Converting Trailer Tires, 12" to 8"

[wingo]

Hey Guys, I haven't seen this in the forums, so I'm sure its the one stupid question that shouldn't have been asked,
I have a 1970 15' Cobia on a 1971 Gator Trailer, boat fits well on it. The thing is the trailer sits high, I'm thinking someone put heavy leaf springs on it at one time. Its as if I can't back down the ramp enough to launch or load. I always have to get out of the boat and manhandle it back on or off. I weigh 210lbs. The water is getting colder, and I don't wanna get into hip high water to boat.
Here's the dumb question..could I change out the twelve inch tires and rims (four bolt 4.80X12) for eight inch(4.80X8) in order to lower the trailer? Are 8" able to handle this boat? Thanks for any advice.

 

[Willyclay]

Re: Converting Trailer Tires, 12" to 8"

Downsizing to the smaller wheels is the reverse of what most people do but I understand what you are trying to accomplish. The link below discusses some alternatives such as extending the trailer tongue. I chose the folding-tongue alternative. One concern about the smaller tires is their load capacity. Maybe 5.30X8 will work for you. Good luck!

http://forums.iboats.com/showthread.php?t=363886&highlight=Trailer+Tongue+extension

 

[jeeperman]

Re: Converting Trailer Tires, 12" to 8"

Your only going to lower the boat by 2.25" with that combo. And your load rating per tire will go from 785lbs to 690lbs.
If you go to afatter and 6-ply tire you can bump the weight capacity back to just under your current set up or to a bit over. But then the tire is a bit taller and thus the boat is only 1.25" lower.

Maybe look at how the boat is sitting on the trailer. Can it be altered to carry the boat lower.
Making sure no part of the boat hits crossmembers, etc.

 

[northernmerc]

Re: Converting Trailer Tires, 12" to 8"

Or find a different boat launch with a steeper drop off into the water.

 

[MRS]

Re: Converting Trailer Tires, 12" to 8"

If your axel is mounted on the bottom of the springs you can mount on top of springs and it will lower the trailer. Or you can pick up another axel with the spindels offset to lower trailer hight that is what I just did but I needed 1" higher.

 

[wtxpatrick]

Re: Converting Trailer Tires, 12" to 8"

I had a similar problem one time. I extended the trailer tongue about 6'. The trailer pulled better, and I could launch, tires dry.

 

[wingo]

Re: Converting Trailer Tires, 12" to 8"

Thank You all for the advice, it looks like I'll be getting some sort of extension, didn't even know anything like that existed. I really appreciate the help with my new hobby/sport.
Thanks Again!

 

[Stachi]

Re: Converting Trailer Tires, 12" to 8"

On my previous boat (16' fiberglass closed bow ski boat)that I towed with a 1987 S-10 Blazer..... I extended the tongue by 30"...... I did it because my winch handle , on an unaltered Sea Lion trailer,would hit the spare tire for my truck... AND to get the trailer in the water deeper for launch / recovery.... I gave that boat away to a friend , and the trailer/boat/engine is still out there having fun...

 

[jeeperman]

Re: Converting Trailer Tires, 12" to 8"

Thank You all for the advice, it looks like I'll be getting some sort of extension, didn't even know anything like that existed. I really appreciate the help with my new hobby/sport.
Thanks Again!

There is probably not a ready made off-the-shelf extension available for your particular trailer.
You will have to figure one out yourself from scratch.
Such as replacing the tongue with a longer tongue. Or adding tongue material to the existing. Or adding a swing-away tongue bracket and then new tongue tube from there, etc.
Either way it won't be a totally bolt-on change.
Check with your local trailer repair shop for guidance and alternatives also.

 

[Texasmark]

Re: Converting Trailer Tires, 12" to 8"

The smaller the tire, the faster it has to turn at a given mph and the more stringent the requirements are on the bearing lubrication. Then there is the pot hole thing where small tires are more subject to pothole damage than larger diameters.

Why can't you put 13" ties outside the boat on a drop axle? Check out Rangertrail trailers for example. The tires are outside the boat which allows for you to have a drop axle and get the boat down low.

Mark

 

[Jeep Man]

Re: Converting Trailer Tires, 12" to 8"

A picture says a thousand words they say. If you can post one we could maybe give you some other ideas. Is it leaf spring, coil or other? Bunk or roller? BTW welcome to the forum.

 

[kenmyfam]

Re: Converting Trailer Tires, 12" to 8"

A picture says a thousand words they say. If you can post one we could maybe give you some other ideas. Is it leaf spring, coil or other? Bunk or roller? BTW welcome to the forum.

Completely agree. Photos would be a huge help. Could be something obvious we are all missing.

 

[jay_merrill]

Re: Converting Trailer Tires, 12" to 8"

The first thing that I would look at, is the bunk and roller height, relative to the frame. If you can lower them, without having contact issues (boat to frame), I would start there. You can lengthen the tongue too, but don't forget that the longer the tongue, the more stress you will put on the point at which it is joined to the rest of the frame.



???

 

[jdsgrog]

Re: Converting Trailer Tires, 12" to 8"

you don't mention the type of trailer you have. I have a gator trailer and the boat sits high also, but it's a tilt trailer. When you use the lever, the bunks lower and also releases a lock for the tilt. This allows the boat to roll off the trailer by the keel rollers. But again, I'm not sure if your trailer is the same type of trailer.

 

[wingo]

Re: Converting Trailer Tires, 12" to 8"

The trailer has bunk boards and rollers, they are down about as far as they can go (I think). The keel sits about 1.5" above one of the cross members, so I really don't see lowering anymore. I will post a picture as soon as I can. I'll wait before I jump on the extension until the picture goes thru for further input. Thanks for stayin with me on this guys..........

 

[wingo]

Re: Converting Trailer Tires, 12" to 8"

Hey Guys!,
Here is a picture of the boat and trailer, OK, now that I really look at it. DUH!
It looks like a 2x6 and some other wood have been place as some sort of support? Or does this belong on the trailer. I will post another picture of just this area.

 

[wingo]

Re: Converting Trailer Tires, 12" to 8"

I'm having to re size these pics, Hope you can see them OK. Here is the 2x6 wood configuration I was talking about:

 

[reelfishin]

Re: Converting Trailer Tires, 12" to 8"

Its hard to tell if that board is there to support the trailer somehow or just as a walking plank so you don't get wet while loading the boat? I do see that bolt sticking up that looks dangerously close to the hull.

I have a Starcraft Capri that looks similar to your boat, it also sits high on the trailer. I plan to flip the axles, (It's on a tandem trailer with 13" wheels). Trailer fit on a trihull can be tough unless the trailer is wide enough for the wheels to clear the outer hull. Your boat looks close enough to the frame now, your best options will be to make sure the springs are mounted over the springs and extend the tongue a bit. If not, find a better fitting trailer for the boat.
Look for one that has a wide axle as mentioned above, then sell the old trailer. I say this because you can most likely find another trailer better suited for what you need for less cash than buying a new axle, fenders, and other parts.

A 4" drop axle with low slung springs which is wider than the boat may be an option but being that's a trihull, you may not be able to get one wide enough to fit the boat between the fenders comfortably. A wide trailer with a drop axle, and down slung crossmembers may be your best ticket.

 

[jeeperman]

Re: Converting Trailer Tires, 12" to 8"

I am guessing that 2x6 is not suppose to be there. I suspect someone added it because the keel was bumping into the end of the tongue tube.
Or heaven forbid that 2x6 is added in there to secure the end of the trailer tongue because the steel crossmember below the 2x6 is rotted out???

 

[jeeperman]

Re: Converting Trailer Tires, 12" to 8"

From those two pics I am gonna guess the trailer started life as nothing more than a trailer for a good size aluminum row boat with 9.9hp outboard.

Per the welded on angle iron (bow side of that 2x6) and the concrete re-inforcing rod tongue truss, the tongue has been lengthened quite a bit.