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How will an incorrect aspect ratio tire affect my car?

1K views 4 replies 5 participants last post by  mather 
#1 ·
The stock specs for my car, 1984 mustang svo, call for 225/50/16 tires. I just saw that mine are actually 225/55/16.

I've calculated that my current tires result in a circumference that is 3.56% larger than stock specifications. Besides the obviously incorrect speedometer reading, how else will this affect me?

I figured slightly less horsepower, slightly better MPG, but I'm not sure at all.

Any tips?
 
#3 ·
Both specs you mention are 16 inch tires so how can the aspect range have changed.
Tires are made to fit rims of various diameters and your ones are 16 inches in Dia.
All the manufacturer has done is offer you tires that will fit your rims (16") and given
you a choice of wider fitting with low profile tires or wider fitting with high profile
tires.The difference between 225/50 and 225/55 is negligible.The 50 series tires
will give more grip than the 55s but the 55s will be a little more comfortable over
bumps and ruts in the road. You should try driving a car with 205/45/18. You can
feel every twig or ant you run over.
 
#4 ·
Since you have effectively changed your axle ratio to a taller one (fewer revs per mile), your car should accelerate more slowly (not likely noticeable "from the seat of your pants"). Your horsepower and torque output from your motor doesn't change, but torque is now multiplied less. You guess about better fuel economy (again, not noticeable except over a long period of time) should prove correct also. BTW, nice car - you have something that's quite rare nowadays.
 
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