Can You Speak Tyre - part two
Tuesday, 30 July 2019
Where we left off, you were mastering the basics of sidewall information.
Before we level up, make sure you are on top of the size information on your sidewall.
Those numbers will make sure you are always fitting the right size rubber to your ride. What follows assumes you understand those basics.
Let’s get into it. As a caveat, you should note that not every brand of tyre uses consistent labelling, but for the most part, this will help you divine the details.
SPEED AND LOAD RATING
Your tyres maximum speed and how much weight is combined on the sidewall.
Typically, this designation will come after the basic size information, and is expressed as a two-digit number (load) and a single letter (speed).
To refer to our example from Part One, a tyre might read 235/45R17 91W.
Referring again to our example tyre, (235/45R17 91W) we now know it can handle 615 kg per tyre, and should not go any faster than 270km/h.
That’s a pretty sporty tyre! What is your tyre’s speed and load rating?
UTQG? WHAT DID YOU JUST CALL ME?
UTQG stands ‘Uniform Tyre Quality Grading’.
It’s principally an American and European rating from controlled testing, but it can be used to give you an idea of how fast your tyre will wear.
Get down next to that sidewall, you can generally spot these numbers above the tyre size.
They comprise treadwear, traction and temperature ratings.
The higher the treadwear rating the longer the tyre will take to wear down.
The ‘control’ tyre for this testing is assigned a 100, so a treadwear rating of 300 means your rubber will last three times as long.
These aren’t definitive figures, so tread lightly.
Traction is simpler. It is rated from highest traction to lowest as AA, A, B and C.
The better the rating, the shorter the braking distance on a wet surface.
Driving makes your tyres hot and the faster/longer you go the hotter they get.
Overheated tyres can puncture, or separate.
The temperature is a rating of heat resistance from A, B and C, A being the best.
It’s important to remember that these ratings haven’t been created in Australia, and that each tyre is built for a balance of these attributes.
Longer wear can mean lower traction, for and vice versa, for example.
Ever noticed a really old set of tyres that just never seemed to wear?
That’s not a good thing. As tyres age, the tread compound hardens.
Your tread compound is built to be soft enough to provide you with grip, but not so soft that it wears too fast.
You don’t have a pit crew with a fresh set of Pirellis waiting for you every few laps.
As such, tyre makers mark a date on the side of their product, so fitters and drivers know whether or not they are going to get the grip they need.
As a (very) general rule, five years on the shelf means those tyres should be knifed.
Manufacturers all use different codes, so you may need to ask for help from the supplier on this one.
The code will normally follow the DOT marking on the tyre.
DOT indicates the US Department of Transport has approved the tyre for sale, so if you ask and see the salesman reading from somewhere else, eyebrows should be raised!
So, you are now an intermediate tyre-wizard.
Go forth into the world, spread your knowledge and check out the rest of our tyre content for your official certification* as an advanced tyre warlock *certification not official.
Remember, being an intermediate tyre-wizard does not mean you automatically now have the skills to replace your own tyres.
We recommend using AutoGuru to book in with a local Tyre Specialist (and certified full-blown tyre-wizard) to replace your tyres.
AutoGuru is Australia’s largest online marketplace for booking automotive services.
We’ve got a passion to remove the stress, hassle and ambiguity from booking automotive servicing and repairs, both for the mechanic and the motorist.