P235/70R16 104S vs. P235/70R16 104T…Is there really a difference?

The answer to this question is yes.  But, the real question is, how much of a difference.  Is there enough of a difference to merit a price difference?  Is one safer than the other?  All legitimate questions with real answers.

Let’s start with breaking down what those numbers mean.

P = P-Metric not Passenger

This is common misconception.  Many years ago tires use to only be in European Metrics which are very similar to what they are now with the difference now being in load rating.

235 = Width of the tire in millimeters

70 = Indicates the height of your sidewall as a percentage of the width.  So, this particular tires sidewall is 70% of the width (235 mm).  Or, that the sidewall above and below the rim is 6.4 inches.

R = Radial

There are still some tires out there that are a bias-ply but the majority of the tire market is a radial tire.

16 = Rim size in inches

104 = This number references to a load rating index (found here) stating how much weight each tire can hold at a max psi.

S & T = These two letters designate the speed rating of the tire.  In a previous post I mentioned how a speed rating designates how stiff the tire is. (Click here to view post.)  It does this by referring to a speed that the Rubber Manufacture Association and your vehicles manufacture decide on as the fastest speed your vehicle can maintain and still have the tires be safe.  Now, that doesn’t mean you can go out and cruise down the road at 120+ mpg thinking your tires will handle it.  What it means is that your tires sidewalls won’t flex so much that they will roll off your tire as you corner or that going down the interstate you don’t need to worry about your tire blowing out when you hit a bump.

These letters also provide you with the ability to get a tire that will last you for the guaranteed mileage.  Take for example two vehicles, same in nearly every way except for one is a sport package and one is the base package.   The sport packages typically have a stiffer suspension than base models.  When it comes to tires, if you get too soft of a tire (tires with a slower speed rating than recommended) it will wear to fast.  You also run the risk of the tire affecting handling which puts you, your passengers, and other drivers at risk.

Due to the difference in stiffness of tires, there will be price differences.  The ones I have seen vary the most are with Toyota’s and Mazda’s.  Their base packages generally run an H speed rating, but their sport packages will run a V rating.  Depending on the width of your rim and rim the price difference can be as much as $50 per tire.

The best thing to do when you are looking for new tires is first start with the driver side door.  Either on the door itself or the door frame, there will be a placard indicating the size of the tire.  Newer vehicles typically will have the speed ratings.  In the event yours does not a quick visit to a local tire store and an associate there can help you.

Below are some additional links about speed ratings and load indexes.

Speed Rating & Load Index

How to Read a Sidewall Image

Additional Tire Tips

Is it time to change those winter tires?

With the warmer weather, at least here in Cache Valley, many folks out there are starting to wonder if it is time to take off those snow tires and get on their summer tires.

That is a great question.

To start off by answering that question lets look at what makes a snow tire different than your regular all-season tire.  The first thing different is the stiffness of the tire, or speed rating. (Click here for a Speed Rating Chart).  Nearly all snow tires have an “S” speed rating.  This rating indicates that your snow tire is guaranteed to be stable at speeds of 112 mph.  That doesn’t mean you can go cruising along I-80 in a snowstorm at 90 mph.  What it means is that your tire will stay put when you corner and that the sidewall won’t flex to much if you load it heavy.  (Most all-season tires start at a “T” rating and go up from there.)  Another difference is that many snow tires out there are studded.

What does all this mean?

A tire with an “S” speed rating is also a tire with softer rubber than your typical all-season tire.  This softer rubber holds up fine in cold conditions but once the temperature is consistently above 45 degrees, that softer becomes very soft and wears much faster.  That is one reason why most folks take their snow tires off in March or April.  In regards to the studs, most state laws require studded tires to be removed by the third or fourth week of March. (Click here for Utah, Idaho, and Wyoming State Laws)

So, to answer the question of whether or not to take off the snow tires.  I would say yes.  The temperature is steadily increasing and your softer rubber tires will wear faster.  Basically you won’t be getting what you paid for out of your tires.  Also, with state laws requiring you to have the studded tires off the road soon anyway, I would say get it done.

You can stop in at any Discount Tire & Automotive or Plains Tire Co. to have your tires swapped from your snow tires to your summer tires.  Now we need to just hope it stays warm.

Stay safe out there!