Trailer tire size

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Seadoc
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Trailer tire size

Post by Seadoc » Sun Sep 13, 2020 10:58 pm

Hi!
Can anyone tell me how much lower my trailer would sit if I reduced the tire size from 15 inch to 14 inch? I don't think that it's a simple one inch difference.

Thanks!

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kurz
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Re: Trailer tire size

Post by kurz » Mon Sep 14, 2020 3:35 am

To do the correct math you need the exact tire dimension of both tires, the 15 And 14 inch ones

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Tomfoolery
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Re: Trailer tire size

Post by Tomfoolery » Mon Sep 14, 2020 4:13 am

Looking at a couple of similar tires on etrailer, the OD for the 14" (inflated, but unloaded) is almost exactly 1" smaller than the 15" tire. So the trailer would sit 1/2" lower, assuming similar deflection in the tire with the same load on it.

Not enough to bother with, if you ask me.

https://www.etrailer.com/Boat-Trailer-W ... 3S560.html

https://www.etrailer.com/Boat-Trailer-W ... 32397.html

But as kurz said, you need to compare the actual tires under consideration.

If you want it to sit lower, consider replacing the axle with one with a greater drop, but then, you have to watch that the tires don't rub on the hull. :|
Tom
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Seadoc
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Re: Trailer tire size

Post by Seadoc » Mon Sep 14, 2020 9:58 pm

Thanks for the input.

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1st Sail
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Re: Trailer tire size

Post by 1st Sail » Tue Sep 15, 2020 1:24 am

I would be more concerned about load capability of the tire. I presume the larger the tire the greater the load capability. There have been previous posts about tires overheating or operating near the load capability of the tire set which in turn has lead to premature tire failure. IIRC the general consensus was to purchase high quality tires with a load rating that exceeds the weight of the boat and trailer by as much as possible.
:macm:

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Tomfoolery
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Re: Trailer tire size

Post by Tomfoolery » Tue Sep 15, 2020 5:05 am

If you really want to drop the trailer for easier loading, you can hinge it at the pole tongue to make it closer to level while on an angled ramp. Like the hydraulic trailers they use for launching and hauling boats that are stored on blocks and stands. There isn't actually very much bending moment there (it's a puny 3 x 3 x 3/16" tube, after all), and dropping the trailer at the tongue would make it much easier to load a boat.

This sketch is from the Mac Bump® sketch I made long ago, but it illustrates the principle at least.


Image
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kurz
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Re: Trailer tire size

Post by kurz » Tue Sep 15, 2020 6:24 am

Before changing the coupler...
This year I put a roller before the V on the trailer. It makes lunching Much easier! The V can completely be put of water. Just watch the stern is floating. Then winch the boat easily on the trailer.

For long distance I take the roller out.

May be the easiest mod with the best value.

Maybe I can find a Pic later.

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Tomfoolery
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Re: Trailer tire size

Post by Tomfoolery » Tue Sep 15, 2020 8:00 am

Funny you should say that. The sketch I posted had the bow roller scrubbed out for clarity, but here's the original sequence where I was figuring out if it would work or not. It did.

I don't remove it for travel, but it is slightly below the hull when in the little forward vee bunk. If it's contacting the hull but no carrying the full weight, the boat wiggles and wears a flat spot in it. Which I know from experience. :x

But dropped down low enough to clear, it still performs flawlessly. One of, if not THE, best improvements to the trailer I've ever done.

Image

Image

Image

Image

Image
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kurz
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Re: Trailer tire size

Post by kurz » Tue Sep 15, 2020 10:58 pm

Hey Tomfoolery
Your roller setting looks quite smart.

here you can see my mod with the :macm: trailer (alu):

Image
This is a stock roller including holder, just screwed onto the trailer frame. To remove the roll I crank the trailer up as much, put a wood under the boat, then crank the trailer down. So I can take the roll out. Quite low tech... Takes some minutes... As I trailer max 2 times a year it is ok. Your setting with the roller lower seems the smarter solution.

But when the roll is under the boat and you crank the boat ONTO the V: Will it not get quite hard to crank as the boat is not anymore on the roll?

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Tomfoolery
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Re: Trailer tire size

Post by Tomfoolery » Wed Sep 16, 2020 4:09 am

kurz wrote:
Tue Sep 15, 2020 10:58 pm
But when the roll is under the boat and you crank the boat ONTO the V: Will it not get quite hard to crank as the boat is not anymore on the roll?
Short answer is yes, it does not sit on the roller. But neither does the rest of the boat, on the other two bunks. So I would have to do the Mac Bump® anyway. But at least my roller isn't getting a big notch worn into it. :|

Having that bow roller allows me to not put the trailer as deep into the water. My goal posts are much higher than the originals, and at my main marina ramp, even those have to be completely submerged in order to get the little front bunk low enough to get the bow onto it. With the roller, I can keep the trailer much higher out of the water, with the goal posts actually able to guide the boat. I lifts the bow just enough to get it into the vee bunk even well out of the water, and that's all I need it to do. 8)
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Re: Trailer tire size

Post by Dougiestyle » Fri Sep 18, 2020 5:30 pm

When I got mine the tires were shot. I put on the same size 205/75/R15, class C, single axle = 1820lb. After I got home I took them off because of some moderate rubbing and they looked like the boat was squashing them (empty). I replaced them with 205/75/R14,Class D, single axle = 2040lb. No rubbing and they don't look squashed. I think the extra rating of a class D tire is good.

I believe my 98 came with 14" tires originally
Dougiestyle
1998 26X , Nissan 50D, "Water Buffalo"

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Tomfoolery
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Re: Trailer tire size

Post by Tomfoolery » Sat Sep 19, 2020 4:11 am

I think you’re right - 14” were original. And nobody’s 26X plus OEM trailer weight is 3500 lb or less like the trailer plate says, and I’d bet the OEM tires and axle were overloaded from the moment the new owner put an engine on it, let alone enough stuff to be useful.
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