downsize rims

[gulfvet]

wondering if I can downsize to a 12 inch rim and tire from a 13 inch rim and tire. The trailer in a rollco double axle hauling a 1978 sea sprite 18ft tri-hull. any suggestions would be appreciated. thanks.

 

[Gun Dog]

Re: downsize rims

May work. What are the tire ratings of the 12's. Whats the weight of the full load and trailer? Whats the tongue weight?

 

[bitterboater]

Re: downsize rims

I would think, as long as the weight rating on the tires is sufficient.
As well as the bolt pattern of the wheels matches the trailer, it should work.

However, the thirteen's should be less stressful on your bearings (they spin slower).
Also, the thirteens should also give a smoother ride, since they would roll over obstacles more easily.

 

[Silvertip]

Re: downsize rims

So what's the reason for the switch? New tires would be about the same cost as four new 12 inch wheels and tires with a load rating equal to or greater than the 13's you now have. Not to mention the things already touched on.

 

[Titanium48]

Re: downsize rims

ST145R12 are nearly 3 inches smaller in diameter than ST175/80R13, so your boat will be lowered by about 1.5 inch (I'm guessing that's the reason for the tire downsize). The 12s are readily available in load range D (1220 lb load rating), so I doubt you will have load capacity problems with an 18 ft boat on a tandem trailer. Only issue I can think of would be if you have 3500 lb axles with brakes - 12 inch wheels won't fit over 10 inch brake drums.

 

[gulfvet]

Re: downsize rims

Reason for the change was, I blew a tire on the way home from the lake and upon further inspection of the other tires they all need replaced. I have 2 12 in rims and tires off another trailer with the same bolt pattern. 250 bucks for 4 new tires or 130 for 2 12 in rims and tires. The bearing load on a 12 inch rim is something to think about though. Thanks for all the suggestions!

 

[Silvertip]

Re: downsize rims

Make sure those 12 inch tires have the same load capacity or higher than the 13's. Bearing load is the same. Bearing "speed" will be higher because the wheels will rotate faster. But 12 inchers are used on all sorts of trailers and they do just fine at highway speed.