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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > X Series > X3 F25 (2011 - current)

X3 F25 (2011 - current)
The latest X3 brings some added style and some new features to the BMW SUV family. Talk about the new F25 now!

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  #1  
Old 10-13-2010, 09:26 AM
X3forlife X3forlife is offline
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Tire Size

So the 28i will have 17 inch tires while the 35i will have 18 inch tires.

Could one of you car geniuses please explain in English what effect tire size has on driving? Is bigger better?

Thanks
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  #2  
Old 10-13-2010, 12:40 PM
Huey52 Huey52 is offline
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No, bigger wheel size is not necessarily better, especially in winter driving where you want a tall tire sidewall (profile). Bigger wheels do tend to look better however as they better fill the wheel wells. So, it really depends on your climate and intended use.
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  #3  
Old 10-13-2010, 01:40 PM
X3forlife X3forlife is offline
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Quote:
Originally Posted by Huey52 View Post
No, bigger wheel size is not necessarily better, especially in winter driving where you want a tall tire sidewall (profile). Bigger wheels do tend to look better however as they better fill the wheel wells. So, it really depends on your climate and intended use.
So are you saying that bigger tires are worse in winter (snow) or is this more theoretical?

Thanks
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  #4  
Old 10-14-2010, 06:31 AM
Huey52 Huey52 is offline
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You're confusing wheel (rim) size and tire size (profile or aspect ratio).

Again, for winter snow driving (and poor pot-holed roads) you want a smaller rim (in this case 17") with a narrower and taller tire profile. For summer driving (and aesthetics) you want a larger wheel (18") with a lower profile tire.

The narrower tires cut through snow more easily and the taller sidewall provides more clearance and shock absorption. Larger wheels with low profile tires and pot-holes don't play nice together.

So again, you have to determine your climate and typical driving regime.

Of course in snow country the best option is to have dedicated snow wheels/tires.

In Maryland you should do fine on the 18" rims with all season tires, unless your local roads are very poor.

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Originally Posted by X3forlife View Post
So are you saying that bigger tires are worse in winter (snow) or is this more theoretical?

Thanks
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  #5  
Old 10-14-2010, 04:32 PM
X3forlife X3forlife is offline
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Quote:
Originally Posted by Huey52 View Post
You're confusing wheel (rim) size and tire size (profile or aspect ratio).

Again, for winter snow driving (and poor pot-holed roads) you want a smaller rim (in this case 17") with a narrower and taller tire profile. For summer driving (and aesthetics) you want a larger wheel (18") with a lower profile tire.

The narrower tires cut through snow more easily and the taller sidewall provides more clearance and shock absorption. Larger wheels with low profile tires and pot-holes don't play nice together.

So again, you have to determine your climate and typical driving regime.

Of course in snow country the best option is to have dedicated snow wheels/tires.

In Maryland you should do fine on the 18" rims with all season tires, unless your local roads are very poor.
Thanks

I knew we were talking about rims but maybe I used it interchangably because i figured 17" tires go on 17" rims and 18" tires go on 18" rims. lol

Thanks...so 17 is better in the snow it sounds like. The reason I ask is in case it becomes a tiebreaker and I decide to go for the 35i, I'd like to know the extras are better for me, not worse. Also I'd hate for the snow capability to somehow get worse than the current model.

I get it that 18" is for looks but has a stiffer ride.

Thanks for your help.
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  #6  
Old 10-21-2010, 08:01 AM
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Talking Tire and wheel size

In my E86 X3's I have had both 17 and 18 inch diameter wheels with different tyre sizes. The 17's were 235X55 and the 18's were 235X50 Scorpions. The rolling diameter was 27.2" for the 17's and 27.3" for the 18's. These diameters are almost identical and considered interchangable as long as all 4 wheels are identical. I suspect the new F X3 will have similar sized tyres.
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  #7  
Old 10-31-2010, 06:40 AM
X3forlife X3forlife is offline
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Everytime it crosses my mind that the 18" wheels/tires on the 35i might make for stiffer ride and might not be good in the snow, I have to remind myself that all of this talk is theoretical hocus pocus and BMW has likely adjusted for all of this.

For one, they are not likely to ignore the dynamics on their higher end model of the two.

Secondly, and most importantly, the X5 comes standard with 18s and nobody is worried about how that handles in the snow or if the ride on the X5 will be too stiff. They have made their adjustments and know what they are doing.
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  #8  
Old 11-01-2010, 07:12 AM
Huey52 Huey52 is offline
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Yep; 18" with all season run-flat tires will be fine for you.
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  #9  
Old 11-01-2010, 09:01 AM
X3forlife X3forlife is offline
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Quote:
Originally Posted by Huey52 View Post
Yep; 18" with all season run-flat tires will be fine for you.
It should be fine for most I would think. Again, the most powerful argument in my mind is that those are the wheels/tires that are standard on the X5. If the 17s were so much better in snow or comfort, they would find away to get it on the X5. That is their flagship (for the X series).

It's probably true that given the same suspension...but they just adjust the suspension for it.

Last edited by X3forlife; 11-01-2010 at 09:37 AM.
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  #10  
Old 11-01-2010, 05:14 PM
X3forlife X3forlife is offline
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So...I just watched a video of the X6 in the snow and it looked good to me...and that has 20" tires.

So i think this tires size only matters if the car cannot adjust suspension and handling to account for it. If it is thought about ahead of time and BMW adjusts handling, suspension, the X-drive, Dynamic dampening etc. to that particular tire (while testing ride quality), it probably doesn't matter.

Their mother of all flagships the 760Li has 19 inch tires yet is comfortable and probably handles well in the snow (I watched a video but I'm not sure how much spinning the driver is trying to do on purpose). They just need to adjust things.
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  #11  
Old 11-01-2010, 06:04 PM
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raleedy raleedy is offline
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Wheel size = aesthetics. Tire size =performance. A wide tire with a big contact patch spreads the weight of the car over more road surface. This is great in the dry and (depending on tread compound and pattern) wet, bad in the snow. A skinny tire with a smaller contact patch won't handle as well in non-winter conditions, but it will be better in the snow (and maybe in standing water that could cause hydroplaning). A low-profile tire (say, aspect ratio of 40 or 35) may affect the car's ride by providing less cushioning over the road surface, and may expose wheels and suspension parts to damage from potholes, as well as exposing wheel rims to "curb rash" because there isn't enough tire there to protect the wheel from curb contact. A low profile tire may also produce more road noise, higher rolling resistance (and inferior fuel economy as a result) and some handling problems like "tramlining" and pulling to the outside on crowned roads. Of course, on a given car, there are limitations for the circumference of the mounted tire, for the combined diameter of the mounted tire and wheel combination, and for the width of the tire.
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  #12  
Old 11-01-2010, 06:54 PM
X3forlife X3forlife is offline
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Quote:
Originally Posted by raleedy View Post
Wheel size = aesthetics. Tire size =performance. A wide tire with a big contact patch spreads the weight of the car over more road surface. This is great in the dry and (depending on tread compound and pattern) wet, bad in the snow. A skinny tire with a smaller contact patch won't handle as well in non-winter conditions, but it will be better in the snow (and maybe in standing water that could cause hydroplaning). A low-profile tire (say, aspect ratio of 40 or 35) may affect the car's ride by providing less cushioning over the road surface, and may expose wheels and suspension parts to damage from potholes, as well as exposing wheel rims to "curb rash" because there isn't enough tire there to protect the wheel from curb contact. A low profile tire may also produce more road noise, higher rolling resistance (and inferior fuel economy as a result) and some handling problems like "tramlining" and pulling to the outside on crowned roads. Of course, on a given car, there are limitations for the circumference of the mounted tire, for the combined diameter of the mounted tire and wheel combination, and for the width of the tire.
Interesting...sounds like you are saying we should be focused on the width (and thickness) of the tire when considering weather. I haven't been paying much attention to the width but again, if the higher end cars can handle it, then an X3 should be able to handle it too.

So it sounds like the two components of the tire are the width and the "thickness" of the tire (I don't want to say radius or diameter since that will depend on the wheel size).

I wonder if most people even know these numbers. I'll try to pay attention next time I look.
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  #13  
Old 11-01-2010, 07:07 PM
X3forlife X3forlife is offline
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Pretty cool explanation

http://www.tinytears*****Technical%20Tips/tire_size.html

I never understood the numbers before.
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  #14  
Old 11-01-2010, 07:21 PM
X3forlife X3forlife is offline
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So looking at it the tires on the X3

28i = 245 mm wide, 134.75mm tire thickness

35i = 245 mm wide, 122.5 mm tire thickness

So for the X3, the width is not adjusted, only the tire thickness. I'm sure they will adjust the suspension to account for this as far as ride. How would tire thickness affect snow/ice?

By comparison, the 18" tires on the X5 are wider and thicker than both of these.

255 mm wide, 140.25 mm thickness

Last edited by X3forlife; 11-01-2010 at 07:30 PM.
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  #15  
Old 11-01-2010, 08:21 PM
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raleedy raleedy is offline
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Quote:
Originally Posted by X3forlife View Post
How would tire thickness affect snow/ice?
I think it doesn't. But most low profile tires are wide, and width does.
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  #16  
Old 11-01-2010, 09:39 PM
X3forlife X3forlife is offline
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Originally Posted by raleedy View Post
I think it doesn't. But most low profile tires are wide, and width does.
Oh OK. You saw my numbers above. You see that the X3 has tires that are less wide than the X5. Are you suggesting that the X3 should handle snow better than the X5 (they both have the x-drive, HDC, etc.)?
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  #17  
Old 11-01-2010, 10:27 PM
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Quote:
Originally Posted by X3forlife View Post
Oh OK. You saw my numbers above. You see that the X3 has tires that are less wide than the X5. Are you suggesting that the X3 should handle snow better than the X5 (they both have the x-drive, HDC, etc.)?
No. They're different cars.
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  #18  
Old 11-02-2010, 01:05 PM
X3forlife X3forlife is offline
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Originally Posted by raleedy View Post
No. They're different cars.
Even thought they have all the same X-drive and stability systems, i guess one could argue that weight, wheel axle length anfd other factors make a difference.

All in all it seems like the cars they have been testing the most are the 35i and 20d. I have not seen any reviews of the 28i or seen it out being tested anywhere.

I can't wait until somebody compares the 2 cars. I just didn't want to give up snow handling for looks.
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