DB18 Torque Values

[Mark Bullen]

Does anyone have a list of torque values for the DB18. I'm mostly interested in wheel nut value as I've changed a wheel. I've tried the usual sources David Beale manual, DB18.org and this website but nothing has come to light.
Any help gratefully received.

[Bob Frisby]

I have a couple of manuals for Daimlers of the era, and neither shows the wheel bolt torque. But the best sources for such info are the various charts of fastener info, available on the web (via Google) or in general engineering manuals. You'll need the diameter and pitch of the wheel stud. If you don't have a grade value, you'll have to use the lowest, which is probably correct anyway, for these wheel studs. These charts in general apply to all applications (not just wheel studs).

My DF302 Empress II has 5/8" BSW threads. According to the chart found on the "Jag-Lovers" forum, the proper torque is 64 ft-lb.

Bob Frisby
Boise, Idaho USA
DB18 Empress, DF302 Empress, and other old Brit iron

[grahamemmett]

This question was asked before and the best answer was:
“Bloody tight but not so bloody tight you can’t undo them at the side of the road”

Not bad advice.

[Sydsmith]

The old adage was as tight as you can get them with the cars original wheel brace, as Graham says, always worked for me never had a wheel come off.

How often do you see the AA changing a wheel for members these days, that's because the driver cant remove the wheel nuts, or studs as most are these days, because they are too tight for the brace supplied, I carry an old torque wrench with a long arm on it. Syd

[Brian-H]

I've got one of these (extendable wheel brace)



In the image below, shortened for righty-tighty is on the left, extended for lefty-loosey is on the right (or if you never want to undo a wheel nut ever again, righty-tighty is also on the right)



Available from screwfix, eurocarparts, ebay, amzon for ~£10 (usually including sockets)

[Stan Thomas]

Wheel nut torque:

35 lbs/ft or 52kgm or 52Nm.

Do not severely overtighten otherwise they will come loose.

[qantasqf1]

Absolutely right, Syd. The wheel brace supplied with the DB18 has an effective radius of around 8”, maybe less. That’s pretty much the same with all UK cars so the message is wheel nuts don’t need to be very tight and I wince every time I see a mechanic on the end of a rattle gun torquing the hell out of them. It’s completely unnecessary and a thoroughly bad practice. The thread specification of the DB18 wheel nuts is 5/8” BSF.
Steve

[Brian-H]

I feel Driven (or is there something Driving) to give the correct answers LOL

Wheel nut torque:

35 lbs/ft or 52kgm or 52Nm.

Do not severely overtighten otherwise they will come loose.

At 52kgm they wouldn't come loose - the threads would strip !!!

Fully extended, those "telescopic braces" are about 50cm, so 52kgm would require 100kg at the end of that particular 50cm "brace" i.e. a 16 stone person standing on the end !! Nobody was suggesting that !!



In fact, there is a label on those which says "IMPORTANT! DO NOT TIGHTEN NUTS WITH WRENCH EXTENDED"



My quip "or if you never want to undo a wheel nut ever again, righty-tighty is also on the right" was actually a warning not to do such. The issues with over-tightening are either 1. some degree of thread stretch 2. thread stripping 3. stud snapping. Whichever of those occurs depends on the amount of over-tightening and the quality of the stud/nut. But you try explaining that to a youngster who's not been driving for long !!

Anyway, what you've done is converted linear mass density rather than torque.

i.e. 35 lbs/ft is not the same as 35 lbf.ft , the former is linear density, the latter is torque.

So yes -- 35 lbs/ft = 52 kg/m --- but in no way can you convert lbs/ft to kg.m

Indeed (using the correct nomenclature for torque) --- 35 lbf.ft = 4.84 kgf.m (= the torque of a typical 6 month baby held at arm's length)

But, I must say that 35 lbf.ft is too low, and 52 kgf.m is too high (and I don't know which one was derived from where)

For my modern car with 5-stud alloys with slightly smaller studs/nuts, it's recommended in the handbook as 108 N.m (11 kgf.m or 80 lbf.ft) and, unless Daimler were making their studs/nuts out of the same material used in the titanic rivets, I'd go with that torque setting.

Absolutely right, Syd. The wheel brace supplied with the DB18 has an effective radius of around 8”, maybe less. That’s pretty much the same with all UK cars so the message is wheel nuts don’t need to be very tight and I wince every time I see a mechanic on the end of a rattle gun torquing the hell out of them. It’s completely unnecessary and a thoroughly bad practice. The thread specification of the DB18 wheel nuts is 5/8” BSF.
Steve

The picture below shows the wheel brace supplied with my Consort alongside the "telescopic brace". I know which one I prefer for compactness and ease of use.




Brace radius - the wheel brace supplied with my Consort is 6 inch radius , the un-extended telescopic brace is close to double that. This makes it easier to tighten the nuts up to about 80 lbf.ft




The socket I use is 9/16 WW.




EDIT: a useful pdf for modern cars (and as I say, I don't see why Daimler would use anything dissimilar for a car of similar car mass, wheel size, and stud size)

https://blobs.continental-tires.com/www ... s-data.pdf

To roughly convert N.m to kgf.m , divide by 10.
To roughly convert N.m to lbf.ft , divide by 4 then multiply by 3.

[qantasqf1]

Er...quite. 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.
Steve

[Brian-H]

I think that you're right. But 35 lbf.ft does sound low. I'd like to know if there's an "official" spec somewhere, I can't find a spec in the Consort owners book, nor in the Conquest service manual. Probably use “Bloody tight but not so bloody tight you can’t undo them at the side of the road” if using the brace supplied with the car, and, “not quite bloody tight if using a telescopic brace un-extended".