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Old 04-04-2010, 05:19 PM   #1
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Small Car Towing Improvements

We're always looking for ways to improve our Honda CRV's ability to tow our little Sunline (and our future 20 foot trailer).

To aid my search for improvements I frequently read English Web sites where towing fair sized rigs with small cars and small SUVs is the rule rather than the exception.

I have noticed that many people stiffen their rear springs with rubber coil stiffiners. These stiffiners slide between spirals of the spring's coils reducing the effect of rear loading keeping the tow vehicle flatter.

We do not see much of a loading effect from our trailer but I suspect the new trailer will be a little heavier and this is a potential solution. The following website shows the product. As well I have found I can buy them on EBAy for $28.

http://www.towbex.net/www.towbex.co.uk/info.php?p=12

Page down the screen to see the rubber coil inserts.
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Old 04-04-2010, 08:58 PM   #2
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Norm,
I don't feel very comfortable with this kind of "stiffener" of a compression coil spring.
Each element of a coil spring imposes primarily a twisting action on its "neighbor" elements, like a torsion spring. The "stiffener" interrupts this and eliminates part of the spring, as it reduces the available space for the coils to collapse. At the transition from free flexing coils to inhibited coils, it seems to me, there will be a bending force, which will impose significantly higher stress in the spring wire. This is mitigated to some degree by flex of the rubber stiffener itself, but there will be a transition area of higher bending stress. This can not be good.
I like the helper springs in form of concentric coil spring or air bladder inside the primary spring.
Just my thoughts.
Roar
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Old 04-05-2010, 02:15 PM   #3
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Roar,
Interesting thought. I guess it depends to some measure on the rubber's spring constant.

Today I measured the seperation of the coils, compressed (1 inch) and uncompressed (1.25 inches). Since the Honda weighs about 4000 pounds, the springs seem to individually compress an inch per 4000 pounds.

The addition of the trailer with a tongue weight of less than 200 lbs, 100 lbs per tire/coil spring, will only compress the tires a small fraction of an inch further under normal conditions. Braking may increase this some, possibly causing the rear end to be depressed (or maybe lifted). I've actually never noticed.

My suspicion is that it will cause the Honda to ride a little stiffer. In some sense like having progressive, non-linear springs. My main reason for trying them is that others say they work. Time will tell and I will post the results.
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Old 04-05-2010, 04:25 PM   #4
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Norm,
Progressive springs are typically wound with very close coil spacing at one end. This is done so that initial compression makes the tightly wound coils touch each other.
When this happens, there will be fewer coils actually deflecting, and the spring will be "stiffer", as in having a higher "spring rate".
You essentially do the same thing when you put in the "stiffeners".
Fewer coils are flexing, and the spring rate goes up. The spring rate is inversely proportional to the number of "active" coils.
My worry would be the increased stress at the ends of the inserted stiffeners.
FWIW.
Roar
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Old 04-06-2010, 09:42 AM   #5
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Quote:
Originally Posted by Viking
My worry would be the increased stress at the ends of the inserted stiffeners.
FWIW.
Roar
I agree, and wouldn't go near a spring "insert."

IMO, air bags or even air shocks would be a much safer solution. I've seen way too many broken springs from people trying inserts/clamps/whatever.

- Frank
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Old 04-06-2010, 11:00 PM   #6
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FWIW I used those gizmos when I upgraded from a small block 302 to a 351CJ in an old ford years ago. Worked fine, no troubles, and I was far rougher on them then you'll be I bet.

All I did was bought 2 sets (4 total) so I could place 2 on each spring so the spring stayed straight and didn't assume a < profile...
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Old 04-07-2010, 07:57 AM   #7
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FWIW - For What Its Worth - I do need an Internet Dictionary.

Thank you for all your inputs. I think the most important thing is I am not attempting to correct some significant problem, just a small improvement.
Unlike most of you I'm towing a very light trailer that weighs half what out tow vehicle weights.

One saving grace is that I'm not trying to compensate for excessive loading on the rear Honda axle but rather attempting to ensure equal loading on both axles.

This spring I'm going to move my ball 2-3 inches closer to the rear axle, a 7 or 8% improvement. The addition of stiffeners intended to be a similar improvement. Personally I'm not convinced that it will add much but I do want to try it.

Ted's approach of using multiple stiffiners is interesting because this moves the solution closer to inserting stiffer springs. If stiffiners of different stiffness were available this would be a safer solution.
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Old 04-07-2010, 08:19 AM   #8
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Quote:
Originally Posted by Honda03842

One saving grace is that I'm not trying to compensate for excessive loading on the rear Honda axle but rather attempting to ensure equal loading on both axles.
This spring I'm going to move my ball 2-3 inches closer to the rear axle, a 7 or 8% improvement. The addition of stiffeners intended to be a similar improvement. Personally I'm not convinced that it will add much but I do want to try it.
Norm

This might help

Air bags, stiffer springs or even moving the tow ball closer will not shift weight from the rear axle to the front if that is what you are attempting to do to help axle loads. When you drop the dead weight of the TT on the tow ball, the rear axle will take more load and the front axle will reduce load. Even if there where no springs in the back, a solid connection, the weight on the rear axle will still be there and the lose on the front the as well.

Moving the tow ball closer to the rear axle will change things. The rear axle will gain a little less and the front will loose a little less.

If changing axle loads is what you are wanting to do a WD hitch does this if your receiver can handle a WD hitch. Reese makes a mini WD hitch for PU’s that may work on your TT.

If you want to know how many pounds the tow ball move will actually accomplish in axle load changes, I can work you up an estimate. Tell me the truck wheel base, the distance from the back of the rear axle to the center of the ball now and the amount of inches you want to move the ball forward. If you have a scaled tongue weight I can use that too but do not need it to give you the amount of change.

Hope this helps

John
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Old 04-07-2010, 09:09 AM   #9
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John,

We have a very light situation. Our ball loading is only 165 pounds. I'm just nerking around will small things hoping to make things just a little better. We have now towed 20,000 miles and have had virtually no problems except when we once overloaded the rear bumper with a generator and got a little sway.

Moving the ball closer to the rear axle does a couple of things. One it decreases the lever arm to the rear axle, I assume this diminishes motion of the rear axle from side to side when the trailer gets off axis. Two, it reduces lift of the front end because the seesaw effect is reduced by moving the ball closer the rear axle trying to get to a fifth wheel like situation.

Also stiffening the springs doesn't reduce the load on the rear axle except in the extreme where the rear spring has totally collapsed to coil contact, of course we're no where near that situation.

Our new trailer, some 7 feet longer than our existing trailer but a similar weight, does cause concern because the side forces from wind and passing trucks will be twice as great since the side area is twice as large.

As well, the new trailer will also be a single axle trailer though with a heavier duty axle.

With this thoughts in mind I've considered other approaches to trailer straight line stability. I've considered adding a single wheel to the rear of the trailer that is virtually locked into straight line travel, acting like a rudder, functioning like seperated axles on semis.

The third tire, smaller than the primary tires, would not need to be heavily loaded by trailer weight since it's primary goal is to prevent side motion at the rear.

To prevent excessive tire scrubbing in corners it's possible to release the wheel for turning or more simply to lift the wheel when turning significantly and/or when speeds are low.

After looking at the Living Lite trailer we have decided on an all Aluminum frame. Unfortunately I have not found an aluminum axle. The axle with brakes weighs as much as the whole trailer frame including base, walls and roof frame.

If anyone knows of an aluminum axle I'm interested.

Maybe I have had too much time to think this lazy winter in Florida.
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