Hi, I read thru all the similar topics but didn't really find an answer here..
I just changed wheels & tires and my tire diameter is nearly and inch less now.. will my obc figure this out afa my odometer & speedometer?
I know it's not the most accurate but I use the obc for avg mpg as well, and would like to know if it's going to be way off now as well..

Thanks!

 

I like this tire calculator for that kind of thing:

http://www.miata.net/garage/tirecalc.html

 

Well, I am certainly no expert on MINIs, as I am still waiting for mine to be delivered. However, my sense of logic tells me that your OBC will NOT figure out the change, since there is nothing to indicate it is wrong. I would be interested to see if your mileage calculations are wrong, though. It seems to me that the relationship between how far it THINKS it goes (more tire revolutions per mile) and the fuel used will remain constant. However you will see that you actually use more fuel because your car will think it has covered more miles than it actually did. I can't wait to hear answers from someone that actually knows what they are talking about!

I have had other cars where I had to tell it the outside diameter of the new tires in order to make the adjustment. I am sure you will have to do the same. I bet your Service Advisor can help, but maybe the Tire Rack guys can, also.

We'll see how many people agree with me.I have often found a significant gap between my sense of logic, and reality. Note my signature quote!!

 

thanks. I have used that before, and I know how to figure it out, but does my Cooper?

 

yeah, so I should probably expect to have to reset the obc, or flash it or something?

 

Sorry - I misunderstood what you were asking for in your first post.

No, your car will have no idea what's going on. If your new tires are shorter than your old ones, your speedometer will read faster than it did before for any given true road speed, your OBC-calculated fuel economy will read higher than actual, and your odometer will tick off the miles faster than it should.

 

I was afraid of that. I went from 205/55R16 to 175/65R15.. the speedo I can live with but I would like the odometer to be accurate.