It doesn’t matter what car it is, tyres are a sure-fire way to improve it. Here’s all you need to know about how to choose a car tyre.
What’s so special about tyres?
OUT OF ALL the components on any vehicle, tyres are about the most critical for performance. This is true for extreme 4WDs, solar-powered economy vehicles, racecars and certainly your daily driver.
Tyres are so important that many car racing series have “control” tyres, which means everyone has to use the same tyres. The series that don’t, such as Formula 1 a few years ago, often see huge disparity in car performances purely due to which manufacturer is producing the better tyre at any given time.
It may be surprising, but the standard tyres on your car are unlikely to be the best on the market, or the best for you. This is sometimes because manufacturers choose cheap tyres as standard, but even if the most expensive tyres were fitted…would they be right for you? Unlikely. You can choose what you want – that might be sharper handling, better grip, improved fuel economy or just a different look, your choice.
Tyres are also about the simplest and quickest modifications to make for improved performance of any kind, and one of the least problematic to keep the car road-legal.
What can a new tyre offer you?
So let’s look at the process of tyre changing, and I’m going to use my Toyota 86 as an example. First up is to decide what you want to achieve, or another way, which tradeoffs you want to make. Here’s what you can improve for a roadcar:
- Grip and handling
- Dry
- Wet
- Comfort
- Ride (smoothness, refinement)
- Quietness
- Fuel efficiency
- Tyre life
Six criteria, and for roadcars we’ve grouped them into four related categories. It is true that very high-performance tyres may be great in the wet and bad in the dry or vice-versa, but that’s getting into niches and this article is general purpose. Anyway, the rule of thumb with tyre choice is the more you have of any one of the above, the less you have of all the others.
There is one factor missing and that is cost. Like most things in life, the more expensive the tyre, the better it is in overall. So if you want the least compromise you’ll typically find it in the most expensive tyre.
The criteria above is only for roadcars. We’ll cover choosing a 4WD tyre another time (or you can read my book which has a whole chapter on the topic), but to that list above you’d add offroad grip and strength which would see you opting for a light-truck construction tyre.
What’s what – tyre terms you have to know
A “wheel” is the combination of a rim and a tyre. The rim is the metal bit. The tyre is the rubber bit. Well, it’s rubber, silica and a lot of other ingredients, but that’s for another time. Here are the basics:
This particular tread pattern looks a bit odd. That’s because this tyre is what is known as a directional tyre, which means it is designed to work in one direction. Directionals are a common high performance design, but because the design means you can’t swap tyres from left to right it’s not great for practicality, and no good for offroad 4WDs which need traction in both directions and the ability to put a spare on either side. There’s also asymmetric tyres… but that’s for another article.
The first step to new tyres – knowing your specifications
Before you can choose a tyre you need to work out the specification your car needs:
- Tyre size – diameter and width of the tyre
- Load rating – how much the tyre can carry
- Speed rating – how fast it can go
You don’t need to run the same sort of tyre as what’s on your car now, within limits. You can choose a tyre that’s narrower, taller, wider or shorter. You can also choose a different profile, which is the relative size of the rim to the tyre. Best to use an image to make the point:
The overall tyre diameter stays the same, it’s just how much of that overall diameter is tyre, and how much is rim. Changing profiles might mean going from a 17-inch diameter rim to an 18-inch rim. There’s no fixed definition as to when a tyre is low or high profile.
Moving away from the standard tyre size is quite a process (if done right as opposed to she’ll be right mate) and will be covered in another article, but for the moment let’s just stick with the diameter and width the car manufacturer intended. Changing either won’t give you as much benefit as is popularly imagined, but it does make the decision much more complicated and there’s warranty concerns as well as roadworthy rules to comply with.
And for this article to keep things simple and legal, we’ll keep the same load rating and speed rating as standard.
Finding your tyre’s specifications
There’s three ways to find your tyre’s specs. You can look at the:
- tyre itself
- tyre placard
- owner’s manual
The tyre itself is the best place…provided the tyres on the car are of the same specification and type as the ones you want, and are road-legal. It is possible that you bought a secondhand car with different-sized tyres to normal.
Both the owner’s manual and the tyre placard are likely to list at least two specifications of tyres, as it is very common for different trim levels of the same car to run slightly different specification tyres. You then need to ensure you pick the right one for your car – no point buying tyres for 17-inch diameter rims if your car has 16-inch diameter rims.
Method 1 – Look at your tyre to find the specs: 
In the case of my Toyota 86 the tyre is marked 215/45/R17, which means the tread is 215mm wide, the rim size is 17 inches (yes, mixing metric and imperial, don’t ask). The tricky bit is the sidewall – that is 45% of the tread width, so 215mm * 0.45 = 97mm. The R is for radial, a type of construction used in all modern tyres (crossply was an older method).
The 87 means a load rating of 87, which is equal to 545kg. No, there’s no mathematical relationship between 87 and 545. The W means a speed rating of 270km/h, way more than the 86 can manage, which is the point. Higher numbers and letters mean more load and speed. When choosing new tyres:
You must ensure any replacement tyres are at the same load and speed rating or greater.
Unless you have a 4WD, in which case you can ignore the speed rating and just use N-rated tyres (140km/h) or above – but load rating definitely still applies in that case. The other exception is if your passenger car has a speed rating of greater than S (180km/h) then you only need to fit S-rated tyres – this applies in all locations except NSW and SA, and that rule is part of the NCOP light vehicle modification standards.
But the above is a bit detailed and niche, and for most road users the rule is just to ensure the load and speed rating are the same or greater.
Method 2: look at the tyre placard
The tyre specification rating will be on the tyre placard:
But what is this? It says 205/55/R16 91V. That is not the same as what the tyre itself says. The answer is simple; my car is the poverty-pack GT, and I run luxury wheels and tyres from the top-spec GTS so I can pretend I’m rich. For some reason the GT86 placard doesn’t list both specs of tyre which is unusual. Normally the placard has all types of tyres listed, like this from a BMW 220i:
Quite a selection there as you can see, and so you’ve then got to look at the tyre to see what’s actually on the car. The “M+S” is mud and snow. The placard also shows recommended inflation pressures, which as you can see do not vary with the profile, but do vary with weight. Another topic for another time. The placard is law.
Method 3: look in the owner’s manual
If all else fails…
And there it is. The Toyota 86 manual lists both types of tyre, so again we need to look at what’s actually on the car.
The moral of this story is that you can’t just call a tyre shop and say “I have a Toyota Camry” or something, because there’s slightly different tyre sizes for Camrys based on model year, trim specification and more.
What you can say is:
“Hello, Tyre Professional. I would like options for 205/55/16s with a speed rating of V and a load rating of 91. What have you got?“
Seriously, try that. If they don’t understand, end the call and find another shop. The tyre guys will be moderately impressed. And they will be really pleased if you can mention which of the six criteria above you value most.
A few cars, mostly high-performance sportscars, have different sized tyres front and rear, so be careful about that.
Choosing a tyre
Now you’ve got the specs, and decided what you want from your tyre, it’s finally time to choose your new shoes.
The easiest way to select a new tyre is to do what we all do these days for research – Google, find the tyre manufacturer’s websites and enter either your car’s details, or better yet, the tyre size specifications we found above. The website will then list all of the tyres that fit the specs, and you can make your choice.
For my 86 I’m going to look at the Toyo tyres range. This is because Toyo have a good range of rubber in 215/45/17 to choose from, six choices in fact, are sponsoring the NSW 86/BRZ Club, and they have offered us a set of tyres on test. To get an idea of prices, I rang five Toyo dealers around Melbourne and made up the table below:
| Tyre | Description | Dealer prices – fitted and balanced, each | Average (each) | Four & wheel alignment | ||||
| NanoEnergy3 | long life, low rolling resistance for good fuel economy | $165 | $195 | $165 | $165 | $194 | $173 | $760 |
| Proxes 4 | entry level performance tyre | $170 | $205 | – | $179 | – | $185 | $809 |
| Proxes C1S | comfortable ride, good grip levels. An example of an expensive tyre that is a good all-rounder. | $180 | $209 | – | $185 | $230 | $191 | $835 |
| Proxes T1 Sport | great grip and handling, but starts to compromise tyre life | $185 | $219 | – | $190 | $201 | $198 | $862 |
| Proxes R1R | the grippiest tyre, but compromises everything else; is expensive and shortest life, not quiet or comfortable | $220 | $259 | – | $230 | $247 | $236 | $1,015 |
Allow around $70 for a four-wheel alignment on a roadcar.
You can see from the summary that there’s no perfect tyre. Don’t let anyone tell you that you can have it all for any given tyre. Also, it pays to ring around. One dealer swore the R1Rs would be $150 each but I think he had been inhaling his own sealant.
I’ll talk through my requirements as an example. The 86 is a toy car (hence the numberplate) and it’s really for driving in circles on Sundays. We have a Ford Ranger for long trips, and most of the time we’ve got some new car or other on test, so I’m not bothered about fuel economy or ride comfort. I also bought an 86 rather than a Cayman so I could afford to track it and spend money on it… always leave budget to enjoy the car and maintain it, rather than spend every last cent on the car itself. So with all that in mind, the R1R is the tyre for me. A quick check of the specs and yes, it is load rated for 87 and speed rated for W – remember, not just the size you need to check. So all good and legal. If the tyre was rated 88 or X (higher than 87 W) that would be fine too.
The extra grip will certainly improve my laptimes which will be of academic interest, as for me track days for me are more about the enjoyment of driving. Instead, I’ll be looking for how much extra fun the R1R can deliver, and check back here on Practical Motoring for periodic updates.
Up until now I’ve run either the original-equipment manufacturer (OEM) tyres which are the Yokohamas that come on the GT86, or the Michelins which are standard on the GTS and Subaru BRZ. These tyres aren’t exactly high-grip, but they’re cheap and fun (interesting factoid – the Yokohamas are the same tyres as on a Prius). I’ll retain a set for use on dirt-road events like autocrosses and for skidpan fun, or for any long-distance trips where I don’t want to wear out the R1Rs. It takes about 20 minutes to swap tyres over using an electric rattle gun to undo the wheel nuts, and a trolley jack to lift the car.
So that’s the process to get to the R1Rs. Next up will be initial drive impressions, a track test and a long-term test until they wear out. Watch this space.
Tyre FAQs
How many tyres should I buy?
Ideally, five if you have a full-sized spare or if not, four. This is so you get consistent performance across the vehicle. Never buy just one new tyre as there will be differing grip levels across the axle. It is not legal to run different spec tyres on the same axle either, they must be identical. Any offroad 4WD should definitely have five tyres.
How often should I check my tyre pressures?
Every month. Tyres lose a little bit of pressure over time, and under-inflated tyres are prone to blowouts, cost you fuel and handle poorly. Use a tyre pressure gauge readily available from any auto store like Autobarn, Supercheap Auto or Repco. You cannot tell the pressure from looking at a tyre unless it is so badly under-inflated it is almost flat.
What tyre pressure should I run?
At least what it says on the tyre placard which is close to the driver’s door when open – see pictures above. It doesn’t hurt to add 3-4psi over that figure, especially if you’re heavily loaded. Over inflation is bad, under inflation is deadly.
What’s a wheel alignment and do I need one?
Your car tyres are not lined up to be perfectly vertical or aligned with the car. Strange, but true. This is all to do with the intricacies of handling, and there’s terms like camber, caster and toe-in which are collectively known as “wheel alignment”. Each car is different, and over time the alignment gets slightly knocked out of line. A wheel alignment checks the alignment and if necessary puts it back where it should be, so you get the best handling and performance from your vehicle. Have it done every time tyres are changed as otherwise you can get excessive tyre wear, and have to change your new rubber well ahead of time and that’s a waste of money. Also, your old tyres may have settled into an incorrect wear pattern that seems ok, but with new rubber on the incorrect alignment becomes apparent.
What’s a wheel balance?
A tyre and rim cannot be perfectly made. There will be slightly more weight somewhere on each, so when the wheel rotates a slight vibration will set in because the tyre/rim combination is not perfectly symmetrical. The solution is to balance the tyre, which involves putting the wheel and tyre on a special machine which spins it, and detects where the weight isn’t perfectly symmetrical. Special weights are then fitted to the rim to even out the imperfections. Whenever you get a new tyre fitted it must always be balanced, and if you find vibration creeping in then it is possible that one or more of the weights has fallen off.
Is it worth filling my tyres with nitrogen ?
No. This is why. Still waiting for proponents of nitrogen to send me evidence it is anything other than a scam.
How do I know when to replace my tyres?
If you drive a roadcar replace when the tyre tread depth gets to just below 2mm. The legal limit is 1.5mm but that’s a bit too shallow. If you drive a 4WD with offroad tyres then replace at 1/3 tread depth, as even 2mm is way too shallow – 4WD tread depths might be as much as 20mm to begin with.
You also need to replace tyres before they get too old, regardless of tread depth. More on that here.
How does changing tyres affect my car?
We’ll go into this in more detail another time, but more grip from the tyres has significant knock-on effects throughout the car although for road use it is unlikely to be critical. On the track, with the standard tyres I can brake hard enough to activate the ABS from about 150km/h, with gripper tyres that may not be possible so if I want to maximise the potential of the tyres upgraded brakes may be in order. The extra grip means the car will go quicker through the corners, which means suspension tuning. Camber, toe and caster might need slight changes too.
What about the rims?
Another topic for another time, but changing rims can be a great way to improve the look of the car, like this:
Most of the time rim changes are done for cosmetic reasons. If you want to change rims for performance reasons ensure you buy lighter rims. Whatever you do, ensure the new rims have at least the same load rating as the originals and are otherwise in specification limits for the car. Lighter wheels are very important as the wheel is a rotating mass.
Remember, you cannot fit any tyre to any rim – there are limits to tyre width for a given rim width. Consult the tyre specification which will list the permitted rims you can fit the tyre to. In the case of the 215/45/17 R1Rs the permitted rim width is 7 to 8 inches, so a 7 inch, 7.5 inch or 8 inch wide rim will work. A 9 inch rim will be too wide, and if you’re lucky the tyre shop will refuse to fit the tyre and slap you for asking.
If you have a cooler 86 or BRZ than the BRZ above – and frankly, I doubt that’s possible – post an image in the comments with a brief description of your car. I’ll make a post up with the best of them.
Thanks to Road Track Rally who fitted the tyres, and I look forwards to cutting some laps to see how much quicker these R1Rs are than the stock tyres!
Would love to see a test between all the low roll resistance economy tyres, some big claims are made
Don’t forget noise, big difference in noise, Yokohama A460 on Lancers can send you deaf 🙂
I’ve found that the “best” tyre is car dependent. One type and brand which works wonderfully on one vehicle can be terrible on a different type of car. To define a good tyre, state the vehicle it’s on.
That is true Doug, and is also dependent on use and preference.
Minor typo – “somwhere”
Thanks, fixed. Proofreader has been sacked
My 4WD came with 245/70/16. Dueller 693. In fact the tread width measures 170 mm. Does the 245 refer to the max sidewall width?
No, it refers to the width of the tyre tread in mm which should be close to 245mm. A 170mm tread width is very narrow.
As I said, the tread is 170 wide, 175 if you’re generous.
Odd isn’t it. I’ve spent a lot of time getting across tyre specs and buying on the basis of them to hit a use and legal target and never thought to get out the ruler to check until recently.
I can only assume that the maker decided to include the shoulder in the width spec. But it’s a steep one and would only help in soft stuff. Or it applies to the max width of the cross-section.
Got the big calipers out for some more measurements.
200 mm wide where the shoulder ends on the sidewall.
Max sidewall width 240 mm.
I been robbed!
2 questions:
Alignment with new tyres… now if the alignment is already good with old tyres, why would new tyres make it better?
Speed/load rating – I don’t get this ignore this bit. My understanding is that load MUST be same or greater and speed can be avoided with a sticker on the windscreen warning that the tyres rated at x km/h
*If* the alignment was good. Often it isn’t, and it is worth checking. Post amended to clarify. Also, tyres can wear into a certain incorrect pattern, and what kind of worked on the old tyres doesn’t work on the new.
Speed/load – you can’t ignore it. For 4WD tyres there is a dispensation to speed rating of N. There is no dispensation for any load ratings.
Hi Mike, no, sorry, putting nitrogen into your car tyres won’t help you save fuel or keep your tyres inflated ‘at the correct pressure’ for longer. All you need to do is get into a habit of once a week taking a quick look at all four of your tyres and checking them with a tyre pressure gauge, which you can purchase at any auto supplies store (I keep my gauge in the glovebox for ease of access) and then, if you’ve lost a bit of pressure simply head to a local service station and then top them up, using your pressure gauge to make sure they’re running the correct pressure. Don’t rely on the digital readout on the service station pumps. – Isaac
I see, hmmm, thanks for these awesome insights, Isaac. Will surely take note of this
Thank you for this extensive guide regarding tyres! My friend is planning to get a Subaru Impreza WRX next month and he’s still clueless about tyres. I find it interesting to learn that you can figure out the tyre’s specs by looking at the actual tyre itself. I should probably share this to him so he’ll have a guide regarding car tyres.
Thanks so much for this – great article. I’m just about to put a new set on my car & didn’t want to bother hubby with taking care of the task. Now I know what I’m looking for!
i like to read your blogs regularly because of your informative blogs
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