Changing Wheel and Tire Size

Got_da_booze · 12-30-2009, 10:23 PM

Hello.

I have 17 inch stock wheels on my 335i and I am looking to change to 18s or 19s. What needs to be done for the car to acknowledge that it has bigger wheels and tires so I am not off on the odometer and speed readings? I've searched around the forums with no results on this. Thanks and Happy New Years.

superduty · 12-30-2009, 10:54 PM

Out of the box there is already a speedo error, at least there was on mine before I swapped wheels/tires. According to some, it's by design (but not the odo for some reason). As best I've been able to determine there is no way to correct the speedo. This doesn't seem reasonable to me since there should be a simple correction factor that is entered into the ECU unlike the old days when you had to swap speedo drive gears. I've been unable to find out if the dealer can make the correction. If not, it also seems unreasonable the more of us making more noise about this issue.

Every vehicle I've owned with an ECU I've been able to calibrate the speedo with easily obtained ECU programming software.

remmib · 12-31-2009, 07:17 AM

The overall diameter of the wheels and tires shouldn't be bigger, because you should use tires with a smaller sidewall when you use a bigger wheel.

superduty · 12-31-2009, 07:55 AM

Quote:

Originally Posted by remmib

The overall diameter of the wheels and tires shouldn't be bigger, because you should use tires with a smaller sidewall when you use a bigger wheel.

Not necessarily. You'll need to determine the rolling circumference of the old and new tires. Chances are there will be a difference.

remmib · 12-31-2009, 08:15 AM

It might be 1-3 % off, but that's not a problem.

superduty · 12-31-2009, 10:03 AM

Quote:

Originally Posted by remmib

It might be 1-3 % off, but that's not a problem.

Well if you live in a police state (like me) that is full of automated speed devices, it pays to know if your indicated speed is correct.

cb1111 · 12-31-2009, 10:30 AM

Quote:

Originally Posted by superduty

Well if you live in a police state (like me) that is full of automated speed devices, it pays to know if your indicated speed is correct.

Not really, because your speedometer reads fast for that exact reason.

While we in the states take speed limits as guidelines (30mph really means under 41 in MD) most European countries go by "50kmh means 50kmh" so the speedometer is calibrated to keep you out of trouble.

Got_da_booze · 12-31-2009, 11:46 AM

I was thinking that the ECU could be reprogrammed for larger tires. Is this something uncommon in the BMW world? I'm just looking for a viable solution so I can ditch these 17s.

remmib · 12-31-2009, 07:39 PM

Quote:

Originally Posted by Got_da_booze

I was thinking that the ECU could be reprogrammed for larger tires. Is this something uncommon in the BMW world? I'm just looking for a viable solution so I can ditch these 17s.

If you use the OEM size for 18" and 19", i.e 225/40/18 and 225/35/19, the difference to the 225/45/17 is less than 1 %.

Got_da_booze · 12-31-2009, 08:09 PM

Quote:

Originally Posted by remmib

If you use the OEM size for 18" and 19", i.e 225/40/18 and 225/35/19, the difference to the 225/45/17 is less than 1 %.

I see what you mean now. I would be going from my stock 225/45/17 to 235/35/19 on the front and 265/30/19 on the rear, which is a very small change. Looks like from the calculator on here that it would be a 1 mph difference in speed.

welkerbrads · 01-01-2010, 01:28 PM

I have a 08 e90 with 205 x 55 x 16. At 75 mph I was only going 70mph. I went to a 215 x 55 x 16 and now my speedometer is on the money. This tire is a 1/4 inch bigger on the top and bottom.

Craig@SupremePower · 01-01-2010, 03:58 PM

what he said...

Quote:

Originally Posted by remmib

The overall diameter of the wheels and tires shouldn't be bigger, because you should use tires with a smaller sidewall when you use a bigger wheel.

Quote:

Originally Posted by remmib

It might be 1-3 % off, but that's not a problem.

12-30-2009, 10:23 PM	#1
Got_da_booze Boozila 19 Rep 264 Posts Drives: Black Sapphire '07 335i Join Date: Sep 2009 Location: Alexandria, VA iTrader: (13) Garage List 2007 335i [10.00]	Changing Wheel and Tire Size Hello. I have 17 inch stock wheels on my 335i and I am looking to change to 18s or 19s. What needs to be done for the car to acknowledge that it has bigger wheels and tires so I am not off on the odometer and speed readings? I've searched around the forums with no results on this. Thanks and Happy New Years. __________________ 2007 BMW 335i, Black Sapphire, with some goodies. I have OEM E90 tail lights for sale!
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12-30-2009, 10:54 PM	#2
superduty Private First Class 10 Rep 141 Posts Drives: 2010 E91 M Sport Join Date: Dec 2009 Location: Tucson, Az iTrader: (0)	Out of the box there is already a speedo error, at least there was on mine before I swapped wheels/tires. According to some, it's by design (but not the odo for some reason). As best I've been able to determine there is no way to correct the speedo. This doesn't seem reasonable to me since there should be a simple correction factor that is entered into the ECU unlike the old days when you had to swap speedo drive gears. I've been unable to find out if the dealer can make the correction. If not, it also seems unreasonable the more of us making more noise about this issue. Every vehicle I've owned with an ECU I've been able to calibrate the speedo with easily obtained ECU programming software. __________________ "Did I say something abnormal?" "You're an engineer, everything you say is abnormal."
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12-31-2009, 07:17 AM	#3
remmib General 1584 Rep 29,215 Posts Drives: 2013 F10 520d M-Sport Join Date: Feb 2006 Location: Norway iTrader: (0)	The overall diameter of the wheels and tires shouldn't be bigger, because you should use tires with a smaller sidewall when you use a bigger wheel. __________________ F10 520d M-Sport Alpine White \| HRE P43SC 20x9+20x11 \| Michelin PSS 255/35+295/30 \| KW V3 Coilover \| M5 Front Sway Bar + M550d Rear Sway Bar \| 3DDesign Front Lip \| BMW M Performance CF Spoiler \| BMW M Performance Diffuser \| BMW M Performance Black Grills \| BMW M Performance Pedals \|
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12-31-2009, 08:15 AM	#5
remmib General 1584 Rep 29,215 Posts Drives: 2013 F10 520d M-Sport Join Date: Feb 2006 Location: Norway iTrader: (0)	It might be 1-3 % off, but that's not a problem. __________________ F10 520d M-Sport Alpine White \| HRE P43SC 20x9+20x11 \| Michelin PSS 255/35+295/30 \| KW V3 Coilover \| M5 Front Sway Bar + M550d Rear Sway Bar \| 3DDesign Front Lip \| BMW M Performance CF Spoiler \| BMW M Performance Diffuser \| BMW M Performance Black Grills \| BMW M Performance Pedals \|
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12-31-2009, 11:46 AM	#8
Got_da_booze Boozila 19 Rep 264 Posts Drives: Black Sapphire '07 335i Join Date: Sep 2009 Location: Alexandria, VA iTrader: (13) Garage List 2007 335i [10.00]	I was thinking that the ECU could be reprogrammed for larger tires. Is this something uncommon in the BMW world? I'm just looking for a viable solution so I can ditch these 17s. __________________ 2007 BMW 335i, Black Sapphire, with some goodies. I have OEM E90 tail lights for sale!
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01-01-2010, 01:28 PM	#11
welkerbrads Private First Class 10 Rep 120 Posts Drives: 2011 white X3 Join Date: Apr 2009 Location: cape girardeau mo iTrader: (0)	I have a 08 e90 with 205 x 55 x 16. At 75 mph I was only going 70mph. I went to a 215 x 55 x 16 and now my speedometer is on the money. This tire is a 1/4 inch bigger on the top and bottom.
	Appreciate 0 Quote