What is radial runout on a shaft?

Radial runout (TIR) is the total variation in distance measured from a shaft surface to a fixed reference as the shaft rotates one full revolution. TIR equals twice the eccentricity.

How do I measure runout with a dial indicator?

Mount the shaft on V-blocks, place a dial indicator perpendicular to the surface, zero it, then rotate one full revolution. The total needle movement is the TIR.

What causes excessive radial runout?

Common causes: bent shaft, manufacturing eccentricity, bearing journal wear, improper coupling alignment, and assembly errors.

What is the relationship between runout and unbalance?

If a shaft has eccentricity e (half the TIR), the equivalent unbalance is U = e × m, where m is rotor mass. Runout creates mass displacement producing centrifugal force.

What is acceptable runout for different applications?

At G6.3 / 3000 RPM: TIR ≈ 40 μm. At G1.0 / 6000 RPM: TIR < 5.3 μm. At G6.3 / 1500 RPM: TIR ≈ 80 μm. Always calculate for your specific conditions.

Free Engineering Tool

Shaft Radial Runout Calculator

Calculate permissible shaft radial runout (TIR — Total Indicator Reading) based on balance quality grade and operating speed. Compare measured runout against ISO 21940 limits.

ISO 21940-11 TIR / Eccentricity Pass / Fail Check

Balance Grade G

Operating Speed (RPM)

Shaft Diameter (mm)

Rotor Mass (kg)

Measured Runout — optional, for Pass/Fail check (μm TIR)

Quick presets

Results

Permissible TIR (Total Indicator Reading)

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Permissible Eccentricity (e_per)

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Equivalent Unbalance (U_per)

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Angular Velocity ω

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Balance Grade

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Permissible Eccentricity

From the balance quality grade G and operating speed:

G — balance quality grade (mm/s)
n — operating speed (RPM)
ω — angular velocity (rad/s) = 2πn/60

Total Indicator Reading

TIR measured by a dial indicator is twice the eccentricity (peak-to-peak):

Equivalent Unbalance

Practical Example

Example — Pump Shaft G6.3 at 3000 RPM

Given: Speed = 3000 RPM, Grade = G6.3, Mass = 45 kg, Diameter = 40 mm

ω = 2π × 3000 / 60 = 314.16 rad/s

e_per = 6.3 × 1000 / 314.16 = 20.05 μm

TIR = 2 × 20.05 = 40.1 μm

U_per = 20.05 × 45 = 902.3 g·mm

Permissible Runout Reference Table

Grade	Speed (RPM)	e_per (μm)	TIR (μm)
G6.3	750	80.2	160.4
G6.3	1500	40.1	80.2
G6.3	3000	20.1	40.1
G2.5	3000	7.96	15.9
G2.5	6000	3.98	7.96
G1.0	6000	1.59	3.18
G1.0	12000	0.80	1.59

Shaft Radial Runout Calculator — Free TIR Tool | Vibromera

Published by Nikolai Shelkovenko on February 15, 2026 March 5, 2026