Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) 5 Stud Wheel torque for a 2009 Roadster

Could anyone help me regarding the wheel torque for 5 stud wheels on my Morgan 2009 Roaster, I have seen on a Morgan site that it should be 65 lb/ft but my local garage say's that this is far too high, can anyone give me some advice please

Andy

I set mine to 65 to 70 ft/lbs as per my 1974 Plus Eight factory handbook. Are you sure that your garage isn't referring to an Nms figure?

Incidentally, your wheels should have five ferruled inserts that sit in the wheel around each stud hole. The wheelnuts bear on these and not directly on the aluminium of the wheel.

Hope that this helps. David.

65 lbs ft was also the setting for MGBV8 alloys (with sleeve nuts), and a setting I also use on the VW.

If you have a 2009 Roadster, the figure is in your handbook. From memory it's something like 82Nm / 60 lbs/ft.

Most modern cars (Not sure if Morgan has caught up) specify between 80-85 ft lbs. At the track most recommend running 85-90 ft lbs. Is there a reason Morgan would be much lower? The studs shouldn't stretch unless they're just bad metal.

I have spin ons.

I've not heard of anyone historically having problems with the nuts coming loose at the recommended torque so I guess Morgan have got it right. They've been using the alloys for 4 decades now.

Google "recommended torque 7/16 UNF" - the thread size used on Morgan 5 stud wheels. The studs will be high grade steel and the google results will show a torque setting of circa 65 to 70 ft/lbs.

The torque setting is relative to the diameter of the stud or screw, its material grade and its inherrent stretch.

65 to 70 ft/lbs is the setting that I've always used whether for road use or over 10 years of circuit racing, sprinting and hillclimbing in my Plus Eight.

Personally, I wouldn't use higher torque as this increases the load on the thread; go too far beyond and you will reduce the elasticity of the material, weakening it and risk stripping the threads. Overtightening will also risk splitting the inserts that provide the face on to which the wheel nuts tighten. I have had a few split over the years and once damaged compromise the wheel nut's ability. Always replace damaged ones asap.

As an aside, for those inclined to use stainless fasteners on suspension components, think carefully before you use them. Stainless has a much lower elasticity than steel graded fasteners; it's the elasticity that holds enerything tight. Stainless used in applications subjected to vibration and stress is a less reliable material for holding components together. It's also more inclined to fatigue, fracture and shear.

I agree.

Majority of the common stainless steel have an elastic limit around 22 kg/mm², generaly 50% less than common lower quality steel. The class of a quality screw is indicated on the head, by exemple 8/8, this means breaking limit 8*10= 80 kg/mm² and elasticity limit 8*8 = 64 kg/mm². Unmarked screw, low quality, correspond to a 4/8 class, this means an elastic limit of 4*8= 32 kg/mm²... 50% higher than common stainless steel. It exists higher quality of stainless steel, but difficult to find and used by exemple for nuclear or offshore pièces of equipment.

Well now I know!! Seriously, it's useful information. Stainless is good but there are applications where it is unadvisable. Thanks for sharing this!