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SimpleTire.com offers a easy to use tire size calculator to calculate differences in speed, rating and fit based on a change to wheel or tire size. Try our tire calculator to see how changing your tire or wheel size will impact your vehicle performance and handling. 


OE Tire Size

After Market Tire Size


OE Tire

After Market Tire

Speedometer Difference


Speedometer Reading

Actual Speed

20 mph
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25 mph
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30 mph
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35 mph
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40 mph
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45 mph
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50 mph
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55 mph
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60 mph
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65 mph
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70 mph
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75 mph
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80 mph
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85 mph
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How to Read Your Tires - Quick Reference

Read Your Tires Sidewall

P – Passenger car
195 – Section width in millimeters, measured from one edge of the tread all the way to the other edge
60 – Aspect ratio (sidewall height, as a percentage of the tire’s total width)
R – Radial construction
15 – 15” rim
87 – load rating (in this case, 1200 lbs per tire)
S – Speed rating (in this case, 112 mph)

Learn About Speed Ratings

Speed ratings are designations for a safe speed for any given tire, with low risk of overheating, tread separation or other types of tire failure. Remember, though, that higher speed ratings than you actually need don’t necessarily mean a better tire.

Check speed ratings below:

M – 81 mph
N – 87 mph
P – 93 mph
Q – 99 mph
R – 106 mph
S – 112 mph
T – 118 mph
U – 124 mph
H – 130 mph
V – 149 mph
Z – in excess of 149 mph
W – 168 mph
Y – 186 mph