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Home Tires Compare Size 245/50 R18 vs 245/40 R20

Compare 245/50 R18 vs 245/40 R20

Tire Size and Comparison Calculator calculate tire diameter from code and compare speedometer differences for tire sizes.

The first number 245 is the tire width in millimeters.

The 2nd number 50 is used to calculate the sidewall height or "aspect ratio", by percentage. So, the sidewall height of a 245/50 R 18 tire is 60% of 245 = 192

The 3rd number 18 (generally preceded by an "R") is Rim Diameter in inches. This is the diameter of the rims bead seat base, not the diameter of the outer rim edge. The rim edge, or lip, extends past the tire bead seat to hold the bead and stop the tire slipping off the rim.

When we say a rim has a 18 inch diameter, we mean that the diameter of the bead seat base measures 18 inches. The outer rim edge diameter will actually measure more, depending on the design.

Tire 1
/ R
245
50
R18
Tire 2
/ R
245
40
R20

Odometer Reading

If you replace 320/60/18 with 235/60/18 for Odometer reading 1000 the actual distance traveled = 879 ~ (-12.1%)

(If your Odometer is accurate for original tires)

Edit and Copy Tire diagram above to compare or print.

Speedo Difference between Wheels 12.1%
320/60 R 18 KPH 235/60 R 18 KPH
5 4.4
10 8.8
15 13.2
20 17.6
25 22
30 26.4
35 30.8
40 35.1
45 39.5
50 43.9
55 48.3
60 52.7
65 57.1
70 61.5
75 65.9
80 70.3
85 74.7
90 79.1
95 83.5
100 87.9
105 92.3
110 96.7
115 101.1
120 105.4
125 109.8
130 114.2
135 118.6
140 123
145 127.4
150 131.8

Comparison Table

Model
245/50 R18
245/40 R20
Section Width
i

The TrueContact Tour is Continental's Standard Touring All-Season tire developed for drivers of family sedans, coupes, minivans and small

245 mm
245 mm
Sidewall Height
i

The TrueContact Tour is Continental's Standard Touring All-Season tire developed for drivers of family sedans, coupes, minivans and small

4.82"
3.86"
Overal Diameter
i

The TrueContact Tour is Continental's Standard Touring All-Season tire developed for drivers of family sedans, coupes, minivans and small

27.65mm
27.72mm
Rim Size
i

The TrueContact Tour is Continental's Standard Touring All-Season tire developed for drivers of family sedans, coupes, minivans and small

18x8.0, 18x8.5, 18x9.0
20x8.0, 20x8.5, 20x9.0
Circumference
i

The TrueContact Tour is Continental's Standard Touring All-Season tire developed for drivers of family sedans, coupes, minivans and small

86.86 "
87.08 "
Revs per mile
i

The TrueContact Tour is Continental's Standard Touring All-Season tire developed for drivers of family sedans, coupes, minivans and small

729.45/mi
727.61/mi
Speedometer
i

The TrueContact Tour is Continental's Standard Touring All-Season tire developed for drivers of family sedans, coupes, minivans and small

Considering this is the manufacturer’s tire size and speedometer readings are correct.
Note: speedometer's 60km/h actually mean 60 km/h
Car height
i

The TrueContact Tour is Continental's Standard Touring All-Season tire developed for drivers of family sedans, coupes, minivans and small

Basic
0 mm
Typical Weight
i

The TrueContact Tour is Continental's Standard Touring All-Season tire developed for drivers of family sedans, coupes, minivans and small

32.4 kg
27.8 kg
Ground Clearance
i

The TrueContact Tour is Continental's Standard Touring All-Season tire developed for drivers of family sedans, coupes, minivans and small

Stock
0 mm
Tire with the same height
i

The TrueContact Tour is Continental's Standard Touring All-Season tire developed for drivers of family sedans, coupes, minivans and small

Performance
Result
Impact
Design
The same
Road holding ability
The same
Precision of steering response
Enhance
The steering response and behavior during turns will be improved. For instance, adding a larger rim diameter and a smaller tire height can enhance cornering stability and also increase the speed at which such turns can be safely executed.
Grip on dry pavement
The same
Grip on wet pavement
The same
Grip on dirty surfaces
The same
Hydroplaning resistance
The same
Ride comfort and noise
The same
Fuel consumption
The same
Treadwear
Worsen
Tires and rims are more likely to be damaged. The lower the tire height, the greater the risk of damaging the rim or tire itself when driving over potholes and other road imperfections. Low-profile tires are more prone to side damage.
Cost
Increase
Larger diameter wheels and low profile tires are more expensive than smaller diameter wheels and taller tires.
Weight
Increase
Generally, wheel weight is included in the overall weight of your vehicle. Cars that are lighter will be able to accelerate more easily and slow down more easily when necessary. They will also consume less fuel overall.

Popular comparisons

245/50 R18 VS

245/40 R20 VS


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