Hydraulic Disk Brake Retrofit
I recently bought a new truck to tow my vintage 19’ Alpenlite 5th wheel trailer. I had to raise the trailer 4 inches because the new truck sits quite a lot higher. This was easy to do – I replaced the 4” drop axle with a straight one. While I was doing suspension work I added hydraulic disk brakes. I had seen an article in Trailer Life last year that provided a lot of information about this project. I had to replace the brake shoes and magnets anyway, so there was a bit of an offset on the cost. If any of you want a PDF of the Trailer Life article let me know and I will email it to you.
Sources. I am lucky in that there is a major running gear supply house in Seattle. They have the unlikely name of “Six Robblees” and have been in business for about 90 years. I have dealt with them many times, and they really know their stuff. http://www.6robblees.com/ They have branches all over the Pacific Northwest. I just took my old axle down to them and they fixed me up out of stock for all of the items that I needed to make the conversion. Prior to buying the parts I had taken digital photos of the existing setup and visited them with high-res photos on the laptop. They really liked this approach and it made it easy for them assist me in buying the parts. I do love those digital cameras!
Anyway, there are five major components to a trailer hydraulic disk brake system. I will discuss them in the order that I installed them:
- Rotors
- Calipers
- Actuator
- Controller
- Brake lines
Please note that I have included web addresses for these components. I spent a lot of time on the web reading up on these items and it made component selection a lot easier. It is also nice to download the various manuals for future reference.
1. Rotors. The rotors are a direct replacement for the old drums. I bought “Tie-Down” brand rotors. Their website is at: http://www.tiedown.com/boemm.html . To identify the proper rotor I suggest that you take all of the information that you can put together to your supplier. It would help to take an entire drum, including the bearings. The bearing numbers will tell them what they need to know. Installing them is easy – it is just a matter of packing the bearings, installing the grease seal, slipping them onto the shaft and putting the washer, nut and cotter key in.
2. Calipers. The calipers bolt onto the flange at each end of the axle and fit over the rotors. You will need to buy the same brand rotors and calipers. To install them, remove and discard the old backing plate and replace them on the flange with an adapter plate and the calipers. They make adapter plates to fit all major axles. To get the right one you will need information about your axle brand, hole spacing, etc.
3. Actuator. The actuator is an electric powered hydraulic pump. It mounts in the trailer and you connect a 12V DC line to it to run the pump and the blue (trailer brake) line from the controller to it. It should be mounted inside in an accessible location that is as near to the axle as possible. I mounted mine in some useless space under the bathroom vanity. This worked out well because all of the electrical lines went through this space and I was able to make connections with short electrical leads. I bought a Carlisle brand pump. The service and installation manual for their actuators is available in PDF at: http://www.carlislebrake.com/spec_tbp.html The only trouble I had with this part of it was with the ground - make sure that the ground line goes to the truck ground.
4. Controller. The controller is a key item. It is essential that it be compatible with your actuator. I would double check this with the manufacturer of the actuator. It is possible that your existing controller will work, but you need to know for sure. The controller mounts in the tow vehicle in whatever location you choose. I bought a Tekonsha Primus controller. Information is at: http://www.tekonsha.com/primusintro.html .
5. Brake lines. Now the fun begins! I bought a set of brake lines designed for a surge brake and lucked out – I only had to make one flared end. On a single axle you will need three lines:
- Controller to a Tee
- Tee to right caliper hose
- Tee to left caliper hose.
Note that you will need additional tees and lines for a double axle trailer.
I used steel brake lines and had no trouble. The lines can be bent at about a 2 inch radius with no kinking and are easy to work with - just take it easy and you will have no problems. They should be tucked up alongside the frame out of the way. You will need to terminate them in a block that the caliper hoses will fit into. You have to have hoses going to the calipers because the axles move up and down on the springs.
I would carefully check your clearances. I could not go straight into my calipers with the hoses because the springs were in the way. I wasted an afternoon working around this. I drove all over Seattle, and could not find elbows for the double flare fittings. I ended up buying a pair of Tees at NAPA and plugs for the extra hole at a hydraulic supply place.
You will have to flare one or more fittings. Double flares are required. I bought a nice little double flare set at Sears for about $15. An identical (same manufacturer, different packaging) set sells at NAPA for over $50. They provide good instructions on how to do the double flares. I also found a web site at http://www.pharmacy.arizona.edu/staff/wunz/NoABSTCS/DoubleFlare.html. on how to do double flares. The information on this page was invaluable. I have always had bad luck with plumbing flares, so I was a bit worried about this part of the project. You will need to practice a few flares, especially if you plan to do one while laying on your back under the trailer. The chamfering that he talks about on the website is very important. I found that if you don’t have it evenly chamfered that the flare gets malformed. I used a fine file for this job and followed it up with a polishing with emery cloth. The website suggests de-burring with a drill bit. I chucked up a bit in an old drill chuck and found that this made it very easy to do. A careful inspection of each flare, preferably under magnification, is very important.
Once you have it connected up you are ready to bleed the brakes. Everything went fine for me up until this point, and then things went straight to hell. I outsmarted myself and put powerpole connectors on the actuator control. This made it easy to fire off the pump by connecting the powerpoles so I didn’t need any assistance. This was a big mistake. I was lying on my belly in the bathroom reaching into a cabinet and found that it was impossible to do three things at once – power up the actuator, loosen the adjusting nipple with a wrench and hold the bleeding hose on the nipple. Things really went to hell in a handcart when the brake fluid started flying and things got nice and greasy. The surgical tubing refused to stay on the bleeding nipple once it got oily, and I managed to soak everything in sight.
I later figured out that the controller provides variable voltage to the actuator which delivers appropriate pressure to the lines. By connecting a 12V battery to the actuator I was hitting the lines with maximum pressure which made things really hard to control.
You first have to bleed the actuator. I bled the daylights out of it, and after putting about a quart of fluid into it I decided that something was wrong – there was no place for all of that fluid to go. With a sinking feeling I looked under the trailer and discovered a helluva mess. It seems that the bleeding nipples on the calipers were not tightened down at the factory, so I had been spraying brake fluid all over the underside of the trailer. At this point I gave up for the day and hunted up a cold beer. It took a while to get the brake fluid out of my hide. My hair felt greasy for days.
Anyway, the next day I got it all under control and got the system bled. I also cleaned up the mess and made sure that I got all of the fluid off of the brake rotors. Fortunately, none of it got onto the brake pads.
Success! That is all there is to it. I didn't keep track of the time it took, but it was really a pretty easy job. I took it slow and careful and the only problems I had were self inflicted - the bleeding fiasco. The only tricky part is doing the double flares in the lines, but the lines are cheap, so you can afford to make mistakes.
I have since put about 8000 miles on the new brakes and love them. They are very smooth and provide terrific braking action. There is no grab, no fade and the control is very linear. They work beautifully in reverse which is a bonus. I am happy with the Tekonsha Primus controller. It has a LED display that shows a “C” when you are connected to the trailer. This lets you know that your system is connected, and quickly becomes one of the items that you check when scanning the gauges. It also shows the voltage that is being delivered to the actuator. This makes it very easy to adjust the whole system.
The brake system is easy to check – when you step on the brake pedal or activate the manual slider on the controller you will hear the actuator fire off with a loud buzz. The manual states that you should not sit for long periods of time (like at a railroad crossing) with the actuator on, so in situations like that you should put your parking brake on and take your foot off the brake.
The cost of this entire system for a single axle trailer was about $1100. The biggest expense was the actuator at $600. A double axle trailer would cost about $1500 since you only need one actuator. I had to buy a new controller which cost over $100, so if you are able to use your old controller you could save some money there.
Selection of parts is interesting. When you get down to it, the components are very simple, and they are generic. I bought a Dexter axle and had intended to mount Dexter rotors and calipers on them. Robblees talked me into buying Tie-Down brand rotors and calipers. They felt that they were better made and there was a big advantage to the calipers – they use pads from a 1992 Chevy Cavalier that should available anywhere. The Tie Down parts fit perfectly onto the axle, and I am very pleased with them. They are well made and work flawlessly.
Likewise I bought a Carlisle actuator on Robblees recommendation. I have nothing to compare it to, but am quite satisfied with it.
Do I think it was worth it? Absolutely! I have a bad habit of heading up steep forest service roads pulling the trailer, and they are so twisty that you have to come down on engine compression and brakes. A few thousand feet drop will really eat brake shoes and magnets. I had come to hate the old electric magnet brakes. This is really a pretty crude arrangement and a real bother to work on. They worked OK when I had new shoes and magnets, but they required frequent adjustment, and I spent a lot of time and money keeping them in repair. The adjustment slots on the backing plate was behind the drop in the axle and it was almost impossible to get to them. Changing the pads on the new disk system will be easy, and I think that I will get much longer life. Disk brakes do not require adjustment and are easy to inspect (just crawl under the trailer and take a look) and to work on.
On another note, I gifted myself with a digital infrared thermometer – the Sears model that is mentioned in the Trailer Life article. It cost me about $80 and it is invaluable. Every time I stop the trailer I inspect all of the running gear, and this makes it a snap to check the hub temperature. This will let you know how hot your brakes are and will also give you some advance warning if a bearing is getting hot. See it at:
Anyway, if you have any questions email me and I will do my best to answer them.
Lynn