD width="100%"><TABLE class=quote cellSpacing=0 cellPadding=2 width="100%"><TBODY><TR><TD width="100%">THEM BRAKE DRUMS HAVE BEEN BLUE HOT. you can see it in the pix. what you,ve done is cristalize your brake shoes. they,ll do it from now on till you change the shoes. thats why semi,s do it because they get em too hot at times like on long down grades or panic stops loaded heavy.
bob</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>

Robert: The color reproduced by the camera is not very good. These drums all look normal -- very bright cast steel color no bluing, crazing, cracks, or scaring. They still have some paint on the inside. The shoes, on the other hand, could be crystallized. I did see some flaking on one edge. Yes they need to be replaced with a good quality lining.
Thanks.


Quote: <TABLE class=bordercolor cellSpacing=1 width="90%"><TBODY><TR><TD width="100%"><TABLE class=quote cellSpacing=0 cellPadding=2 width="100%"><TBODY><TR><TD width="100%">I had a booster like that once on a Chevy Grain/Farm truck. It works like any of the old 1950's large truck ones, that boost using Vac. Works great when they work.</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>

919maint: Thanks – I have no idea what this came from or where to get parts. It is a single line system hooked to the stock single reservoir master cylinder.

Thank you all for the great advice. I'll keep you posted.

Re: What's up with my brakes????
Post by osut362 on May 18, 2006, 11:31pm

your brake booster is called hydro-vac, I have a working '54 chevy dump truck and my brake booster looks like the one in your 1st picture. i had to have mine rebuilt last year. they must have gold plated the inside for what it cost...stops good however.

Re: What's up with my brakes????
Post by barrman on May 19, 2006, 12:35pm

The stock brake drums are too big to mount on a normal automotive sized brake lathe. Therefore, you need to mount the hub to the lathe first. I use wedge or actually rounded ball shaped collets that fit inside the bearing outer race to mount the hub to the lathe. So, the bearing race placement is what centers the hub. I only tested one hub, but it had less runout than the tolerance on the brake lathe shaft. That means that any runout I had on the hub could have been the hub or the lathe itself. I think it was less than .003" if I remember right.

Now, here is the weird part. When you add a drum, the runout on the drum will change depending on which of the three possible ways you can bolt the drum to the hub with the three set screws. I tried all three locations and marked the best. that is when I went ahead and cut the drums to make them as round as possible. I cleaned all the dirt and paint off the hub mounting surface and the drum mount surface. I don't know if our drums are just "Lowest bidder" huge tolerance parts or the center of the hubs are that off center from the factory and the extra size of the drum makes the small runout at about 4" really evident at 13".