I'm used to seeing tightening torques listed with a "plus or minus" value, e.g. "89 +/- 7 ft.lbs." But what does this mean: "22 - 4 ft.lbs"?

 

I have a torque sheer spec page ,

What bolt are you refering to

maybe I can help

Thanks
victor

 

I haven't seen that convention before for torque, but at least for dimensional tolerancing that looks like 22 +0/-4, which is sort of like 20 +/-2, but biased to the upper end of the torque range.

At least that's what it looks like to me, but again I haven't seen a torque called out that way.

 

Page 340-15 in the Bentley manual (Brake pads, calipers and rotors) gives:
That's kind of what I'm guessing, too...

 

It looks more like 18 to 22 ft/LBS

If you have a accurate torque wrench, I woulg go 22.

Victor

 

Looks like 22-24 ie 22-4.I think they are showing a range of acceptable torque.That to me makes more since,+ or - 4 would be too large a range ie 18-26.

 

With the benefit of reading a few other posts, I interpret it as tighten to 30.5nm or 22.4ft/lbs.

30.5nm is 22.4ft/lbs (22.49ft/lbs).

Sometimes, when a document is translated, numbering schemes, decimal usage, gets kinda goofed up.

I suspect this is what's happened here. 30-5 and 22-4 are not implying a +0/-n torque tolerance, but simply giving one the values in both units.

Sincerely,

RockC.

 

That's an interesting interpretation that hadn't occured to me. Not sure what you mean by "translated." The MINI is an English car and the Bentley manual is published in America.

Besides, I've never seen a hyphen used as a decimal point. (Though some Europeans use commas, I believe.) I mistyped the way it appears in my earlier post above. In the manual, it is very clearly given as: "22(space)hyphen(space)4" not "22-4" (without spaces). And in other parts of the manual, periods are used as decimal points, the way an American would expect. For example, on page 340-32, the gap between the parking brake actuator lever and the notched pin is listed as:(Note the correct "American" use of the period as decimal point, with hyphens to denote a range.)

After further digging in the manual, I'm beginning to suspect that pooch1 might have the right answer. See, for instance, page 340-41, where it gives the tightening torque for the "heat shield to plastic bulkhead" as:Interpreting the hyphen as a "minus" (as DiD and I did) would make nonsense of the last line above.

I take a short cut like this all the time - for example, "see pages 41-7" to mean "41 to 47" in casual correspondence at work. But I'm surprised to see engineers being this casual with something as critical as torque specs. (And, as far as I know, this notation isn't an established "convention.")

Anyway, I just had my torque wrench calibrated. I'm going with 22 ft-lbs. At least I know that's right!

 

Actually it's a german car that is translated to british english, then translated to american english. Some of the programming directions/descriptions are absolutely maddening and can bring your veiw of symantics to a whole new light.

Just set the wrench to the first number, most people I've seen don't even use torque wrenches. Unless the bolt/nut is self locking (not the plastic lined, but oval nut or stretch bolts) then bottom out and turn 1/8 to 1/4 of a turn. This will usally get you right there. Also, I suspect that most people will cause problems over tightening not under.

 

If anyone is still interested, I went over to Bentley's website and discovered that they have a forum there. The definitive answer is what Dave suggested: 22 ft-lbs is the optimal number, but anywhere from 18 to 22 ft-lbs is acceptable.