taller wheel conversion

[Bill J]

I have seen a lot of small cargo trailers whereby the frame might work to build a tear but what I do not like are the small wheels/tires. As you all know a smaller wheel will turn faster than a large one and I would like to at least keep the trailer wheels the same size or as close to the tow vehicle wheel size.
Can bigger wheels be used on these axles? Basically is the lug arrangement the same or am I restricted to using the small wheels which I do not want to do? Any problems with bearings?

[caseydog]

I am interested in the responses to this, too.

For me, it has nothing to do with utility. The small wheels will work just fine. I just like the looks of a 15-inch wheel with some moon caps -- and maybe some white walls.

CD

[Bill J]

I wish I could say I like them as they are but years back some fellow passed me on the highway pulling a tent trailer with those small wheels. Of course I couldn't tell but it certainly seemed those wheels were turning quite a lot compared to the car wheels. No sooner did I think that when one of the tires started to come apart. Fortunately the rig was able to stop before more damage to him and me occured. Was it because of the small tire going too fast? I can't say but it did scare me.

[brian_bp]

If the hub bolt pattern is the 5-on-4.5" common with axles from 2000 lb capacity and up, wheels are readily available in at least 13", 14", and 15" sizes; however, if the hubs have a four-bolt pattern, there will be much less choice in larger sizes.

Some small, low-capacity hubs are specifically not allowed to use larger wheels. Two potential reasons:

• the hub face area may not be as large as expected in the design of the centre section of larger wheels (this is listed by some axle manufacturers);
• the greater leverage of the larger overall diameter tire under lateral (sideways, as in cornering) force may be too much for the bearings (this is just my guess).

Certainly a lot of people replace relatively small wheels (10" and 12") with larger wheels (it seems mostly 14" and 15"); the options for an axle intended for use with 8" wheels may be limited.

While I think that the slower rotational speed of larger tires is a good thing, the speed of the smaller setups probably isn't really a concern for the bearings. I randomly chose a trailer to look up (Red Trailer 4x8) and it has 4.8-8 tires, which are about 16.3" tall overall. A common small car of the 1980's would have 155/80R13 tires, which are about 22.8" tall (they tend to be bigger now). That means the little trailer tires spin the bearings 40% faster than the car... but the trailer is unlikely to ever break 60 mph and the car bearings live fine at 40% faster than that (84 mph). In my exposure to race cars, I've never heard of a problem with stock wheel bearings handling higher-than-normal speeds. Also, for comparison real (original ) Minis had something like 145R10 tires, which are only 19" tall, and while they had their problems, I don't think that wheel bearings were among them.

I would be a lot more concerned about the speed capacity of those little tires than of the bearings.

[Bill J]

Excellent reply. My main concern is also the strength of the tires. This is after my experience as mentioned above.

[caseydog]

Excellent reply. My main concern is also the strength of the tires. This is after my experience as mentioned above.

Why would a large tire necessarily be stronger than a smaller tire?

When it comes to a tire coming apart, I'd be more concerned about the manufacturer, the age, inflation and the maintenance of a tire, when it comes to a potential for failure.

Actually, those small tires are "trailer spec" tires, which means they are rated to carry more weight than the trailers they support are rated to carry. They have sturdier sidewalls than a passenger car tire.

I trust the small trailer tires -- I just like the looks of a nice set of 15-inchers with classic moon caps.

CD

[Gerdo]

I've towed them all. I've had them all blow out. Maintance is the biggest thing with having a tire and bearings staying together. If a tire is allowed to be run low on air pressure it will heat up and maybe not then but eventualy it will fail even after the pressure has been corrected. The damage to the tire has been done. I have an ATV trailer with 20.5x8.5x10 tires and It has been to Oregon, Utah, Califorina and back without any problems. I also pump a few squirts into the bearings every few trips and every long trip. I will travel at 75 mph all day long. I have another utility trailer with 15" wheels and had the bearings disinigrate on a long trip. I "knew" that the bearings were well greased, WRONG! This was my bad. My TD has 15" wheels on it and grease fittings on the bearings. The tires are car tires and even after ~10,000 miles the tires still have the center molding seam.

The moral of this story is... Maintain the tires (pressure) and the bearings (grease and adjustment) and anysize tire/wheel will be fine. If you don't you will have a failure on the road.

With that said. I personaly like the look fof bigger tires.

[brian_bp]

Why would a large tire necessarily be stronger than a smaller tire?

I don't know if "stronger" is the ideal term, but any given part of the tread of a larger tire will be in ground contact less frequently, and thus have less of a heat buildup problem - heat is the big killer of tires.

Also, comparing two tires of the same sidewall height and section width, the one on the larger wheel (and correspondingly larger outside diameter) will be less severly distorted (there's that heat production and stress again) by conforming to the road to form the same contact patch than the one on the smaller wheel. It also has a better approach to bumps than the little tire - compare hitting a bump with a mountain bike tire tire to the same bump with a wheelbarrow tire.

When it comes to a tire coming apart, I'd be more concerned about the manufacturer, the age, inflation and the maintenance of a tire, when it comes to a potential for failure.

I agree that these are all important, but given two tires of the same manufacturer and model, of the same age, condition, and inflation pressure, the larger tire will have more ability to safely and reliably carry load.

Actually, those small tires are "trailer spec" tires, which means they are rated to carry more weight than the trailers they support are rated to carry. They have sturdier sidewalls than a passenger car tire.

The tires on any axle (trailer or motor vehicle) must have at least enough capacity to meet the axle rating; that means that on a trailer the tires must always be rated to carry at the least the weight carried on the axle, which in turn is typically 90% of the weight of the trailer... there's nothing special about the "trailer spec" tires in this respect.

In practice, most trailers are supplied with tires which are rated to barely carry the trailer on which they are mounted, and then only when inflated to exactly the ideal pressure and never run at high speed. They have at best 10% more margin than a passenger car tire from their rated capacity to what they can really stand without failure, which is why passenger car tires are generally permitted by the manufacturer to be used for trucks, vans, and trailers, as long as you "derate" them by 10% (e.g. if the published capacity is 1000 lb for use on a car, you can use it on a trailer for loads up to 900 lb).

Special Trailer (ST) spec tires are designed for a higher load in the same size than a passenger (P) tire, but mostly due to higher inflation pressure. The stronger sidewall construction is simply a function of the design pressure. My car and van both run on tires which happen to be built to XL (extra load) spec, rather than SL (standard load) - just because that's the only way this particular model of tire is available - and so they have 51 PSI inflation pressure, two-ply sidewalls, and high load capacity... just like a Load Range C trailer (or Light Truck, or commercial) tire.

If you could buy car tires in XL form in tiny sizes, they would be nearly identical to the trailer tires.... but cars here don't come so small that this size of tire would be useful, and cars (and light trucks and vans) typically use tires which are larger and run at lower pressures, for better ride and handling. If you look at a compact truck with a 3500 lb rear axle capacity and the trailer it is towing, also with a 3500 lb axle capacity, the truck most likely has wider and taller tires, running at lower pressure. The trailer tires are not better - they are the smallest and therefore cheapest available choice. In big commercial trucks where the tractor and trailer are operating under the same requirements, they typically use the same size and construction of tire to carry the same load... not big tires on the tractor axles and tiny tires on the equally loaded trailer axles.

[brian_bp]

Still using that Red Trailers 4x8 as an example, the listed GVWR is 1180 lb, and the tires are 4.8-8 (load range B)... which have a load capacity of 590 lb each (maximum, which is at 60 psi), or 1180 lb total. Not much margin there!

A 4.80-12 tire - still in Load Range B - has a 780 lb (per tire) capacity... so even with no width or sidewall height increase, the extra diameter buys a lot of capability. The increase is in proportion to the change in the diameter (of a point roughtly at the the base of the tread rubber).

Of course, nothing is free... using Carlisle examples, each 4.80-12 tire is 3.7 lb heavier than a 4.80-8 (10 lb versus 6.3 lb), and the required 12" wheel is 5.5 lb heaver than the 8" wheel (10 lb versus 4.5 lb), for a total of 18.4 lb more trailer weight. Go even bigger and the penalty keeps getting greater.

[sseaman]

A bigger tire may not be stronger, but most likely has a high load limit. You may be able to put a larger tire on the axle that is on the trailer, as long as the tire doesn't rub on the side, or you may have to order a new axle that is a little wider. A new axle can cost less than $150 custom to your length.