Torque Education Needed

[BlackBart]

I used to work for a shop where my colleague forgot to tighten the lugnuts on a customer car. Twice. He was out smoking so much so he forgot.
Thank god the customers survived and that they didn't sue. Since then I tight lugnuts probably more than they need to.

My son was in a P2 wagon with 4 teammates on a university bike team. Lugs started falling out and it got squirrely. Luckily they stopped safe. Out in the middle of nowhere, so they spread the remaining lug bolts around so there were at least three per wheel. Got them to the next town where they randomly found some more at an auto parts store. The car had just come from a well-know chain tire shop.


Something I might add to the conversation is if you Ugga Dugga in your garage but then have to change a wheel on a two-lane in the rain and mud, you might wish you hadn't Ugga'd so hard back at home. I have a big NAPA breaker bar and socket in the trunk of each car instead of the factory lug wrench.

[kallekula]

Its usually enough to stand on the lug wrench. Otherwise we have AAA

[BlackBart]

Kinda hard to read.

tork-calibration.gif (3.79 KiB) Viewed 820 times

[BlackBart]

I seem to live in that f-ing tight to STRIPPED world. Like, click the torque wrench four times to make sure it’s really tight enough to click. Then push a little more “just to make sure.”

But then.... I’ve had tasks like the front crank nut on an Audi 1.8 that required a 4’ alum angle with holes drilled for the three flange bolts to get it to the crazy torque number.....and THEN the book calls for another 1/4 turn!?!

I helped a friend put his 356 P-car crank nut back on. It’s a great big hollow nut. Three of us to hold the engine down on the floor, and me hanging on the end of a long pipe. Something ridiculous like 300 ft-lbs?? We figured we got to about 250 when my nice big NAPA breaker bar sheared off into several pieces. We decided that was “Tight Enough.”

[volvolugnut]

For the really high torque jobs, the pros use a Torque Multiplier tool. This device is added between the fastener and the 3/4 (or 1 inch) leverage bar and will multiple the applied torque by normally 4 times. The only practical way to get over 250 foot- pounds.

volvolugnut

[BlackBart]

Wow, those seem like magic! Is it geared inside, with a racketing mechanism to hold it from backing off?

[darylrobert]

some of the torque specs are funny, for the front sub frame stage one 105nm NOT 100nm because the engine will fall off? but no ambient temperatures given, in freezing to hot weather the torque will be different because the metal shrinks/expands

[abscate]

Torque is a surrogate for clamping force, which has to perform functions of

- stopping stuff from falling off ( fuzzy dice)
- coupling power transfer ( lug bolts, driveshaft bolts)
- providing seal function ( water pump , oil pump l cylinder head bolts)

Clamping force can be critical for either value or evenness , or both, or neither, to a point

When you reuse a bolt that Volvo says to replace, you probably not reaching the design clamping force or damaging the fastener.

The clamping force is a function of the thread wear, thread corrosion, head corrosion, and lubrication.

I just finished a cylinder head cover with 43 M6 bolts. Torque setting from Volvo is 14 Nm, not very tight.

This is a non critical torque for both value and evenness as the clamping force on the cover comes from the sealant, the bolts basically hold the cover on until the glue sets

Underneath are critical value and evenness cylinder head bolts. Can’t mess those up.

[RickHaleParker]

Boy have things changed at MVS. A few years ago I was belittled for using Torque wrenches instead of guesstimating it.

[BlackBart]

Haha! "Tight Enuf!"

Mine only goes down to 20, but I've always figured "anything attached at less than 20 ft-lbs is not going to kill you." An old mechanic once showed me, one hand on the head of a 3/8" ratchet (not a weight lifter, or horsing it) is about 12-15 ft-lbs for spark plugs. That's what I've always used.