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JBarca
Radnor, Ohio, USA
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Joined: 12/16/2004
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Timeking wrote:Tired of worrying. Ordered new nev-r-adjust brakes. there was something ground into one of the pads that cut grooves in the hub. Will have the hub turned or buy a new hub (btw ALL "new" hubs are out of round, as in ALL have to be turned).
Out of round hubs, yeh. A heads up, when the drums come back from the machine shop, ideally you check the drum shoe surface for total runout with a dial indicator. I can attest to the fact, the drum shoe surface (diameter) has to run within 0.015" total indicator reading (TIR) with the hub bearing bores. Ideally they are down in the 0.005" or 0.010" TIR range. Being at the edge of the Dexter spec of 0.015" is on the ragged edge. You will have issues with the brakes over-adjusting and getting hot if the drum runout is much over 0.015" TIR. Been there and proved that. Trailer tolerances are way different than auto tolerances.
A good machine shop can handle 0.005" TIR and less without issue. But, some auto parts places will not guarantee much of anything. I gave up around here trying to get the local auto parts store to turn brake rotors or drums. After getting them back worse than when I gave them to them, I gave up and just bought new brake drums & rotors. Also, make sure the magnet surface is good and cleaned up.
Good luck and let us know how this comes out.
John
John & Cindy
2005 Ford F350 Super Duty, 4x4; 6.8L V10 with 4.10
CC, SB, Lariat & FX4 package
21,000 GCWR, 11,000 GVWR
Ford Tow Command
1,700# Reese HP hitch & HP Dual Cam
2 1/2" Towbeast Receiver
2004 Sunline Solaris T310SR
(I wish we were camping!)
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Chum lee
Albuquerque, NM
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Joined: 08/03/2015
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JBarca wrote:
A good machine shop can handle 0.005" TIR and less without issue. But, some auto parts places will not guarantee much of anything. I gave up around here trying to get the local auto parts store to turn brake rotors or drums. After getting them back worse than when I gave them to them, I gave up and just bought new brake drums & rotors.
John
In modern times, once brake drums/rotors are out of tolerance, a good machine shop can get them round/flat again, BUT, the problem is that when they remove material, it takes the castings out of tolerance from a thickness variation standpoint. Once the rotors/drums are heated up in use, they usually go out of tolerance again very quickly because the thickness variation causes too much differential heating (expansion/contraction) and the shuddering/pulsing returns. The older "boat anchor" style drums/rotors no longer exist because engineers are trying to save unsprung weight and reduce rotational inertia to the detriment of durability/longevity.
Best bet: once drums/rotors are out of tolerance for any reason, replace them with like and kind. (new) Truck/trailer components are usually more robust, but, . . . . do you feel lucky?
Chum lee
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JBarca
Radnor, Ohio, USA
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Joined: 12/16/2004
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Chum lee wrote:JBarca wrote:
A good machine shop can handle 0.005" TIR and less without issue. But, some auto parts places will not guarantee much of anything. I gave up around here trying to get the local auto parts store to turn brake rotors or drums. After getting them back worse than when I gave them to them, I gave up and just bought new brake drums & rotors.
John
In modern times, once brake drums/rotors are out of tolerance, a good machine shop can get them round/flat again, BUT, the problem is that when they remove material, it takes the castings out of tolerance from a thickness variation standpoint. Once the rotors/drums are heated up in use, they usually go out of tolerance again very quickly because the thickness variation causes too much differential heating (expansion/contraction) and the shuddering/pulsing returns. The older "boat anchor" style drums/rotors no longer exist because engineers are trying to save unsprung weight and reduce rotational inertia to the detriment of durability/longevity.
Best bet: once drums/rotors are out of tolerance for any reason, replace them with like and kind. (new) Truck/trailer components are usually more robust, but, . . . . do you feel lucky?
Chum lee
Hi Chum lee,
I fully agree with you. The issue is the trailer industry (the smaller types used in RV's) quality is not like years ago. A brand new brake drum running 0.015" TIR out is, well, poor. The 2 bearing bores can be dead on, just the shoe surface diameter runs out in relation to the bearing bores. The shoe diameter can be dead true also, it is just that the machine was allowed to run off center when turning the shoe diameter. Either the operator just plain set it up wrong or they allow the machine to drift since the spec is, 0.015" TIR, and they let it run.
On a standard manual adjust brake, many folks may never know or realize you have a problem. When you are adjusting the brake, you tweak the adjuster close and listen/feel for the drag while spinning the wheel. Well, when the drag skips, then gets hard to turn, the skip is the drum rotating off center. You are setting the drag to the part of the rotating surface that touches the shoes, whatever portion of less contact in the 360 degrees of the drum. If the shoe surface ran true, you would have even light-drag the full 360 degrees.
Now insert the self-adjusting trailer brake. If the shoe surface runs out much more than 0.015" TIR, and even some may be a little under that, over time when the shoes press into the max out of the round area, the adjuster has enough travel to move a click on the adjuster. The first click is not a problem, that click may only be a 0.0005" movement. But, after enough stopping sequences, the adjuster keeps on adding 0.0005", and soon that turns into a lot of thousands. Now the brake is too tight and there is no way to back it off automatically. You end up with a locked-on mega hot brake.
I have said before, one learns a lot more when things do not work right. If I had not had this happen to me, I never would have realized it. In today's modern machines, holding a brake drum to spin true within 0.005" TIR is a walk in the park. Automotive does it all day long on disk brake rotors that have to run close to dead true. Why does the trailer industry allow such wide tolerances that they ship all the time? It all comes down to $$$.
Sorry for the rant, I come from a machine shop background and it's just poor the stuff we get that could easily be made lots better with just a little more time and pride added.
Thanks for listening...
John
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monkey44
Cape Cod, MA and Central Fla
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Joined: 11/12/2002
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test - ignore
Monkey44
Cape Cod Ma & Central Fla
Chevy 2500HD 4x4 DC-SB
2008 Lance 845
Back-country camping fanatic
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deltabravo
Spokane, WA
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Joined: 09/08/2003
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ford truck guy wrote:Throw ALL those Math problems Into the trash can and stop over thinking.
IF the brakes a low, AND your taking that multi thousand mile trip ( 6,000 - 10,000 ) , just replace them and be done with it.. ![[emoticon]](http://www.rv.net/sharedcontent/cfb/images/doh.gif "doh")
DITTO
ford truck guy wrote:piece of mind = priceless
Correction: "peace" of mind
A piece of someone's mind makes them only have a partial brain...LOL
2009 Silverado 3500HD Dually, D/A, CCLB 4x4 (bought new 8/30/09)
2018 Arctic Fox 992 with an Onan 2500i "quiet" model generator
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