I would like to put a taller tire on the xb. I am keeping the stcok rims on it but the tires look so small compared to the car itself. So if I put a taller tire on this will screw up my speedometer?

 

as long as its not more than 3% of the original size.
go here http://www.miata.net/garage/tirecalc.html
to compare the difference.
I think 2 mph difference is manageable.

 

^^ what he said. I believe the speedometer is off at 60mph and higher, slower than that it's not that noticeable.

 

I'm running a set of 205/55-15s on the stock rims, using them as my "winter" driving wheels for now. They look a lot nicer and handle better than the stock-size tires.

 

If you are looking for a taller tire, and you do not want your speedometer/odometer to be off, there is not any real good options. If you want the tire to look larger (more black sidewall showing) then you will change your reading on both. Getting a taller tire would smooth out the ride, if this is what you are looking for, then you could drop to 14" rims, and then mount a taller tire to match the original tire diameter. I am looking into doing this when the factory tires wear out. It is just a little stiff for me, being way out of the xB target group. Good luck Just looked it up on the miata site above, and a 225/55-14 gives you 1/2" more sidewall, but is the same diameter as stock. Or a 215/60-14 you gain .7" in the sidewall, but still only +1.8 diff. in overall diameter. I printed out the info for future reference.

 

Thanks. I am not in the target market either but I want the XB to ride better, sit a little higher and not look like it is riding on baby training wheels. Part of my issue is with snow here in Ohio. We had a lot and because it is sitting so low the front air dam and the ground effects around the car were basically all in the snow, hitting chunks of ice, etc. The front air dam was plowing the snow so it needs to be get off the ground.

 

So, I think you just need to be aware that your speedometer/odometer will be off by a bit (that miata site listed in a post above will tell you how much) and staying with the stock rims, perhaps go with a 205/70-15. This would raise the car 1.3 inches, and give you a taller tire that would improve your ride also. Because they commonly drop the car almost 2", you wouldn't have any problem with the vertical clearance. But when you are in full steering lock, can't be sure but by checking (you would gain about .8" in wheel width. If not, the 205/65-15 would give you a .9 in raise on the car, (same wheel width, but not as tall). I will be checking on this exact thing once the stock tires wear out. I may try going with a 14" rim, that way a taller tire would improve the ride, but not really raise the car. Being in Calif. high desert, snow is never a problem. I just want a smoother ride. Good luck. Also, if someone made a progressive spring that did not drop the car, that would be on my mod list for sure. Will be looking into that down the road also, as I decide to put out more money for something that is not really necessary.