HarryMann: It is good practice to make an attempt to tighten most bolts and nuts to a sensible torque for their size,
whilst for some it's very important.
Here are some sensible torque values for the following metric bolts (these are the bolt diameters not the head sizes, which can be found here General ISO Metric threads).
NB. Use specific quoted VW, Haynes or Bentley workshop manual values in preference, if known.
Failing a torque wrench, choosing the right length spanner help limits the torque to sensible amount - but a good tip is always to clean dirty threads and try to repair damaged ones Thread file
Then they give a better feel as they come up to tightness. Ditto clean and flat mating faces help, to clamp parts together sufficiently without horsing up nuts and bolts too much.
NB. Bolts and nuts are primarily torqued up to clamp the parts together sufficiently, not to stop the bolt coming loose.
Metric thread size
Imperial thread size
7/16" dia. 50 to 60 lb-ft
12mm dia. 70 to 80 lb-ft
1/2" dia. 80 to 90 lb-ft
5/8" dia. 110 to 125 lb-ft
- 1 Newton-metre approx 3/4 lb-ft and 1 lb-ft = 1.35582 Newton-metre(N-m)
NB. lb-ft and ft-lb is same thing as is ft-lbf (foot - lb force)
NB. For easy conversions see the Toque Converter in the Links section below
Restricting the spanner size is good way to prevent overtightening, small bolts no more than 6-8". e.g. an M-6 - picture a 20lb weight just resting on end of a 6" spanner = 10 Ft-lbs; a 180 lb wt bloke standing on the end of a 18" power bar, when horizontal (the bar not the bloke!) = 270 lb-ft.
If jerk weight on it rather than slowly put weight on it multiply by 1.5 ~ 1.8 i.e. could be about 500 lb-ft.
Rear hub nut on all T25's - 500 N-m (360 lb-ft) then next split-pin hole
Wheel nuts/bolts on T25's (Lug nuts in the US) - 180 N-m (133 lb-ft)
Front drive-shaft/hub nut (SYNCRO ONLY) - 350 N-m (258 lb-ft)
Wheel-bearing nut correctly for 2WD NON-SYNCRO - Read service manual/instructions to set, do not torque load this nut!
To remove rear hub nut - either shock it loose (General EMPI Rear hub nut spanner) or circa 500 lb-ft could well be required. Follow service instructions on using vehicle weight and wheel on ground to restrain hub movement when loosening.
[Unknown entry] Peening nut on front wheel hub, take off to get to front wheel bearing 27mm, recommend 24" breaker bar (£20 halfords pro) and 27mm impact socket (£9 Halfords also called diesel injector socket)
The reason for tightening to a specified torque is to provide a preload in the bolt or screw. This ensures the joint can transfer the required loads, through its clamping force. Most of the torque goes into overcoming friction both under the head and in the threads, only a small part of this (15-25%) creating the preload in the bolt shank. This means that a) the preload is rarely accurately achieved b) the condition of threads, surface under the bolt/nut heads is important. Washers that are not hardened can crush, unclean, damaged threads mask the correct preload etc. If a reasonable preload is not obtained, bolt/stud failure through fatigue is the most common problem i.e. for important load-carrying screws/bolts, under tightening threatens the long term joint integrity just as much as overtightening. So make some effort to clean the threads, the joint's bearing face (that area under the head) and don't use nuts/bolts/screws with obviously damaged threads or where the bolt is bent or has suffered yield. Spring washers are not very good at preventing loosening and to a large extent, can cause more problems than they solve, often preventing the achievement of adequate preload in the fastener's shank. Don't assume a nut or bolt tightened to a specific torque will undo at or near that same torque, after a few days the torque will be less than the set-production torque, after a few years it could be much more. Generally, torque figures are for clean, dry or lightly lubricated threads. Some spring washers can drastically reduce the clamping force for a given bolt torque.