I thought this might be of interest: Sorry it's a bit wordy.
Torques settings are always a matter for wide ranging discussion and as time goes on perhaps even more so due to the fact that older engineers are reducing in numbers and newer ones or even DIY maintenance guys are increasing in numbers, (thus these guys are more likely to do it by the book without ever trying to do it by feel)
So, as an older type my instincts have shifted over the years depending on what I am doing. As someone here has said already things like big ends, cylinder head bolts etc are almost sacrosanct and always torqued up correctly.
So what about the rest of the car?
Wheels - Torque for alloys is never a bad practice given the structure and material of these wheels. In turn why would you not torque a steel wheel? A pattern of bolts tightened to the same setting ensures that all parts in that assembly are stressed the same, or under the same pressure. Just as you would do so for a cylinder head. An alloy wheel can fail catastrophically, suddenly and a steel wheel might 'fret' and perhaps suffer fatigue around a fixing point - neither is desirable.
Brake callipers and frame to hub bolts - Some brake frame to hub bolts are old style and therefore wired but again you would still tighten the bolts correctly before wire locking them, so why not torque them? Brakes save your life!
Brake frame to carrier bolts although these are newer than the old non sliding frame types but if you have this type then these bolts you will find are smaller diameter as low as 8mm and the smaller the size the more important the accuracy of the tightening process becomes. (doing this by feel on a smaller size can easily be as much as +or- 40% out. Much harder on larger sizes to be this much out from the correct torque range.
Any suspension or steering bolt should be as correct as you can get it (a track rod lock nut has to be torqued with a special torque wrench able to use a 'crows foot' head. Most other nuts and bolts on suspension & steering are usually able to be torqued up.
As someone who has been tightening bolts all my life I think I can get fairly close to the correct specifications so why do I bother to torque things up? Well that is easy, I know that if I do so I can sleep at night safe in the knowledge that it is correct to specification. Particularly that is on a car that belongs to someone else.
Are there alternatives or things that mitigate not using torque values?
Yes - (to a degree) Locking devices can be used, tab washers, wire locking, locking compounds and instinct / experience. All of these (except the last) work best if the bolt is done up right in the first place. Doing something up too much can lead to fractures, potentially catastrophic indeed! The bigger the muscles the bigger the likelihood of 'it's blooming tight' might be too tight. (not to mention that the older you get the weaker your muscles are, your brain doesn't seem to understand this)
There is another factor to consider the condition of the threaded components- Are they new, old and cleaned up, old and not cleaned up, good quality, poor quality, compatible or incompatible material (e.g. a stainless nut on a grade 8.8 steel bolt). All of these things are again down to availability of new source fixings, sometimes time constraints, experience when looking at wear and tear / stretch / fit etc. Cleanliness is key in how a bolt will do up and torque correctly. (and a dirty bolt will not lock properly with a compound)
As engineers we all learn as we grow through life experiences. It is not 'Namby Pamby' to use the correct tools in the correct applications primarily when safety is a key factor. I use a check list to make sure that the car is right before I drive it.
So I say 'Torque if you can and if you can't because of lacking equipment or knowledge then ask yourself should you seek advice'. Or if you have to ask are there torques for particular fixings then you do need to take advice!
Old hands are the bedrock of home engineering and maintenance but they too can learn new tricks. After all if you don't tighten some component in a washing machine then it might go 'Bang' but 70MPH in a Morgan might end very differently if something fails.
Last edited by Steve Rose; 20/05/21 06:40 PM. Reason: Correction to context
