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tires tyres x3
3K views 7 replies 6 participants last post by  dukedkt442 
#1 ·
Sorry if this an old question! I need to buy new tyres for my X3 2007 3ld sport but am getting a bit confused! Would really appreciate if anyone can advise. I am in a remote location and need to order them.

Many forum posts strongly suggest 4x4s need the exact same tyres size/type on all 4 wheels or you will cause transmission drive problems.

However my X3 has 235/50 R18s on the front and 255/45 R18s on the back. The technical notes suggest this is correct, as do tyre shopping websites. It is also suggested I could also put 235/45 R19s on the front if I put 255/40 R19s on the back! Now I have found other sites suggesting should be 235/50 R18s on all wheels!

Can anyone advise? Should all 4 be the same?

Also if I am buying different specifications for the front and back its quite hard to find the exact same tyre or even brand to match on most tyre websites. Is this a problem?
 
#3 ·
Tire sizes are given in a combination of English and metric units: widths in millimeters, and rim diameter in inches.

The "aspect ratio" is the ratio of the sidewall height/width; "60" would mean that the sidewall height is equal to the tire width times 0.6.

There are 25.4 millimeters in one inch.

Here's a good picture showing what the size markings of tires mean.

Cars in general, and BMW's in particular are sold with different combinations of tire and wheel sizes. The short answer to your question is you should replace your tires with the same size or sizes as the tires that came on it originally.


There are so many combinations of brand, model, and size of tires that it's likely a 'brick and mortar" tire store will not have the size tire you need. That's the advantage of buying tires off the internet. A large internet retailer of tires will have literally millions of tires in stock and is therefore more likely to have the exact brand, model, size, and performance spec' you need.
 

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#5 ·
Tire Rack has 2.4M square feet of warehouse space spread out over nine locations, and they have annual sales of over $1B. Tire manufacturers like to sell tires by the truckload, and price them accordingly. Tires stack well. I can't find anything on the Interwebs about the exact number of tire they have in stock at the moment. But, I recall reading or hearing that it is over 1M.

When determining the amount of anything to keep in stock the variables are capital cost (less stock the better), volume pricing (more stock the better), and storage costs (less stock the better), stock replacement time, and sales rate fluctuations.
 
#6 ·
In my experience with my X3 e83 with //M package, my car was issued with front and back tires and wheels with different sizes -still consistent on being 19" all of 4 corners - i recently got a Continental set from Discount Tire, they had no trouble fitting me with the tire size difference in front and back axles. Now stepping out of my comfort zone, i understand your concern on 4x4s needing tire size consistency, that applies to that type of vehicle's suspension, however, X3s are considered by desingn and function as All Wheel Drive AWD, and not at all requires that specification. 4x4 are made for truly roaming difficult terrain, an AWD are made to get you off a messy terrain and better grip to the roads.

Sent from my SM-G930T using Bimmerfest mobile app
 
#7 ·
Second M-sport post in as many days. Here's my retort to the other one. Assuming your wheels are all the same dims and they just did +1 sizing on the rears, you should be fine with all 4 "normal" non-sport tires sizes, or running the staggered. I don't see the issue with staggered. No need to worry about fancy tires and the "star" system blather.

Screw the star system, all BS in my opinion. I have a 2006 M-sport and run the cheapest Sumitomo's I could find on tirerack no problems. The TC on an m-sport is the SAME as stock, so just go back to the stock size for all 4 and you'll be fine.

I ran the math and the staggered tires on the M-sport can be out of factory tolerance right off the factory floor. I researched manufacturing tolerances of the tire circumference. STEALER tried to sell me a new $3,500 TC and 4 new Starred Michelins when I came it with a TC light combo. Turned out I just needed to change the TC fluid.
 
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