Changing wheel/tyre combination - rolling radius & speedo accuracy

[trapdoor]

Am thinking of getting a set of 19" wheels. Currently have 18's on which are all 235/50/18 but looking at a set of staggered wheels which are 255/50/19 and 285/45/19. Calculations suggest that there will be a speedo error of 6.6% under-read which will mean that a speed of 60mph I will actually be doing about 64mph.

Is there a setting so that the dealer can change the speedo calibration to take into account the different wheel/tyre sizes available for the X3 or is it that I HAVE to put on only the correct combination?

Thanks.

[motordavid]

I don't recall reading any post about success in a speedo recalibration for
diff tire sizes. Otoh, the speedo reads optimistic anyway, so maybe you
will be very close to actual speed with the new wheel/tire combo.

I went from 18s to style 132 19s and with some fuzzy arithmetic I came to
that conclusion. Different tire size vis a vis the new wheel combo would get
your closer, but for ~6% in combo with the notoriously optimistic speedo,
I would call it a draw and not give it much worry, imo.
GL,mD

[PHT]

I bought a set of X5 wheels in the same size as trapdoor. It's style 63 (9x19 ET 48 front and 10x19 ET 45 rear). The tires are 255/50 and 285/45. I thought this tires were too big for the X3....? Have anyone tried it?

I planing to change the tires to 255/40 in front and rear. Is this a better choice?

And last question: Have anyone tried "style 63" rims on a X3 ?

[chasem3]

Somewhat related question - I am looking to get winter tires and wheels in 18 inch. I like a meatier look to the tires so I am thinking of getting 245/60/18 tires. Do you guys think this will cause any issues? Will they rub? I am basically looking to see what the max tire series is that i could go. Any input would be greatly appreciated.

Thanks!

[AzNMpower32]

Originally Posted by chasem3

Somewhat related question - I am looking to get winter tires and wheels in 18 inch. I like a meatier look to the tires so I am thinking of getting 245/60/18 tires. Do you guys think this will cause any issues? Will they rub? I am basically looking to see what the max tire series is that i could go. Any input would be greatly appreciated.

Thanks!

That tyre size is not going to work. The best size for 18" would be P235/55R18. Even for the 17", the sidewall ratio is 55-series.

I'm pretty sure when I put on my 18", my speedo read a bit low. I was following the mile post signs along I-85 in NC with the trip meter. At first it seemed okay, but after a while, the trip computer changed perhaps a second or two after the xx,0 sign.

[chasem3]

Thanks for the response. Do you think it wont work meaning it wont fit in the wheels well or it wont work as far as keeping my speedo accurate? i remember seeing someone on here that had 255/55/19 tires from an X5 Sport and they looked good and the owner had no rubbing. Thats why I think 245/60/18 would fit at least. i am not worried about speedo error.

Amr

[AzNMpower32]

Originally Posted by chasem3

Thanks for the response. Do you think it wont work meaning it wont fit in the wheels well or it wont work as far as keeping my speedo accurate? i remember seeing someone on here that had 255/55/19 tires from an X5 Sport and they looked good and the owner had no rubbing. Thats why I think 245/60/18 would fit at least. i am not worried about speedo error.

Amr

I'm concerned about them rubbing. Someone once tried P235/65R17 tires and there was some rubbing around parking lots and parking. X5 and X3 wheels aren't perfectly interchangeable, since the offset is different.