Trailer tire size

[talbot]

I recently aquired my second DS II (the first having perished in a traffic accident). The new trailer has long bunks under the stern of the boat (as opposed to short pivoting supports) and a tire size larger than my old trailer. I find that the new boat is very difficult to launch at ramps that I previously used. On shallow ramps, the trailer bunks are still above waterline, and the fixed bunks don't let me tip the boat off into the trailer.

Questions:
1. What about those easy glide plastic patches you install on top of the bunks? Do they make a difference? Do they damage the hull?

2. What would be the consequences of using a smaller wheel size on the trailer? Lower gas mileage, I guess. Anything else? I'm trying to get the boat a little closer to the water.

[Roger]

I flipped my axel to the top of my springs, and gained (lost) 3 inches in height. If you are highway driving fairly long distances I would not want to go below 12" wheels. Going down to 8" wheels would make launching easier, but would burn out bearings faster. Some people have opted for launching tires. The spare and one extra wheel are carried for launching. They are smaller that the highway wheels.

Another option may be to add a tongue extender which puts your trailer deeper into the water. I did this on mine and was able to back it in a further 7'.

I assume your bunks are as low as possible aleady.

[algonquin]

The slides should make a difference but depending on the steepness of the ramp you could loose your boat quicker than expected. I recently saw a power boat depart the trailer about 20 feet before the owner expected it as he backed down a steep ramp.

As Roger suggested I modified my trailer by moving the axel above the springs which helped a lot. An extended trailer tongue would also help.

What size tires are you curently using ?

[metrounit9]

Is there any concern with having the axle be above the leaf spring rather than below?

It would think that the better arrangement would be to have the spring on top of the axle with the u-bolts fastening the two together rather than than having the u-bolts carry the entire load of the trailer.

I'm curious because I could use the lower trailer height, but have been hesitant to flip the axle/springs.

Dan

[adam aunins]

The u-bolts on your trailer axle are more than strong enough no mater which way you mount the axle. " as long as there in good shape" ie not rusted away or twisted up. If you can undo the nuts without the bolts breaking I think you'll be OK. If you have any dout new ones are dirt cheap and might be worth it if there's any rust at all , just to make things easyer.

Make sure you check for proper clearance between the boat/axle/tires. You wouldn't want to find out that you were making contact as things bounced down the road.

[Roger]

I had similar concerns as your common sense logic indicates in your previous post. It is intuitive that there is increased strength below. So off I went, with the similar concerns to my trailer manufacturer and posed the same issue to them.

They indicated to me that each 3/8" inch U bolt is individually rated at 3900#, and there are typically 4 of them per axel arrangement, so their combined strength should be able to share a load of 15,600 pounds, significantly more than the tires are rated at. They said they flip axels all the time, (for the same reason), with no concerns. When I suggested that I go to 7/16" or 1/2" bolts, they kinda laughed and asked me what I was planning on carrying anyhow!

They advised me to inspect the U bolts similarly. Rust was not a concern, unless it was pitting, and there was significant loss to the body of the U bolt, especially the thread. If the threads were in good shape, they indicated no concerns. New ones were $5 each.

They also indicated that tires typically toe in to trail better, and that I should ensure that I maintain the original orientation of the axel when I put it atop the springs. The also indicated tha springs usually have an aligning stud, that I would have to place a flange over or drill a hole in the axel to accommodate the stud.

I can sent you detailed pictures if you wish. roger02 att mts dott net

[talbot]

Before we got onto axels and springs, there was the question about what kind of tires I was talking about in the first place. My old boat used 4.80-80. The new trailer has 5.7-80. As the old trailer worked fine for 15 years with the smaller tire, it didn't seem like it would be too radical a change.

[algonquin]

Doesn't the 80 series designation indicate an 8 inch rim ? If so you really can't get much smaller. Maybe slightly narrower but the rim diameter would still be 8 inches.

[Roger]

The difference in side by each tire height is only about a inch, so that only translates to a 1/2" in actual lowering of the trailer deck if you used the 4.8 inch high tire. (your hub being in the middle halfs the actual hight lost) Not worth the change unless you must upgrade to new tires anyhow.

Mine are 570 x 12, so moving to 480x 8 would drop my trailer (12 minus8=4 divided by 2= 2" lower less another 1/2" for a smaller tire height.

Another thing to watch for when changing tires is to maintain the load range. On a larger tire like a 570x12 a load range B would do, but if dropping to a 480x8 I would have to go up to a load range C to be able to handle the same weight of boat and trailer.