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| [GMCnet] Brake problems [message #271283] |
Fri, 06 February 2015 07:09  |
Advanced Concept Ener
Messages: 112
Registered: December 2014
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If I were to need the brake shoes cam ground does anyone know where I could get this done? I called around this area and have not found anyone that does this or even that re-lines the old brake shoes. I was thinking of using a contour gage on the drum and sending that along with shoes since shipping the drums is not an option. What does anyone think about grinding them myself. They won't be perfect but will soon wear in. I can use contour gage to keep close during the process. Thinking about using a bench belt sander/ grinder.
Sent from my iPad
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| Re: [GMCnet] Brake problems [message #271314 is a reply to message #271303] |
Fri, 06 February 2015 15:57  |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Larry,
Thank you for this response, I agree 100%!
Ken Frey found two things wrong with his brakes that could have affected his problems; one of the adjusters had a tooth missing and
another one had a broken or incorrectly installed adjuster spring (I can't remember which one it was).
Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
-----Original Message-----
From: Larry
Oh for goodness sake...put the shoes on and drive it. Even if you do find an arcing machine, rarely have I seen a perfect match.
You will have a spongy pedal but in a couple of hundred miles, they will self arc. You may need to adjust the brakes several times
during break-in just to keep the pedal up. If your pedal does not firm-up you either have not used the brakes enough or you've got
another problem to address...like air in the lines.
JWIT
--
Larry
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Brake problems [message #271323 is a reply to message #271314] |
Fri, 06 February 2015 17:54 |
GMC.LES
Messages: 505
Registered: April 2014
Karma: -2
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Rob,
You also reported that Ken identified the drums had been turned, and shoe fit was not ideal.
The big problem with RV brakes is that we expect them to work perfectly after a brake job, and don't give them the time or conditions in which they can seat in. Driving a long highway trip, it might take way over a thousand miles before the linings seat in correctly. Even if we drive in stop and go traffic, it might take several hundred miles before you get decent brakes, and it will likely require several adjustments along the way.
Larry's comment to drive it is valid, keeping the above comments in mind. If you don't have the ability or patience to drive it until the brakes get better, then cam grinding the shoes might speed up the process.
If it were my coach, I'd be using it as my daily driver for a week or two to give the brakes a good workout and help seat in the shoes. I'd much rather go through that process close to home, so I don't have bad luck on a long trip.
Les Burt
> On Feb 6, 2015, at 4:57 PM, Robert Mueller wrote:
>
> Larry,
>
> Thank you for this response, I agree 100%!
>
> Ken Frey found two things wrong with his brakes that could have affected his problems; one of the adjusters had a tooth missing and
> another one had a broken or incorrectly installed adjuster spring (I can't remember which one it was).
>
> Regards,
> Rob M.
> The Pedantic Mechanic
> Sydney, Australia
> AUS '75 Avion - The Blue Streak TZE365V100428
> USA '75 Avion - Double Trouble TZE365V100426
>
>
>
> -----Original Message-----
> From: Larry
>
> Oh for goodness sake...put the shoes on and drive it. Even if you do find an arcing machine, rarely have I seen a perfect match.
> You will have a spongy pedal but in a couple of hundred miles, they will self arc. You may need to adjust the brakes several times
> during break-in just to keep the pedal up. If your pedal does not firm-up you either have not used the brakes enough or you've got
> another problem to address...like air in the lines.
> JWIT
> --
> Larry
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] Brake problems [message #271324 is a reply to message #271323] |
Fri, 06 February 2015 18:22 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Les,
Agreed.
On Double Trouble I wound up installing rebuilt 80 mm calipers on the front and middle wheels and new drums on the rear. The pads
and shoes were all carbon metallic.
Short of installing a reaction arm system the brakes are as good as they get.
Regards,
Rob M.
-----Original Message-----
From: Les Burt
Rob,
You also reported that Ken identified the drums had been turned, and shoe fit was not ideal.
The big problem with RV brakes is that we expect them to work perfectly after a brake job, and don't give them the time or
conditions in which they can seat in. Driving a long highway trip, it might take way over a thousand miles before the linings seat
in correctly. Even if we drive in stop and go traffic, it might take several hundred miles before you get decent brakes, and it will
likely require several adjustments along the way.
Larry's comment to drive it is valid, keeping the above comments in mind. If you don't have the ability or patience to drive it
until the brakes get better, then cam grinding the shoes might speed up the process.
If it were my coach, I'd be using it as my daily driver for a week or two to give the brakes a good workout and help seat in the
shoes. I'd much rather go through that process close to home, so I don't have bad luck on a long trip.
Les Burt
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Brake problems [message #271328 is a reply to message #271283] |
Fri, 06 February 2015 20:31 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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Advanced Concept Ener wrote on Fri, 06 February 2015 06:09If I were to need the brake shoes cam ground does anyone know where I could get this done? I called around this area and have not found anyone that does this or even that re-lines the old brake shoes. I was thinking of using a contour gage on the drum and sending that along with shoes since shipping the drums is not an option. What does anyone think about grinding them myself. They won't be perfect but will soon wear in. I can use contour gage to keep close during the process. Thinking about using a bench belt sander/ grinder.
Sent from my iPad
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Here's the scoop based on real lab work in conjunction with some of the largest brake manufacturers in the world. Most quality brake shoes are already cam ground out of the box. Many Chinese manufactured linings (regardless of the brand name on the box) are not cam ground. This is only an issue when installing new linings. Place the new linings in the drum and see if they contact in the center, at the ends, or all around. You should only install linings that contact in the center--preferably about 2/3 of the length of the lining or less. If they contact on the ends or fit perfectly, you will encounter problems such as locking, grabbing, chatter or lack of seating in over time. If you have any doubt, take the lining and manually rotate it in the drum with a slight pressure against the drum. If it slides effortlessly, you will be OK. If they bind or drag even the slightest bit, you will have problems. Our rear brakes are self energizing and linings that touch on the ends will self energize and cause all kinds of problems. If you feel that your linings are not ground correctly, you can take a power sander and sand down the ends for a length of about 2" top and bottom. Don't be afraid to take off a lot of material--it won't compromise performance or wear. The other option is to just slap them on and drive like others here appear to say--you be the judge.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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