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i just picked up my proxes and was wondering since i went from a 60 series to a 50 series will i have to recalibrate my speedometer? any info's appreciated.
 

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if your overall diameter is within .75" of what it used to be, no you really dont need to.
 

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You don't HAVE to. I don't know how to do that if you actually wanted to.

Just know that it will be different. I went from 205-50-16 to 195-50-15. That changed my 22MPH/1000RPM in 6th to 20MPH/1000RPM in 6th. The speedometer reads ~10% high. I don't know how close that is to using the rolling circumference and math. I just checked it with a GPS. My speedometer was broken on my old car for a long time. I got used to using the tach.
dB
 

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Supposedly, with my tires I am actually going 1.2 mph faster than the speedo says I am. If, you calculate it using the size of my rear tires LOL, then I am going 1.3 mph slower than my speedo says.
 

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BUMP FROM THE DEAD

Because unlike you other fools... IIIIIIIIIIIIIIIIIIIIIIIIIIIIIII SEARCHED! :werd:

So if you buy a bigger profile tire for a GT (stock 195/60/15), say 225/40/18, a VERY popular size, according to miata.net you will have a...

Speedometer reading with a non-stock tire is 3.6% to slow
When you speedo reads 60mph, you are actually traveling 62.2 mph

Now assuming you are traveling faster that your car reads, you will theoretically save 2.2 miles every 60miles on your odometer? ;)

Now if you drop that tire down to a 215/35/18 you get different results..

Speedometer reading with a non-stock tire is 1.2% to fast
When you speedo reads 60mph, you are actually traveling 59.3 mph

Now assuming you are traveling slower that your car reads, you will theoretically add 0.7 miles every 60miles on your odometer? :marky:

So in a ricer perspective it's better to go with the 225 since you will...

1. Have a bigger profile, thus less wheel gap with the same spring / shock setup than you stock tire

2. Have a slightly more comfortable ride running a bigger profile

3. Save a few miles on your car since you are tricking the odo.

4. wider = better

:wiggle:

Thoughts? Input? Hate?
 

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why bump?


and yeah might as well go with a a 215/50/whatever size wheels unless you got ome good proxies like T1R's and plan to race in them and then a meaty tire will do you good but really you would need to change your speedometer.
 
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