Disc Brake MPG Loss, Issue Found

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Since installing the disc brakes on the RV, we’ve pulled it approximately 1,000 miles over the course of two trips. At the end of the first trip, I noted 6.4MPG and the second, 8.1MPG. Both of those trips included some unloaded driving, so actual MPG was lower. Normally under the same circumstances, I would book between 9.5 and 12MPG. Since this seemed to happen after the install of the disc brakes, I lifted the trailer off the ground and spun all four tires by hand. The rear-left tire had a metal-on-metal grinding sound, so I pulled the wheel to inspect it. When I went to touch the caliper, I found it was loose and pivoted freely from the top bolt. The bottom guide pin had backed itself out and the lower section of the caliper was resting directly on the rotor.

I called the vendor, explained the situation, and requested a replacement guide bolt. They told me that they have seen this issue on a few of these, and to re-assemble it with some extra Loctite (the bolts come with some thread locker, but it is insufficient). After I got off the phone with them, I ordered a replacement bolt from E-Trailer, since it is only a few dollars and I half expected them not to send one (they did, it arrived a couple days ago). So I had two bolts on the way, but the trailer was still sitting on the side street nearest my house and I didn’t want to move it again knowing the caliper situation.

Since the HOA was probably going to start complaining, I hit the message boards. I found a few people who said that the pads are the same as late 80s to early 90s Buick Celebrity Limiteds, so I decided to take a chance and see if the caliper bolts for one would fit. Advance Auto had them in stock, and two of them and replacement guide sleeves cost something like $7. I picked them up and, comparing them to the Titan bolts, found they were the same length and threading, with the only difference being the machining of the head. The head of the Titan is machined in such a way that you can use either a socket or an Allen key to grab onto it, while the Celebrity bolts could only be turned with an Allen head. This would be a problem for me if I wanted to use them on the upper caliper guide, since I could not get an Allen bit on my 3/8″ torque wrench in there due to the leaf interfering, so I left the OEM bolt on the top where I could grab it with a shallow socket and installed the Celebrity bolt on the bottom. I made sure to use extra Loctite Blue on both the top and bottom bolts during the reinstall.

After reinstalling everything, I towed it to the RV lot in rush hour, stop and go traffic, averaging 7MPG. Considering the conditions, I think that is a good number and and that it was the entire reason for the loss in fuel efficiency. We’ll know for sure on our next trip.