We replaced both rotors and brake components on the trailer, but it wasn't without headaches.
May 15, 2025
By Thomas Allen
Catch up on the series:
Part 1
If you’ve ever overhauled a trailer, you know full well the most important part is the wheel and hub assembly, and they never cooperate. Just expect there to be rusted-on parts, sized bolts, incorrect sizes side-to-side, and more. It’s going to be a headache, but if you expect problems, your overreactions will be less severe, at least that’s what I tell myself. And then I freak out anyways.
I’ve done this a number of times, and none of them were the same or presented the same problems. I’ve learned a few things, most of all, if you’re into the hubs and brakes and then some, it’s worth noting that you can often get a new axel for cheaper than that of new kits—especially on a double-axel trailer. Nowadays, you can easily find a complete axel with hubs and calipers already attached.
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The boat came with two different size tires, neither was correct, so we got to work overhauling the rotors, brakes and calipers. After digging into this rig, it sure seems the original axel was modified for one reason or another, which isn’t that uncommon among DIY boat owners. Sometimes the OEM axel and hub kits are not as user-friendly as they could be. Looking back, I should have swapped the old axel out from the get-go. For this project, it would have been slightly more expensive, but I’d have said way fewer cusswords. The next time I have to do brakes and rotors on this rig, I’m getting a new axel.
The existing rotors were deeply grooved and covered in crumbly rust. Looking back, a new axel would have been an easier process, and next time that's what we'll do for this rig. Here's a look behind the rotors. Securely attached, but clearly needing updates. As we worked to take the assembly apart, things just fell off making it clear everything needed replaced. The other problem we ran into is the brake caliper was evidently seized, and to make matters worse I was unable to find the same caliper to update with a new version. And I made a number of trips to our local trailer parts store—no dice. Due to the “customized” nature of the mounting bracket, I had to customize the rotor and caliper rigging job.
The existing caliper seemed seized, but an exact replacement was not available. Here you can see the brake line and old caliper. We hoped to keep the brake lines intact as that's a difficult job we were not qualified for. Fortunately, the brake lines were salvageable. Here is a look at the spindle, which was in fine shape and ready to take a new hub assembly. When it comes to kits to purchase, Dexter almost always has a solution, and they are durable parts.
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Dexter has an extensive selection of brake and rotor assemblies, and a number of other parts that would have worked with this job. We took adequate time to fully clean the spindles, and of course to end the saga of finding the right bearings and rotors, I ended up having to use a digital measuring caliper to be sure I had what I needed.
You can see the bracket is slightly twisted, which I felt indicated the axel was modified at some point in the past. Another example of why we should have swapped the entire axel altogether. To be sure we bought the right bearings, I had to accurately measure the spindle. This one was straight, not tapered like most boat trailer spindles. This one required two bearings per side that were exactly the same size. I also had fun with the tires … I got a pair of tires for $65 a piece, and they seemed to be the right size based on the listed payload. On paper it made sense, but after we dropped the full weight on the tires, they were super squatty. In fact, I added 10 additional pounds of compressed air hoping they’d pick up a tad, but no dice. The first pair of tires were not going to work. So, I went back and exchanged them, straight up, for a taller set of tires that better filled the fenders and carried the load. Lesson learned.
This was the first set of new tires I purchased, but later determined they were too small and not suitable to carry the weight of the boat. We traded them in for a taller set. The completed rotors and brake calipers shined up nice, but we still had a few hurdles to get over before the job was done.
Here is the passenger side caliper and rotor assembly. The brake caliper originally was on the back side of the rotor, but due to the twisted bracket we had to mount it on the front side, which required some mild manipulation of the brake line. Be sure to carefully move the hard lines and don't kink them! With the calipers on, the passenger side had to be fitted to the front of the rotor to accommodate the “customized” mounting bracket. I’d rather it had been on the back side, and this created an issue with the existing brake lines. The brake lines are hard, not rubber so there wasn’t a lot of give to accommodate the front mounting position, but we made it work. Be sure you don’t kink brake lines!
The brake line connection and the bleeder valve are reversible to accommodate opposite mounting positions. The bleeder valve is on top. The calipers also allowed for the brake line connection and bleeder valve to be swapped. So, it worked for our purpose.
It’s also important to have a buddy who’s better at brakes than you are. My friend Evan came and bailed us out when we realized we bit off a little more than we could chew. And this wasn’t the first time he’s been a good help.
Securing the assembly to the bracket took some time and extra help from a qualified buddy. Here's a look at the new assembly from the inside, a much cleaner look and fit. You can see how snug the fit was. And when it comes to brakes and rotors, snug is good. Make sure every part and connection are clean and free of debris, that’ll make for a simpler reinstall.
Gently tap the bearing buddy into position, make sure it’s square up and not crooked.
Carefully tap the bearing buddy into position, make sure it's squared up and don't force it. We had to adequately grease the bearings, which was a fine teaching moment for my young boat owner, it’s a super messy job, and you really can’t use too much grease. Once the bearings are greased and set, you will need to add grease to the zerk to top off the needed grease. A handy grease gun will make your life easier.
Once the bearing buddy was installed, we added grease through the zerk to top off the grease requirement. It’s a fair assumption that most boat trailers run on malfunctioning brakes and dry brake lines. Do better. We put in the better part of a bottle of DOT 3, operated the actuator to fill the lines and then Evan helped us bleed the brakes. He had a handy-dandy brake bleeder thingy and thank God for it—made the job much easier.
Once the brake lines were reattached, we filled the reservoir with DOT 3 brake fluid and began the bleeding process.. This is the brake line junction. It seemed to be original, and could have easily been replaced, but we determined it was in fine shape. Replacing brake lines is a complicated process that for us would require professional help. Thankfully, it worked. Bleeding the lines is fairly straightforward, and with a helpful tool like this it's an easy job. Again, thanks to Evan for the help. Also be sure to thoroughly clean the rotors with brake cleaner, as they are covered in a bit of oil from the milling process. You need that oil cleaned off or the brakes could malfunction. Take this part seriously.
Clean the rotors thoroughly with brake cleaner as the they are typically covered with oil from the milling process. You don't want any residual oil on the rotors. Here is the completed hub assembly. Finally, get those lugs put on and torqued to 118-foot-pounds. And then re-torque them after a few trips to the boat ramp—or 50 miles, whichever comes first.
Be sure to torque the lugs to spec, and then retorque after you've pulled the trailer for a few trips to the ramp. It was a saga indeed, but we got it done and the new rotors, brakes and tires work wonderfully. I’d still buy a new axel if I had it to do over. Like I said earlier, you must expect busted parts, seized bolts and more headaches than you may think is fair. This part of your trailer is critical to getting you there safely, and home again. Stay patient and persistent. Without a functional trailer with good wheels, you ain’t going nowhere.
New hub assemblies and new tires. Ready to roll. Safely. It was a fun project. Mostly. Anytime you buy a new boat, it’s a good and safe practice to dig into your wheels … Maybe a bearing repack is required, brake pad replacement, or the whole component. It’s smart to start new there—it adds confidence.
Onto the next project. Some cool stuff coming—stay tuned.
