Can I change a single worn tyre instead of a pair?

Question

In April last year I bought a 2008 Ford Focus. The tyres were relatively new, all apart from the front right which was more worn than the rest. I've driven the car roughly 7,000 miles in nearly 11 months.

I measured the tread depth on each of the tyres and 3 of them have around 4.5mm of tread left but the front right has only about 2mm left (legal limit being 1.6mm). The worn tyre is a different brand to the others which suggests to me the previous owner replaced just that one (maybe after an unrepairable flat or something?).

My question is: Would it be alright to change just the worn tyre for a new one with the intention of swapping the others to the same tyre make (Pirelli P7) once they need it? Would it be better to swap both front ones and just accept I will lose 4.5mm of good tread? (The spare is a space saver).

I've found a couple of other questions on this subject but none that seem to discuss changing a tyre that is much more worn than its opposite tyre when the other tyre in the pair still has reasonable life in them.

As far as I understand there could be differences in the characteristics of tyres so that in heavy breaking it might behave differently. I also read there might be insurance implications due to 'improper maintenance'.

I'm not so concerned about the cost of this (if they need replacing, they need replacing...) but I don't necessarily want to throw away a part worn tyre if I don't have to.

Update: I'm specifically interested in how this might affect the handling and if the effect would be adverse.

Outcome: Based on the comments here I actually ended up changing both front tyres for new Pirelli P7s and moving the less worn tyre from the front to the back where there was evidence of cracking in the side-wall of one of the rear tyres. I disposed of a cracked side-walled tyre that had roughly the same 4mm wear on it as the front one I'd swapped. I guess I lost out a little bit but really the equal front grip is probably worth it in the end!

Answer 1

You can do that if you wish, there is no law against miss-matching tyres however some people prefer to have the same brand and tread depth on each axel, which is why they change two at a time so that the front two match and the back two match.

As for heavy breaking the newer tyre will provide more grip which could cause the back end to crab sideways however this will only be under severer emergency breaking conditions. This is the same for different branded tyres as one brand may offer more grip than others.

Other than that there are no extreme dangers to this, the choice is up to you.

Answer 2

It all depends on the cause of the wear on that tire, the condition of the rest, and the tread of the new one.

If you have 3 new tires and one got punctured in the sidewall, many companies have a limited warranty and you can replace the one for free.

If you have an alignment problem, get an alignment before replacing tires to avoid early wear.

Better tires should be mounted on your drive wheels. FWD in front, RWD in the rear.

If you replace one tire and you have any less than 80% of tread on the rest, try buying a used tire with 70-90% tread. When buying a single tire, it's always best to get a matching tread pattern to your good set.

Answer 3

Given that you already have different tread depths on different brand tires on the front axle, replacing the single worn tire with a new tire won't be significantly different than what you have now.

What I have typically done in such situations is buy a new pair of tires to replace the front tires, and save the better used tire and mount it on a used wheel to make a cheap full-size spare. The one caveat to this approach is that this will set up a situation where the front axle has more traction than the back axle. If your car is old enough that it doesn't have ABS, then the rear axle will lock up first and try to pass the front axle under heavy braking. That can be solved by rotating the new tires to the rear and the used tires to the front.

Or, as another answer suggested, you can buy a used tire that's similar to the other front tire.