A drum brake squeal

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Paul Vernon
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A drum brake squeal

#1 Post by Paul Vernon » Fri Mar 05, 2010 11:22 am

Hi All,

I have now done an amazing 500 miles or so in my rebuilt A coupe, but now the brakes are squealing, I've never had drum brakes do this before, all the components are refurbished or new. Any top tips on how to stop it?

Thanks

Paul

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David Jones
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#2 Post by David Jones » Fri Mar 05, 2010 11:33 am

Congratulations on getting the car back on the road. It's probably the salt in the air in Brighton causing the squeal.
Paul, were the leading edges of the brake shoes chamfered? How did you break in the shoes? Knowing the roads around there in any 10 mile drive your brakes get more of a work out than mine do in a week of driving back and fore to work every day, but I would pull one drum and have a look to see if the shoes are at all glazed. If they are then you need to break them in a little more carefully. Check with the friction material supplier for correct break in procedure.
If I had known I would live this long I would have pushed the envelope a little harder.
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Paul Vernon
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#3 Post by Paul Vernon » Fri Mar 05, 2010 11:45 am

David,

Forgive my ignorance, but I didn't know you had to break in the linings. I have no suppliers instructions as the linings came with the car. I'll have a look at the leading edge, if there isn't a chamfer should I file one?

Thanks

Paul

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David Jones
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#4 Post by David Jones » Fri Mar 05, 2010 1:24 pm

Paul;
There are plenty of procedures written about breaking in disc brake pads and rotors but very little about drum brakes any more because they are not very common now. As I raced a car with drum brakes it was common knowledge that one could not go out with new brakes and expect them to work perfectly immediately so there was an established break in procedure and as I mentioned we always put a 45 degree chamfer on the leading edge of the shoe as Porsche also recommend for brake shoes, this lowers the propensity for brake grab and chatter. I would use the brakes early and lightly for the first few dozen applications so as not to overheat them and cause them to glaze over which can cause the squealing. Gradually increase pedal force over the first 500 miles and then they can be considered bedded in. This of course is doing it by the book but use good judgement and sensible brake use and they can be considered bedded in much sooner. I would also examine the drums very carefully to see if there was any component touching the drum which could cause the squeal.
If I had known I would live this long I would have pushed the envelope a little harder.
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Alan Lay
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#5 Post by Alan Lay » Fri Mar 05, 2010 1:45 pm

David, my drums squeal on my T5. I found the brake shoes back edge hits the backing plate. I put a little grease on the edge and the squeal goes away. However, over time it comes back as the grease is removed.

Have you had that problem?

Alan

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Bob Blackwell
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Squeaking Brakes

#6 Post by Bob Blackwell » Fri Mar 05, 2010 7:55 pm

Please don't put any grease on your brake shoes to stop the noise! Use a file or some abrasive paper to chamfer (taper?) the edges and remove the squeaking noise. If necessary, the drums may need to be turned on a lathe to restore the proper shape. Brakes and grease do not mix. Good luck, Bob Blackwell.

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Steve Domenicone
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#7 Post by Steve Domenicone » Fri Mar 05, 2010 8:06 pm

I had a backing plate nut fall off and bounce around in the drum. Make sure you dont have any FOD (foreign object debris) bouncing around in there!

Steve

Dick Weiss
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rake squeal?

#8 Post by Dick Weiss » Fri Mar 05, 2010 9:43 pm

The shoes should have a flat surface (including the lining's edge) to contact the little pads on the face of the backing plate; some relined shoes have only the steel edge in contact and will tend to wear into the pads unevenly if the drums aren't truely round.
There should be a chamfer one each end of the linings (allowing changes to either side for direction) and suggested by a tech bulletin to add 2-cuts across the linings (but NOT completely to the steel backing!) to divide the lining into 3-segments.
Slot width=about 2,5mm (I use double blades in the hacksaw). The slots act as dust collectors, but allows the linings to meet the drum's surface easier. There were times where the slots were cut at an angle to be self-cleaning if aimed outward and discharged to the vent holes in the drum's face--mostly in 'B' drums, but a bulletin was issued to add the holes using a template for the 'A' drum.
Braking-in the linings will take place w/in 50-100 miles BUT they must be arced as close as possible to match the drum's ID and NOT 'lightly' using the brakes will minimize glazing!

Dick

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A drum brake squeal

#9 Post by Guest » Fri Mar 05, 2010 10:23 pm

Paul,
Check the basics, drum cut true, no leaks and the shoes
arced correctly. The shoe arc should be so that there is a
slight "rock" in the shoe as you lay it in the drum. In
other words the radius of the shoe arc should be slightly
smaller than the arc of the drum. If you lay the shoe in the
drum and hold one end of the shoe against the drum the other
side should show a slight lift, 1 mm would be good and more
is not too bad. If all these are good then its a lining
issue. Is the shoe old? I have had great results with the
lining that NLA provides. Not an empty plug, they really are
good linings.

Alan

Paul Vernon wrote:
Hi All,

I have now done an amazing 500 miles or so in my rebuilt A coupe, but now the brakes are squealing, I've never had drum brakes do this before, all the components are refurbished or new. Any top tips on how to stop it?

Thanks

Paul





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roy mawbey
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#10 Post by roy mawbey » Sat Mar 06, 2010 2:48 pm

Paul,

Dick's advise about the slots is a good tip. When I changed by front shoes many years ago they had no slots and they squealed. My old linings were slotted and although nearly worn out I took the measurments and used the hacksaw to put some in on the new ones. It stopped the squeal for me. ( double blade also a good idea from Dick )

Roy
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bruce tuffli
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Re: rake squeal?

#11 Post by bruce tuffli » Sun Mar 07, 2010 8:49 am

Dick Weiss wrote:The shoes should have a flat surface (including the lining's edge) to contact the little pads on the face of the backing plate; some relined shoes have only the steel edge in contact and will tend to wear into the pads unevenly if the drums aren't truely round.
There should be a chamfer one each end of the linings (allowing changes to either side for direction) and suggested by a tech bulletin to add 2-cuts across the linings (but NOT completely to the steel backing!) to divide the lining into 3-segments.
Slot width=about 2,5mm (I use double blades in the hacksaw). The slots act as dust collectors, but allows the linings to meet the drum's surface easier. There were times where the slots were cut at an angle to be self-cleaning if aimed outward and discharged to the vent holes in the drum's face--mostly in 'B' drums, but a bulletin was issued to add the holes using a template for the 'A' drum.
Braking-in the linings will take place w/in 50-100 miles BUT they must be arced as close as possible to match the drum's ID and NOT 'lightly' using the brakes will minimize glazing!

Dick


dick

while your text is very helpful, nothing does it like photos. would you happen to have one of a brake shoe with the cuts shown? also, a copy of the bulletin(s) you mention?

thanks,

bruce

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Barry Brisco
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Re: A drum brake squeal

#12 Post by Barry Brisco » Sun Mar 07, 2010 11:05 am

Hi Paul,

There's been lots of helpful advice posted in this topic, but just wanted to mention that on the Registry website in the tech section there is an article at http://356registry.com/techinfo/repair/brakesqueal.html that you might find useful. I don't know how old that article is (it's undated, I didn't publish it) but it looks like it would be worth your time.

I've published several of the posts in this topic at http://356registry.com/techinfo/repair/ ... queak.html for permanent reference.

Best regards,

Barry Brisco
Paul Vernon wrote:Hi All,

I have now done an amazing 500 miles or so in my rebuilt A coupe, but now the brakes are squealing, I've never had drum brakes do this before, all the components are refurbished or new. Any top tips on how to stop it?

Thanks

Paul
Barry Brisco
1959 356A Coupe 105553, Ivory / Brown
2009 987 Cayman, Carrera White / Beige (daily driver)

Vincent Chiaro
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Re: A drum brake squeal

#13 Post by Vincent Chiaro » Tue Jun 28, 2022 10:32 pm

Sadly, once again I find a useful thread here but the links to the technical articles are broken, presumably due to the site migration.
1960 356B Roadster -- http://www.youtube.com/atypicaldriver

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Doug McDonnell
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Re: A drum brake squeal

#14 Post by Doug McDonnell » Thu Jun 30, 2022 2:24 pm

Click on Registry Home then click on Technical Library, then click on Chassis and scroll down to see the 2 articles on drum brake squeal Yes the new website takes some getting used to,and no you cannot link those articles and paste in The Forumn.
1965 356C 2000 BMW 740i Sport 1967 Honda CL77 There is never enough time to do it right, but always enough time to do it over.

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Re: A drum brake squeal

#15 Post by Vincent Chiaro » Sat Jul 02, 2022 1:40 pm

Found it, thank you.
1960 356B Roadster -- http://www.youtube.com/atypicaldriver

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