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MG MGA - Lost an eared knock-off wheel nut due to stress!

I am interested if anyone has had this same experience. I hear a fellow club member (name suppressed to protect the innocent) lost a knock-off wheel nut (and wheel) while participating in a recent hill climb - slid along the road on the brake drum! This was no ordinary MGA - 1800 worked motor, lowered, LSD and 5.5" rims with Dunlop Direzza tyres (sticky). It appears the knock-off nut popped off the the adapter thread - suspicion is that the thread on the knock-off was worn. Even so it sounds scary - has anyone heard of similar problems?
Mike
Mike Ellsmore (1)

Mike

I might be asking the obvious, but did he have the correctly handed hub on? When fitted on the wrong side they have been known to come undone.

Steve
Steve Gyles

Mike. Yes, that is one of the other, less common, problems with wire wheels. Broken spokes, out of round, spoke flex, and weight are the more commonly cited problems. But, I had a friend who lost a wire wheel while coming to a stop one time. I had a second friend who had an A-H 100 with a high performance engine which would loosen the spinners on acceleration.

As you know, the spinners, in theory, will tighten on braking when the hubs are installed on the correct sides. What many do not realize is that they can loosen when the ability to accelerate is increased beyond the design specification of the hubs. I have seen several wire wheel spinners that had been safety wired to the wheel for use in competition or fast driving. If the car is to be used in competition, and the spinners not safety wired in place, they spinners should be checked for tightness on a regular basis. What defines how often this will be necessary is based on experience--be careful to check too frequently, extending the time period only slightly, until you get to the point where you have about one quarter turn of looseness. At that point, shorten the time interval to the last one which showed less than one quarter turn of looseness.

But, in normal driving, with the hubs on the correct sides and the spinners correctly tightened, you should never have a problem with spinner loss. I never did over many thousands of miles of normal, road driving.

Les
Les Bengtson

I lost a spinner and wheel one time. I had been hearing a sort of ratcheting sound when I came to a stop and promised myself that I'd look at it when I got home. I braked as I approached a stop sign and the front left wheel went rolling down the road without me.

The problem was worn out splines on the hub and wheel. The ratcheting was the splines slipping past each other. New hub and wheel and no problems in the last 5 years.

Randy
Randy Myers

Mike, I've never heard of the threads failing on a knock off nut, but I guess it's possible. Perhaps that's why MG went to a heavier coarse thread on the MGBs with the 8 turn per inch thread instead of the 12 turn fine thread of the MGAs.
Bill Young

As this thread concerns my car I thought I might add some more detail. The hubs and spinners were on the correct side of the car. All spinners were knocked on very tightly before the run. The RH front wheel came off on a very hard left hand hairpin bend on the hillclimb. I heard the spinner clink on the bitumen but did not realize that it was the spinner. Shortly after there was a gently right hand curve and half way through this the front right dropped on to the rotor with the a grinding sound and the wheel appeared at my elbow. I concentrated on keeping on the track, as there was a severe drop off to my left, and brought the car to a stop. The wheel did a little damage to the wheel arch and of course the rotor showed signs of where it had run along the roadway but is still true. We looked for the wheel in the ditch beside the track but to no avail and it was finally located about 15 metres up the RH embankment and was unmarked. I subsequently heard from the marshalls on the previous corner, which was a hairpin to the right, that they had heard something "let go" whilst I was cornering. This was probably the spinner slipping off the thread. On recovering the car we noted that the spinner (brass) was quite sloppy on the hub, even after a few turns, although it still tightened up OK. The brass spinners are now paperweights and I have a replacement set of stainless steel spinners which are very firm on the hub thread. The car is booked in next week to have the axle crack tested and the front end integrity and alignment checked. It should be back on the track to give the originator of this thread some curry in the near future!


Mike Ellsmore (1)

Above is my "fellow club member" writing under my sign in - I am not sure how he did that from another computer, I must ask!

Anyway he did not write anything slanderous and now you have the full scary story - it looks like we need to take the micrometers to the spinner and the adaptor to see what difference is - does anyone have the correct dimensions for these threaded areas - OD and ID?

Regards
Mike
Mike Ellsmore (1)

Mike, this might be what you need. I'm pretty sure that all the MG hubs are Rudge type 52
http://www.wirewheels.co.uk/wornhub.htm
Bill Young

Thanks Bill,
That is just what we needed, the good old "go, no go" gauge dimensions for the thread and lock nut. It may be worth our club getting a set made so everyone can check their wheels.
Regards
Mike
Mike Ellsmore (1)

Reading the details on http://www.wirewheels.co.uk/wornhub.htm more closely it appears there could be two size nuts in use, one for use on worn rethreaded adaptors - I have not heard of this before.
Mike
Mike Ellsmore (1)

I hadn't either, but figure that since MG knock offs and hubs are so available it wouldn't apply to those as much as to some of the really rare cars which came with wire wheels. For us, if the parts are worn we can just order new ones from Moss or such without problem. May not be the case for something like a Riley or Singer. There you might have to have the special nuts made to save a hub. Evidently this company builds wheels and hubs for some really rare stuff as well as our "run of the mill" MGs.
Bill Young

More questions,
Does anyone know for sure whether original MGA wire wheel hubs were Rudge-Whitworth Type 42 (a rough check of the dimensions show mine are slightly larger than that shown on http://www.wirewheels.co.uk/wornhub.htm for Type 42 and a lot smaller than Type 52?

Does anyone have the original dimensions for nut and hub threads?

Were the original spinner nuts made of brass or steel (mine are steel, chromed - magnetic)? Were they ever made out of stainless steel as someone locals here suggested?

Do you know the thread angle originally - was it 55 deg (Whit) or 60 deg (Unified). What threads are the Moss adaptors and spinners? (my nuts and adaptors are 12 TPI).

Regards
Mike

Mike Ellsmore (1)

I've never heard of a spinner failing either. I wonder if the spinner somehow came loose, and the abuse of cornering then damaged the threads while they had no grip. That could account for the looseness they now show on the threads. Regardless, I would be looking into a new set of hubs AND spinners.

I believe early MG spinners were stainless, and changed to brass sometime around the MGA.
Steve S

I should also have noted that spinners coming loose are almost always due to worn splines, which allow the wheel to twist forward and back on the hub. Having them on the wrong side can of course do it also, but this isn't as common a problem.
Steve S

Mike, you are correct and my memory was at fault. MG hubs are indeed the type 42 Rudge. Here it is in print on the price page for the special (Turrino)aluminium wheels. http://www.wirewheels.co.uk/turrinop.htm
Scan down the page to MG and it shows two sizes for the MGA and lists both as a type 42 hub. Wow, we could have polished alloy rim wheels for only 595 pounds each, what a deal!
I've heard of both brass and steel knock off nuts, but never stainless steel. I believe that the brass items were original and most common. I think the steel nuts are aftermarket items. I have never seen stainless steel knock offs listed through any of the wire wheel dealers I've checked on line. That would be great though, no worry about chrome plating peeling if you damage the wing with the hammer.
Bill Young

I had a couple of knock-off spinners come loose many years ago due to worn splines. The previous owner had used a steel sledge to remove and replace the knock-offs. But I never lost a wheel. In fact, the wheels were nearly impossible to remove from the hub after they had spun on the splines. One of the wheels went to the scrap yard still entwined with the hub. I have bolt-on wheels now.

Ken
k v morton

Stainless steel hubs still have the problem that they can gall on the thread area. I don't know but Brass sounds best to me.
mike parker

The Twin-Cam MGA used steel knock-offs for racing.
Twin-Cam wheels are interesting as they are located by pegs rather than splines. I have them on my ZA Magnette. I do the brass knock-offs up very tight and have found no tendancy to loosen at all. Many people seem to be more concerned about the finish on their knock-offs rather than getting them knocked up tight. I use a 2lb Thor hammer and don't spare the welly when tightening them. I previously used a lead hammer and foundc that it deformed easily and didn't tighten as much as I liked.

Rich


Rich McKIe

I do not agree with all this excessive tightening. All it does is deform the tapered surfaces on the wheel, which are not all that strong.
You will soon have the inside taper spread open until the wheel center contacts the non-tapered surface of the hub, and then you will be wondering why you have to keep applying more, and ever more, force to keep them tight.
Only the wire wheels have an inner taper, the Twin Cam wheel does not, but both wheels will suffer problems with the wheel outer tapered surfaced being forced inwards.
I seat the spinners with light taps and then only two medium hits to finish, with a brass hammer.
I have never had a spinner come loose on a MGA, a Triumph, nor a Jaguar. They all become tighter after some driving. Also, tighter after only a few laps of racing.
There are many books and articles on the self-tightening of wheel spinners, and why they have left hand and right hand threads on opposite sides.

Mick
M F Anderson

The inexpensive dead blow plastic coated hammers are becomming more popular for knock off tightening these days. Don't mar the ears and protects the finish of the wheel if you might miss. A 3 or 4 pound hammer seems to do a great job on the nuts.


Bill Young

I agree with Mick. It seems to be overtightening the knock-offs that begins the downward spiral to deformed and self-loosening knock-offs.

Ken
k v morton

This thread was discussed between 01/03/2009 and 07/03/2009

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