Optimal trailer set up

[Bimmer-Bob]

So I'm shopping a couple different car haulers and I have a question. When choosing a trailer, would it be more desirable to have a lighter weight, or have the capacity to accept a weight distributing hitch? I'm looking at both aluminum and steel trailers, and while the aluminum models will save me a few hundred pounds, they generally will not accept a weight distribution hitch. The owners manual says that with loads over 2000 pounds that an appropriate sway control device should be used. I would like to comply with the manual, and for safety reasons, I think weight distribution and sway control are both good ideas. Unfortunately, if I go with a steel trailer, I can use the hitch but I'll end up with a gross weight somewhere around 4500 pounds. Technically still under, but not by much. So, given those two choices, which do you think is the better option? Thanks.



Edit: let's assume for this discussion that the aluminum trailer has a weight advantage of 500 pounds.

 

[G8RB8_12SR5]

I tow a 4800lb RV with a WDH and sway control and a Tekonsha P3 brake controller. Outside of going up hill and accelerating onto the interstate, I actually barely notice it's back there just rolling along. Sway control makes a big difference as do Air Lift 1000 airbags, I'd go that direction.

 

[racerjb]

What trailers are you looking at? I own dealership in Oregon and you can for sure run a weight distribution kit on a aluminum trailer. You just have to use the kind that clamp around the frame with integrated sway. With aluminum your are going to be able tow more due to the curb weight of the trailer being lighter. Which is important for the 4 runner with limited towing capacity. If you had a half ton truck then I would say go with the steel. We sell a fair bit of trailers to norcal but probably long drive for you. Are looking at open trailer or enclosed?

 

[Bimmer-Bob]

Looking for an open car hauler. Most recently the Aluma 7816, but the manufacturer said it wasn't compatible with a WDH. Said it might snap the tongue? I was hoping to use an Equal-I-zer.

 

[JeremyB]

The owners manual says that with loads over 2000 pounds that an appropriate sway control device should be used. I would like to comply with the manual, and for safety reasons, I think weight distribution and sway control are both good ideas.

I don't think Toyota spent much time updating the 2014 manual. The stated tow rating is wrong, GCWR is wrong, and they state you need an appropriate sway control if the load is over 2000 lbs. The 2014 4Runner comes with Trailer Sway Control built into the VSC. It's not a bad idea to add mechanical sway control, but the built-in TSC should be adequate for loads over 2000 lbs.

One interesting difference between the 2013 and 2014 manual is the removal of any references to a weight distributing hitch for 2014. 2013 - p301. 2014 - p181.
Are WDH no longer acceptable? Who knows... :dizzy:

Unfortunately, if I go with a steel trailer, I can use the hitch but I'll end up with a gross weight somewhere around 4500 pounds. Technically still under, but not by much. So, given those two choices, which do you think is the better option? Thanks.

Keep in mind that the hitch is rated to 5000 lbs. The 4700 lb rating is power limited, something that can be mitigated by route selection. If you weren't power limited and had a beefy enough hitch, 6500 or greater isn't a problem -considering stability and brakes. (The GX shows us this).

If you chose a WDH, be sure to set it up right. The 2013 Owner's Manual requests 100% FALR (Front Axle Load Restoration). Essentially, the front axle ride height is the same w/o a trailer as it is w/trailer + WDH. SAE J2807 (towing standard) tests at 50% FALR and several OEMs have been trending to 50% FALR. Whatever you decide, take the setup to the scales and make sure your FALR and TW (Tongue Weight) are within the ballpark.

Lastly, regarding tongue weights. Too much and you sag like a mofo and add oversteer to the setup. Bad. Too little the trailer is prone to sway. Very bad.

The 'ideal' tongue weight is one where you minimize TW, while keeping the trailer stable. You can read the nuts and bolts behind the physics here, but suffice to say, the simple equation is:

m*a*b=I

where,
m = mass of trailer
a = distance from the ball coupler to the trailer's axles
b = trailer's center of gravity to the trailer's axles
I = polar moment of inertia

This equation is why European RV trailers can get away with 4-7% tongue weight. The lower your trailer yaw inertia, the smaller 'b" can be. "b" directly relates to TW. So they put propane tanks, spare tires, water tanks, ect all near the trailer's center of gravity, greatly reducing the polar moment of inertia. In the US, the market uses much larger vehicles to tow, so propane tanks and spare tires are up front, and water tanks are wherever - resulting in the greater TW% requirements (10-15%).

For the tl'dr crowd: Tongue weight required for stability is dependent on the trailer's polar moment of inertia. Which comes out to 10-15% for most trailers.

Emtpy, my 5x8 utility trailer requires 8.4% TW to make m*a*b=I (I used it for CAD practice a while back). Actual TW is 10.7%. Thus is is stable. If you remove the 70lb rear gate, m*a*b=I at 6.8%.

Okay, enough rambling. Messed up my knee yesterday and I've nothing better to do than sit here and talk trailer stability. ound:

 

[racerjb]

Looking for an open car hauler. Most recently the Aluma 7816, but the manufacturer said it wasn't compatible with a WDH. Said it might snap the tongue? I was hoping to use an Equal-I-zer.

Uh. I can't say I have run into that. They must be using thin wall tubing or it might be a single tube tongue with just outer supports, not a true aframe or triangulated tongue... I know ATC and Mission trailers you can so maybe worth looking into one of those at the nearest dealer to you. The EqualIzer brand version is one of the best WD kits so your good with that. Or I guess you can airbags instead of a WD kit but I am new to 4runners so I am not sure how they will impact ride on it.

 

[Bimmer-Bob]

I don't think Toyota spent much time updating the 2014 manual. The stated tow rating is wrong, GCWR is wrong, and they state you need an appropriate sway control if the load is over 2000 lbs. The 2014 4Runner comes with Trailer Sway Control built into the VSC. It's not a bad idea to add mechanical sway control, but the built-in TSC should be adequate for loads over 2000 lbs.

One interesting difference between the 2013 and 2014 manual is the removal of any references to a weight distributing hitch for 2014. 2013 - p301. 2014 - p181.
Are WDH no longer acceptable? Who knows... :dizzy:


Keep in mind that the hitch is rated to 5000 lbs. The 4700 lb rating is power limited, something that can be mitigated by route selection. If you weren't power limited and had a beefy enough hitch, 6500 or greater isn't a problem -considering stability and brakes. (The GX shows us this).

If you chose a WDH, be sure to set it up right. The 2013 Owner's Manual requests 100% FALR (Front Axle Load Restoration). Essentially, the front axle ride height is the same w/o a trailer as it is w/trailer + WDH. SAE J2807 (towing standard) tests at 50% FALR and several OEMs have been trending to 50% FALR. Whatever you decide, take the setup to the scales and make sure your FALR and TW (Tongue Weight) are within the ballpark.

Lastly, regarding tongue weights. Too much and you sag like a mofo and add oversteer to the setup. Bad. Too little the trailer is prone to sway. Very bad.

The 'ideal' tongue weight is one where you minimize TW, while keeping the trailer stable. You can read the nuts and bolts behind the physics here, but suffice to say, the simple equation is:

m*a*b=I

where,
m = mass of trailer
a = distance from the ball coupler to the trailer's axles
b = trailer's center of gravity to the trailer's axles
I = polar moment of inertia

This equation is why European RV trailers can get away with 4-7% tongue weight. The lower your trailer yaw inertia, the smaller 'b" can be. "b" directly relates to TW. So they put propane tanks, spare tires, water tanks, ect all near the trailer's center of gravity, greatly reducing the polar moment of inertia. In the US, the market uses much larger vehicles to tow, so propane tanks and spare tires are up front, and water tanks are wherever - resulting in the greater TW% requirements (10-15%).

For the tl'dr crowd: Tongue weight required for stability is dependent on the trailer's polar moment of inertia. Which comes out to 10-15% for most trailers.

Emtpy, my 5x8 utility trailer requires 8.4% TW to make m*a*b=I (I used it for CAD practice a while back). Actual TW is 10.7%. Thus is is stable. If you remove the 70lb rear gate, m*a*b=I at 6.8%.

Okay, enough rambling. Messed up my knee yesterday and I've nothing better to do than sit here and talk trailer stability. ound:

I understand the concept of having enough (but not too much!) tongue weight, and have heard the 10-15% figure several times. I even had someone tell me 12% specifically, so I was going to sort of shoot for that. I might just have to play around with your equation up there and see what I can come up with, though.

Totally confused with this FALR thing, though. The '14 T4R manual doesn't mention it. And what sort of "set up" does the WDH really require? I get positioning the load & using a scale to get the TW right, but what exactly is being adjusted on the hitch? And how are you checking your adjustments?

 

[Biggcrisp]

I'm following your planning and am excited about the adventure you are undertaking. You are Certainly doing some homework.

I tow just over 5,000 lbs. with close to 600 lb. tongue weight. Using a 2012 sr5, wd hitch & sway control. The wd hitch has no effect on the front axle height with my setup. It does lift the rear a little, maybe 3" of sag removed. The sway control makes a world of difference (tried with & without). I am satisfied pulling across the Midwest and have no desire to upsize my tow vehicle- even after reading the 2014 "guide to towing" that showed up in the mail today.

My thoughts on your trailer choice is that you are not going to notice a few hundred pounds either way once you pass 4,000 lbs.

Keep us posted.

 

[Bimmer-Bob]

I'm following your planning and am excited about the adventure you are undertaking. You are Certainly doing some homework.

I tow just over 5,000 lbs. with close to 600 lb. tongue weight. Using a 2012 sr5, wd hitch & sway control. The wd hitch has no effect on the front axle height with my setup. It does lift the rear a little, maybe 3" of sag removed. The sway control makes a world of difference (tried with & without). I am satisfied pulling across the Midwest and have no desire to upsize my tow vehicle- even after reading the 2014 "guide to towing" that showed up in the mail today.

My thoughts on your trailer choice is that you are not going to notice a few hundred pounds either way once you pass 4,000 lbs.

Keep us posted.

Thanks for the info. My gut feeling is that the relatively modest weight advantage of an aluminum trailer is probably not worth the exponential increase in price, especially if it negates the ability to use a WD hitch with sway control, which I'm thinking is going to make the tow much easier. I actually have a lead on a pretty inexpensive, fairly lightweight (1560#) open deck steel car hauler. My only concern is that the build quality seems pretty mediocre. I wish I could find a middle road between the super expensive aluminum models and the bargain basement steel haulers. I'd love a steel trailer with more of a premium fit and finish (loomed wiring, LED lights, torsion axles, painted undercarriage, etc). I've actually been exchanging emails with a builder about such a project, but I'm not sure we're getting anywhere.

 

[JeremyB]

Totally confused with this FALR thing, though. The '14 T4R manual doesn't mention it. And what sort of "set up" does the WDH really require? I get positioning the load & using a scale to get the TW right, but what exactly is being adjusted on the hitch? And how are you checking your adjustments?

They deleted any reference to WD hitches in the '14 manual.

From the '13 manual.

If using a weight distributing hitch when towing, return the front
axle to the same weight as before the trailer connection.
If front axle weight cannot be measured directly, measure the
front fender height above the front axle before connection.
Adjust weight distributing hitch torque until front fender is
returned to the same height as before connection.

WDH setup is basically setting FALR by adjusting the tension on the spring bars. More tension on the bars = more weight transferred from the rear axle to the front axle of the tow vehicle.

Drive on scale sans trailer and record tow vehicle front axle weight (W1).
Connect trailer.
Re-weigh tow vehicle. Record tow vehicle front axle weight (W2).
Tighten the spring bars to some guessed amount.
Re-weigh tow vehicle and record tow vehicle front axle weight (W3).
At this point, you'll have some amount of FALR.
Say W1 is 2000 lbs, W2 is 1500 lbs, and W3 is 1750 lbs.
2000-1500=500 lbs.
1750-1500=250 lbs.
250/500 = 50% FALR

If you tightened the springs such that W3 was 2000 lbs, you'd have 100% FALR.
2000-1500=500lbs
2000-1500=500lbs
500/500 = 100% FALR

If you don't have scales, you can just measure the height of the fenders and substitute those for the weights. If you started at 35" front fender height, then added the trailer + spring tension and ended up with 35" front fender height, you'd have 100% FALR

I tow just over 5,000 lbs. with close to 600 lb. tongue weight. Using a 2012 sr5, wd hitch & sway control. The wd hitch has no effect on the front axle height with my setup. It does lift the rear a little, maybe 3" of sag removed.

It's impossible to remove rear sag without decreasing the front ride height when using a WDH. The nature of the WDH is to transfer weight from the rear to the front. You may have not noticed it, but the front came down.

 

[Bimmer-Bob]

It's impossible to remove rear sag without decreasing the front ride height when using a WDH. The nature of the WDH is to transfer weight from the rear to the front. You may have not noticed it, but the front came down.

So does this mean that Toyota wants you to set up the hitch so that it basically is not distributing any weight to the front axle? How does that make sense? Or am I misunderstanding you?

 

[Biggcrisp]

Suppose I could clarify...ok maybe the front dropped 1/4" or less lol, after all my driveway is gravel where I measured.

My little springbar WDH is pretty weak as is the factory hitch when it comes to actually redistributing weight.

It appears that these modern type WDH systems use the trailer tongue as a pivot to raise the rear of the vehicle versus the old style that used a heavy hitch/frame combo to push down the front end. I've seen but never used the old style, only thing I'm sure about is that my system appears to be just adequate to lift the rear end a little.

On the airbag equation, my rear springs have a large solid rubber cushion thing in them. No way to use airbags without removing them as far as I know?

 

[JeremyB]

So does this mean that Toyota wants you to set up the hitch so that it basically is not distributing any weight to the front axle? How does that make sense? Or am I misunderstanding you?

No, I'm a terrible writer. Let me try again.

When using a WDH hitch, Toyota is asking that the load on the front axle without a trailer be the same once you add the trailer and tighten the WDH springs.

Here are some actual weights, but from something that isn't a 4Runner.

Sans trailer:
TV Front Axle: 2139 lbs
TV Rear Axle: 1913 lbs

Adding a 3500lb 5x8 trailer with 12.5% tongue weight.

With trailer:
TV Front Axle: 1888 lbs
TV Rear Axle: 2602 lbs

So we've lost (2139-1888)=251 lbs off the front axle and added (2602-1913)=689 lbs onto the rear axle.

If we follow Toyota's recommendations, we need to use the spring bars to redistribute 251 lbs to the front axle to get 100% FALR. 100% of the weight you lost by adding the trailer will go back on the front axle.

Working the math on my example vehicle, you'd need 895 lbs of total spring force (irrelevant to this example ) and would end up with:

With trailer + WDH force:
TV Front Axle: 2139 lbs
TV Rear Axle: 2183 lbs

You end up back to the original front axle weight, and much more manageable (2183-1913)=270 lbs to the rear axle.

If you assume the rear axle wheel rate is 200 lb/in, you can calculate the rear sag difference between stock, trailer, and trailer + WHD.

Stock: 0 (Since it is our baseline)
Trailer: 689/200 = 3.4" rear sag
Trailer + WDH = 270/200 = 1.3" rear sag

The WDH would bring the rear (3.4-1.3)=2.1" up when compared to not using a WDH.

Does this make any sense? :shrug:

 

[Bimmer-Bob]

No, I'm a terrible writer. Let me try again.

When using a WDH hitch, Toyota is asking that the load on the front axle without a trailer be the same once you add the trailer and tighten the WDH springs.

Here are some actual weights, but from something that isn't a 4Runner.

Sans trailer:
TV Front Axle: 2139 lbs
TV Rear Axle: 1913 lbs

Adding a 3500lb 5x8 trailer with 12.5% tongue weight.

With trailer:
TV Front Axle: 1888 lbs
TV Rear Axle: 2602 lbs

So we've lost (2139-1888)=251 lbs off the front axle and added (2602-1913)=689 lbs onto the rear axle.

If we follow Toyota's recommendations, we need to use the spring bars to redistribute 251 lbs to the front axle to get 100% FALR. 100% of the weight you lost by adding the trailer will go back on the front axle.

Working the math on my example vehicle, you'd need 895 lbs of total spring force (irrelevant to this example ) and would end up with:

With trailer + WDH force:
TV Front Axle: 2139 lbs
TV Rear Axle: 2183 lbs

You end up back to the original front axle weight, and much more manageable (2183-1913)=270 lbs to the rear axle.

If you assume the rear axle wheel rate is 200 lb/in, you can calculate the rear sag difference between stock, trailer, and trailer + WHD.

Stock: 0 (Since it is our baseline)
Trailer: 689/200 = 3.4" rear sag
Trailer + WDH = 270/200 = 1.3" rear sag

The WDH would bring the rear (3.4-1.3)=2.1" up when compared to not using a WDH.

Does this make any sense? :shrug:

Okay, so to break it down Barney-style because I didn't have time to read your whole post in detail (I'll go back to it, promise):

Basically, 100% FALR means that you're simply re-adding to the front axle whatever load was lost after the trailer was hitched up, effectively negating the effect of the trailer on the front axle. But NOT redistributing any more weight than what was lost in the first place. Right?

 

[JeremyB]

Basically, 100% FALR means that you're simply re-adding to the front axle whatever load was lost after the trailer was hitched up, effectively negating the effect of the trailer on the front axle. But NOT redistributing any more weight than what was lost in the first place. Right?

Yes.

 

[Bimmer-Bob]

Yes.

Cool. Thanks for taking the time to explain.