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      04-19-2018, 12:07 AM   #1
daninla21
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Tire question - 2013 X1 /w M Sport Package.

Got a 2013 X1 with the M Sport upgrades.

Went to get 4 new tires today. Found a decent deal. Guy at the store offered either the 225 or 255 at the same price - recommended I get the wider tire, so I figured why not.

BMW recommended specs on the car is 225/40R19 up the front and 255/35R19 at the back. Now the car has 255/35R19 front and back. Car handles fine - steering seems a bit stiffer. I've read online about 'tire rubbing' - none so far and I've tested full steering lock in both directions There is decent clearance between wheel and well.

My question -is there an obvious advantage to having a thinner wheel up front? Is it ok to have all tires at the wider 255/35 size? Will this mess with the handling? I'm a pretty regular driver - use the car for work, kids etc.

Any advice would be much appreciated.
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      04-19-2018, 02:39 AM   #2
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Quote:
Originally Posted by daninla21 View Post
Got a 2013 X1 with the M Sport upgrades.

Went to get 4 new tires today. Found a decent deal. Guy at the store offered either the 225 or 255 at the same price - recommended I get the wider tire, so I figured why not.

BMW recommended specs on the car is 225/40R19 up the front and 255/35R19 at the back. Now the car has 255/35R19 front and back. Car handles fine - steering seems a bit stiffer. I've read online about 'tire rubbing' - none so far and I've tested full steering lock in both directions There is decent clearance between wheel and well.

My question -is there an obvious advantage to having a thinner wheel up front? Is it ok to have all tires at the wider 255/35 size? Will this mess with the handling? I'm a pretty regular driver - use the car for work, kids etc.

Any advice would be much appreciated.
The second number is your aspect ratio which is a percentage of the total width. Since you went from a 225 to a 255 the aspect ratio should go down to keep the same overall diameter. I assume you're running the stock wheels right? A 255 is pretty wide for a 8 inch wheel. I would think it would look funny as well. The front tire would be too wide for the wheel and the rear tire would look normal.
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      04-19-2018, 10:26 AM   #3
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As mentioned above, technically the 255 is too wide for an 8" stock front wheel. It will be fine, but it's pinched a bit, and therefor not properly supported. The end result will be a bit of vagueness in the steering feel department, particularly on turn-in.

The other downside of running the front 255 will be some additional tramlining on uneven road surfaces (wheel tugging you into road depressions) and some added numbness of the steering in general (from running a wider, heavier tire, not just because it's on a narrow wheel).

If you're fine with the way it drives now, then no reason to change up really. Not ideal, but fine.

Is it still tucked under the fender well-enough...if not, you could see some more road rash over time down the sides of the car.
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      04-21-2018, 09:44 PM   #4
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is your x1 a S drive or X drive? the larger tire in the rear is really there to allow a RWD car to put down more power on exit. many manufactures have the smaller tire up front to induce some understeer. considered safer by them. however the wider matched tire up front will give you better turn in at corner entry. if you have X drive or AWD it is probably less relevant as the computer will adjust torque front to rear.
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      04-22-2018, 12:24 PM   #5
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Quote:
Originally Posted by sayemthree View Post
however the wider matched tire up front will give you better turn in at corner entry.
On an 8" rim, a 225 is going to give noticeably quicker turn-in response vs. a pinched 255,without question. Ultimate front grip, even pinched the 255 probably wins, but by less than you might think.

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Originally Posted by sayemthree View Post
however the wider matched tire up front will give you better turn in at corner entry. if you have X drive or AWD it is probably less relevant as the computer will adjust torque front to rear.
At turn-in, F/R torque split is irrelevant as you're off the throttle. I assume you mean corner exit.
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      04-22-2018, 07:15 PM   #6
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I doubt the rim width is enough to have negative effects. Wider tires, assuming all other factors are equal, normally have stiffer side-walls and experience less roll. thus less slip angle, therefore quicker turn in.
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      04-23-2018, 10:11 AM   #7
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Quote:
Originally Posted by sayemthree View Post
I doubt the rim width is enough to have negative effects. Wider tires, assuming all other factors are equal, normally have stiffer side-walls and experience less roll. thus less slip angle, therefore quicker turn in.
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      04-23-2018, 11:01 AM   #8
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Quote:
Originally Posted by hooligan_clt View Post
A 1/2 inch oversized rim wont decrease sidewall stiffness. In will likely increase it
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      04-23-2018, 12:45 PM   #9
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Wider tires, all else being equal, do not have stiffer sidewalls. In fact, as apex pointed out, mounting a "too wide" tire on a narrower rim (resulting in tire "pinch") could very well result in decreased turn-in response.
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      04-25-2018, 12:12 PM   #10
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Quote:
Originally Posted by sayemthree View Post
I doubt the rim width is enough to have negative effects. Wider tires, assuming all other factors are equal, normally have stiffer side-walls and experience less roll. thus less slip angle, therefore quicker turn in.
What? The sidewall of the tire is the same. The point is, it's pinched on the wheel, and therefore extends from the wheel at an outward angle WHEN MOUNTED vs. relatively vertical with a proper sized wheel. Hence, softer turn in as it's not as ideally-supported by the wheel. You think manufacturers give approved wheel widths for no reason at all?

Less slip angle? Do you even know what slip angle is?

Quote:
Originally Posted by sayemthree View Post
A 1/2 inch oversized rim wont decrease sidewall stiffness. In will likely increase it
Where you drunk when you posted this? It's a 1" undersized wheel in width, and it will certainly effect how a tire responds at turn-in. 1/2" oversized? What are you talking about?



This is all common knowledge BTW...I think you need to do some reading.

I track 255's on 8" wheels regularly (undersized wheels), and also have run them on 9" wheels...there's a noticeable difference. The response on the 9" setup is much improved. I've also run 275s on 6.5" in my autox days. Unapologetically giving up turn-in response for ultimate grip.
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