My stock rims have bald tires on them (wires popping out). I have 2 tires of each set sitting around with good tread on them 205/55/16s and 225/50/16. Tread depth on both sets is equal. Would it be ok to put them on there?

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


according to that calculator it would change the circumference by .1 inches which is acceptable. I know that rally guys also use different tire setups and what not and never have issues with the differential. Anyone educated on the matter want to chime in on if its acceptable or not?

 

been wondering the same thing. I hear people doing the fwd setup but idk why

 

I wouldn't. The actual tire diameter can be quite different, even with tires of the same marked size on the sidewall. As an example, look at specs for tires on Tirerack.

And they will wear differently as you drive.

 

Do the math, if the height of the tire is different, it will change overall gear ratio between front and rear. 24.877" for the 205's, 24.858 for the 225's. You will probably be ok.

Math is first number devided by 25.4 multiplied by second number in decimal, times 2 + rim height

(((205/25.4) .55) 2) + 16 = 24.877

 

Also not sure if any of you noticed that our spare tire is about 4-5% different in circumference than the actual tire size. now i know we're not supposed to drive a long time with the spare tire but why would subaru do that if the center differential couldnt handle that much tire difference.

how about people with alignment issues. im willing to bet their tire sizes are .1-.2 inches off.

 

also what about porsches. they run wider wheels in the back as well from teh factory on a 4wd car. the circumference isnt off by much. i might just decide to guinea pig this..

its the same brand tire. the tires came off a friends slk230

 

Bad idea.

-Brian

 

Have fun replacing your diffs. Read this. Get educated. Don't play games with your diffs.
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=18

Porsches have a different awd set up than we do and some of their awd do use the same size tires.

 

I wouldn't do that. My friend drove for few miles with spare tire (other 3 wheels were 17") and blew up the diff.

 

Yeah the spare is lent for the stock 16s. I blow a tire I get a flat bed. Period.

 

I need to get a pair of tires too, front tires inside wore down way faster than expected (alignment a bit off), no tire shop will flip them even though the tires have like 80%+ tread left, might just buy two and shave or try to sell them somewhere, not sure

 

I dont think our center diffs like that.

 

i guess i got lucky then... i drove 10 miles with the donut and 18's

 

well was it front or rear and with a diff or not. if it had a diff... then your diff will go out..

 

Are they directional? If so, what's your plan for rotating them front to back? Or, is thus a temporary solution?