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  1. #1
    Join Date
    Mar 2013
    Location
    Anchorage, Alaska
    Posts
    568

    Default Torque Education Needed

    Hello folks, I would need some clarification on the science/physics of torque specifications.

    A. 2006 Toyota Sienna, AWD has a lug nut torque of 75 ft.lbs

    B. 2001 Volvo XC70 owner's manual specifies 100 ft.lbs for lug nut.
    On line specifies 105 ft.lbs, which is 5 ft.lbs more than the OEM manual.
    1. Logically, 5 ft.lbs is not much of a big deal, right?
    2. Why would a 2001 Volvo XC70 have a higher torque than a 2006 Toyota Sienna?


    C. 2001 Volvo XC70 Vibration Damper (4 screws)
    Stage 1 = 18.5 ft.lbs
    Stage 2 = 30 Degrees
    3. First stage means to torque to that set amount, then turn 30 Degrees.
    4. If so (#2), why isn't the "30 Degrees" calculated and included to the Stage 1 torque. In such case, there would be only one torque to say, example, instead of the specified "Stage 1 18.5 ft.lbs" it would be just one 20 ft.lbs torque?


    Thanks, for I am still work in progress!
    2001 Volvo V70XC/AWD/Auto/Turbo/164k Miles (Maroon)
    2001 Volvo XC70/AWD/Auto/Turbo/151k Miles (Brown)
    2005 Volvo XC90/AWD/V8/Auto 111K Miles (Black)
    2006 Toyota Sienna LE/AWD 124K Miles(Green)
    --------------------------------------------------------------------------------------
    1985 BMW (E23) 735i(US)/AUTO/209K Miles (Parked since 2011)
    1997 Mazda MPV/AUTO/4WD/173K Miles (Parked since 2008)
    2002 Subaru Outback L.L. Bean/3.0/131K/AWD (Parked since 2017)

  2. #2
    Join Date
    Feb 2010
    Location
    Virginia Beach
    Posts
    4,030

    Default

    The torque for wheel bolts depends partly on bolt size. Volvo uses a 14mm bolt. Much larger than the Toyota. 5 ft lbs doesn’t matter for wheel bolts. I thought it was 103, whatever, just make certain that the threads are clean and dry. No rust, no junk, but also no oil or grease, which includes anti seize. If you’re worried about corrosion, as I am because of the salt water around here, hit the bolt holes with some pure zinc primer (available at Lowe’s Home Depot, etc and sold as cold galvanizing compound) that way the threads will be clean, dry, and protected from corrosion.

    Angle torque is more precise than just torque.

    Here’s why - all torque values are a proxy for bolt stretch. The stretch in the bolt is what clamps the parts together. Clean dry threads are the basis for torque, but there are still variations, and the same torque may, or may not, result in the stretch that is needed if the threads, or the fitting have some roughness, or contamination.

    But an angle results in precisely the same stretch each time. Pure geometry. 30degrees of angle on a 14mm x 1.5 pitch bolt gives you a tension of .125 mm on the bolt. Every time.

    Where clamping forces are critical, angle torque is often used. The torque value gets rid of slack, the angle sets the stretch.
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  3. #3
    Join Date
    Mar 2013
    Location
    Anchorage, Alaska
    Posts
    568

    Default

    Quote Originally Posted by Astro14 View Post
    The torque for wheel bolts depends partly on bolt size. Volvo uses a 14mm bolt. Much larger than the Toyota. 5 ft lbs doesn’t matter for wheel bolts. I thought it was 103, whatever, just make certain that the threads are clean and dry. No rust, no junk, but also no oil or grease, which includes anti seize. If you’re worried about corrosion, as I am because of the salt water around here, hit the bolt holes with some pure zinc primer (available at Lowe’s Home Depot, etc and sold as cold galvanizing compound) that way the threads will be clean, dry, and protected from corrosion.

    Angle torque is more precise than just torque.

    Here’s why - all torque values are a proxy for bolt stretch. The stretch in the bolt is what clamps the parts together. Clean dry threads are the basis for torque, but there are still variations, and the same torque may, or may not, result in the stretch that is needed if the threads, or the fitting have some roughness, or contamination.

    But an angle results in precisely the same stretch each time. Pure geometry. 30degrees of angle on a 14mm x 1.5 pitch bolt gives you a tension of .125 mm on the bolt. Every time.

    Where clamping forces are critical, angle torque is often used. The torque value gets rid of slack, the angle sets the stretch.
    It's all geometry and physics. Read some lines more than twice to get a grasp.
    Thank you!

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