Different tread depth on same axle?

[TomPaine]

As above - how ok is it? Google it and you get alarmist stuff saying you should always replace in pairs etc, but is 2-3mm in practice ok?

I had a blowout last night [Saab 9-5 Aero estate] so one rear needs replacing. They're Michelin Primacy 4 Plus. The other isn't very old, probably at least 4mm and I suspect 5mm. Depth of a new Primacy is, I read, 6.5mm. So I was hoping not to have to replace the pair.

Both fronts are at 3mm so if the fitter is coming I was thinking: rotate the 5mm and the new to the front and put two new on the rear.

Perfectly sensible or riotous folly?

[sgould]

Although the legal limit on tread is 1.6mm, 3mm is about as low as I tend to go.  So getting at least three new tyres is probably a good move.  When I had Michelin tyres, they were fine at first, but they got very noisy when getting towards the limit of wear.

Alternatively, you could change all four for the newer all-season tyres,  not the old ones with just a coarse tread, but the ones that are winter rated, like the Michelin Cross Climate.  I fitted a set of Goodyear Vector 4season tyres.  They have performed well over the last 2½ years, and are lasting well enough, even though I don't do somany miles now.  They have travelled abroad and survived higher speeds.   Look for the "mountain & snowflake" symbol on the sidewall.

[TomPaine]

But if committing to my current course is say 6.5mm on one side of the axle and 4mm on the other ok?

[sgould]

I've never had a problem that.  The rear wheels are not connected to anything, and the differential will cope with the rest at the front. I've have a punture that destroyed the tyre and it was replaced with a new tyre, the other side was half worn.  The car is on 188,000 miles and had probably been driven for a third of its life with different trad depths each side.  One of the perils of working on construction sites.

[TomPaine]

Peace of mind - thanks Will.

It says something about the state of today's roads that having gone about 15 years without a puncture I've had three blowouts / rapid deflations in two years.

[sgould]

It's one of the downsides of directional tyres that you can only swap then front to rear, not side to side.  A few years ago with Vredestein Wintrac tyres, I hit a deep pothole that was disguised as a puddle, and punctured the two nearside tyres and bent the two wheels.  I ended up with two new tyres on the nearside and the two original half worn ones on the off side.  It drove with no problem.

[welshwizard]

I'd say on the rear axle two tyres of different depths are ok.

I'd be careful on the front.  At least I'd make sure they are the same tyre.  Our Golf arrived with 4 different brands, the previous owner must have driven through B&Q after someone had dropped a box of nails on the floor.  Now all 4 finally match.

Like SGould I have the Goodyear Vector4 seasons but they are coming up to 6 years old now.  Pretty satisfactory all round, but great on wet roads.

[sgould]

Mine have been on nearly 3 years. They seem to be lasting well, but my mileage is fairly low these days.

[TomPaine]

I should have reported back. I had three new tyres with two going on the front; the remaining one on the rear was only about 1mm less than the new so it stayed where it is.