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wheel/tire size diameter effect on odometer

Shiftingshaddow

Shiftingshaddow

New member
mustang wheels

these 245 40 18s are about 1% smaller in diameter with the tires on them than the stock rims and tires according to this Tire Size Calculator - Tire & Wheel Plus Sizing.

there is about a 2mph speed difference. so if you put 100 miles on the car, with these rims will it register as 101? 1000 as 1010 and so forth?

and the brakes....will the width have any effect on the brakes--or added weight if there is any? i've never put aftermarket wheels on anything before.

what would be involved in adjusting the speedometer and odometer for the difference in wheel diameter? and cost? i can't even think of how to phrase that for a google search. when the tires are toast i would probably try to get bigger sidewall profile to match again but that would be a few years down the line probably.
 


the stock size is 225/60R16, the size you want is 245/40R18.

that's a -3.43% difference in outside diameter. typically this is outside of the ~3% you want to stay within. typically we'll recommend 245/45R18.

will they work? yup. they'll be fine with that tire size. it'll increase wheel gap from the tire-fender because they are shorter than stock and they're a decent margin heavier than stock so they'll increase acceleration/deceleration times.

adjusting the speedo will take more effort and time than is really necessary. the tires aren't off THAT much to make a huge difference.
 
thank you mr eastwood.

i misremembered the difference. i looked at 6 or 7 different sizes last night.

i was hoping that the extra width would kind of offset the weight because of better traction (wider tires?). and i've got over a hundred pounds in the truck that can be shed so maybe it will balance out a bit more.
 
since i'm not drag racing at the track it probably will never make any noticeable difference in any type of performance, then? maybe a .1 on a quarter or something.....
 
after your advise, bio248 (coming from mr eastwood i had to listen), i went with the 245/45. quite an illusion. they are almost exactly the same diameter outside to outside of the tire but the 18s look bigger. the width is what is the coolest, though.

i wanted bullitt rims but all of the mustang wheels have 245/40 on them and i'm not looking to spend on new tires yet for those wheels.
 


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