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How much wear on semi drums and shoes before discarding?
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School Of Hard Knock
Posted 7/27/2013 23:59 (#3233218)
Subject: How much wear on semi drums and shoes before discarding?


just a tish NE of central ND
What should the min. thickness of the shoes be? How much wear off the drums before throwing them away??
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jcfarmboy
Posted 7/28/2013 00:22 (#3233240 - in reply to #3233218)
Subject: Re: How much wear on semi drums and shoes before discarding?



South Western Ontario, Canada
The wear for the drums is stamped on the outer ring on the drum. Our rule of thumb, when the shoe wears down to the "step" on the shoe its time for replacement, always replace both shoes and drum on the whole axles.

Drum costs are so low that we don't even think twice about replacing them.
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hillfarmer
Posted 7/28/2013 05:36 (#3233298 - in reply to #3233240)
Subject: Re: How much wear on semi drums and shoes before discarding?



Was in a Truck store

they had like 6 piles of shoes

pair of cheap pads
one cheap pad and one better

pair of better pads
one better and one good bpad

pair of good pads
one good and one great pads

pair of great pads
one great and one "super" pads

Take your pick !!!!!!!!!!!!!!
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Wizard
Posted 7/28/2013 07:02 (#3233358 - in reply to #3233218)
Subject: Dot says there must be 1/4" shoe lining visible


Fletcher, OH
So if your drums are cut in 1/4" and you have 1/2" linings on the shoes, its time to change them since only 1/4" is visible.

The trailer brake job this week a shoe kit was $37 with hardware, and drums were $80 each. This did one wheel end. Parts came from Trailer Supply Depot in Dayton (Vandalia).
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Mark@Northern Iowa
Posted 7/28/2013 09:32 (#3233621 - in reply to #3233218)
Subject: Per DOT 393.47



Floyd County, Iowa
per DOT

Subpart C - Brakes
393.47 Brake actuators, slack adjusters, linings/pads and drums/rotors.

(1) Steering axle brakes. The brake lining/pad thickness on the steering axle of a truck, truck-tractor or bus shall not be less than 4.8 mm (3/16 inch) at the shoe center for a shoe with a continuous strip of lining; less than 6.4 mm (1/4 inch) at the shoe center for a shoe with two pads; or worn to the wear indicator if the lining is so marked, for air drum brakes. The steering axle brake lining/pad thickness shall not be less than 3.2 mm (1/8 inch) for air disc brakes, or 1.6 mm (1/16 inch) or less for hydraulic disc, drum and electric brakes.

(2) Non-steering axle brakes. An air braked commercial motor vehicle shall not be operated with brake lining/pad thickness less than 6.4 mm (1/4 inch) or to the wear indicator if the lining is so marked (measured at the shoe center for drum brakes); or less than 3.2 mm (1/8 inch) for disc brakes. Hydraulic or electric braked commercial motor vehicles shall not be operated with a lining/pad thickness less than 1.6 mm (1/16 inch) (measured at the shoe center) for disc or drum brakes.

(g) Drums and rotors. The thickness of the drums or rotors shall not be less than the limits established by the brake drum or rotor manufacturer.

Website:
http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmc...

-

Edited by Mark@Northern Iowa 7/28/2013 09:35
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RodInNS
Posted 7/28/2013 11:32 (#3233835 - in reply to #3233218)
Subject: RE: How much wear on semi drums and shoes before discarding?


The DOT specs aside... the general rule of thumb that's applied here is that if the shoe is at 1/4" at any point it comes off. The Q-Plus shoes I run have a 1/4" indicator on each end of the lining. As far as the drums go... if there's any appreciable wear shown on them you're just as well to toss them. The way I've come to view this issue... you may technically be 'legal' running a shoe down thinner than what I've described... but you're also diminishing the braking performance by a significant amount. For the cost involved I think it's just as well to change them out and keep GOOD brakes. Also make sure to free/replace the shoe pivots/bushings and check for wear on the s-cams and their bushings... A worn cam also seriously imperils brake performance.

Rod
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runningbehind
Posted 7/28/2013 21:39 (#3234841 - in reply to #3233218)
Subject: Re: How much wear on semi drums and shoes before discarding?


NC ND
Steve you will save yourself alot of trouble if you keep good drums on. During the winter when you get the ridge on the edge a little snow will blow in there, melt freeze then you have frozen brakes every time you go to use the truck/trailer. Also when the shoes wear down in a bit they tend to stick from rust also. Bad on trailers even worse on your drives, somebody gets in pops the clutch, now you are working on a rearend.
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Browtrucking
Posted 7/29/2013 06:27 (#3235248 - in reply to #3233218)
Subject: Re: How much wear on semi drums and shoes before discarding?


halfway between Lapeer and Port Huron, MI
1/4 inch at the center of the shoe, sometimes you can get two to three sets of shoes out of them they can be measured against the spec stamped on them. When buying new drums be careful of the price some of the cheaper drums are only 80#'s the better one are 100#'s (for hub pilots) premium linings on cheap drums eats drums faster because they can't take the heat like the heavier drums. I generally feel the lip on the edge of the drum if it's cut in good and deep I replace if not reuse, school buses get new drums regardless the constant stopping and heavy feet of bus drivers results in lots of heat cracks and heavy wear, I have one that burns up shoes in 7/10,000 miles even severe duty linings!
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School Of Hard Knock
Posted 7/29/2013 07:31 (#3235347 - in reply to #3233218)
Subject: RE: How much wear on semi drums and shoes before discarding?


just a tish NE of central ND
Thanks for the quick reply's . It amazes me how reasonable the truck drums and brakes pads are compared to the tiny ones used on cars.
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