- Lippert Electric Brakes Owner's Manual
Lippert Components has found through extensive brake testing that the break-in period for our drum brakes can range from 20 to 50 brake applications. Brakes can be seated in by applying approximately 8-10 volts to the coach brakes at an initial speed of 40 mph and allowing the truck/coach combination to slow down to 20 or 25 mph
- Dexter Electric Brake manual
your trailer brakes should be burnished-in by making 10-12 full stops from approximately 20 m.p.h. This allows the brake shoes and magnets to slightly “wear-in” to the drum surfaces.
Note that first, the above is just the bare minimum to have reasonable braking. Full break-in, where the shoes are fully fitted to the drums and the brakes can operate at full efficiency, takes much more. Second, drums take much more time to fully break in than the disc brakes most people are familiar with on modern cars.
Federal Mogul has this to say:
(then describes basically the same procedure as above)
An effective burnish cycle to seat the friction materials into the opposing rotor and drum surfaces requires approximately 200 stops. The 200 stops is consistent with the burnish procedure in the FMVSS 105. As a practical matter for installers, 200 stops probably will not happen since few installers have all day to make that number of stops. Therefore, we recommend the following burnish procedure:
The referenced Federal regulation (FMVSS 105) says:
Quote: S184.108.40.206 Burnish. Burnish the brakes by making 200 stops from 40 mph at 12 fpsps (the 150 lb control force limit does not apply here). The interval from the start of one service brake application to the start of the next shall be either the time necessary to reduce the initial brake temperature to between 230 °F. and 270 °F., or the distance of 1 mile, whichever occurs first. Accelerate to 40 mph after each stop and maintain that speed until making the next stop.
Note that the full burnish procedure is 200 full stops from 40 mph, while the minimum procedures are only 20 stops of slowing down by 20 mph. the "12 fpsps" is the rate of deceleration, about 0.4g, which is more braking than most people normally stop with. And my guess is people towing trailers are typically even more cautious and brake sooner and with less force. From a British study of driver's braking behavior:
In a test involving 23 drivers over 300 miles of European driving , the average of the maximum decelerations observed on a number of different test routes varied between .21 g and .34 g, the mean being .26 g.
So, you can see why new brakes can't be fully broken-in in just a few hundred miles of highway driving and a few miles around town.