One tire picks up a nail on Marine Drive, it cannot be repaired, and the shop tells you that you need to buy four. It is the single most common point of friction in this trade, and most people assume they are being upsold. Sometimes they are. Often they are not. Here is the honest version.
The short answer
- Front- or rear-wheel drive, tires nearly new: one replacement is usually fine.
- Front- or rear-wheel drive, tires part-worn: two, fitted as a pair on the same axle.
- All-wheel drive: often all four — and the reason is mechanical, not commercial.
Why tread depth difference matters at all
A tire with deep tread is very slightly larger in diameter than the same tire worn down. It sounds trivial — a few millimetres of rubber — but that difference means the two tires turn at fractionally different speeds for the same distance travelled.
On a front- or rear-wheel drive car, that is mostly a handling issue. On an all-wheel drive car it is a drivetrain issue, and that is where it gets expensive.
When one tire is genuinely fine
If your tires are close to new — say the damaged one has done a season or two and the rest still have most of their tread — and the car is front- or rear-wheel drive, replacing the single tire is perfectly reasonable. Match the same make, model and size, and you are done.
Anyone who tells you that you must always buy in pairs, regardless of condition, is not being straight with you.
When you should buy two
Once your tires are meaningfully worn, a single brand-new tire alongside a half-worn one on the same axle gives you noticeably uneven grip — particularly under braking in the wet, which on the North Shore is most of the year.
The fix is to replace both tires on that axle so the pair matches. You do not need to touch the other axle.
And put the new pair on the back
This one surprises people. Regardless of which wheels drive the car, new tires belong on the rear axle. Worn rear tires let the back of the car step out in standing water, and a rear-end slide is far harder to correct than a front-end one. Any decent installer will do this by default — we do.
Why all-wheel drive is different
An AWD system is built on the assumption that all four wheels are turning at close to the same rate. When one tire is a different diameter to the others, the centre differential, transfer case or viscous coupling has to absorb that difference continuously, every kilometre you drive.
It does that by generating heat and wearing itself out. The failure is gradual and then sudden, and the repair bill is in the thousands — considerably more than the tires you were trying to avoid buying.
This is why most AWD manufacturers publish a maximum permitted tread-depth difference across the four tires, commonly around 2/32″ (about 1.6 mm). Subaru specifies it as a maximum difference in tire circumference. Your owner’s manual will have the exact figure for your vehicle, and it is worth a look before you decide.
What that means in practice
If your AWD vehicle is on a nearly new set and one tire is destroyed, a single matching replacement is usually within tolerance. If the set is half worn, it very often is not, and four is the honest answer.
One thing we cannot do — and will not pretend otherwise
You may read that the solution to an AWD mismatch is to shave a new tire down to match the others. It is a real technique and some specialist shops offer it.
We do not. We do not have the equipment for it, and we would rather tell you that plainly than send you away thinking it is an option we are choosing not to mention. If shaving is genuinely the right answer for your vehicle, we will say so and point you at someone who can do it.
How to check where you stand
A tread depth gauge costs a few dollars and takes the guesswork out entirely. Measure all four tires across the middle of the tread, and compare the readings.
For reference, the legal minimum in British Columbia is 1.6 mm. A winter tire needs at least 3.5 mm of tread to still count as a winter tire — below that it is legally a summer tire, whatever the symbol on the sidewall says.
If you would rather not crawl around the driveway with a gauge, we measure all four as a matter of course on every visit and will tell you exactly what the spread is.
What we would actually recommend
When we come out to a non-repairable tire, we measure the other three before saying anything about buying. If one will do, we will tell you one will do. If your AWD car is outside its tolerance, we will show you the numbers rather than ask you to take our word for it.
And if you are stuck in the meantime, a loaner tire keeps you driving while we source the right rubber — that is included in the call-out rather than charged as an extra.
Talk to us
Mobile tire service across North Vancouver, West Vancouver and Lions Bay. Call or text 604-900-8453, or book online and we will come to you.
