Different front and rear tire size and speedometer

Will the speedometer on a Mazda3 be off if you put 225\40\18 on the front and 235\40\18 on the rear wheels? Tire calculators I found on the net were mostly based on all four tires. Any pros and cons on this setup for Mazda 3?
Simular configuration on the Nissan 350z:

<TABLE cellSpacing=0 cellPadding=2 width="100%" border=0><TBODY><TR class=table-sub><TD width="50%">alloy rims </TD><TD width="50%">17 x 8 in. rims </TD></TR><TR><TD class=stripe-five width="50%">17 x 7.5 in. front rims </TD><TD class=stripe-five width="50%">P235/50WR17 tires </TD></TR><TR class=table-sub><TD width="50%">P225/50WR17 front tires </TD><TD width="50%">performance tires </TD></TR><TR><TD class=stripe-five width="50%">temporary spare tire </TD><TD class=stripe-five width="50%">steel spare wheel </TD></TR></TBODY></TABLE>

Err...why would you ever want to put wider tires in the rear of a FWD car? (scratch)

slipangle said:

Err...why would you ever want to put wider tires in the rear of a FWD car? (scratch)

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Agreed. (huh)

But if you insist on the insanity, your speedometer runs off your transmission, therefore is connected to your drive wheels. The fronts, in your case. Putting larger wheels on the back will have no effect on your speedo (except to make it rise slower because of the extra drag).

225/40-18 on the front will maintain the proper tire diameter.

Having a different sized rear wheel/tire could do interesting things when braking.

Just noticed that you said,

carz8 said:

Simular configuration on the Nissan 350z:

Click to expand...

Yeah... the 350Z is rear wheel drive. It would make sense to have larger tires in the rear.

re

True...most cars that have larger wheels on back are rear wheel drive. I just like the look but it would also mess up tire rotation.. I think I'll stick with 225 40 18 on all wheels. thanks for input

carz8 said:

True...most cars that have larger wheels on back are rear wheel drive. I just like the look but it would also mess up tire rotation.. I think I'll stick with 225 40 18 on all wheels. thanks for input

Click to expand...

Good call on not going through with making the rear wheels wider than the front. It's funny though, think of how many car's out their changed their wheels so they can look better or faster, even though the new wheels made no sense performance wise. This wouldn't be all that much different.