Trailer woes

[snydzy]

Just replaced for the third time (this season) broken brake line(s) on the aluminum trailer for my 25SC. Deflection of the front wheels while cresting on steeper boat ramps is causing the brake lines to shear on the trailer frame. The tandem axle trailer I use has torsion axles. Lots of positives about torsion axles over traditional leaf spring setups. They tend to be quieter because of the independent wheel movement, more responsive to small bumps, and because of the rubber tend to dampen vibration better..... but.....
The key with multiple axles is making sure they will share the load.  There really is no point to having multiple axles if they don’t work together.  Call it “Load Share” or “Equalization”.  Since the road is not always flat, and the trailer not always level, the axles need to accommodate uneven ground while still sharing the load. That means, as you go over a bump, or crest on a steep boat ramp, the wheel up on the bump can end up carrying nearly all the weight, with the other axle(s) carrying much less.  It’s only a short time overload, but obviously severe enough to cause enough deflection to shear the brake lines. This time I turned the front caliper adaptor ports to face aft, rather than perpendicular to the wheel, which should allow enough clearance to alleviate this issue.
But it did get me thinking,... almost all the trailer tire problems I’ve had, (and I’ve had a few), has been those front tires on the tandem axle setup. They have been the ones that have failed, blown out, blistered, or worse...abused more because of this kind of overloading, and who knows what internal damage is sustained....? Is it better with a triple axle set up? Leaf axles? Without load sharing, I don’t see how. What are boat trailer manufacturers thinking?

 

[scross]

We tow our R-25 Classic about 1,200 miles a year (3,200 miles this year) and have never had any issues with trailer brake lines. To be fair ramps in the PNW don’t tend to be that steep. We have a 5 year old Tuff aluminum frame trailer.
Have you been checking with a digital level to ensure your trailer frame is parallel with the ground when towing normally to within a degree or two? Sounds like you are towing nose low. Perhaps your your tongue weight is too high. For tandem axle trailers it should be 7-9% of gross weight, not the 10% commonly mentioned for single axle trailers. We typically tow at an average of 6.8% tongue weight (660 pounds) and it tows great. Be sure your Load Range E tires are always inflated to just at 80 psi cold, assuming that is the max pressure for your specific tires. We are on our second set of tires in 5 years. Changed out the old ones after 4 years due to tread wear getting low. Other than one nail, we have never any issues with the tires.

 

[snydzy]

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We tow our R-25 Classic about 1,200 miles a year (much more this year) and have never had any issues with trailer brake lines. To be fair ramps in the PNW don’t tend to be that steep. We have a 5 year old Tuff aluminum frame trailer.
Have you been checking to ensure your trailer frame is level when towing normally to within a degree or two? Sounds like you are towing nose low. Perhaps your your tongue weight is too high. For tandem axle trailers it should be 7-9% of gross weight, not the 10% commonly mentioned for single axle trailers.

I assure you, that’s not the case. I’m towing in the vicinity of 5000 miles per year.... my setup is correct. What I’m describing is enough load to have the axle arm rotate higher than the trailer frame. After launching the boat, picture the trailer rising out of the water, then cresting on the top of the ramp where the two front tires actually elevate off the ground the two rear tires. That load shifts completely to the front axle. Now imagine that with the load from the boat weight. That’s all the load on the front axle at that moment...

 

[scross]

Ok, I’ve just never seen a ramp so steep to cause what you are describing! Most ramps here are too shallow. My rear truck tires need to be 6-8” deep in the water before the boat floats off the trailer.
Our rear axle almost leaves the ground for about a second or two at the top of the ramp when retrieving the boat but I just can’t imagine the front axle rotating that much.

PS: Each of our torsion axles are rated for 6,000 pounds.

 

[snydzy]

Our rear axle almost leaves the ground for about a second or two at the top of the ramp when retrieving the boat but I just can’t imagine the front axle rotating that much.

PS: Each of our torsion axles are rated for 6,000 pounds.

I have similar rating on my axles, trailer rated at 10000 lbs.
What happens if you drive a wheel up on a curb? What kind of load is the tire and axle sustaining? Tire changing ramps do the same thing. That axle and tire are basically picking up the other axle’s load. There is no load sharing. Is a pothole any different? That’s my point. What are the trailer manufacturers thinking?

 

[iggy]

Maybe am missing something? But why not use a longer brake line? Just make sure that parts of it are secured to the trailer to protect it.

 

[scross]

This article discusses the issue you are raising and one design solution.

https://mechanicalelements.com/tandem-t ... le-design/

For us, with shallow launch ramps and never considering going over a curb (ever!) the load sharing problem with torsion axles hasn’t been a problem....

 

[trailertrawlerkismet]

I had this happen once, after having the trailer serviced....without the boat loaded onto the trailer. The brake lines that attach to the hubs were reinstalled at a wrong angle and when the boat was loaded the brake line got pinched, cut in half and then no brakes. This may not be your situation but make sure the angle of the brake lines at the hub takes into consideration the angle the brake fitting will be with the boat loaded. Again, may not be your situation.

Jim F