Brakes on One or Two axles?

[Jack O'Brien]

Those of you who have tandem axle trailer please advise whether you have brakes on one or both axles.

Disc or drum?

If on one axle, which one, front or back. Why that one?

Also, please comment if you think your trailer wheels ever skidded because of the braking of the trailers's wheels and under what conditions.

[Chip Hindes]

Two axles, four wheel discs.

Champion Trailers says specifically, if you have tandem axles with brakes on only a single axle, those brakes must be on the rear axle. Reason being, if the single braking axle is on the front, when you brake, the braking torque tends to rotate the axle to the rear and up. As the front axle rotates up, the the tandem pivot rotates the rear axle down, further lifting the front axle off the road. When the axle doing the braking lifts itself off the road, well, you can probably figure out the rest: severe axle hop.

You've probably heard my philosophy a few times before, but here it is again. If you're going to spend $1000 or more for the second axle, spend an extra $250 and get brakes for the second axle.

I was going to describe a tandem axle trailer with only single axle brakes as half assed, but I know several people who have done it, so maybe I shouldn't.

[Jack O'Brien]

I think that Champion article says to put the brakes on the rear axle because the EQUALIZER causes the weight shift to the rear axle when braking. Only spring suspensions have equalizers. Torsion axles don't. So, which torsion axle is the better one to have the brakes?

Does a tandem trailer with one axle brakes brake more or less effectively than a single axle trailer?

Assuming a slippery road where the braked wheels might lock up, would a tandem with one axle brakes be less likely to fishtail because the non-braked wheels would not lock up? (A poor man's ABS)

[Bill Millar]

Two axles, drum brakes on both.

No problems in 1000 miles of towing during the summer and about 6 launch and recoveries. Ensure good fresh water flushing system for drum brakes if you sail in salt water.

[Chip Hindes]

Jack, yes it is the equalizer which causes the brake torque to lift the front axle.

There's nothing unique about a torsion axle which allows it to be mounted without an equalizer. You can mount a conventional spring axle with no equalizer as well, it's just that, conventional axle or torsion, either is inferior to the tandem setup with equalizer. Whatever advantages the torsion axle has over the conventionally sprung axle, the lack of an equalizer isn't one of them.

One thing that's very important with no equalizer is that the trailer be level when towing. Otherwise, the weight of the trailer is not equally distributed on the two axles, and you've compromised some of the advantage of the two axles right off the bat.

As to your question which axle to put the brakes on minus an equalizer, it comes down to what is the geometry of your entire system, including the tow vehicle. When you brake hard, is the trailer tilted forward or back? If forward, then more weight of the trailer is on the front axle and that's the one which should have the brakes. And vice versa.

A better answer would be: the rear axle, after you've replaced the torsion axles with conventionally sprung axles with equalizer.

Other things being equal, a two axle trailer with or without equalizer is carrying roughly half its weight on each axle. Even when braking the "correct" axle and with optimum weight transfer, yadda yadda, some of the weight is still being carried by the freewheeling axle. With less weight, the braking axle will lock up earlier than it would have if it were carrying all the weight.

Regarding the fishtailing question, just keep in mind that weight which is on the freewheeling axle is weight that's not helping the braking axle to stop the trailer. If the braking axle is not stopping the trailer, the tow vehicle must do it. This is the classic cause of a jacknife, when the trailer overpowers the stopping ability of the tow vehicle.

This is from somebody who's just as cheap as the next guy: If you're going to sink over $1000 into a tandem axle conversion (more for the tandem torsion axle setup) or well over $2K for a new two axle trailer, why would you cheap out at the last minute and not spend a couple hundred extra for brakes on all four wheels?

[Jack O'Brien]

Chip H said:

"why would you cheap out at the last minute and not spend a couple hundred extra for brakes on all four wheels? "

I won't cheap out. I will get the new trailer with new SS disc brakes, on which ever axle the builder prefers, and then install my existing SS discs on the other axle.

Don't think I have seen a torsion suspension with an equalizer, wonder why.

Thanks for good answers to interesting questions.

[Chip Hindes]

Your question made me look at the torsion axle more closely and I have now "revised" my previous answer.

If I were like some politicians I have heard recently, I would redifine the original parameters or deny I said what I said, or simply change the subject completely. In any case, I would staunchly maintain I was not wrong.

However, I'm not, I won't and I was wrong.

A tandem torsion axle system with two trailing arms must have two axle brakes. If one leading and one trailing arm axle, the leading arm axle should have brakes, the trailing arm axle should not. If two leading, either or both may have brakes.

Here's the reasoning: When you brake a trailing arm torsion axle, the brake torque will tend to rotate the torsion arm toward the rear and up, regardless of whether the trailing arm axle is the front axle, the rear axle, or both. If a single braking axle, this will transfer additional weight to the other, non braking axle, in effect lifting the braking axle. Bad.

With leading arm axles, brake torque rotates the arm to the rear and down. With a single braking axle, additional weight transfer to the braking axle. Good.

If both axles are braking, and both are leading or both trailing, there is no weight transfer during braking and all will brake equally. Good.

Finally, with one leading and one trailing, both braking, both axles will transfer additional weight to the leading arm. The trailing arm will then lift and lock up prematurely. Skip the brakes on the trailing arm.

The torsion "axle" mount is essentially fixed, and welded directly to the frame rails. This is necessary because, even at rest there is there is a tremendous amount of torsional force trying to twist the axle loose from its mounting on the frame rails.

No matter what you did to articulate a tandem torsion axle, the parts would have to be extra beefy to handle the torque. The geometry, particularly under braking becomes fairly complex.

Airstream had been running a tandem torsion axle on their trailers since the early sixties, and they are legendary for their ride and ease of towing. The difference is, the Airstream system is fully independent. Obviously Airstream is doing something right. Perhaps Moe will comment; he owns one.

Most torsion axles are not fully independent, but they do have the advantage of low profile, light weight, less unsprung weight and therefore less inertia resulting in the tires spending more time in contact with the road, always an advantage.

Still with me? I should also temper my previous comment somewhat. If you brake both axles, and pay attention to keeping your trailer level, tandem torsion axles should be OK. The disadvantage would be that most of your existing parts are not reusable; If you plan to do so you need to be careful that anything other than the wheels and tires would even fit. I would also be careful about mixing rotors, calipers, etcetera of different manufacturers, even if the differences were confined to different axles.

[Moe]

On their Classic models, Airstream uses independent Henschen torsion axles. I don't know for sure, but on some of the lower priced models, particularly those less than 8'6" wide, they may now also use Dexter. I just can't remember.

Our 34' has triple-axles, while most Airstreams, other than the single-axle Bambi, use tandems. The independent feature, combined with shock absorbers at every wheel, make for a great handling trailer.

I thought the Mac handled pretty well behind the F250, but I do keep in mind the 24 gallon fuel tanks way behind the axle were empty. After losing two tires, one catastrophically taking out a fender, on the way home, I don't have a lot of confidence in towing this boat loaded any distance without a dual axle or 15" tire upgrade.
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Moe