FAQ
TL;DR: For 1.69 Nm pinion preload, use 2.5 kg at 6.9 cm or 0.25 kg at 69 cm; "the arm would be 1.69 Nm/24.5 N = 0.069 m." [Elektroda, Rafikusa, post #17468831]
Why it matters: This helps DIY car owners set tapered-roller bearing preload accurately without an inch‑pound torque wrench.
Quick Facts
- Typical factory rotational preload for new pinion tapered bearings: about 12–23 in‑lb; check your service manual. [Elektroda, kiffe, post #17462712]
- Lever equivalents for 1.69 Nm: 2.5 kg @ 6.9 cm; 0.5 kg @ 34.5 cm; 0.25 kg @ 69 cm. [Elektroda, Rafikusa, post #17468831]
- DIY method: horizontal setup with a tared kitchen scale; use a light, rigid spoke as the arm. [Elektroda, kiffe, post #17468687]
- Cancel arm-weight influence with a symmetrical arm centered on the axis. [Elektroda, invisibleman, post #17468670]
- With a crush sleeve, tighten firmly to crush, then verify by rotational torque; a pipe on the wrench may be needed. [Elektroda, kortyleski, post #17462822]
How do I convert 1.69 Nm preload into a weight and lever length?
Use torque = force × radius and force = mass × 9.81 m/s². For 1.69 Nm, 2.5 kg at 0.069 m works because 2.5 × 9.81 × 0.069 ≈ 1.69. Alternatives: 0.5 kg at 0.345 m, or 0.25 kg at 0.69 m. These give the same torque while reducing sensitivity to arm mass and scale limits. This approach lets you set rotating torque without a dedicated inch‑pound wrench. [Elektroda, Rafikusa, post #17468831]
What arm length should I use if I can pull with 2.5 kg?
Compute radius r = 1.69 Nm ÷ (2.5 kg × 9.81 m/s²) = 0.069 m. That is 6.9 cm from the rotation center. Keep the arm horizontal and light to minimize errors. This compact setup fits inside most pinion flanges and allows steady readings on a small kitchen scale. [Elektroda, Rafikusa, post #17468831]
Is 1.72 kg at a 10 cm arm correct for 1.69 Nm?
Yes. 1.69 Nm ÷ 0.10 m = 16.9 N. Convert to kilograms: 16.9 N ÷ 9.81 m/s² = 1.72 kg. That means a scale reading of 1.72 kg at a 10 cm radius matches the target rotating torque. It’s a convenient midrange option when your scale resolution is best around 1–2 kg. [Elektroda, Rafikusa, post #17468864]
Can I measure pinion bearing preload without a specialized torque wrench?
Yes—use a kitchen scale and a light arm. How-To:
- Attach a rigid, lightweight spoke or bar to the flange, horizontal.
- Rotate the scale 90° and tare it to zero at your chosen radius.
- Pull steadily until the scale shows the target kg equivalent.
This substitutes for an inch‑pound wrench for rotating torque checks. [Elektroda, kiffe, post #17468687]
Does the arm’s weight affect the reading, and how do I cancel it?
Arm weight can bias readings, especially at low torques. Use a symmetrical arm with equal mass on both sides of the axis. That cancels the gravitational effects as you rotate and keeps the indicated force focused on bearing drag. It’s a simple way to improve accuracy when using makeshift tools. [Elektroda, invisibleman, post #17468670]
Do I need to worry about gravity if I push horizontally on a scale?
If the scale reads 2.5 kg, you are applying about 24.5 N, regardless of orientation. As one expert put it, “it does not matter how and where you pull this weight, if it shows 2.5 kg, then you pull with a force of 24.5 N.” Focus on steady pull and correct radius. [Elektroda, Rafikusa, post #17468831]
What’s the difference between nut torque and bearing rotational torque?
Nut torque crushes the sleeve or seats the bearings. Rotational torque is the drag measured while turning the assembled shaft. You set the nut, then verify rotating torque with your scale-and-arm fixture. “This is not just the tightening torque but the tightening torque of the bearings.” Measure rotation, not only the nut. [Elektroda, kortyleski, post #17462711]
What preload range should I expect for new vs worn bearings?
Manufacturers specify different rotating torque values for new versus used bearings. The thread cites a common example of about 12–23 in‑lb for new bearings. Always use the service manual value for your axle model and bearing state to avoid noise or overheating. [Elektroda, kiffe, post #17462712]
How do crush sleeves change the setup process?
Crush sleeves require significant nut torque to collapse to the correct distance. Then confirm by measuring the rotating torque of the pinion assembly. As noted, “the determinant of this proper dimension is the force needed to rotate such a twisted assembly.” A pipe on the wrench may be needed, e.g., Mercedes W107 hubs. [Elektroda, kortyleski, post #17462822]
What if my pinion threads or nut are not perfect?
Edge-case warning: damaged threads or burrs add friction and can mislead torque feel. With such small torques, any defect risks under-preload or variability. Replace questionable fasteners and sleeves before setting preload to protect new bearings from early failure. [Elektroda, ociz, post #17462686]
My kitchen scale tops at 3 kg. Which combinations work for 1.69 Nm?
Use these equivalents: 2.5 kg at 6.9 cm; 0.5 kg at 34.5 cm; 0.25 kg at 69 cm. All produce about 1.69 Nm. Pick the combo that fits your workspace and keeps the scale within its best measurement range. Longer arms with lighter weights often give smoother control. [Elektroda, Rafikusa, post #17468831]
Do I need to tare the scale when changing its orientation?
Yes. If you rotate the scale 90°, tare it to zero again. Orientation changes how the plate’s weight loads the sensor. Taring ensures the display shows only your applied pull, not the apparatus weight. This makes horizontal pulling measurements consistent and repeatable. [Elektroda, kiffe, post #17468687]
Any tip to minimize measurement error at such low torques?
Use a short 0.1 m arm and increase the weight proportionally to reach target torque. A lighter arm reduces inertia and balance issues. Keep the arm rigid and the pull smooth. Recheck readings after minor adjustments to the pinion nut. [Elektroda, kortyleski, post #17462711]
Why doesn’t 10 N equal exactly 1 kg?
Force depends on gravity. Use F = m × g with g ≈ 9.81 m/s². Example: 2.5 kg corresponds to 24.5 N, not 10 N. When converting between newtons and kilograms on a scale, always multiply or divide by 9.81 to stay accurate. [Elektroda, Rafikusa, post #17468831]
= 0.0676m
