Larger tire size

[handle]

I have an old sears trailer which hauls a 15 foot starcraft with a 40hp four stroke; running stock 4.80/8 B rated tires. The smaller tires can not seem to handle the extra weight of the larger motor and are blowing out. My local VIP auto parts store can not get the C rated tire in a 5 hole pattern which can handle more weight. If the 5.70/8 B rated tire fits under the fender , why not go bigger, it will also slow down the rotation of the hub, less heat?

[lckstckn2smknbrls]

A "B" rated tire won't have the capacity of a "C" tire regardless of size. If you already have 5 lug wheels just get the "C" rated tires and have them mounted on your old rims.

[MH Hawker]

well I have a question or two, to start out what dose the boat and trailer weigh, how do you know that C range tires will do you may need D range, and what is the trailer and axle rated at. And is this a sudden problem, have you made changes, it may be a symptom of another problem. Tires just don't blow out with a cause.

[handle]

Thanks for the feed back, for the record a larger 5.70/8- B rated tire carries a load of 715 lbs. @ 50 psi., compared to a 4.80/8- B rated tire can only handle 590 lbs. @ 60psi. The larger tire does carry more load. I Know what the motor weighs how do I find out the weight of the boat & trailer? This is an old package except for the newer motor. Do you actually put the whole rig on some large scale? I was getting some where around 1200 to 1500 miles out of the tires. What is considerd normal?

[64osby]

Gravel pits, scrap yards and truck stops all have scales. The gravel pits by me weigh for free.

1500 miles sounds very low. If you post some pics, maybe some of the experts here could pick up on some issues you may have.

[Silvertip]

If you are blowing out tires at 1500 miles you have a seriously overloaded trailer. Most truck stops have scales and for a small fee they will weigh it. Drive on the scale so only the trailer is on the platform. When you get home, put a block of wood on your bathroom scale and set the tongue on the scale. Add that to the trailer weight for a total GVW (gross vehicle weight). Tires, springs and axle must be capable of supporting that weight. If you had 4.80 x 8 tires, chances are the axle is either 1000, 1250, or 1500# capacity. Even at 1500# I suspect the rig is seriously overweight.

[MH Hawker]

I expect to get at least 15,000 miles on a set of trailer tires. I had mine weighted at a local feed store and they didnt mind if I unhooked it to get the weight. In order to get the right tire load range you have to know what it weighs. And with that low tire milage you really need to know whats going on. It may also be out of alignment or the wrong axle size but weight is the place to start.

[handle]

This boat and trailer I believe are a stock package except for a new hard wood center console versus plywood and a couble of other small details. The motor used to be a 25hp omc now up graded to a Yamaha 40hp 06 fourstroke. The hull is rated to handle a 45hp motor, I have troubles believeing the extra motor weight estimated 60lbs. has seriously over loaded this package; maybe so. Appreciate the inputs.

[MH Hawker]

It more than likely isn't. When trouble shooting trailers it is often eliminating things till you find the problem. The 2 most common problems are over weight and out of alignment. To check alignment you measure from the center point where the hitch ball hooks to the trailer to the closest point on each tire that should be with in 1/8 of a inch and if that passes then take the trailer to a lever spot and hold a framing square on the ground by each wheel to check for a bent axle.

But you do have some sort of a serious issue to make tires wear out in 1500 miles a set should last 15,000 plus and it will be from over weight or out of alignment. What dose the wear pattern on the tires look like one outside and one inside, or bouth centers, or cupping.

We are trying to help but not getting much information to work with.

[handle]

Have not checked for alignment and no visual wear when the tire blows. I believe the extra weight of the new motor is the problem. I see a rating of 750lbs. on the trailer so I am right at the limit with no gas or supplies I believe. I intend to have the whole package weighed and subtract the weight of the trailer. What do I assume that weight will be?

[kenmyfam]

Our trailer tires usually rot out before they wear out.
Weigh the outfit as mentioned and do the math. Go from there.

[MH Hawker]

The weight includes the trailer its all riding on the tires.

The 750 pound rating is the max load the trailer is designed to carrie the tires are rated by the total max load boat and trailer the axle and spring are also rated at the max total load.

Once you know the total load then you know what you may be able to do, depending on the springs and axle you may be able to just change the tires to a higher load rating or you may have to change the axle, springs and tires.

As a pure guess right now I would say the axle and springs are rated at 1000 pounds that would allow 750 pound load and 300 pounds for the trailer. Which would be with in a B rated tire of 590 pounds.

[handle]

MH, measurerd for wheel alignment, looked good. Found I.D. plate on the trailer and it states as follows,-Maximum Load Capacity 750lbs. Including Boat Motor Alt. Gear-. So as soon as I get the carbs back on I intend to have the whole package weighed. Wish I knew exactly what the trailer weighed! I would be happly surprised if the whole unit weighed in under 1000lbs. Doesn't leave much room for gas and gear. Still believe the larger tire may handle the heavier load a little better. Will update you.