Trailering 101
TIRE SIZE: Can it make a difference?
DISCLAIMER: Always read all operating manuals, for tow
vehicle, trailer, hitch and related components for towing suitability and compatibility
before operating.
In our continuing education of towing vehicles and their
capacities we came across something we thought we would like to share, since It
can make a difference.
In our travels and customer relations, we have gathered a few brochures published by
manufacturers relating to towing. Some of them are extremely detailed and very
straight forward, laying out gooseneck vs. bumper pull towing weights and the coinciding
vehicle specifications like: engine size, cab style, transmission type, axle ratio
and surprisingly, TIRE SIZE. These charts are very easy to
read, but you need to read the entire chart even the little (*) footnoted items.
When reading one of these footnotes on a large SUV and even a 1/2 ton truck we found that
the customers had a choice between a 16" and 17" tire. What was
surprising, sort of, was that the exact same vehicle with different sized tires had different
towing capacities. And if you haven't guessed it already, the SMALLER
tire had the higher rating, by 400 to 500 lbs depending on the vehicle. Could this
make a difference to the buyer/already owner?, maybe depending on the type of trailer you
intend to tow.
Now you may be asking why is this? To give you a non-mechanical,
non-scientific explanation we believe it goes back to the "10 speed up a hill"
analogy which we use often to help folks make sense of "axle ratios".
Basically, if you are heading up a large hill on a bike in tenth gear, there won't be many
revolutions required by the peddles to get to the top. BUT, your going to work really hard
to get it there. Now, If you put that same bike, on that same hill in a lower gear,
like 1st, the peddles will make several revolutions but you won't work any where near as
hard to get to the top. So what does that have to do with tires? We believe by increasing
the tire size you are once again making fewer revolutions, working a bit harder, and in
turn lowering your towing capacity. (For those technical types out there, we are sure
there is a much more complicated explanation, but for our purposes, we are just trying to
make a complicated issue a bit easier to understand.) NOTE: With "axle
ratio", the higher the number the more revolutions it makes and in turn working less
and pulling more.
As usual, we are sure there some exceptions to the above. However,
once again we just want to make you aware of this issue, and you can at least ask the
questions.
Happy Trailering... See you Next Month.
If you have any comments, suggestions or topics for
a "Trailering 101" article we'd be happy to take them. Trailering
education is our goal.
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