[Roche]

Over the weekend, one of my front tyres was damaged by a nail. Unfortunately, it was right on the sidewall and so couldn't be repaired (these are runflats). So it had to be replaced. That's fine - sh!t happens. The tyre technician recommended I do the other front as well as they should normally be done in pairs. That's fine, both tyres would probably have needed replacing within the year, anyway! So far, so good. Flipping expensive, tho.

Yesterday, while telling a friend my financial tale of woe, he suggested that I might have to change the rears as well! So as not to avoid messing up the xDrive system. Urrrrgh!

I measured the tread depths. Both new front tyres are on 8.0. The rears are on 4.9 (passenger side) and 4.7 (driver's side).

With all of your collective knowledge, can I drive my X3 with these differences in tread depth front and rear? Will I knacker the 4WD system if I do so?

I'm loathe to spend out more money to replace the rears right now. But hey, if it needs to be done, then I have no choice. Anyhow, let me know!

EDIT: BTW, the tyres are 275/40/20 at the rear, and 245/45/20 at the front, and they are all the same Pirelli P Zero brand (not sure if that makes a difference, but added it just in case).

[spangle1980]

There is much technical to and fro on this. Firstly replace both sides was a good idea :-)

Tha bad news is that, depending on where you read (and there are some better brains on this than I) You have a tolerance of up to 2mm, e.g.

https://g20.bimmerpost.com/forums/sh....php?t=2071693

It's not gonna break soon, but the concept is that of wear/more stress to x-drive over a longer period.

[avi66]

Originally Posted by spangle1980

There is much technical to and fro on this. Firstly replace both sides was a good idea :-)

Tha bad news is that, depending on where you read (and there are some better brains on this than I) You have a tolerance of up to 2mm, e.g.

https://g20.bimmerpost.com/forums/sh....php?t=2071693

It's not gonna break soon, but the concept is that of wear/more stress to x-drive over a longer period.

That could get very expensive, very quickly.

[Roche]

Originally Posted by spangle1980

Tha bad news is that, depending on where you read (and there are some better brains on this than I) You have a tolerance of up to 2mm, e.g.

It's not gonna break soon, but the concept is that of wear/more stress to x-drive over a longer period.

Thanks for the quick reply!

But.... yikes - this is depressing news! My difference between front and rear is just over 3mm, so if that post is correct then I'm 1 mm over

I suppose that, if it's not going to go bang immediately, I could probably replace the rears in the next few months?

[Roche]

Originally Posted by avi66

That could get very expensive, very quickly.

Indeed. Hopefully I'll be good for the next few months before I change the rears. This will have cost over £1000 in tyres, though!

I think, for my next car, I'm going back to a VW Golf which I used to drive before the X3. Much more economical to maintain!

[avi66]

Originally Posted by Roche

Indeed. Hopefully I'll be good for the next few months before I change the rears. This will have cost over £1000 in tyres, though!

I think, for my next car, I'm going back to a VW Golf which I used to drive before the X3. Much more economical to maintain!

The front/rear tyres are a different ratio on my staggered setup i.e 245/40 v 275/35. Is the sidewall height not 98mm v 96.25mm, so 1.75mm different, before tread ware is even considered. So does that reduce the 2mm tread difference even further as I don’t recall any mention of this.

[Roche]

Way too technical for me, I'm afraid! Sidewalls, etc...

I'm just surprised that 1mm here or there can cause such problems. Especially when you consider some tyres are overinflated, some underinflated, some X3s carrying heavy loads, some no loads at all, etc!

[avi66]

Originally Posted by Roche

Way too technical for me, I'm afraid! Sidewalls, etc...

I'm just surprised that 1mm here or there can cause such problems. Especially when you consider some tyres are overinflated, some underinflated, some X3s carrying heavy loads, some no loads at all, etc!

Does make you wonder considering the variables involved.

[spangle1980]

A bit of an extreme example but consider this URL

https://www.blocklayer.com/tire-size-calculator

If you use the a tyre size (just to pick one) of 275.45.R21 and for the other 275.40.R21 (just play with it :-) for that one example if you hit calculate at the bottom you see for 1000 miles on one tyre, the other will journey 960ish. Not a great deal but when multipled over 50-60k miles can mount up. That's the issue I believe - long term wear.

Just a thought :-)

[avi66]

Originally Posted by spangle1980

A bit of an extreme example but consider this URL

https://www.blocklayer.com/tire-size-calculator

If you use the a tyre size (just to pick one) of 275.45.R21 and for the other 275.40.R21 (just play with it :-) for that one example if you hit calculate at the bottom you see for 1000 miles on one tyre, the other will journey 960ish. Not a great deal but when multipled over 50-60k miles can mount up. That's the issue I believe - long term wear.

Just a thought :-)

Do G01 front/rear tyres ware at the same rate ?

As the op mentioned above, tyre inflation, vehicle weight distribution/loaf could vary significantly from car to car. Even xdrive power distribution based on driving style/road conditions would come into play.

[fdpxfunix]

A pothole burst both my 245/40R21 and 275/35R21 off-side tyres a few weeks ago. Both replaced with new tyres of 8mm depth. On the near side... the front was at 6mm and the rear at 6.5mm. Front changed about 14 months ago (a screw in it) and the rear (both sides) roughly 12 months ago as original tyres at 2mm. I've only done 7K miles in the last year so tyres and car hardly used really.

I asked the mobile tyre guy (who seemed to know his stuff from E-Tyres in Worthing West Sussex) if the difference in mm was an issue. First of all he laughed at me and smiled. He said on Audi's (especially older TTs) yes it can affect the 4-wheel drive, but on modern SUVs like the X3, if the tolerance between the tread depths is no more than 3 or 4mm he wouldn't worry about it.

Personally, I would change tyres in sets if depths were very different (like +/-6mm per side) and would only change all 4 for the same reason. Although you may end up long-term putting more stress on the Xdrive with 8mm up front, 4mm at the back (for example), the British roads, weather, difference in tyre inflation PSI/BAR, and god damn pot holes will stress it more.

Going off topic... Tyre insurance is one of the best things I've bought in the last 3 years and claimed 4 new tyres out of a possible 5. Cost me about £700 in 2021 and I've now claimed for £1230 of new tyres (3 pot holes, 1 screw). That £700 covered me for 5 tyres and 10 alloy wheel refurbs over 3 years. I'm now on the hunt for similar insurance.

J.

[BMWbiker]

Originally Posted by Roche

EDIT: BTW, the tyres are 275/40/20 at the rear, and 245/45/20 at the front, and they are all the same Pirelli P Zero brand (not sure if that makes a difference, but added it just in case).

Another option is to buy a square set of 19” rims and tires. It would be less bling, but could be significantly less expensive in the long run. At least it would be here in the U.S. I have never priced anything auto related in the U.K.

[avi66]

Originally Posted by fdpxfunix

Going off topic... Tyre insurance is one of the best things I've bought in the last 3 years and claimed 4 new tyres out of a possible 5. Cost me about £700 in 2021 and I've now claimed for £1230 of new tyres (3 pot holes, 1 screw). That £700 covered me for 5 tyres and 10 alloy wheel refurbs over 3 years. I'm now on the hunt for similar insurance.

J.

I also have tyre only insurance. It covers 12 tyres over 3 years, so a max of 4 per year. I did this because of issues on our other cars being nail magnets, but so far not needed to use it. Cost around £260 for the total cover, so one tyre replacement and I’m in the black.

[lfdal54]

For those of us who owned Subarus, especially back when everything was purely mechanical before they diluted it with electronics (the current system is inferior to what it was 20 years ago IMO) it was pretty much lose one tire, replace all 4. The test was the circumference of all 4 tires had to be within 0.25 inches or 6.35mm circumference of each other.

From poking around on the web I see much conflicting info on BMWs tolerance specs, but one of the AI searches pulls up a 2 mm difference in treadwear maximum.

For someone like me who never runs one until it's out of warranty, I'm not going to worry about it unless it's egregiously different. But if I was planning on keeping the car for a long time, then yeah, I'd pay closer attention to the tread matching.

[fdpxfunix]

Originally Posted by avi66

I also have tyre only insurance. It covers 12 tyres over 3 years, so a max of 4 per year. I did this because of issues on our other cars being nail magnets, but so far not needed to use it. Cost around £260 for the total cover, so one tyre replacement and I’m in the black.

Can you point me at the name of the provider please? That's sounds awesome.

J.

[avi66]

Originally Posted by fdpxfunix

Can you point me at the name of the provider please? That's sounds awesome.

J.

My tyre cover is with this company https://easygap.co.uk/other-insurance/844

[lfdal54]

Originally Posted by avi66

I also have tyre only insurance. It covers 12 tyres over 3 years, so a max of 4 per year. I did this because of issues on our other cars being nail magnets, but so far not needed to use it. Cost around £260 for the total cover, so one tyre replacement and I’m in the black.

I wish we had a product like that. At best the places I tried would replace the defective tire. The other 3 were out of my pocket.

[avi66]

Re the BMW 2mm difference, is it mentioned in the owners manual ? Can’t seem to find any mention.

[lfdal54]

Originally Posted by avi66

Re the BMW 2mm difference, is it mentioned in the owners manual ? Can’t seem to find any mention.

They make it really difficult to pin down. I can't find a definite answer either and my dealership told me not to worry about it when I asked them. OTOH, I can see them denying a claim if I went there with mismatched tires. They are not nice.

[TXGrey]

Originally Posted by lfdal54

For those of us who owned Subarus, especially back when everything was purely mechanical before they diluted it with electronics (the current system is inferior to what it was 20 years ago IMO) it was pretty much lose one tire, replace all 4. The test was the circumference of all 4 tires had to be within 0.25 inches or 6.35mm circumference of each other.

From poking around on the web I see much conflicting info on BMWs tolerance specs, but one of the AI searches pulls up a 2 mm difference in treadwear maximum.

For someone like me who never runs one until it's out of warranty, I'm not going to worry about it unless it's egregiously different. But if I was planning on keeping the car for a long time, then yeah, I'd pay closer attention to the tread matching.

This is the way…

Check/pay attention… but I wouldn’t sweat a minor variance.

[bocabimmer]

I can attest to it be an issue for 4WD vehicles, not necessarily ours. I just went through this with my Expedition. Rear tires were replaced by dealer with a different brand from the fronts (not my ideal setup either). The differential in circumference between the two was enough to cause juddering when the truck was running in 4WD. Replaced the front tires with same brand and problems solved.

[avi66]

Originally Posted by lfdal54

They make it really difficult to pin down. I can't find a definite answer either and my dealership told me not to worry about it when I asked them. OTOH, I can see them denying a claim if I went there with mismatched tires. They are not nice.

If it ain’t in the manual and there’s an issue, it’s BMW fault.

I can find anything on the BMW UK website, in the owners manual, or any documentation produced with my car. So they would have a challenge denying an x drive claim due to tread difference, if they don’t actually provide official readily available info I suspect.