Let’s face it: most vehicle owners don’t ever think about their tires until they get a flat, their mechanic tells them they have a problem, or some whisper in the back of their head tells them it’s time to replace one or more of them (check out our post on how to know when to change your tires). But when the time does come, an owner faces a slew of unexpected questions, with one of the most prominent being: do all four of my tires have to match?
As is becoming a common refrain, the Internet has posts from reputable sites claiming answers on both sides, as well as somewhere in the middle, leaving every day consumers to decide the answer for themselves. Not cool, Internet. So we did some research – quite a bit of research in fact – and touched base with a handful of tire manufacturers for good measure.
In aggregating all of this research, here’s the best answer for whether or not all four tires need to match and/or whether all four tires need to be replaced at the same time: in an ideal world, all four tires should match, meaning that they are the same brand, model, size and age (as measured by tread depth). The reason why is simply that your vehicle will operate at its safest and most efficient when all four of your tires match.
The primary function of tires is not to get you from point A to point B – it’s to keep your vehicle tractioned to the road in any condition, setting and situation. The most effective way for tires to accomplish this seemingly endless bevy of possible scenarios is if all four of them are as similar as possible.
TireTrend.com has no loyalty or affinity to any one tire brand, but in this matter Continental summed it up quite well:
Matching tires are even more important on AWD vehicles
Tires do not wear evenly on any car, truck or SUV. Front tires are known to wear out much more quickly, which isn’t really a surprise given that they handle the bulk of the workload with regards to steering and braking, as well as acceleration for front-wheel drive vehicles. But AWD vehicles throw an added wrench into this calculus. AWD vehicles have onboard computers that can alter the exact amount of propulsion directed to any of your four wheels. So if the car senses that one wheel is losing grip (on ice, for example) it can redirect power to the other three tires to correct for this uneven equilibrium and keep the vehicle steady.
Tires play a critical role in this AWD equation, making it even more imperative that tires on an AWD vehicle are as matched as possible. Tires of considerably different status – either size, width, or tread depth (i.e. uneven wear) could accidentally trigger the AWD system, sending false data to the vehicle’s computer that would alter the propulsion being sent to each tire.
Why would this happen?
For the sake of explaining this using a gross exaggeration (sorry, we have young kids so so gross exaggerations are pretty common for us), imagine putting a monster truck tire on your front passenger side while all other tires are “normal” car tires. Not gonna work, right? At best you’ll go in circles; at worst, you’ll have no control over the vehicle whatsoever.
Now, there’s a big difference between a new car tire and a monster truck tire, but the theory still holds true and, when you’re talking about AWD computer systems, hundredths (or, more accurately, 32nds) of an inch really can matter.
We spoke to a handful of local mechanics and asked them how likely this scenario was to play out in the real world. Across the board every mechanic said it was very unlikely – especially if you put the same size tire but mismatch the brand (read our post about what those numbers on the side of your tire mean to learn more about tire sizes). But all the local mechanics said it was possible and something to be avoided for both safety reasons and potential damage to onboard AWD systems.
What if I can’t afford to replace all four tires or can’t find an exact match?
So knowing all of this a natural follow-up (and potentially expensive) question is: if one tire goes and I can’t find an exact replacement, does that mean I have to replace all four at the same time?
The thought of replacing all four tires when three of them are perfectly fine can be a frustrating (and frustratingly expensive) prospect. And it’s happened to us recently. Fortunately, though, there is a bit of leeway here.
Replacing all four will always be the safest and most recommended option, but the reality is that sometimes that simply is not possible. This exact scenario happened to one of us when we were forced to find a replacement for the original tires on a 2017 SUV. Yes, you read that right: 2017… just a few years old, and yet we could not find an exact replacement anywhere in our immediate vicinity. Everywhere tire shop we checked said that they could have the tire shipped in, but that it would take anywhere from three to eight days, leaving us stranded and without a car (UPDATE: for those who have asked, we live in suburbia, so no easily accessible transportation to get us to and from work).
In situations when only one tire needs to be replaced and owners are averse to replacing all four, the best recommendation is to replace both the busted tire and its opposite (meaning the other tire on the same axle). So two tires for the price of… well, two (but that’s better than the price of four!).
In this situation, you should look to match the new tires as closely as possible to the existing tires, starting importantly with comparable sizes but extending – when possible – to tread designs so that your vehicle operates efficiently and preserves its safety integrity. This is an area when it’s best to seek the advice of a professional, be it a mechanic, dealer or local tire shop, as they will have the greatest insight into what set of tires most closely mimic those already on your vehicle.
Also, most mechanics suggest that you put new tires on the back of your vehicles, not the front. That may sound counter-intuitive as the front wheels are the true workhorse of most vehicles, but brand new tires actually have slightly less traction than broken in tires, so keeping the tires with more traction on the wheels responsible for steering maximizes the vehicle’s safety and predictability.
The final answer on whether all four tires have to be the same
When in doubt, read the manufacturer’s manual for your vehicle as it will have recommendations on whether your tires need to match or not. Most likely it’ll say to keep all four the same, but in life sometimes that simply doesn’t work. Accidents happen, and when you do get a nail in one tire you’re going to be faced with the decision of replacing one, two or all of your tires. A mix of factors will inform this decision: availability, immediacy, price and condition of your other tires, just to name a few. The best advice is to do what you can to make sure your tires are as identical as possible; when that’s not feasible, do everything in your power to make sure that the wheels on the same axle match.
As we often say in our posts, many of us are carrying precious cargo in our vehicles, so we encourage our readers not to treat tires as an afterthought. Treat your tires well and they’ll provide miles of good – and safe – service.