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X5 E70 (2007 - 2013)
E70 BMW X5 produced between 2007 and 2013. Discuss the E70 X5 with other BMW owners here.

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Old 08-10-2014, 03:10 PM
voiture5 voiture5 is offline
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Location: Ann Arbor, MI
Join Date: Aug 2014
Posts: 12
Mein Auto: 2012 X5 x35d
Thanks - I like the idea of doing that.

All I can say is I've read scare stories, and not limited to people with an interest in selling tires..

For example these postings from 2 threads:

"According to the experts at TireRack, the tires on xdrive cars can be different sizes from original equipment (but must be within 3% of original tire diameter), and they need to be within 1% (not to exceed) diameter size of each other to not cause problems."

(my highlighting)

"Couple of years ago when towing my trailer back from the east coast I got a nail in the sidewall of one of my front tires in the middle of WV- Monday of Labor Day weekend. Went to put the original full size spare on and found that it went flat moments after I lowered the truck down and put weight on it. Local WalMart was the only thing open that Monday on Labor Day weekend. Naturally they didn't have a 255/50-19 in stock. We inspected the spare- keep in mind this spare was OE and had never been out of the spare tire well other than to check air pressure twice a year- and when we pulled the tire off the rim, the inside of the sidewall was abraded, with lots of tire shavings on the inside. This tire had never been mounted from new, there was still virgin paint on the bolt seat of the steel wheel. But it was junk. And of course they didn't have a 235/65-17 tire in stock. But they had some inexpensive 245/60-17 BFG's.

Calculating the rolling diameter, it should be virtually identical to the 235/65, just 2% or so off. Mounted one up. Hit the road. Within 50 miles I had the ABS light flickering, followed shortly by the Trans Failsafe warning. Pulled off the road, shut down, waited a few minutes, restarted. Drove a while then trans failsafe again. So I found an exit with a couple hotels and quit for the day. Next morning found another tire dealer who had a 235/65 in stock. He even took the 100 mile old BFG in trade! Hit the road and never had a problem again. Went straight to my dealer on the way home and had the codes pulled, was told the rolling diameter difference threw off the ABS and confused the stability control, and that resulted in the Trans Failsafe light. And that was with just a 2% difference in rolling diameter."
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Old 08-10-2014, 09:07 PM
ard ard is online now
Resident Curmudgeon
Location: Sierra foothills
Join Date: Jul 2009
Posts: 11,025
Mein Auto: '12 X5 35d/E39M5/996TTX50
You are quoting someone on a BMWCCA forum quoting tirerack (oh, wait- they sell tires...)...tirerack flat out wrong. You dont 'need' to be within 3% if you change all 4 tires- your speedo will be off, but no other issues (unless you are going 10-20% bigger)

And 1% from each other?!?!? OMG, with the sun on one side of the car and shade on the other, the difference in tire pressure will create more than 1% variance..if 1% was an issue, every X5 would be broken down on the side of the road.

Lets look at the other "case study"
Edit: without the model of the tire, there are too many published diameter to pick.... lets just say that the OP likely told the dealer "tire sizes were off" and the dealer parroted back :that's what caused the problem. I reject that a TWO PERCENT delta causes an issue- also keep that that a higher profile (70 profile) will compress much more and the rolling diamter CANNOT be estimated based on the uncomressed tire diameter.

Edit 2: Had some idle time and researched the question of "does the profile./width impact the rolling radius"...short answer is yes. Two tires, same diameter UNCOMPRESSED, the smaller contact patch WILL compress more. So in the example the smaller spare will get much smaller when loaded versus the lager normal tire on the other axle. What looks like a few % on paper isnt.

But let me ask you this...instead of reading scary stories with hyperbolic warnings, did you bother to figure out what % you will have if one tire is 100% and the other tire is say 70%????????? Or pick two numbers to bracket the range of used tires, and use those. Then calculate the rolling diameter, and see what that 3/32 of tire tread ACTUALLY means...

(I have, Ive posted it)

Buy brand new tires, if one gets damage buy 4 brand new tires instead of replacing one.... the tire industry appreciates your fear.

Keep it as simple as possible...but no simpler.

Last edited by ard; 08-12-2014 at 12:30 PM.
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Old 08-11-2014, 01:47 PM
sankom sankom is offline
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Location: NJ
Join Date: Feb 2013
Posts: 28
Mein Auto: NJ
sankom sankom is online now
Registered User
Location: NJ

Join Date: Feb 2013
Posts: 27
Mein Auto: NJ
View My Garage
Tires changed
This is what I did for my tires - 2013 X5 35d

- I had Bridgestone H/L 400 RFTs (i guess). Changed them when 1/8 thread was left (22K miles). Stored them in my shed
- Installed Bridgestone non RFT Ecopia 422 for $846 installed
- Order Spare Tire kit for $380 online

At lease end I will decide, if I buy the car, I will continue using Ecopia 422 and sell the RFTs to someone on this forum who will be stuck at the same situation needing RFTs to return to lease. I am in Central NJ

If I decided to return, I can put RFT back and return and see what I can do with the non-RFTs.

But a decision now can save lots, unless one sticks with RFT till the end ...
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