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-   -   Replacing Just Two Tires on an X3? (http://www.bimmerfest.com/forums/showthread.php?t=402168)

dcmomentum 10-01-2009 09:24 AM

Replacing Just Two Tires on an X3?
 
Guys,

I've tried doing some research, but I can't find a definitive answer. Do I need to replace all four tires on my 2005 X3? I've managed to get 77k miles out of my Pirelli Scorpions. I don't know how, I've never managed more than 30-40k from a tire in my life.

I was going to replace two, and replace the other two in 1-2 months.

cubed 10-01-2009 09:32 AM

I`d replace them all together -- you will have significant differences between diameter of the old and new tires (driveline and electronics dont like that) and they will drive significantly differently. Why not do them all at once?

dcmomentum 10-01-2009 09:43 AM

Quote:

Originally Posted by cubed (Post 4565277)
I`d replace them all together -- you will have significant differences between diameter of the old and new tires (driveline and electronics dont like that) and they will drive significantly differently. Why not do them all at once?

Because fishing season is in high gear in about a week. ;)

UncleJ 10-01-2009 10:32 AM

Bite the bullet and replace them all at once. You got your money's worth out of the OEM tires and why take a chance of messing up the X drive.:dunno:

ducx3 10-01-2009 10:55 AM

AWD. Replace all of them. Most shops won't even replace just 2 with an AWD vehicle.

dcmomentum 10-01-2009 11:14 AM

OK, thanks guys, looks like all four it is!

vrooom3440 10-01-2009 11:18 AM

Hmmm... I would think this is a case of YMMV.

BMW shipped the Sport package X3s with different sized tires front and rear. Very likely for different width/profile tires to have different rolling circumference. So it would seem that replacing tires 2 at a time really would not be a problem if some X3s shipped new that way?

X3-terrestrial 10-01-2009 11:20 AM

Buy two now, store them for 2 months, buy the other two, install the four tires at the same time. :)

Supercourse 10-01-2009 12:40 PM

Quote:

Originally Posted by vrooom3440 (Post 4565530)
Very likely for different width/profile tires to have different rolling circumference.

Good point.

I haven't done the calculation, because I have never been interested in owning a vehicle with different size tires front to rear.
(Unless there was a real performance advantage, rather than looks.)

But I would imagine that BMW carefully selects the tire sizes in a "staggered" set-up so that the rolling circumference difference is very small.
Or tune the X-drive dynamics to compensate.

Given that a new tire has about 10mm. tread depth, I would think that the rolling circumference difference between old and new tires in a standard set-up is more of a concern.

But another factor is that the 2 pairs of tires (old and new) would also have very different road-holding ability on wet roads, for example.
X-drive would have to handle that on a constant basis - not really the intended purpose.

gcopter 10-03-2009 05:41 PM

I'm looking at an x3 with 4 pretty much new tires, however, it has 2 different brand on one side of the vehicle. Curious about this if it would mess up the xdrive somehow.

vrooom3440 10-04-2009 03:25 PM

Tires changed on only one side would make me wonder about why those tires were replaced... typical scenario is accident damage.

It is interesting to note how Xdrive works here... you have full floating differentials front and rear. That means within reason there is no detrimental affect from different sized wheels side to side. A limited slip diff with slipper clutches would have issues with different sizes but that is not how BMW Xdrive is built.

In the middle there is a clutch but it is probably not engaged normally. The whole deal is driven off the ABS wheel sensors and computer. If one or more wheels turns at a rate significantly faster by some margin, then Xdrive makes corrections. This is where it would engage the center transfer case clutch. But the main thing it does is apply brakes on spinning wheels to limit wheel spin and thereby direct more engine torque into other wheels. Brakes do not care much about different wheel sizes.

Likewise since the sensor process is individual per wheel it matters not if some tires are better than others. The computer just adjusts based on conditions. So I would not worry too much about new tires on just one end versus the other.

UncleJ 10-05-2009 07:29 AM

+1 on the possible accident damage with two tires replaced on the same side. Look carefully at this one and get it up on a rack to see what the underside looks like.

X3-terrestrial 10-06-2009 06:51 PM

Quote:

Originally Posted by vrooom3440 (Post 4565530)
BMW shipped the Sport package X3s with different sized tires front and rear.

Sport package came with 18" wheels and same size tires all around, someone correct me if I'm wrong but IIRC the staggered setup was an option.

vrooom3440 10-07-2009 11:31 AM

Quote:

Originally Posted by X3-terrestrial (Post 4579699)
Sport package came with 18" wheels and same size tires all around, someone correct me if I'm wrong but IIRC the staggered setup was an option.

I stand corrected... however the optional 19" wheel/tire package was an option and did have different sizes. I have the 19" wheel/tire package and forget it was not included with the standard sport package :bigpimp:

Supercourse 10-07-2009 02:06 PM

Quote:

Originally Posted by gcopter (Post 4571795)
I'm looking at an x3 with 4 pretty much new tires, however, it has 2 different brand on one side of the vehicle.

Maybe you need to be more specific.
You may be saying that 3 tires are the same make, and the 4th. is different,
or, as most people seem to be interpreting, it has 2 different brands (2 of one, 2 of the other),
and they have been split up side-to-side rather than the more expected front-to-back.

In either case, it suggests that someone has deemed it not important to have 4 matching tires.
I would infer from that the vehicle has not had the best of care in other ways, and pass on it.

Even on a 2WD vehicle, it makes good sense to have 4 matching tires.


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