Can we recalibrate our speedometer?

[Litespeeds]

I have a 2001 540it wagon with the sports package 17x8 and 17x9 wheels in the size 235/45/17 and 255/40/17. When I drive past the radar speed board in my neighborhood at 35 mph, it registers at 31 mph on their radar. I am sure as I increase the speed up to around 70 mph, the actual speed is probably around 63 to 64 mph.

Is there a way that BMW can recalibrate the speedometer so the speed is correct?

[Mattldm]

I have a 2001 540it wagon with the sports package 17x8 and 17x9 wheels in the size 235/45/17 and 255/40/17. When I drive past the radar speed board in my neighborhood at 35 mph, it registers at 31 mph on their radar. I am sure as I increase the speed up to around 70 mph, the actual speed is probably around 63 to 64 mph.

Is there a way that BMW can recalibrate the speedometer so the speed is correct?

In short, No! They are made this way and there is a technical bulletin from BMW telling dealers to not try to fix the optomistic speedo. 10% plus 2.4 mph is allowable according to BMW

Just get used to it - I set my cruise at 80 on the speedo which is closer to 72-74 actual MPH.

[Litespeeds]

That sucks. I guess the only way is to get taller tires that will hopefully get you closer to the actual speed. I have tried a set of 245/45/17 tires on a set of 17x8 wheels and that brought my speedo to within 2 mph different at 35 mph.

Another bad thing is if the speedo is spinning faster than what the car is actual doing, it is putting more miles on the odometer than it really should have. :nono

[thejlevie]

The odometer is supposed to be accurate, and according to my GPS that appears to be the case even though the speedo is fast by about 5mph at 70mph (real).

[Mohamed 525i]

U try this guys I hope it might help

http://www.bmwtips.com/tires/calc.htm

[cdb3113]

i actually noticed this in my car as well. on the highway at 70mph (dash) i reset the average speed calc on the obc. cruise was on while on flat road. the dash said 70, the obc said 66 or so! the difference does increase as speed increases. sounds like a common thing after reading this thread. ive gotten used to it.

[Litespeeds]

U try this guys I hope it might help

http://www.bmwtips.com/tires/calc.htm


There is a formula that I know of to determine the diameter of a tire. If the stock size tire of a BMW 5 series is 225/60/15 is the size that the calibration is set for, then this is how you figure out the diameter:

225 multiply by .60 divided by 25.4 multiply by 2 plus 15 will give you an overall diameter of 25.62".

If the sports package vehicles come with a 235/45/17 front and 255/40/17 rear, this translates to 25.33" front and 25.03" rear.

I am not sure if the information is taken from the front or rear tire for the speedometer but if it is from the rear, the difference is .59".

Running a set of 245/45/17 tires will give put the diameter at 25.68 which is almost identical to the stock size. I tried that with a set of 17x8" all around and my speedo was still off a couple of miles at 35mph on my speedo, I was clocked at 33mph.

To make sure the radar was correct, I drove my 2000 S-Class with sports package 18" AMG wheels and the speedo was right on with the radar at 35mph. Also was right on for my 2003 Honda Pilot.

[Mohamed 525i]

Check this site give ur original size plus the installed one and get the result


http://www.1010tires.com/TireSizeCalculator.asp?action=submit

[joyfret]

That sucks. I guess the only way is to get taller tires that will hopefully get you closer to the actual speed. I have tried a set of 245/45/17 tires on a set of 17x8 wheels and that brought my speedo to within 2 mph different at 35 mph.

Another bad thing is if the speedo is spinning faster than what the car is actual doing, it is putting more miles on the odometer than it really should have. :nono

Wow, this is so true. I have 245/45/17 tires and while I was passing by one of those mph meters, I ran 40 and the meter said 42!
Does this mean I can fight a traffic citation? 2 miles x $10.00 = $20.00 is
what I can save off any speeding tickets.