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MG MGB Technical - Mystery Nuts or Change Back to Levers?

Am still stripping back the rear suspension on my B and have been told that the rear suspension tube shock conversion is now illegal within the context of an MOT pass. Apparently this is because the lower fixing hangs down below the leaf spring by 2-3", which is no longer considered safe, and new kits use shorter shocks bolted straight to the original rebound strap eyeplate. On top of this I'm struggling to find a source of 1/2" 16-pitch nylock nuts to replace those that came off when I stripped the shocks down.

Can anyone suggest a supplier for these nylocks? Alternatively, since the setup is apparently not legal, what's the feeling on converting back to lever arms at the rear? It's going to be costly but then so will buying new tube shocks and fixings to bring the setup back to legality.

I have to say though that I had the car for 5 years passing MOT after MOT, and nobody mentioned the rear shock system (including an mg specialist).

Thoughts?
A Riddett

As far as I am aware that is rubbish. If you are not in too much of a rush I will check: and yes I am a tester! I assume the fixing is the original mount (as used for lever arm links) that is usually reversed (side to side)for tube shocks. As a matter of opinion I would not want shocks bolted to the rebound eyebolt fixing-many of which are badly corroded.. The mount is at least bolted round the axle.

Michael
Michael Beswick

Michael, brilliant, thank you. The mount isn't an original though, it's an aftermarket piece that bolts in place of the original shock absorber bracket. I've attached a picture of that bracket.


A Riddett

Try this

http://www.transportoffice.gov.uk/crt/doitonline/bl/mottestingmanualsandguides/mottestingmanualsandguides.htm

You are Class 4. look at 2.4 Suspension general.

As far as I can see the only thing is if the bracket has been modified in such a way as to be weakened.

Alternatively if the car is so low as to be unable to get on the ramps/over the pit,they can refuse to test it. (This would equally apply to a low exhaust etc). The scheme says a Fail certificate must be issued with the reason given as "Refusal to Test" (possibly with a reason in the narrative part. A third reason is that they simply don't want to test the car.


Your part is not standard but it is not within the scope of the MOT scheme for a tester to judge that (even assuming he knew).

FWIW I have never heard of bolting the shock to the rebound rubber fixing. Apart from anything else how do you refit the rebound rubber. (Tho technically the rubber should not fail the test by it's absence). See tube shock offerings from MGOC, Moss, and most others. I assume your bracket (which does appear to mount the shock lower) is fitted to allow more standard modern adjustable shocks to be fitted. Or perhaps it is just an old arrangement, before the current crop of parts were designed.

I would ask the tester to explain what section of the MOT test manual prohibits this fitting. Or more practical, take it somewhere else. Remember you can have it tested whenever you like (for the fee and it will be dated for 12 months from that date).In any event you can do it within 29 or 30? days before the expiry of the current MOT. Should it fail you still have time (and an MOT) to "fix" it. Tho if the car is "unoadworthy" due to the "defect" you are still liable and your insurance may not cover you.

I would advise against "making a stand" by having the tester failing it and then appealing (as is your right). Appeals tend to take a while to set up, during which time you cannot use the car.


Michael Beswick

Michael, fantastic - that site is now bookmarked! I agree, I can't see why the design would fail the MOT and based on previous passes, no reason why it should in future.

For info, the upper end of the shock is bolted to a plate where the lever arm unit used to be, nowhere near the bump/rebound stops which are still in place (and also renewed). The shock thus runs down following the line of the original rebound strap, but the lower eye ends up sitting, as I said, about 2-3" below the level of the leaf spring on that bolt in the picture. All the parts have been removed, blasted clean, inspected and recoated so no cracks and it's all perfectly solid.

Now to find some nuts...
A Riddett

Michael: "....In any event you can do it within 29 or 30? days before the expiry of the current MOT."

The vehicle's current MOT Test Certificate shows the earliest date the car can be presented for the next MOT without affecting your annual expiry date.
Brian Shaw

The only ones I have come across are as you describe for the top mount, but utilise the original lower plate. I have heard discussions about how the tube is not vertical with the standard bracket, so perhaps your brackets are set to compensate for this.
Being a touch pedantic, it is not that the design would fail the MOT. It it that it is not within the scope of the MOT to judge.

Can't help with nuts but there used to be a company called Namrick I think. Also Tracy Tools (01803 328603) do every conceivable tap and die so may know who supplies the nuts to fit.

Brian yup thats it.
Michael Beswick

Namrick it is! Have located them and researching around a bit have identified the nut as a BSF so happy days. Thanks for the steer!
A Riddett

BSF? Golly, they could be fairly old spring mounts, bearing in mind that, for example, the post-'62 MGB is largely UNF/UNC and the BSF/Whitworth threadforms had largely fallen into disuse by the late '60s.

Peter
P A Allen

BS fasteners went out of BMC production at the end of TF - MGA/MGB are all UN threads, excepting pipe fittings etc. These things were built by some old fart in a closet.

FRM
FR Millmore

Nyloc's should not be used in suspension systems; use an all metal lock; like the type used on main bearing caps and brake drum attachment nuts.
Rich Boris

Well I could be wrong on the BSF, but it's definitely 0.5" diameter and a 16 TPI count, which Wikipedia led me to believe was BSF.

If these are indeed a home built effort then that could be a little worrying. There is no record in the documentation I have relating to the rear shock upgrade, but there is a mysterious collection of photographs showing the car being rebuilt in someone's garage, in the original (?) Harvest Gold colour (which is still evident in a few areas under the dash where the current BRG hasn't reached). The best I can do to date this mystery rebuild is somewhere before 1995, when I have a recipt confirming that a new bonnet was sprayed in BRG. A few are attached here - maybe some of the pros here can see anything obviously iffy!

That said the rear shock brackets aren't especially dodgy looking, in fact they do look fairly uniform and manufactured. The shocks do not sit vertically however; they are canted forwards slightly. Can't measure now as the car is in bits, but will check when reassembled.


A Riddett

The brackets look professionally made. I wouldn't worry about the MoT - the tester will just want to see that the shocks aren't leaking and that the bushes are in good cond. Took mine for the test last Friday, and thinking about it, he didn't even do a bounce test.

Peter
P A Allen

I seem to remember Spax conversions used a bracket similar to that.
Is there still any paint left on the shocks i.e yellow ?

I have fitting instructions for a front set up and they are noting 1/2" UNF.

R.
richard boobier

Yes, and still have the original Spax labels too. Have had the shocks stripped back and recoated to try and extend the life of them.
A Riddett

I had that Spax comversion and went back to lever arms. it was on for nearly 20 years and was never mentioned at the MoT.
Stan Best

I might point out that 16TPI is right close to 1.5mm pitch, and that measuring threaded stuff is not always straight forward. So maybe 12x1.5mm

FRM
FR Millmore

that bracket is from a Koni modification set, which came with 2 Koni shocks, back in the 70s. I'm still using them.
Siggi
Siggi

This thread was discussed between 14/07/2012 and 25/07/2012

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