View Full Version : Trailer Brakes

06-17-2007, 09:34 PM
I have a 1600 pound boat on a trailer without brakes. We are looking at purchasing a new (to us) vehicle and SWMBO really wants a Subaru Forrester, but it's rated towing capacity is 1900 pounds - practically the exact weight of the boat when it left it's manufacturer 25 years ago...before they put it on a trailer and other owners added good things like compasses and a solar panel etc. Subaru does increase towing capacity to 2400 pounds if the trailer is equipped with brakes.

So, has anyone here ever retrofitted brakes onto a trailer which wasn't made with them?

What trailer brakes in general would you recommend? electrical or surge?

Which would be easier to retrofit? electrical or surge?

Any website recommendations for a how to? or product info?

Any information is greatly appreciated.

Frank Wentzel
06-17-2007, 10:14 PM
I've never dealt with these people but they seem to have full information on all options. I lean toward surge brakes myself because they seem simpler in operation. That is, you slow down and the hydraulics automatically activate without pendulum boxes or electrical hookups or any need to properly adjust the system for weight braking action etc.


/// Frank ///

Rick Starr
06-18-2007, 12:05 AM
There are some seemingly snazzy stainless steel disc brake options available for retrofitting to trailers. Being hydraulic, they'll need a surge actuator. All in all you're talking about an expensive project, though.

I think the first thing I might do is take the boat-and-trailer over to a quarry, dump or other place likely to have a scale and weigh the rig, with tow vehicle, then go back and weigh just the tow vehicle. Do the math and see what sort of weight you are really talking about. With that bit of info you'll be able to make smarter decisions about how to proceed. (You could even launch the boat and go back to weigh the vehicle and trailer, which could also be useful to know.)

I should also say that I have never, nor do I know anyone who has ever, paid the slightest attention to the weight/tow rating recommendations made by manufacturers. I do bear in mind the relative frequency of tows and the severity of the travel conditions, though.

Good luck.

Gold Rock
06-18-2007, 01:17 AM
Hey B.B.
I used to do this for a living. Retro fitting brakes isn't necessarily a big deal. Necessarily. If the trailer is of a domestic, commercial make you should have no problem. Here's the breakdown:
1) Remove a wheel/tire and then remove the hub
2) Remove the inner/outer bearings; if this requires destroying the inner seal, so be it. It often does, but you must take the bearings out because..
3) Note the inner & outer bearing numbers. These will be either sand etched or stamped on the inner race(s). Look carefully, they'll be there 95% of the time. Also note the seal number. This will be embossed on the outboard surface of the rubber part. You do this because the bearing combination identifies the spindle. You note the seal number because a given bearing combo doesn't always take the same seal. Here are some common exambles - the smallest spindle of common highway application is the "BT8" type. This takes a bearing combo of either a 44643 inn/out, or a 44649 inn/out. The two brgs. differ by a 1/16" ID. The BT8 spindle is rated at 1100/1350 lbs. cap. @ hwy. speeds, depending on the brg. combo. Next up the commonality ladder would be the "84" spindle. This takes a 68149 inner/ 44649 outer combo. This is rated at 1750 lb.@ hws. The point here is..
4) You'll have to replace your plain hubs with a suitable hub/drum. The hub drum is a one piece casting, so no just adding drums to your existing hubs. That's just the way it is.. The good news is, commonly, that for every plain hub, there is a hub/drum avail. that will pop right in place with no alterations necessary.
5) While the hubs are off, look to see if your axle has flanges welded in place to bolt a brake backing plate to. These will be obvious if they're there. They'll be sqare w/ four holes, though the mounting hole spacing differs between the BT8 and the 84. If you don't have brake flanges, they can be purchased separately and welded in place, though now you'll have to measure the dimension of the axle beam cross section to get the correct ones (ie, the axle is round, square, rectangular, etc.). Assuming you have suitable flanges,..
6) You must identify the bolt mounting pattern of your wheels. A trailer of your size will most likely have either four or five bolt wheels. The easiest way to do this is to measure from the center of one stud or hole, to the center of the one furthest from it. In the case of a four bolt pattern, this will give you the actual dimension of the bolt circle diameter. If it's a five holer, you won't be measuring the correct dimension, but a competent parts person can make use of it and set you right. Point is, you need to order hub/drums that have the correct bolt pattern to accomodate your tire/wheel assys.
7) Once you've identified a suitable hub/drum, it will determine the correct brake assembly to go with it. BT8 axles run a 7" x 1 3/4" brake. 84 axles run a 10" x 2 1/4" brake. You buy a complete brake backing plate assembly for each side of the axle (don't forget the mounting bolts/nuts/washers). If you run hydraulic surge brakes, you must specify a "free backing" brake assy. Without going into detail, this type of brake allows for backing up w/o the brakes applying when using a surge coupler.
8) If the scenerio goes down perfectly to this point, you need merely purchase the appropriate set of hub/drums and brake backing plates (and, if you're wise, which you are, new bearings, seals, and grease caps) and install them, and you'll be ready to consider the actuation system.
9) Once you have the brakes mounted on the trailer, you need to purchase and install some means of actuating them. This gives us need to divert for a moment here -
On small trailers, as you observed, there are two primary types of brakes; hydraulic or electric. Electric brakes are avail. in a large range of capacities for axles up to around 12 thousand pounds capacity. They're rugged, durable, and good performers when set up and tuned properly. They are not the most desireable for marine use largely because the wiring system is so vulnerable to corrosion. Properly sealed and grounded, they would function when submersed, but it would be unrealistic to presume such a condition would last for long. Marine trailers overwhelmingly use hydraulic brakes. So...
10) There are two common means of actuating hyd. brakes; surge actuation, or electric/hydraulic. The elec./hyd. systems have improved greatly in the last ten years, but for simplicity in a small trailer (not to mention economy), it's hard to beat a surge system. If you're interested in ele./hyd. I'll leave it to you to research on your own. I'll give you some sites to check out later. Let's presume, for now, that you're going surge. A surge system consists of a surge coupler and the required plumbing to connect it to your brakes. A surge coupler is a device that mounts a brake master cylinder to your trailer and connects it to your vehicle via a sliding or pivoting coupler. As the tow vehicle decelrates, the trailer's inertia compresses the master cylinder between the trailer and coupler displacing fluid w/i the system. It's simple and elegant. The smallest surge couplers made are manufactured for gross trlr. wts. of 6 thousand pounds. They can be had to accomodate ball type couplings of various sizes, pin/clevis mounts, pintle mounts, and others as well. Again, assuming a best case scenerio here, you purchase a surge coupler and a plumbing kit, which consists of the various pre-flared lengths of rigid brake lines, flex hoses, fittings, and various other hardware to plumb the system, and install it. Then you will carefully read and perform the appropriate adjustment regimine that the components require. Read that last sentence. Virtually every call I ever recieved in seventeen years in the biz could be traced to improper installation or adjustment regardless of the type of system. Believe it.
So, theoretically, it's pretty simple to put brakes on an axle. However, for every point I've made above, there are likely upwards of a dozen exceptions. For instance, the brg. combo found on a BT8 spindle is also used on a BTW spindle. The difference? The distance between the bearings along the length of the spindle. There are no brakes avail. for BTW spindles. The 7"x 1 3/4" brakes used on BT8 equipped axles require tire/wheel sizes of 10" dia. or greater. If you have 8" wheels you'll have to upgrade these to larger sizes too. The list of caveates goes on and on. Lot's of home built trailers use axles for which there are no brakes avail. If push comes to shove, scraping everything off from the trailer frame down and buying an entire new brake axle/suspension package is not appreciably more expensive than retrofitting an existing axle.
It's also worth mentioning a few more considerations here. Last I was in the game, federal regs. dictated that trailers of a minimum g.t.w.r. (gross trailer wt. rating) did not require brakes, thus brake systems are engineered to satisfy not less than this minimum. Surge systems in particular have limited performance potential for gtwr less than about 3 thousand pounds. There's just not enough weight to get them to perform as effectively as they could. Also, last I checked, a basic tenet of towing a trailer in the US of A was that the gtwr could not exceed a certain percentage of the gvwr (gross vehicle wt. rating) of the tow vehicle. I want to say 35%, but check with your local state patrol for sure. Point is, at best it's not much more than 50%, so if your Subie grosses at, say, 3500 lbs., the law's gonna say you can't tow anything more than half that, or 35% of that, if my memory is correct. Rules is rules. Plus your tow vehicle just can't stand the strain.
Here's a few places that'll answer everything you ever wanted to know on the subject of trailer running gear. I'm gonna hook you up w/ the manufacturers directly, though some/all may not sell direct, but they'll have dealer locators so you can find a local source. These are just the biggies:
All things small trailer axles is Dexter Axle http://www.dexteraxle.com

A major force in sm.trlr. hyd. components is Titan Industries http://www.titan-intl.com/titan-trailer

A leader in surge couplers and plumbing kits is Atwood Mobile Products http://www.atwoodmobile.com

Hope this helps.


Gold Rock
06-18-2007, 01:35 AM
Sorry B.B., I spazzed out. Didn't notice that you were in Canada. We used to ship a lot of product up there, and I believe that the towing regs are similar between you and the USA. Check to make sure, though. Also, w/ regard to disc brakes; mfrs. have been struggling to perfect that "better mouse trap" for decades. I've never run into a package yet that, for the money, outperforms a drum brake setup, though it's a fine idea. Things may have changed in the last five or six years though, so no harm in checking if that route interests you. They were usually more expensive than drums and, last I was involved, the biggest issue with them was finding a suitable means of actuation. The disc brake calipers used at the time displaced so much more fluid than the industry standard(s) master cylinders, that most surge brake couplers disclaimed suitablility for disc brakes. You had to go with the much more expensive electric/hydraulic setups, and even these had their problems.


Ian McColgin
06-18-2007, 06:25 AM
In our family we tried both surge and hydraulic-electric on two horse trailors. The hydraulic-electric were really nicer for lots of reasons as the action was smoother, especially when backing over a rough field and up-hill. This might not be so critical on a boat trailor where backing is mostly either on a smooth surface or downhill. The other bit I like about the hydraulic-electric is that you can ease just a little breaking pressure to the trailor only to take a sway out.

06-18-2007, 01:19 PM
I feel a total fool :o ...

Chuck aka Gold Rock - thank you for your absolutely fantastic reply.

After reading your post I thought I had better know a bit about the trailer. Here's the back story: I just bought the boat and trailer last year when it was buried in a snow drift with the intention of bringing it home when the snow melted.

Two days after the cheque cleared I had a car accident and was prevented from lifting anything heavier than "5 or 10 pounds" until January this year - i.e. no manhandling a trailer onto a ball, off the ball, etc. - so left it in the previous owners yard (with his permission of course) until this year.

I brought it home a few weeks ago but have been so busy that I haven't barely looked at the boat never mind done anything with it....we're planning on getting into the family way (someones biological clock is ticking) and SWMBO started to agitate for a new vehicle to accommodate this expansion and she wants a Forrester because our Tacoma isn't 'practical', but I just bought a boat that needs to get pulled and so on and so on.

So after Chucks long and very informative post I went to go look at the trailer and there they were - trailer brakes.

In my defence they aren't hooked up and look like they need a good going over but there they are any how.

So once again thanks to all those who have contributed, please don't feel you wasted your time because this has been very helpful in any case.



So now for a new thread: how does one refurbish old electrical brakes? :p :o

06-18-2007, 02:20 PM
I had luck finding brake info on the airstream trailer forum. They are the same brakes as on your trailer. Jim...

Brian Palmer
06-18-2007, 02:41 PM
As others have alluded to, I would think that the Subaru Forester may be a bit small to tow a 1900 lb boat, plus trailer, even with brakes.

Our single axle trailer with no brakes, 1600 lb capacity, still weighs 450 lbs. The whole package (boat and trailer) weighs 1700 lbs (confirmed by scale). We tow it with a 3.8 liter minivan, and it seems capable and I am within my comfort level going up and down some fairly steep hills where trucks are advised to shift to low gear. I can't imagine doing more weight with less horsepower.


06-18-2007, 04:11 PM
Brian - in the past I have leant more towards Rick Starr's way of doing things:
I have never, nor do I know anyone who has ever, paid the slightest attention to the weight/tow rating recommendations made by manufacturers but this will likely be a new vehicle and I don't want to do anything to negate a warranty.

Of course more power is better (!) but my biggest concern with trailering is stopping and control - the lack of go just means taking longer to get there and planning routes to avoid steep hills ;)

Gold Rock
06-18-2007, 11:08 PM
Hey B.B.
Looks like you've got a run of the mill 10" x 2 1/4" electric there. The forged part of the drop spindle looks like a Dexter part. Can't see the axle beam, but I'd guess it's round and 2 3/8" o.d. If so, you should see a part number cast on the ourboard surface of the drum of 8-247. Servicing electric brakes is as easy as replacing whatever parts need replacing. When you pull the drum off, you'll see a magnet attached to the end of a lever arm. This arm pivots on a pin at the top of the plate and turns an eccentric that spreads the shoes apart. The rest of the assy. is just like any other automotive drum brake; return springs, hold down bits, adjuster, etc. All of these items are avail. as replacements from a dealer, as is a complete brake assy. Get prices for each, as a complete assy. is usually cheaper than the sum of the individual parts. This all supposes that the brake is of a current make. There are many designs that are no longer serviceable, but odds are yours is not one of these, unless the trailer is more than, say, 25 years old. If you stick with these electrics, you'll need to add a brake controller to your tow vehicle. Why?
An electric brake is pretty privitive. The magnet is actually an electromagnet bonded to friction material. It hangs on the end of the aforementioned lever arm which positions it to skim along an armature surface which is machined into the inside surface of the brake drum. When current is put to the magnet, it gloms onto the armature surface and is dragged along in the direction of rotation of the drum from the resultant friction. It also, of course, pulls on the lever arm to which it is attached, and this, in turn, turns the eccentric at the pivot pin and spreads the shoes which engage the brake surface of the drums. Voila. Thing is, an electromagnet is a strictly on/off affair for a given amount of current. If you were to just hard wire the brake circuit into the stop light circuit of the tow vehicle (which is the power source that you will, in fact, tap into), then every time you so much as touched the brake pedal, you'd be giving the trailer brakes the full monty of stopping urge, and they would respond accordingly. Not good. So you incorporate into the system a gizmo called a brake controller. Put simply, this is a black box type affair 'plumbed' into the brake circuit between the stoplight switch at the brake pedal and the connector at the trailer. It regulates the amount of current to the trailer brakes based on the rate of deceleration of the tow vehicle. This is the device that gives most home installers the greatest amount of trouble. The directions must be followed without any variation or exception whatsoever. Also, the trailer brakes and wiring circuit must be in absolute proper working order. The number one supplier of brake controllers is Tekonsha Engineering. They make very good units. There are others; some good, some not so.
I would add again, that you should seriously consider the towing capacity of your vehicle you select. Trailer and boat aside, overloading a vehicle with a tow load is tremendously hard on said vehicle's driveline, suspension, and brakes. It would also be an absolute 'gimme' of an out for a dealer do decline a warranty should anything go astray. Good medicine is something we dispense occasionally on this forum, tasty or not. Cheers.


06-19-2007, 05:41 PM
Thanks again Chuck!
and yes, wrt to tow ratings, warranties and vehicle wear and tear - that's why I am trying to do everything by the book. Manufacturer literature says 2400 pound weigh limit so I'll limit myself to less than 2400 pounds!

Nick C
06-30-2007, 02:23 PM
I built a boat that I put on a dual axle trailer, the combination weighs about 2800 lbs. The trailer has surge brakes on one axle. It works great, I almost can't feel the trailer when I brake.

Your going to need, a surge coupler for the hitch, brake lines and a cylinder behind the coupler. Then you will need to get the drum brake assembly that bolts to the axle. You can still use the original wheel. I'm guessing that by the time you get all the stuff you will have emptied your wallet of 500 to 600 dollars, if you install it yourself.

If you do get talked into disc brakes, pay attention to the disc, you want stainless steel and you want a quality disc which is thicker. The thin ones warp when you do a lot of downhill braking.

You should be fine with a single axle with brakes, it works great for me. Unless, you do a lot of mountain roads and snaky downhills that are long.

07-02-2007, 12:56 PM
I should also say that I have never, nor do I know anyone who has ever, paid the slightest attention to the weight/tow rating recommendations made by manufacturers. I do bear in mind the relative frequency of tows and the severity of the travel conditions, though.

Good luck.

I tow a small boat with my Toyota Sienna. Toyota says it can tow 3500 lbs., with trailers over 1000 lbs. requiring brakes and trailers over 2000 lbs. requiring an anti-sway hitch.

Toyota also says that NO TRAILER SHOULD BE TOWED OVER 45 MPH.

How can you take the manufacturer's recommendations seriously when they put in something like that? The recs must be written by lawyers, not engineers.

George Roberts
07-02-2007, 01:30 PM
I don't know much about trailers, towing, or brakes but ...

I have a mini-van and a trailer. The van is set up to tow 3500#. I think the trailer, 12' with dual axles and no brakes, weighs about 1300#. Even with good anti-lock brakes on the van and only 700# payload on the trailer it is not hard to get into a situation where one prays for better brakes.

Stopping distances on level roads even with a 2000# load are 50% greater. And the ride is so nice it is east to forget the trailer is there. So following distances get shorter, braking is delayed too long. And suddenly something bad happens.

I would suggest planning on more braking ability than less.

07-11-2007, 12:38 PM
Gold Rock, thanks for the tutorial and the info on the preferred reason to use surge brakes on boat trailers. My utility trailers all have electric brakes and I love them. I like being able to actuate the brakes independent of the brakes on the truck, can't do that with a surge. But corrosion issues would be a problem, especially with salt water launches. Well anyway thanks for all that info and the time it took to give it out. I love the forum, so much good info here.

07-11-2007, 11:13 PM
Of course more power is better (!) but my biggest concern with trailering is stopping and control - the lack of go just means taking longer to get there and planning routes to avoid steep hills ;)

That is always my first concern, regardless of the manufacturers specifications. It is one thing to make a trailer go forward, it is quite another thing to stop it. That is why you have the weight difference between braked and unbraked loadings. Beatrice, on the trailer, weighs in at around 2.5 tonnes (that's something like 5500 pounds) with the trailer making up 400kg (880 pounds) of that. The trailer is braked on one axle and uses the 'surge' type of braking. It is fitted with stainless disc brakes, with bronze alloy callipers.

For me, I need to make certain that (a) I can stop, and (b) the trailer, if it does begin to get out of control, isn't going to push the rear of the tow vehicle all over the place. For that I bought a Land Rover Disco which has disc brakes on all four wheels and sway control. Forresters are pretty small, although your trailer weight is also small, but are you certain you wouldn't want something a little heavier/larger?

The type of roads you are driving on are obviously an issue. The roads here are up and down and in places quite uneven.

07-12-2007, 01:55 AM
I have had a Tekonsha contoller for the electric brakes on my Suburban for ten years and it and the trailer have worked just great. I especially like the dial control with 'light guide' for adding a slight drag as mentioned above. I would hesitate to drive faster than 55 with the rig. Remember to disconnect the small trailer battery and keep it trickle charged (2 amp setting on the charger) when it's not in use. It's an 8000 pound load however, so my experience wouldn't necessarily be the same as yours (obviously) http://tinyurl.com/2ncekj

We also have a Forester (no hitch on it yet) and I wouldn't want to have a very long trailer because the car's wheel base is so short.

Eric D
07-16-2007, 05:48 PM
This post needs to get placed into the FAQ or stickied or whatever to save all that typing that Gold Rock did. Right now I have no need for it, but low and behold, I bet in 3 years I will be saying, dang, where did that post go about the brakes. Can anyone do that? Moderators?

Gold Rock, that was awesome, hell, numbers and everything, thank you.

As for the Forester...wow, I believe that is a bit of a stretch for that vehicle to tow effectively. I just can not imagine pulling much with that vehicle given it's wheel base and engine platform. I hope you think further about this before your second car accident please.