DB18 Torque Values

[Mark Bullen]

Firstly thank you to everyone for your replies.

In reviewing what the feedback is i either have 5/8" BSF or BSW (the car is social distancing so can't walk out and check it) and this looks like either 64 of 66 ftlbs according to Jag Lovers, which in metric is 90 Nm which is a bit less than the the bolts I did on a Polo at the weekend (120Nm).

As an engineer (by education rather than trade and hence lots of experience) i am always keen to keep to the specification and it never ceases to amaze me how tight (people without mechanical sympathy) can do up nuts and bolts. Im going to approach the torque in stages and 'feel' what its like.

I wonder if the relatively small tools (its really a bit and brace type of tool) to do the wheels with, reflects that many of these cars could have been chauffeur driven and as such somebody relatively experienced would have been employed for the task?

[Noelex]

A good many people overtighten wheel nuts. And the definition of tight varies significantly between people. But DB18s have relatively large nuts and fine threads so I use a special heavy duty socket and bar but I only tighten them so that nuts are firm never brute force tight. But the best thing you can do in my experience is to periodically walk around with your proper wheel brace and check the nuts! If some are loose assuming threads are okay then you need to apply more torque! Ps standard auto wheel braces dont fit.

[Chris_R]

Also, clean and dry threads and dry nuts.

[John-B]

Also, clean and dry threads and dry nuts.

That's very important!
When I worked in the Falklands we had about 100 landrovers and a very muddy winter. Several people found that wheel nuts worked so loose that they came off and disappeared in the mud. One or two people noticed that a wheel came off and followed them along the road! (Muddy hardcore tracks actually.) I was driving once and heard a rattling from a front wheel. We stopped and found that all nuts had worked so loose they were nearly off.
Leyland, who maintained the landrovers, ran out of nuts and people were stealing one or two from other landrovers. A big joke to all of us, but could have been dangerous.

The cause was wheel sockets that were muddy when nuts were tightened. As vehicles moved, the film of mud worked itself out and nuts started to unscrew.

[Christopher Storey]

Brian H : please do not equate modern high tensile wheel bolts with those of a car designed before WW2 . The advice you have given may well be dangerous , because applying torque appropriate to the modern era to an old car will probably stretch the stud , and this leads to unscrewing of the nut(s) and even if the wheel does not come off the car will become dangerously unstable . I would have thought that anything between 35 and 50 ft/lb would be sufficient

[John-B]

... applying torque appropriate to the modern era to an old car will probably stretch the stud , and this leads to unscrewing of the nut(s) and even if the wheel does not come off the car will become dangerously unstable . I would have thought that anything between 35 and 50 ft/lb would be sufficient

Old steel wheels often get a split in the socket by over-tightening nuts. I've got one wheel where a small split has been welded up.

[Brian-H]

Brian H : please do not equate modern high tensile wheel bolts with those of a car designed before WW2 . The advice you have given may well be dangerous , because applying torque appropriate to the modern era to an old car will probably stretch the stud , and this leads to unscrewing of the nut(s) and even if the wheel does not come off the car will become dangerously unstable . I would have thought that anything between 35 and 50 ft/lb would be sufficient

Well at the end of the first page of this thread, I did concur with Steve (qantasqf1) who said that "if Daimler thought 80 ft lbs (which is pretty damn tight) was the torque required for the wheel nuts then surely they would have supplied a wheel brace about twice the size of the one they actually supplied.". So there is no need to lambaste me in such a fashion.

Also, just because it was designed before WW2 does not mean that the spec was as low as 35 lbf.ft . I say this because, if other studs and set screws in the vehicle are of higher torque (e.g. main bearings) then why would they specify such a poor material to the manufacturer of the wheel studs ?

Note that other people have suggested 64 lbf.ft which is not far off my 80 lbf.ft with which you have taken exception to (and, as I've just said, I did later concur that 80 lbf.ft may be a tad high).

I'd also like to know where these figures of 35 lbf.ft or 50 lbf.ft are coming from (out of genuine curiosity, I've spent a while looking for on the internet and can't find it anywhere else).

Finally, I suspect that the real issue may not be in the studs or nuts, but in the rims.

Old steel wheels often get a split in the socket by over-tightening nuts. I've got one wheel where a small split has been welded up.

This is most likely where any issue would be found on these cars, which is, deformation of the conical/spherical seat in the rim where the nut seats itself. In other words, relative to modern cars, it's probably the rims that are "lower grade".
Note also that nobody has mentioned the equally important tightening pattern.

[Chris_R]

It seems perhaps Daimler did not publish wheel nut tightening torque values, there is nothing in my Majestic Major workshop manual except "tighten the road wheel nuts".
I have a Jensen Interceptor. The factory recommendation for wheel nuts is 50lb ft. This was to avoid stretching the wheel studs.
As I said earlier, dry threads and dry nuts are important. About 85% of the torque value goes to overcoming friction, the rest going into the clamping force. Lubricating the threads reduces the turning friction meaning more of the tightening forces are translated into the clamping force and which is quite possibly where damage to the stud holes arises. It will also make them easier to come undone due to less friction against them turning.
I would suggest 50lb ft with clean dry threads and no lubrication under the nut will be quite adequate and not at all excessive.

[Brian-H]

FWIW I spent a couple hours yesterday evening using Google and come up with a lot of varying specs on wheel tightening torques on vintage cars. Note that I looked at specific workshop manual references, not just "I use this torque".

The problem with Google is that it tries to tune itself to what it thinks you're looking for, so you have to force it to "learn" what you want. After several iterations the following search term started to produce results "vintage" lug nut torque -wire -rebuilding
However , that mostly brings up info on vintage cars in the USA

1942 Maintenance Manual Willys MB 4x4 (aka Jeep) .... 60-70 ft-lbs tighten every 1000 miles
Ford Early V8 (1932-53) ..................1949-1951 Ford shop manual- 65-75 ft.lbs
S.California Classic Cars ..................MK III Midget manual - lugs should be checked weekly with a torque wrench set 44 to 46 ft lb
Vintage Volkswagen Bolt Torque Specifications .... Reference page including Wheel Studs ("lug nuts") 80-90 ft. lbs.
Beetle 1958-1967 ...........................Right out of the manual: Four-bolt pattern 87 to 94 ft. lbs ..... Five-bolt pattern 72 ft. lbs.
Vintage Mustang Forum ..................Ford Shop Manual for '66. Page 3-50. Shows wheel lug nuts for 5 Lug Wheel as 70-115 Ft. Lbs.
Vintage Chevrolet Club ..............................1937-1941 80 to 100 ft. lbs.


The main problem with UK "vintage" car forums, is that they don't use the word "vintage". For that reason it's a tedious searching of various marques and models from the 1950s (e.g. Austin Seven, Austin A40, BSA, Ford Consul, Hillman Minx, MG Midget, Triumph Mayflower, Vauxhall Wyvern) which didn't produce much from 1950s, mostly 1960s or even 1970s

Of several that I found, most of them didn't quote workshop manuals, here's a few that did

Trumph TR6 ROM Ref 545277/E2 section 74 Wheels & Tyres, sub section74-20-01: it is mentioned "Chrome plated dome nuts tightened to 60 to 80 lbf-ft"

British Car Forum Healey Sprite and MG Midget - a reference to this url https://www.gglotus.org/ggtech/wheel-stud/lugtorque.htm screenshot below

MG Midget and Sprite Quite a few references to wheel torque specs in various manuals, mostly at the lower end

AUSTIN HEALEY Bolt Pattern Cross Reference and Wheel Sizes Useful info on types of lug nut

EDIT - adjustments to attachments

[Brian-H]

Firstly thank you to everyone for your replies.

In reviewing what the feedback is i either have 5/8" BSF or BSW (the car is social distancing so can't walk out and check it) and this looks like either 64 of 66 ftlbs according to Jag Lovers, which in metric is 90 Nm which is a bit less than the the bolts I did on a Polo at the weekend (120Nm).

As an engineer (by education rather than trade and hence lots of experience) i am always keen to keep to the specification and it never ceases to amaze me how tight (people without mechanical sympathy) can do up nuts and bolts. Im going to approach the torque in stages and 'feel' what its like.

I wonder if the relatively small tools (its really a bit and brace type of tool) to do the wheels with, reflects that many of these cars could have been chauffeur driven and as such somebody relatively experienced would have been employed for the task?

Sorry if I'm somewhat preempting you Mark with the following.

Realising that my grandfather's Consort hasn't moved very far under its own power since the early 90's, I suddenly remembered having new tyres fitted previous to that. I obtained 4 new tyres and inner tubes from V. Boyd-carpenter and I've found the letter from him in which he recommended that I take the car to Nationaltyres in Nottingham, ask for the manager, mention Boyd-carpnter to the manager, and get them to fit the new tyres. That letter is dated August 1988



None of the wheels has been off since then, the car did about 2000 miles on those wheels up to the early 90's, after which it essentially became mothballed.


I've been out with my torque wrench and checked the torque by undoing each nut on two wheels very slightly. They all moved at around 60 ft.lbs. I then moved them back to position using the torque wrench.

Then I tried to undo them with the car's wheel brace and, with a bit of difficulty, I managed to undo them (some budged more easily than others). Then I tried to do them back up to the same position using the wheel brace, and with great difficulty I managed to do that.

It's possible that the manager at Nationaltyres Nottingham knew what the correct tightening torque should be. Either way, it looks like 60 ft.lbs had been used. I did try to take a couple of nuts a bit further using the torque wrench, .at 65 ft.lbs they'd only moved a few degrees further. So I'd say that 70 ft.lbs or beyond is well out of the question, and 60 is absolute max.