Trailer axle/tire question

Skyco · Mar 28, 2009

You guys are all wet with your car theory about brakes being applicable to trailers.
Weight transfers to the REAR axle on equalized tandems under braking. If you've ever had brakes on both axles and get a lockup you'll see it is always the front axle that locks up first, thereby showing it has less traction.
Gimme a few minutes and I'll find a reference.
Maybe that trailer engineer from Holland will show up- this has been discussed and settled before!

From-http://www.championtrailers.com/techsup.html#techretro

When only one brake axle is being installed on a tandem axle trailer, the brakes should be on the rear axle for maximum system performance. Rotational torque applied to axles during braking shifts the equalizer and applies more weight to rear axle. If brakes are installed on the front axle, the wheel may skid during braking. Brakes on rear axle are more effective as the equalizers shifts and the rear tires dig in to the pavement.

mfreund · Mar 28, 2009

As for tire size, my trailer has the same size as my truck and bolt pattern. I carry a spare for each which makes for 2 spares!!

I know the rear axle on semi tandems do the most work for braking but not sure for trailer axles

wushaw · Mar 28, 2009

Well Skyco that makes sense as to why trailer manufactures put brakes on the rear axle when only one set of brakes are used.

That car theory obviously does hold true with trucks also, since the truck has six brakes and the trailer has four, Who's doin most of the stopping....truck or trailer?? Does that 17k truck really need six brakes to stop itself? Or is it more of a braking platform for doing most of the stopping for a 60K trailer and the trailer brakes help slow down and keep the trailer from jackknifing.

radioman · Mar 28, 2009

Skyco said:
You guys are all wet with your car theory about brakes being applicable to trailers.
Weight transfers to the REAR axle on equalized tandems under braking. If you've ever had brakes on both axles and get a lockup you'll see it is always the front axle that locks up first, thereby showing it has less traction.
Gimme a few minutes and I'll find a reference.
Maybe that trailer engineer from Holland will show up- this has been discussed and settled before!

From-TECHNICAL INFORMATION AND TECH ARTICLES

When only one brake axle is being installed on a tandem axle trailer, the brakes should be on the rear axle for maximum system performance. Rotational torque applied to axles during braking shifts the equalizer and applies more weight to rear axle. If brakes are installed on the front axle, the wheel may skid during braking. Brakes on rear axle are more effective as the equalizers shifts and the rear tires dig in to the pavement.

Thanks for the tidbit skyco. It's always good to have people like you to look out for us idiots .

At least I have learned something today.

Skyco · Mar 29, 2009

- it seems intuitive the front axle would be best..but...

I'm actually struggling a little with this now as I have a dump trailer that wants to lock up the front axle brakes when empty, even with the controller turned down. I'm going to add a resistor to the front brakes to make them work a little less firmly than the back brakes. Loaded it isn't an issue. Somewhere I have a 40+ year old brake resistor from the old days when we actually hooked controllers into the hydraulic lines on the tow vehicles.

BTW I'm firmly in the camp a trailer should ALWAYS have brakes on BOTH axles. The only trailer I ever bought with one axle brakes I added the second axle brakes to immediately.

J_J · Mar 29, 2009

Skyco said:
- it seems intuitive the front axle would be best..but...

I'm actually struggling a little with this now as I have a dump trailer that wants to lock up the front axle brakes when empty, even with the controller turned down. I'm going to add a resistor to the front brakes to make them work a little less firmly than the back brakes. Loaded it isn't an issue. Somewhere I have a 40+ year old brake resistor from the old days when we actually hooked controllers into the hydraulic lines on the tow vehicles.

BTW I'm firmly in the camp a trailer should ALWAYS have brakes on BOTH axles. The only trailer I ever bought with one axle brakes I added the second axle brakes to immediately.

That does bring up a good point. If you are setting the controller for the best braking effort, which axle are you setting? If your theory is correct, you would set the brakes just before lock up but then you are actually setting the controller for the front axle, which leaves the rear axle at diminish capacity. So, if you want the rear axle to have the best braking, or equal braking, you have to some how put less braking effort on the front to prevent lock up, and by adding a resister to the front axle, I believe you will be able to balance the braking effort like you said. The controller setting will vary with each load, and your balanced condition. In theory, to compensate for the above conditions, you need a variable resister on the front axle brakes to fine tune the braking action.

The original poster should measure several trailers to get the correct spacing, for the math has been worked out long age. As far as tires, If you want smaller, boat tires might work. They haul some heavy boats. They also make tire just for trailers that are designed for trailers. At least, get the load range right plus 10 %. Also, select tires and rims that are readily available.

Diamondpilot · Mar 29, 2009

I have 2 trailers, both tandem 7,000#, and one has brakes on the front axle and the other has it on the rear. Can not tell a bit of difference. My buddies down the road also has them on the front but my neighbors has them on the rear. Not any real clear winner. As for the tires and wheels go one of my trailer has 205-75-15 load range C and the other has 205-75-14 load range C. Both are rated for 1760# each. No real problems with either.

13" wheels will not work with 3,500# axles because the rims will not fit over the wheel.

Chris

LBrown59 · Mar 29, 2009

Skyco said:
- it seems intuitive the front axle would be best..but...

I'm actually struggling a little with this now as I have a dump trailer that wants to lock up the front axle brakes when empty, even with the controller turned down. I'm going to add a resistor to the front brakes to make them work a little less firmly than the back brakes. Loaded it isn't an issue. Somewhere I have a 40+ year old brake resistor from the old days when we actually hooked controllers into the hydraulic lines on the tow vehicles.

BTW I'm firmly in the camp a trailer should ALWAYS have brakes on BOTH axles. The only trailer I ever bought with one axle brakes I added the second axle brakes to immediately.

That's my camp also.

Skyco · Mar 29, 2009

J_J said:
That does bring up a good point. If you are setting the controller for the best braking effort, which axle are you setting? If your theory is correct, you would set the brakes just before lock up but then you are actually setting the controller for the front axle, which leaves the rear axle at diminish capacity.

On my particular trailer it is an issue only when lightly loaded or empty, when the trailer it at 14,000 gross I can't lock up any wheel

The trailer still weighs 3500 lbs empty so I'd like some braking with it empty, more than it feels like right before the front locks up. If I add the resistor to the front brake wiring I'll need to add a switch to bypass it when full.

sandman2234 · Mar 29, 2009

I am generally inclined to have a lot more weight on the front of a trailer. Put a truck in the ditch about 30 years ago due to a rear heavy trailer and I haven't forgotten it. I have pulled a lot of different trailers, and when empty, if one axle is "light", it is always the back axle. Why would I ever want to have a set of brakes on the axle that is generally having the lessor amount of weight on it? Granted, if the trailer sets exactly level, with equal amounts of weight on each axle, then maybe, but in my experience, the rear one is the one that usually locks up.
Having brakes on a trailer is a good thing, although not always required. If your towing nothing but a lawnmower or something light, then trailer brakes aren't usually required. Having spec'd out brakes for at least one axle might cover the times when you need to haul something just a little heavier. In this state, any loaded trailer over 2,000 pounds is required to have brakes, and most people's tow vehicles need them to assist braking. Someone with a small dual axle trailer hauling only light loads can easily get away with just having single axle brakes. Depends on the load, the trailer, the tow vehicle, the terrain, the road conditions and probably a bunch more things. Each circumstance requires the driver to consider what he (or she) is doing and allow for just that. If you aren't sure of what your doing, or hauling medium to heavy loads, then by all means dual axle brakes are a way to offset the odds of getting into trouble. To mandate that all trailers have dual axle brakes is trying to require things that aren't always necessary, just because in your case they are. If dual axle brakes were always needed, there would be no single axle trailers on the road.
David from jax