Trailer Tires? or Automotive Tires?
The topic of trailer tires has come up a hundred times. Why can’t I use automotive tires on my trailer?
Let’s explore this question in some depth. I have asked many trailer parts stores (and tire stores) the same question. Most are quite adamant that only trailer specific tires should be used on trailers. Others are a little more humble and admit they don’t really know why. Only a few can articulate the why’s of choosing a tire specific for your trailer. And, unfortunately there is a lot of BS out there, kind of like this guy.
In full disclosure, I’m not a tire expert. I’ve designed a bunch of things in my life, but never a tire. On the other hand, I’ve talked with a lot of tire experts and here’s how I come down on the issues.
- First, trailer tires exist for a reason, and it’s not just to get more money out of you.
- Second, anyone that says trailer tires experience more crazy loads and dynamics than autos are not thinking clearly.
- Third, trailer DON’T have inherently more trouble with tires than cars.
We’ll discuss these in a moment, but let’s set the stage. Tires are really important for a number of reasons, and tire problems have haunted trailer owners for years. The above 3 items really address some folklore laced with experience rather than complete facts. There are arguments on both sides, so I’ll layout some facts, then you put them together to fit your needs. My purpose is to inform, not to sell tires.
First, why Trailer Tires?
From the list above, let’s look at design. I assert that trailer tires are not superior, nor technologically more capable for hauling than automotive — in fact, it’s the opposite. There is a ton more technology in auto and light truck tires, and there are way more of them around.
That said, there are several advantages in using trailer specific tires:
- They have the advantage in load capacity for the size. (Smaller total size, with greater capacity.)
- The narrow form factor allows more space (from left side of the trailer to right side of the trailer) between tires for the same outside trailer width. That allows trailer designers to maximize the frame and load area between the tires. (More space between the wheel wells for utility trailers.)
- Narrower profile tires (like a trailer tire) wear better when not aligned properly. (And this is a frequent problem with trailers that are not setup properly — especially for multi-axle trailers.)
- Trailer specific tires are also better at resisting damage, neglect and abuse (because they’re really tough). See the ply ratings.
- Automotive suspensions are nicer to loaded tires than trailer suspensions, so the beefier trailer tires tend to soak up the abuse better.
- Stiffer sidewalls resist tipping more for trailers with a high center of gravity. (Though this is really an excuse or a compensation for poorly loading a trailer.)
Why Automotive or Light Truck (LT) Tires?
So, what are the advantages of automotive tires? (Including Light Truck tires.)
- Automotive tires have a wider range of available sizes and capacities (except in the really small sizes).
- They come in more weight capacities and material choices (to optimize for your needs).
- They typically ride better, track better (assuming the trailer construction and load distribution are good).
- Automotive tires usually have a larger footprint on the road (especially useful in soft conditions like on the lawn).
- Trailer tires are not as available when you desperately need one, nor do they interchange with tires on your tow vehicle.
- Lower pressures with automotive tires make it easier on equipment (softer ride), and easier to see when one is getting low.
- See the discussion below about dynamic loading.
The Dynamics of Tire Use:
One big error … Some people claim that trailer tires must handle greater dynamic loads, and do better. This is not true. It may seem that way because there are more trailer tire problems per tire than automotive, but the need or ability to handle loading is NOT the reason. Automotive tires are designed for high, simultaneous, steering, breaking and weight shifting loads. They have to be to take what we do to them. Think about your left front tire in a hard right turn when you’re hard on the brakes! Trailer tires don’t / won’t perform at anywhere near that level. Rightfully so, because they just don’t see those kinds of extremes in action.
Please remember, this comparison is all in context of similar tire capacity.
Two places that tires on a trailer do see a different type of dynamic:
- First, if a trailer is loaded improperly, or set-up is poor (axle position or alignment not correct), the trailer may wander side to side — like a dog wagging it’s tail. See this video for an example. These are not high loads, so both trailer and automotive tires do OK, but it’s not good for either.
- Second, when a trailer is virtually empty, they can bounce as they encounter bumps. The bouncing can be mitigated in a few ways, but tire pressure is the main player. This post talks all about trailer bounce. There are good arguments that trailer specific tires handle bouncing a touch better, though automotive tires are better at mitigating the effect.
Trailer Tires DON’T Have Inherently More Trouble:
The other side of the coin is how we contribute. I just stated above that “there are more trailer tire problems per tire than automotive” but that does NOT mean it’s the inherent nature of a tire on a trailer. Rather, it’s because we tend to be lazier and more neglectful with our trailers than our cars.
Again, looking at loading: On your vehicle, the tires are typically at a much lower percentage of total capacity than for most trailers. And we typically don’t take as good of care of them. You drive your vehicle frequently, so the tires usually wear out before having flat spots, dry rot, carbon leaching, etc..
Another thing is our sense of the tire. In your car, if the alignment gets bad, you notice it. If your trailer tires are not aligned or balanced or properly inflated, you probably won’t notice unless it’s really bad.
So why are there more problems with trailer tires? Because we (collectively) don’t take care of them. In a word, Neglect.
I will throw in one other tid-bit, because not all trailer tires are equal. Read this post about “Buying A Used Trailer“.
Keys For Trailer Tire Success
With all tires, the first and arguably most important thing is the axle. If you have alignment issues, or toe issues, or camber issues, the tires get the abuse. Get the axles right. A list of axle parameters is in the Trailer Axles 101 article.
Second, choose the right tires. We recommend tires with a capacity greater than the axle. Example: If your axle rating is 3500#, the temptation is to find tires at around 1750# (3500/2 because you have two tires on the axle). However, with load shifts and other dynamics, the trailer tires will overload at some point. We suggest 10% to 15% + over capacity. For example: If your axle rating is 3500#, then choose tires at 1900# – 2000# capacity each or more. 10% more: (3500 * 1.1)/2 = 1925 or better yet, 15% more: (3500 * 1.15)/2 = 2012.5
For tandem or triple axles, bias the load capacity high, because all things are not as equal as we like to think.
Third, keep proper inflation for the conditions. Running with an empty trailer, the tires can be at quite low pressures. At full load, make sure the tires are inflated to the proper pressures (text on the sidewall). Also, make sure pressure in all tires is the same (especially true for tandem and triple axles). Try this cool tool for inflating / deflating.
Finally, take care of your tires. Cover them to protect them from the sun when not in use. When parked, put them on wood rather than concrete (to avoid carbon leaching). Check them for dry rot (tiny cracks that appear usually on the sidewalls). Watch for tread wear issues. Make sure brakes are adjusted properly (so one is not grabbing more than another). And, load your trailer properly for good tracking.
Note about Tandem Torsions
If you happen to have torsion axles in tandem, go super extra capacity. That’s not a good situation, and one way to help yourself in that situation is to over design your tires. For more information, please follow this link to the article that explains all about it.
The folks at Tire Rack argue for using only trailer tires, but it’s interesting that all of the reasons they give are just a compensation for the things discussed above — like reducing load capacity 9%. I assert — If the tires are the right size, have proper alignment, and are within the load requirements — AND if we take care of them — automotive tires on a trailer will perform great, and in most cases, even better than trailer specific tires. The exceptions are, of course, applications that need small tires (they don’t make automotive tires in those small sizes). And, for applications that need really high capacity tires. Otherwise, I prefer light truck tires over trailer specific ones any day.
Then there’s the discussion of Radial vs. Bias Ply. I’ll let you research that.
Do you agree? Or disagree? Let us know if you have comments or suggestions.