Help, different size tyres?
 

When i bought my car 2 years ago. It came with a set of budget part worns on it.

Over time i have gradually replaced the tyres one by one for contintentals.

The last budget tyre now needs changing and im going for another continental.

Ive had national tyres put on the other 3. on checking the sizes they have put 245/45/17's on the front.

The one tyre they have changed on the back, they put on a 235/45/17 (now a few months ago, so nothing i can do).

The tyre that now needs changing is currently a 215/45/17

What is the correct tyre size? I'm confused and miffed as obviously they should all be the same size.

should i put on another 245/45/17 so i just have one odd tyre? or do i match the size of the one on the back and put on a 235/45/17. Ill then have same tyres on each side but different sizes on front and back?

Lee

You have 4wd and they have mixed the tyres up....

That is messing with your diffs, I would insist they matched the 4 tyres.

Ive been back to them with my receipt in hand, had the area manager come and see me. It is my own fault for not noticing when they put it on. Also has been too long for them to do anything about it.

They have offered me a discount on my next continental as a gesture of goodwill.

It's not your fault they didn't do there job right and they didn't give you what you asked or paid for - trading standards IMO

Replacing tyres one by one is never a good idea all the same

No it is not your fault for not noticing, you gave them a job to do and they effed it up. They should sell you one new tyre of the correct size and fit a new tyre of the correct size to the wrong wheel.

Anything less is leaving you with a dangerous car which is likely to be under-reading on the speedometer, and overstressing your centre diff.

215/45/17 is std on uk wrx newage, think 225 if sti rims
wider ones might rub on the front but they should be all same so take cheapest route to that imo

It may not be your fault according to trading standards or other people's opinions, but the correct way to deal with replacing tyres on a permanent AWD vehicle is understood by few, and that includes the vast majority of garage mechanics.

My advice is to do your homework so you fully understand the unique tyre requirements of an AWD subaru and in future be in charge of tyre replacement and maintenance yourself so you can be sure it's done properly.

I tend to buy my tyres online in sets of 4 and take them to the garage to fit.

So here are a few important points for sizing tyres on a subaru:

• All 4 tyres should always match in size and ideally in brand and model as well.
• worn tyres should be replaced 4 at a time. Rotate wheels front to back, and left to right if possible (not possible on directional tyres unless you get them changed on the rim at a tyre place) every few months to even out wear so all 4 are worn at (more or less) the same rate.
• Avoid where possible installing one brand new tyre when the rest have more than a couple of mm wear. If you must do this, the ideal situation would be to replace the rest as soon as possible so they match. I've also heard it's possible to wear a new tyre down to the same level as the used ones, but not tried this my self.

The reason for all of this is the Limited Slip Diffs on a subaru - even the most basic subarus have one in the centre diff, and most performance versions and foresters/outbacks have one in the rear diff as well. Some imprezas also have a front LSD. The function of the LSD is to limit differential speeds of the individual wheels above a certain slip threshold. Different tyre sizes can be enough to activate this system, but if that happens on a high-grip surface (ie on dry tarmac) it can be enough over time to cause permanent damage to your LSDs. One new tyre on with 3 partially worn tyre of the same size can be enough of a difference to cause issues.

It's the same reason the hand books advise driving no more than 50 miles on the spare wheel.

good advice 'devil new tyres cheaper than new gearbox, camskill or black circle usually have good online prices and get a real spare wheel if possible, those space saver things can really bugger up a long journey.

Or if like me your spacesaver doesnt fit over the 335mm brakes then get rid and get some tyreweld. (Note to self: get some tyreweld!)

I have LPG tank in the spare wheel well, so day-to-day I tend to carry a can of tyreweld, but on longer journeys I always take a full-sized spare.

Some good advice arumdevil.

I always try to replace 4 at a time and rotate tyres every 1000 miles on AWD cars.

One driver I knew of took his car back to VW because he kept getting a warning on his tyre pressures because he had different sized tyres left to right.... the mind boggles.