[IA_BMW]

My son's 2017 M240i X-Drive has 10,500 miles on it and he's got a hole in the sidewall of his front passenger side tire. I'm not familiar with the BMW differentials so I don't know if he can replace just one tire, or if he needs to replace two, or even four. Can someone shed some light on this please?

[Siriso]

As a general rule replace two and move them to the rear, keeping the worn ones on the front. If they're within a 32nd or two you can replace them individually of you like. However, your ride quality and alignment spec can be thrown off somewhat.

[ralawren]

Buy a used one on ebay that is within 2/32nd of the remaining good one. Used MPSS (not sure what you have) are $75-$100 usd. Or buy two new tires and sell the one good old one...

[MetalMK]

I would strongly recommend replacing all four tires, especially if they are close to replacement. Even if they are just half way there, it is much safer to replace all four because of the transfer case on XDrive models will be confused if there is more than 2mm tread difference.

And never buy used tires, you don't know what they've been through. If you can only replace one tire, buy a new one and find someplace that can shave it to the appropriate tread depth for you.

[dradernh]

Originally Posted by MetalMK

If you can only replace one tire, buy a new one and find someplace that can shave it to the appropriate tread depth for you.

Tire Rack will shave tires to the buyer's desired tread depth.

[Lucky13]

The tires should go on the rear not the front, just google it. You do not ever want the rear end slipping out.

[aerobod]

Originally Posted by MetalMK

I would strongly recommend replacing all four tires, especially if they are close to replacement. Even if they are just half way there, it is much safer to replace all four because of the transfer case on XDrive models will be confused if there is more than 2mm tread difference.

And never buy used tires, you don't know what they've been through. If you can only replace one tire, buy a new one and find someplace that can shave it to the appropriate tread depth for you.

That diagram is totally misleading for a tyre that is anything other than 5" in diameter, the red stripe should be about 5 times smaller for any BMW wheel and tyre, and about 4% of the size for a tyre that would more typically be 2 or 3mm different in diameter.

Still better to have the tyres the same diameter through shaving or replacing tyres in pairs, but that diagram is just misleading rubbish.

[IA_BMW]

Thanks for the feedback, guys! We ordered two new tires to put on the rear. Then we have two of his old tires still at 7/32 that we'll put on the front.

[msej449]

When I worked for a tyre manufacturer, because we got tyres fitted in the factory at cost, a lot of us would fit new ones annually. This because a lot of tyres give you disproportionately better braking distance down to 4mm (5/32"), and disproportionately worse on the remaining wear down to the legal minimum:



So you can console yourself that there's an upside to being forced to fit some new tyres e.g. at 4mm (5/32") this tyre stops the car in 24m (79ft) but at 2mm (3/32") the stopping distance at the same speed is 30m (98ft) - and that's on dry tarmac. This is why I generally think about replacing my tyres at some point between 4mm (5/32") and 3mm (4/32") even though the UK minimum is 1.6mm (2/32").

[Caveat: The graph is for one particular brand of performance tyre. As you might expect, different brands may have different profiles. So some make the curve more of a straight line, some wear less/more, some give you less initial adhesion but better worn adhesion etc. But for performance tyres, the common assumption is that if the owner can afford a performance model, then they can afford to replace tyres earlier than the legal minimum and want shortest braking distance before anything else.]

[blitzjb]

Originally Posted by IA_BMW

My son's 2017 M240i X-Drive has 10,500 miles on it and he's got a hole in the sidewall of his front passenger side tire. I'm not familiar with the BMW differentials so I don't know if he can replace just one tire, or if he needs to replace two, or even four. Can someone shed some light on this please?

You will be going through many tires! I hope you do not have Pirelli's - they are the worst tires and always have problems.

[morphomeman]

Ditto! Modern 'bicycle' tires get punctures and worse because their sidewalls have so little room to flex. I have replaced tires on my 235 at the rate of about one a year, all under warrantee. If I replaced two every time, that would be a lot of moolah. I understand the notion that a large difference in diameter will affect performance, but honestly, is it noticeable on a DD?
BTW, who is paying for the tires?

[IA_BMW]

Originally Posted by morphomeman

Ditto! Modern 'bicycle' tires get punctures and worse because their sidewalls have so little room to flex. I have replaced tires on my 235 at the rate of about one a year, all under warrantee. If I replaced two every time, that would be a lot of moolah. I understand the notion that a large difference in diameter will affect performance, but honestly, is it noticeable on a DD?
BTW, who is paying for the tires?

It's my 22yo son's car, so he is.

[Maynard]

FWIW, the stock staggered non-runflats have uneven diameters, with the rear being a bit smaller (25.1fr v. 24.8 rear) - .3 inches, which is about 7mm. Since this is the factory setup for sport driving, I think it is safe to assume it is within acceptable tolerances. This would support putting the new tires on front, since they would be larger, and match up with the factory 'stagger' (but theoretically, reversing this would just work the transfer case the same amount, but in the reverse direction, right?). I think it is more crucial to match on the same axle, via shaving or replacing both.

[Luftwaffe1O1]

On AWD models the conventional wisdom is to replace all 4. But then again it depends on the circumstances. On RWD as long as the tires are close in wear on the same axle.

But I would imagine there are some tolerances, the tire shops will all say you need all 4, otherwise the transfer case will will go boom. Realistically as mentioned the stock setup if its staggered has a slight variation front to rear, so in the span of 1 mile, the rear tires will do about 10 extra revolutions.

If the tires were halfway worn, I would replace 1 wheel on the same axle. If they are all close to being worn, why mess around? Replace all 4.

[CE750Jockey]

Never trust anyone that spells "tires" with a "y". The proper spelling is "reifen".

[morphomeman]

The inflated object in question was invented in Scotland by Dunlop, so I guess that the original spelling had a y. For me, it is a pneu.

[Mollyran]

I would, at minimum, replace both tiers on the same axle and if I am getting closer to 3mm I will replace all 4.

[VasWander]

I recently replaced just one rear tire - took a nail and dealer told me non-repairable due to location. New car has only 5K miles and I am planning on getting 10K with the stock run-flats before I get new tires before winter. Put about 500 miles on new tire now and all good although that damn nail cost me nearly $400!

[HaiDef]

Do you guys stick to the run flats or get rid of them ASAP?

[pgk500]

Originally Posted by Luftwaffe1O1

On AWD models the conventional wisdom is to replace all 4. But then again it depends on the circumstances. On RWD as long as the tires are close in wear on the same axle.

But I would imagine there are some tolerances, the tire shops will all say you need all 4, otherwise the transfer case will will go boom. Realistically as mentioned the stock setup if its staggered has a slight variation front to rear, so in the span of 1 mile, the rear tires will do about 10 extra revolutions.

If the tires were halfway worn, I would replace 1 wheel on the same axle. If they are all close to being worn, why mess around? Replace all 4.

Yup agreed. But they also recommend not to fix run flat tires but I did it anyways and no issues. One flat and dealer and reputed tire shop was asking me to replace all 4. Found a local mom and pop store that fixed run flst for like $25 bucks !

[Kernel Kurtz]

This is an old thread, but just chiming in that I've never had a problem getting my run flats patched just like a regular tire. This assumes you don't drive it a hundred miles while flat of course. If get a flat in the city, I drive it to the local tire shop ASAP and get it fixed. On the highway I carry a plug kit and small compressor so I can do a temporary fix, and then get it properly patched later. Obviously the same caveats apply as to regular tires eg sidewall punctures still can't be fixed.

[Miata13]

I would add...RE: patching a tire... If you intend any performance driving (auto-x or on track driving events) I would not recommend driving on a patched tire.