Do you have a question related to alignment, steering, handling, braking, fuel economy, tires, safety and maintenance of your RV? Robert Henderson, the president of Henderson’s Line-Up Brake and RV and SuperSteer/SuperStop products in Grants Pass, Oregon, is available to answer questions from readers. You may send your questions by e-mail to editor@rvlife.com.

Question:
"My 28-foot Ford E-350 Class C motorhome is constantly warping the front rotors. What can I do to eliminate this problem? The rear drums hold up just fine."

Ron
Lynnwood, Washington

Answer:
Thank you for the excellent question.  This is a problem we run into quite frequently. I’ll list a couple points that contribute to this problem.

1. Disc brakes are more susceptible to vibration because of the clamping forces generated in a disc bake. It transfers into the steering wheel even if warped as little as three- to five-thousandths of an inch. A drum brake may be 20 to 40 thousands out of round and a person may not notice due to its design.  

2. The larger piston volume of a disc brake causes fluid to push back against the fluid in the caliper. This in turn causes the pedal to pulsate.

3. If the rear brake shoes are not as aggressive in holding back the weight of the coach, it puts more load on the front brakes. When getting a brake job done on a vehicle that has drums on the rear and disc up front, it is often a good idea to replace the rear brakes as well, because the rear brakes may be getting hard and glazed over. This causes them to lose their coefficient of friction.

4. I don’t know what year your coach is but the earlier Fords had a load-sensing valve that restricted fluid flow to the rear brakes on the vehicle. The idea is that if the vehicle is heavily loaded it will sit low in the rear, thereby opening up the flow through the load-sensing valve. This is all well and good until someone puts on airbags or overloads to raise the rear of the vehicle up. We used to disable the load-sensing valves to get full pressure to the rear brakes.

5. If you have the earlier rear anti brake skid system (or RABS for short) used by Ford in the early ‘90s, I have noticed some of the same problems with them as well. There is not a recommended way to disable the rear brake antiskid on these vehicles.

6. Every time you turn a disc brake rotor it has less material to dissipate the heat, thereby increasing the tendency to warp once again. You have to pay close attention to the minimum machine to tolerances. I would recommend replacing the rotor once you get close to the minimum machine to spec, not just the discard spec on the rotor. It takes knowledge of both of those numbers.

7. Cheap rotors may warp sooner than a quality well cast rotor. We use the Performance Friction rotors wherever possible. They offer better cooling and better metallurgy than many rotors on the market. I hope this helps. God bless you.
Robert Henderson, president of Henderson’s Line-Up, Brake and RV and SuperSteer/SuperStop products of Grants Pass, Oregon, regularly answers questions on RV steering, braking, handling, fuel economy, tires, safety and maintenance online at the Chassis Solution blog at rvlife.com.  Send questions by e-mail to editor@rvlife.com.