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MG MG Y Type - Wheel Nut Torque

At a recent discussion with two knowledgeable motor mechanic friends I was told that the 115 Newton Meters that are applied to modern 1/2" wheel nuts are much to high for the Y-type's (3/8"?) nuts.
Applying such a high torque might distort the five conical holes that take up the wheel nuts, leading to a whobly rim. - even more so in combination with the "too small" pitch/hole circle of the Y-type Wheels.

In order to avoid damaged rims, my friends recommend to apply a torque of not higher than 80 Newton Meters! Please let me have your opinions on this recommendation. If you agree, I will have the recommendation published in the "Technical Center" section of this website

Anton, YT 4220

P.S.: Check the attached piture of an old unrestored rim. You can cearly see elongated pitch circle holes.


Anton Piller

45 ft/lbs---61nm is the normal tension for cars with 3/8 studs
IF you have been doing them up to 115nm the studs will be stretched/damaged and need replacing
I strongly recomend tensioning wheel nuts up with a tension wrench--------always
If you ever have to stand up in front of a Judge in court as I have you will need the exact answer and it has to be the right answer
William Revit

Thank you William, for the correct torque of 61 Newton Meters. Luckily, my studs do not seem to be stretched - the wheelnuts fit the studs nicely.
Anton
P.S.: I always use a tension wrench when fitting wheels.

Anton Piller

I have seen a lot of stretched and broken wheel studs in Y-Types over the years. The steel is the studs seems to be ductile (soft) when compared to other MG models. Perhaps the post-war steel available was marginal for this application or the heat-treatment post fabrication not up to grade.

For the last 25 years I have done my wheelnuts to 30ft/lbs with a tension wrench. Never had one come loose, and never broken a stud. I use this setting for both standard wheels and tyres and wide rims with radial tyres. I also tension the wheel nuts with no load on the wheel (jacked up).

The elongated holes in wheels are caused when driving on the wheels with loose nuts - not from over tensioning.

It would be interesting to test a standard wheel stud to destruction & compare it to a couple of modern bolts of known grade to see how "soft" they are.

If you use the factory supplied wheel brace, it is very hard to get even 30ft/lbs on the wheel nuts - try it yourself and you will see what I mean. I think most studs are stretched or broken with impact guns set to 80ft/lbs or more !. I do my own wheel changes, so never run the risk.

Good Luck

Tony Slattery
The Classic Workshop
Black Mountain
Australia
A L SLATTERY

There is already a reference on the webpage to torque settings for wheel nuts in "Technical Data" - "Engine Torque and other settings". It says 50ft/lbs, but this should be used with great care - I have found that 30ft/lbs is more than enough.

Cheers
Tony
A L SLATTERY

As you say Tony , it depends on the material the stud is made from
The only real way to know is to measure the length of a stud and then tighten in 5lb steps till there is 5thou stretch in the stud then this is the correct tension

i mentioned 45ft/lb as that was what was on an old wheelstud chart I had but if the spec in the MG specs is 50, then the spec is 50
(If it's acurate--and where did that spec come from)
50 sounds a lot to me, MGB headstuds are 50 on 3/8 studs and they are at the limit at that

Anton
If you have had yours tweeked up to 115nm then they are stuffed---replace them, they may not look damaged but they are
William Revit

Thank you, Gentlemen

I know now, what to do in the upcomming long winter nights - never a dull moment.
To replace all of the 20 studs & nuts to UNF ones, costs a small fortune at about £ 9.- each (NTG price).

Anton
By the way: I never used an impact gun with the Y's wheel, but I do not know what was used by the previous owners and what torques they applied :o)

Anton Piller

Well I tried your stretch measure exercise Willy on a spare hub with original studs and after applying 50Nm, the stud was 0.2mm shorter, so I think I might have to get a new set of calipers or perhaps a 1-2" micrometer.

I have a few stretched studs to show you Anton - you can see the stretch, so if you look closely & see no damage, I would not be too concerned. Photos later today if I get the chance time wise.

Tony
A L SLATTERY

As Willy has put 45lb (61nm) for 60/70s Spridgets wheel nuts that go on to the (3/8") studs, the torque figure I remember very easily as I've had tyre places cause a couple of stud replacements when they've used the air gun and/or torque wrench preset to (used to be) 70lb (95nm).

The Driver's Handbook for my Midget has 44-46 lbs but 45 is easier to remember.

Of course I suppose it depends on the certified calibration of the torque wrench.
Nigel Atkins


I sent a request to NTG, asking what grade steel is used with their replacement 3/8" UNF studs. The person I wrote to will only be back from Holiday by Tuesday, next week. I'll keep you posted.

Anton
Anton Piller

Dear all

1. This is the reply from NTG's supplier of the 3/8" wheel studs:
The numbers your customer is using are modern references. These have been made and heat treated to achieve 75 tons tensile.
These will there fore be approaching "v" grade this will be kinda 10.9 in new money.
From my personnel opinion I would be happy at setting my torque wrench at about 49 Ft . lbs

2. I was lucky, to finde one of my stashed away spares box with a set of second hand hubs - including studs. My knowledgeable Master Mechanc friend tells me that an easy (if crude) way to check, if the studs are stretched is to screw on the nuts, by hand only, and see if they get fully home without any friction. If they do move freely, one can take it that the studs are OK.
I've done this little test on all these 20 studs and they all look to be fit for use on my YT. What do you think of this method?

3. After all that has been written and said about this topic, what is a sensible torque to tighten the nuts of the original Y-Type wheel studs?

Thank you
Anton, Switzerland



Anton Piller

Anton,
IF your nuts are also original and in good condition, and the holes in the wheels in good condition, then why not try Tony Slattery's tried and tested method.

This does of course assume your torque wrench is reasonably accurate (certificated wrenches are tested annually).

Given what Tony has also put, the most I'd go to is 46lb with the original studs and nuts - again assuming your torque wrench is reasonably accurate at this setting.

You could then of course check your technique for tighten the wheel nuts to each wheel and how you ascertain your final torque setting.

In other words you might be overthinking this, yes it is very important that the wheelnuts remain tight but this may be possible over a range of figures rather than just one.

If your torque wrench is reasonably accurate and studs and nuts in good condition then you could using Tony's method and figure and road test (you would check the tightness anyway after about 30-miles) if more than one or two need more than a nip up then try all at 35lb and repeat test (bearing in mind your torque wrench might be inaccurate and/or unreliable at this setting).

Or do the same but start at 44lb and if required got up to 46lb, with the same caution on the torque wrench at these settings.
Nigel Atkins

One important thing not mentioned is that these torques should be with the threads dry,
Do not lubricate the threads as this will increase any torque used!
Stephen Randle


Nigel and Stephen

46 lbs sound good and will be applied (at the max) when doing the job. My quality "Britool" torque wrench was tested in May of this year: in the upper range it shows 10% too little and in the lower range 5% too little.

The step by stepp increase, when tightening sound interesting and I always do a re-tightening round after about 10 miles.

Thank you for pointing out that the threads must be dry when the torques are applied - a feature that I have been aware of (it shows the differences on the Torque Values sheet of the Y-Types website.

With your assistance, I'll become a Super Mech, thank you

Anton
Anton Piller

Anton,
I am at subterranean level of Mech and tech - but those at the level of rarified air may question any given figure to apply to all cases. :)

At 5% and 10% under on your Britool it does depend how wide its range is and the consistency of the results and of course the accuracy of the testing equipment at that point of testing :)

But say you go for 32lbs on your Britool to allow for 5% too little (if this is in the lower range) and after 10 miles, and any further tests at say 30 and 50 miles, if only one or two nuts need only a nip up over the three tests then I'd stop there and consider Tony's method and torque figure proven on your car.

If the figure is too low I would add 5lbs and repeat tests to a maximum of 45lb or 60nm as these figures are easier to remember and read off a shiny chromed torque wrench.

Let us know how you get on.

Nigel Atkins

Sorry, if it is under you would be going for 28/29lbs on your Britool.

Told you I was low mech and tech. :)
Nigel Atkins

I tryed a very low!! tech method. i used a six legged wheel brace AS used in garages in the fifties. Using both hands on two legs of the brace i did it up as tight as i could go,as the garage would have done. I then put a socket on the wheel nut marked the socket and the wheel with a line then started the t/wrench at 40ft lbs increasing in 5ft lbs segments it reached 65ft lbs before wanting to move the wheel nut. i seem to remember that when working in Central garage Leyburn,a foot!! often took the place of a hand!!mind you wheels never fell off.
John YB0362
JC Jebb


Nigel

My Britool's range is 20 to 100lb/ft. The test was caried out at a promotional event of "Hazet" qualitiy tools. As mentioned before, I will only tackle this job during winter, when I also will exchange the differential of the YT. So do not expect any results too soon.

John

Your method sounds sexy, but makes my head spin. I think, I rather stick to my trusted torque wrench :o)

As I will be leaving for a week long Holiday to Ireland on Friday morning, I might not be able to answer any mails as from tomorrow on.

cheers
Anton, YT 4220
Anton Piller

Anton,
do not believe all you are told about German engineering, they probably got the conversion factors wrong and the Britool is spot-on and their's a little out. :)

Enjoy Ireland.

20-100lb, hmmm, bit wide, pop in to Halfords whilst you're there (UK made) -
https://www.halfords.com/workshop-tools/tools/spanners-wrenches/halfords-advanced-torque-wrench-model-60#
Nigel Atkins

JC --65 ft/lb is too tight

45 ft/lb is the tension you should be aiming for and use your tension wrench

If you tried doing the std. 3/8" headstuds on a Midget or MGB up to 65 you'd soon find out it's too much

-----45-----
William Revit


Dear all

Ireland was windy, but great and so was the traditional music, the traditional pints and the book of Kell. I can recommend the country.

45 is the tension that I will tighten the wheelnuts of my YT from now on. But first, I will exchange the differential, which is on its way from England to Switzerland right now :o)

Have a good one
Anton

P.S.: We returned from Ireland, just in time to participate in a beautiful scenic Swiss mountai drive. Natasha, the dog wears a governement approved safety belt...


Anton Piller

This thread was discussed between 19/08/2019 and 15/09/2019

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