125/70R17 Tire Size

All You Need to Know About 125/70R17 Tires

The 125/70R17 tire is used in the temporary spare (T-type) tire class, where reduced width and compact dimensions are intentional. The narrow section and smaller diameter are designed for limited-distance emergency use rather than continuous driving.

125/70R17 size defines a tire that is 125 mm wide, with a 70% aspect ratio and a 17-inch wheel diameter, producing an overall diameter of ≈23.9 inches and a sidewall height of ≈3.44 inches.

Because 125/70R17 diameter differs from full-size tires, for example, ≈23.9 inches for 125/70R17 versus ≈25-29 inches for typical passenger tires, the 125/70R17 tire should be used on a non-drive axle, if possible, to avoid drivetrain stress and uneven rotation speeds.

On the road, 125/70R17 tires are typically limited to short-distance emergency use (≈50 miles) and speeds under ~50 mph, as temporary spares are not built for sustained driving. Learn more about the limits of spare tires in the dedicated guide: How Long Can You Drive on a Spare. 

125/70R17 Size Quick Specs

• Approved rim width range: 3.0-4.0"
• Recommended Tire Pressure: Typically 60 PSI 
• Overall diameter: ≈23.9"
• Section width: 125 mm
• Sidewall height: 87.5 mm
• Fits: 17-inch wheels (temporary spare applications)

Note: The calculated overall diameter of 125/70R17 is ≈23.9 inches. Published temporary spare specifications typically fall within ±0.1-0.2 inches, depending on the manufacturer's design.

125/70R17 Dimensions in Inches

The 125/70R17 tire size measures approximately 4.92 inches in width, 23.9 inches in overall diameter, and has a sidewall height of about 3.44 inches.

At ≈23.9 inches in diameter, the circumference is ≈75.1 inches, which represents the rolling distance per full revolution. This smaller circumference compared to standard road tires is one reason the 125/70R17 temporary spares are intended for short-distance use only.

125/70R17 in Inches: All Measurements

• Overall diameter: ≈23.9"
• Width: 4.92" (≈4.9")
• Sidewall height: 3.44" (≈3.4")
• Wheel diameter: 17"
• Circumference: 75.05" (≈75.1")

Circumference Difference of 125/70R17 vs Full-Size Tires

A 125/70R17 spare has a circumference of ≈75.1 inches, compared to ≈79-90 inches for most full-size passenger tires. This creates a difference of ≈4-15 inches per rotation, or roughly ≈5-20% in rolling circumference. 

Because the 125/70R17 smaller tire must rotate more times to cover the same distance, the drivetrain experiences continuous speed mismatch across the axle. This is the primary reason the 125/70R17 temporary spares are limited to short-distance use, independent of tread depth or compound.

125/70R17 Axle Placement Requirements

On front-wheel drive vehicles, the 125/70R17 temporary spare is best installed on the rear axle; on rear-wheel drive vehicles, on the front. This keeps the size mismatch away from the drive axle, reducing the need for continuous differential compensation and limiting mechanical load.

With an overall diameter of ≈23.9 inches, 125/70R17 is significantly smaller than typical passenger tires, which changes the rotational speed at the wheel. When placed on a drive axle, this difference forces constant speed correction through the differential. Positioning the 125/70R17 tire on a non-drive axle minimizes that effect and reduces drivetrain stress.

Inflation Pressure Requirements for 125/70R17

A 125/70R17 spare typically requires inflation to ≈60 psi to maintain its rated load capacity.

The  ≈125 mm width of the 125/70R17 tire produces a reduced contact patch, which must be offset by higher internal pressure to support vehicle weight. At lower pressures, the sidewall cannot maintain structural stability, increasing the risk of overheating and failure. Maintaining the specified pressure for the 125/70R17 temporary spares is therefore critical for safe temporary use.

Most Recommended 125/70R17 Tires

Best tires in 125/70R17 size include:

• T125/70D17 98M: Continental Spare Tire, Falken FK-090