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XBimmers | BMW X3 Forum > BMW X3 Forums | F25 (2011 - Current) > Second Generation BMW X3 General Forum » Is going from 17" to 18" worth it?

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      05-18-2011, 08:26 AM   #1
Harplayr
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Is going from 17" to 18" worth it?

I have a 28i without sports package or dynamic handling package.
It has the standard 17Ē wheels.

Weíve been having some very windy days (25mph +) and Iíve noticed it makes the car slightly wobbly at least when compared to my previous BMW's.

Iím wondering if going to an 18 inch wheel with the resulting lower profile sidewall would help this in any respect, or is what Iím feeling just a result of the suspension. I donít want to go larger than 18Ē as I still want to keep ride quality a priority (we have terrible roads here).

Can I expect the dealer to give me something on trade in on my original set of wheels (approx 200 miles on them)?
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      05-18-2011, 08:15 PM   #2
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Lower profile sidewall will not help your situation. If you go to an 18" rim with lower sidewall depending of course on tire size, but comparing to X3 18" rim and tire, your overall tire and rim diameter will be about the same as the 17". You could put more "meat" on the road with >245 tread and 17" rim. Your ride quality with 18" low profile could diminish marginally, but susceptibility to the famous Chi Town potholes, good luck!
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      05-18-2011, 08:43 PM   #3
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Quote:
Originally Posted by Radioactive View Post
Lower profile sidewall will not help your situation. If you go to an 18" rim with lower sidewall depending of course on tire size, but comparing to X3 18" rim and tire, your overall tire and rim diameter will be about the same as the 17". You could put more "meat" on the road with >245 tread and 17" rim. Your ride quality with 18" low profile could diminish marginally, but susceptibility to the famous Chi Town potholes, good luck!
I would be sticking with the recommended tire profile for the 18 or 19 inch rims. I think itís a 245/50-R18 thatís recommended.

What difference in handling, road feel, ride quality could I expect by going from the 245/55-R17 setup to the 245/50-R18?
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      05-18-2011, 08:58 PM   #4
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You should get slightly better handling with the tradeoff being a slightly stiffer ride. Tire choice will play at least as big a factor as wheel size, imo.
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      05-18-2011, 09:13 PM   #5
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Quote:
Originally Posted by Harplayr View Post
I would be sticking with the recommended tire profile for the 18 or 19 inch rims. I think itís a 245/50-R18 thatís recommended.

What difference in handling, road feel, ride quality could I expect by going from the 245/55-R17 setup to the 245/50-R18?
Basically you're going from a 5.31" sidewall to 4.82" sidewall with the same amount of tread on the ground, about 9.65". With the 18" tire you're raising the car about .05 inches.

Since you will have about .5" less of flexible material ie tire and air, your road feel is going to be higher, but your ride quality less. Handling probably about the same.
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      05-18-2011, 10:50 PM   #6
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For what it's worth, I have the 18's and have noticed that my F25 is less stable in windy conditions than either my previous X3 or X5. It's not horrible, but definitely noticeable compared to previous BMW's, so switching to 18's might not buy you all that much.
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      05-18-2011, 10:55 PM   #7
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Quote:
Originally Posted by ejp0016 View Post
For what it's worth, I have the 18's and have noticed that my F25 is less stable in windy conditions than either my previous X3 or X5. It's not horrible, but definitely noticeable compared to previous BMW's, so switching to 18's might not buy you all that much.
The lack of stability is due to the fact that this X3 is actually taller than the X5, marginally, and it is also not nearly as wide. The electric steering doesn't help the cause much, as even a slight gust of wind can send you a few inches left or right when in Normal mode.
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      05-18-2011, 11:39 PM   #8
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18" ll work fine with that model...i don't see any problem
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      05-19-2011, 09:45 AM   #9
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I increased tire pressure from the recommended 32psi all around to 35psi all around and it did seem to improve handling a bit. It had a little more of a "connected" feel and didn't impact ride quality.
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      05-19-2011, 10:40 AM   #10
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I have driven the 17 and 18 on the same 20 minute test loop. I could not detect a difference in handling or ride under normal conditions. Personally I think the difference is purely cosmetic.
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      05-19-2011, 10:49 AM   #11
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You might try going with BMW's recommendation of always maintaining a Rear to Front bias of 3 psi (or more under high-load conditions). Running the front's at 34 and the rears at 37 seems to work well on my 35i using the "Normal" suspension setting. the higher rear pressure reduces the rear slip angle a little under hard cornering, but will have minimal effect of the wind deflection "feel" which is more influenced by tread design, toe-in settings and front suspension bushing compliance than tire diameter (and sidewall aspect ratio). Tiny changes of toe-in can have a dramatic effect on the "self-centering" feel on most vehicles, however it opens a "can of worms" when you consider things like stability control programming, tire wear and rolling resistance.

Many new cars are being set up with low rolling resistance tires (including the X3) and are being aligned with minimal toe-in for the lowest possible drag to enhance mileage ratings. The downside can be slightly less self centering and more wind deflection.
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      05-19-2011, 11:27 AM   #12
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Quote:
Originally Posted by Lotus7 View Post
You might try going with BMW's recommendation of always maintaining a Rear to Front bias of 3 psi (or more under high-load conditions). Running the front's at 34 and the rears at 37 seems to work well on my 35i using the "Normal" suspension setting. the higher rear pressure reduces the rear slip angle a little under hard cornering, but will have minimal effect of the wind deflection "feel" which is more influenced by tread design, toe-in settings and front suspension bushing compliance than tire diameter (and sidewall aspect ratio). Tiny changes of toe-in can have a dramatic effect on the "self-centering" feel on most vehicles, however it opens a "can of worms" when you consider things like stability control programming, tire wear and rolling resistance.

Many new cars are being set up with low rolling resistance tires (including the X3) and are being aligned with minimal toe-in for the lowest possible drag to enhance mileage ratings. The downside can be slightly less self centering and more wind deflection.
Thatís interesting.
I have front to rear set the same per the door sticker. Going from the recommended 32psi to 35psi did have a positive effect (imo), so I may try a couple of pounds of differential to see how that impacts handling and feel.


Note: even though Iím looking to tweak things a bit, the current ride / handling is quite acceptable. The old X3 was MUCH stiffer and was better in cross winds, but suffered in the ride comfort category.

Next would come the topic of tires. The Bridgestone Duelerís are rated very low by tire rack. There are few choices in run-flats in the 248/55-17 size but more options in the 245/50-18 size.
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      05-19-2011, 05:03 PM   #13
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Quote:
Originally Posted by Harplayr View Post
Thatís interesting.
I have front to rear set the same per the door sticker. ...
Has the door sticker changed or is it different for cars delivered with 17 inch tires?

The one on my X3 clearly states, as does the on-line owners' manual pdf that that the recommended pressures are 32F & 35 rear for light loads/moderate speeds and should be increased to as much as 38 front/44 rear at high speeds with increased loads for the 245/50 R18 tires.

Here is a pic of the door sticker that came on my X3 35i in Feb.
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File Type: pdf Tire Pressure.pdf (93.3 KB, 97 views)
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      05-19-2011, 05:58 PM   #14
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Yes, the tire pressurea are different for the 17" wheels both on the door sticker and in the manual. They specify 32psi front and rear.

Quote:
Originally Posted by page 207 of owners manual
X3 28iA Tire size Pressure specifications
in psi/kPa Specifications in psi/kilopascal with cold tires
225/55 R 17 102 H M+S 2.2 / 32 2.2 / 32
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      05-19-2011, 06:10 PM   #15
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Originally Posted by Harplayr View Post
Yes, the tire pressurea are different for the 17" wheels both on the door sticker and in the manual. They specify 32psi front and rear.
Sounds like BMW is making presumptions about how 28i drivers and 35i drivers actually drive. they should read this list!
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      05-19-2011, 06:15 PM   #16
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Another thought, for what its worth:

With the thicker sidewall height of the 55 aspect ratio tire as opposed to the 50 ratio, they can spec. a lower pressure for a softer ride for the same chance of sidewall and wheel damage if you hit a given pothole.
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      12-04-2012, 05:49 PM   #17
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I have a similar question -- I have just finalized an offer on an X3 with a promise to get 18" wheels but now they tell me I can only get one with 17" wheels.

Since I am now getting less 'value' at an agreed upon price, I think I should either ask for a price reduction or get something added of equal value.

Does anyone have an opinion on this and how to proceed or what to ask for?
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      12-04-2012, 09:34 PM   #18
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Look at your sales contract. It is a contract afterall.

If the contract says you get 18" that's what you should expect. If the sales guy just told you that you would get 18's and nothing is written down you are SOL.

Quote:
Originally Posted by bartbos1 View Post
I have a similar question -- I have just finalized an offer on an X3 with a promise to get 18" wheels but now they tell me I can only get one with 17" wheels.

Since I am now getting less 'value' at an agreed upon price, I think I should either ask for a price reduction or get something added of equal value.

Does anyone have an opinion on this and how to proceed or what to ask for?
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      12-05-2012, 04:38 PM   #19
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I just bought a 2008 X3 with M3 sport package and 18 inch wheels. I have a set of 17 inch with snow tires off my 2000 328i. Will they interchange? Also whats the deal with tire pressure? The local dealer thinks it should be about 5psi under whats on the the door sticker.
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      12-05-2012, 05:37 PM   #20
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Originally Posted by Tom Wiedeman View Post
I just bought a 2008 X3 with M3 sport package and 18 inch wheels. I have a set of 17 inch with snow tires off my 2000 328i. Will they interchange? Also whats the deal with tire pressure? The local dealer thinks it should be about 5psi under whats on the the door sticker.
First up you're in the wrong forum for a 2008 X3 - try the first gen X3 forum.

But to answer your query - What is the difference in overall tire diameter between those off your 328i and those on your X3? I'm betting its far more than 2-3%. Please read the thread below although keep in mind this refers to the current F25 X3 - may not be the same for the previous X3.

http://x3.xbimmers.com/forums/showthread.php?t=773561

Tony
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      12-06-2012, 05:48 PM   #21
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Thanks for the info, Tony. I will check out the difference before I try. Local dealership told me there would be no problem since I was putting on all four. Also have manual six speed.

Tom
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