upgrading 225/45/17 tire to 245/45/17 yes or no?

[naples53]

I've done this on my vette from 285/35/19 to 305/30/19 with no problems.
On the BMW can I go from 225/45/17 to a 245/45/17 or a 245/40/17?

[mryakan]

use http://1010tires.com/TireSizeCalcula...?action=submit and make sure you stay withing 2-3%.
Both are close enough, but the latter is better:

Stock Tire - 225/45R17 >Search Tires	Tire 1 - 245/45R17 >Search Tires	Tire 2 - 245/40R17 >Search Tires
Section Width: 8.85 in 225 mm	Section Width: 9.64 in 245 mm	Section Width: 9.64 in 245 mm
Rim Diameter: 17 in 431.8 mm	Rim Diameter: 17 in 431.8 mm	Rim Diameter: 17 in 431.8 mm
Rim Width Range: 7 - 8.5 in	Rim Width Range: 7.5 - 9 in	Rim Width Range: 8 - 9.5 in
Overall Diameter: 24.97 in 634.23 mm	Overall Diameter: 25.68 in 652.27 mm	Overall Diameter: 24.71 in 627.63 mm
Sidewall Height: 3.98 in 101.09 mm	Sidewall Height: 4.34 in 110.23 mm	Sidewall Height: 3.85 in 97.79 mm
Radius: 12.48 in 316.99 mm	Radius: 12.84 in 326.13 mm	Radius: 12.35 in 313.69 mm
Circumference: 78.44 in 1992.3 mm	Circumference: 80.67 in 2049.0 mm	Circumference: 77.62 in 1971.5 mm
Revs per Mile: 832.9	Revs per Mile: 809.9	Revs per Mile: 841.7
Actual Speed: 60 mph 100 km/h	Speedometer1: 58.3 mph 97.2 km/h	Speedometer1: 60.6 mph 101. km/h
Speedometer Difference: -	Speedometer Difference: 2.839% too slow	Speedometer Difference: 1.056% too fast
Diameter Difference: -	Diameter Difference: 2.77%	Diameter Difference: 1.05%

[Kingrye]

why does it matter
I thought 2 to 3 % was front to rear rolling diameter for awd cars.. and who cares if ur speedo is off. also if rear rolling diameter is less on rear wheel drive cars it can cause stability control errors...

Other then that I know of no issues going with bigger tires sizes.. please inform me...

[mryakan]

Bigger tires can rub. Your speedo and odo will be off (whether you care or not is another issue). Your handling with higher profile tires will also not be the same. Gas consumption also changes. Not sure if DSC is affected if all tires are same rolling circumference, but if front to rear are off too much, it will be affected.

[ezbmr]

I would say that the 245/40 would be closest, but you have to be worried about rubbing the inner fender well. Also, with most of the handling coming from great rear tires, I would be more worried about that

[mryakan]

Also, with most of the handling coming from great rear tires, I would be more worried about that

Who told you that? if you do not have equally great tires in front, you'll understeer like crazy. The car drives on 4 tires still, even if RWD.

[318isam]

i went from 205/60/15 bottlecaps to my current 235/45/17's on squared 7.5 contours,best size for me as she is my DD.

[modularhalfpipe]

I'm not seeing any concern about Transfer cases, so I have to assume either that is so obvious to those in this forum,(or they don't have AWD cars) that it is just assumed ( I hope), or, it hasn't been addressed. I have a 328xi and dealt with a tire store which put the wrong size rears (225-45-r17) with my 245-45-r17s. the shifting from 2nd to third was not smooth, it would act like the clutch was starting to go, So I had a new clutch put in for $1000.00. it was going to need one fairly soon anyway, but still...I had 2 garages look at it and the second guy finally figured it was tires sizes, not the clutch. when you mix tire sizes, your ratios of front to rear are not what they should be, and this messes with the transfer case; its like having 2 differently made gears, with different teeth, trying to work together...they don't! if you have a AWD drive car (XI or X-Drive) forget cosmetics and keep the front the same with the rear. You do not want to replace your transfer case ($2600 rebuilt) BTW the guy who put the wrong size tires on was forced to give me a new set of matching size tires, to the new ones I just had bought, so 4 tires for the price of 2, and no damage to my transfer case because I caught it early. Lesson learned: check tire sizes!!