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Re: do taller tires affect the car's computer?? (archive)

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Posted by Gregg on July 09, 2000 at 11:41:39:

In Reply to: do taller tires affect the car's computer?? posted by james on July 09, 2000 at 10:47:32:

: i am thinking ultimately of putting 50 series tires on my 528 17" sport wheels in place of the 45 series when i have to replace the tires. does anyone know whether the different tire size will adversely affect any of the the car's computer data, other than the speedo readout??

: thanks

: : I mentioned this before on the list but I have a quick followup question. I put bfgoodrich g-force tires on my 98 540iA sport and overall the only downside has been the general sense of slower all around acceleration.

: : I know these bfgoodrich tires are wider (245/45/17) versus the previous dunlop sp8000 (235/45/17), so if the compounds were the same it would still be a more massive and heavier tire (bad for acceleration). But I'm curious, assuming same dimension tires -- are other high end tires such as pirelli lighter weight?

There is no "correct" 50 series fitment that (mathematically/dimensionally) matches up to your sport tires--at least that are worthwhile--that would be EXACT same o.d. as you have. This would theoretically be a 215-50-17 and you don't want to go that skinny, sport or not. 245-45-17 mentioned is the correct "Plus One" from factory NON-sport 16s (as would 225-50-17s, as minimal (no width change) Plus Ones). While both of these are taller (by about 1/2") than your sports, I've read several posts that have put 245-45s all around w/o problem--no clearance problems (due to lowered Sport aspect) reported anyway. I'm not sure (but doubt) that factory ever mae any ABS, speedo/odo or other computer changes in the first place to accomodate the Spor's slightly shorter (than base 5er/oem non sport) tires, and so would not think that "going back" the other direction would be a problem. Any other noticed any speedo inaccuracies as a result of going slightly taller on your Sports? (and if so, BMW must have made minor computer compensation for the Sport).

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