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MG Midget and Sprite Technical - Lowering and Number Plates

Anyone know the bolt sizes for the spring pan bolts please? I have a very good engineering supplier who will supply what I want; I just don't know the diameter. It seems most people have lowered their 1500 by about an inch (1/2" spacer on the pan) can anyone tell me the length of bolt best to go for? I can cut them but it would be good to be somewhere near. Its the usual speculation on my part. Daily driving prevents disassembly to look at the parts and measure.

Also I have everything else ready to take off the bumpers. I know what I am doing with the front number plate but can't find any pics or descriptions of how people have arranged the plate and number plate lights on the back. Any descriptions and or pics would be much appreciated.

I really enjoy using the car daily but of course it means that being well prepped before jobs is essential.

Thanks in advance, Dave
Dave Squire

Dave,
if you mean the (times) 8 bolts they're 5/16" and I think 3/4" long but I think I used 1" or 1¼” long to make things easier on my non-lowered.

Check the tightness of the nuts and bolts after a certain mileage, once mine seemed to settle (if that the right word).
Nigel Atkins

ETA: obviously you'll need to allow for spacer on those lengths, and I put a plain washer under the bolt/screw heads as at least one of the old bolt heads seemed to have sunken in slightly which also made it more difficult to get the spanner on, offset ring spanner seemed the easiest to use.
Nigel Atkins

Thanks Nigel, that's the one and that's the dimension I was looking for.
Dave Squire

Dave, what year is your car?
J Tickle

Hi Jeremy, Its a 78 1500. Sorry, removed that info from my details. Doh.
Dave Squire

I can confirm that they are 5/16" UNF x 3/4" They appear to be listed in the catalogues under a different part No. to the standard set screw, given the application is it likely that this is a special, maybe grade 8? I recently ordered some from a well known supplier but despite ordering the correct part (and being charged the higher price) they sent standard grade 5.
Bill
W Dunsmore

I must admit I find it difficult that a trade supplier can get such a thing wrong in that direction Bill. I am not a mechanical engineer by trade but like you I know the difference. Good job we do.

Thanks for the confirmation of size.

Anyone any rear number plate pics of what they did with the boat anchor removed?
Dave Squire

Yes, they should be high-tensile bolts/screws.

For the number plate light, you could just use one of your originals.

Dave O'Neill 2

Grade 5 is considered a high tensile fastener and is roughly equivalent to the metric 8.8 designation. I would expect them to be fine for the spring pan to wishbone application.
David Billington

Hi Dave,

sorry can't help with the rear numberplate as mine's a 71; otherwise I'd have popped out and posted a pic! :)
J Tickle

Hi Dave,

RE: number plates, I used special bolts with LED lights in them, as used on some motorbikes I believe. Readily avalible through eBay.

They aren't very bright though, although I don't see why that is much of an issue in reality.

Cheers,
Malc.
Malcolm Le Chevalier

David,

Reinforces how little I know. And that it takes a lifetime to become a capable engineer.

So grade 5 is imperial?

Is that one of the standards that is denoted by markings rather than letters and numbers on the bolt head?

Just wondering.

Dave
Dave Squire

Yep Dave.

Grade 5 is the imperial equivalent of metric 8.8, grade 8 imperial is 10.9 metric (I think, maybe it is 12.9).

Grade 5 is marked as three / on the bolt head. 8.8 are marked (cleverly) 8.8.

To confuse things, the grade you get in B and Q is something like 4.8. NOT equivalent to imperial grade 5, they are soft cheese grade and should only be used for non structural stuff.

Clear as mud? :-)

Malc
Malcolm Le Chevalier

At least the metric grading tells you something about the material properties without having to look it up. The first number is the ultimate tensile strength (UTS) in 100s of Newtons per square millimetre and the second number is the minimum yield strength percentage of UTS in 10s. So an 8.8 has a UTS of 800 N/mm^2 and a yield strength of 80% UTS or 640 N/mm^2.
David Billington

Excellent, I like Cheese and order it from Grommitt regularly thanks.

And just to muddify the clear my supplier gave me high tensile UNF 5/16 2.5" with two different sets of markings. One says some letters and one looks like a 5. The other is 3 I's pointing out from the centre with what is similar to a 7 in between 2 of them.

Description is UNF HT Sets.

Bring back SI I say! Ha ha.
Dave Squire

From my very limited knowledge the three radial bars indicate grade 5, six bars means it's a grade 8. Just to add to the confusion there appears to be another grading system which describes them as "S", "T" and "V". I'm happy to take David Billington's advice that grade 5 is good for the spring pans.
Bill
W Dunsmore

I've got some bigger ones that say jh on them. What's that all about?
Rob Armstrong

Thanks for the help on clarification David.

'Grade 5 is considered a high tensile fastener and is roughly equivalent to the metric 8.8 designation. I would expect them to be fine for the spring pan to wishbone application.'

I am sure that Jason (and his dad who inherited the business years ago and is now the - retired - helper) have supplied as you say. It was always gobbledy gook to me as a child. I understand they will have the old style markings as they are imperial / old (UNF) and any other marking would be a translation that could be misleading in some apps. Your confirmation is reassuring. Thank you.

Think I have everything sorted for the bumpers off now. I just need a weekend to get to it.

Cheers, Dave
Dave Squire

Interesting Dave Bill', never realised that is what it stood for. Always just took it at face value and never made the link between the designation and strength.

Yes, three "/" or three "" on the head is grade 5. Just depends on which way round you are holdiding it ;-)

Generally any other markings are the makers stamp. I have some JH 3/8" bolts in front of me right now.

Happy Friday everyone. Good luck for the weekend Dave Squire.

Malc.
Malcolm Le Chevalier

I had a quick look recently and found this page if you want more markings http://www.americanfastener.com/astm-sae-and-iso-grade-markings-for-steel-fasteners/ . That's enough to get me running screaming out of the room.
David Billington

Great David, I love it, chortling, and tears to the eyes stuff.

But also seriously informative.

Thanks, Dave
Dave Squire

Dave, I cant see clearly from your pic, but is that Lucas (467?) light mounted on the proper plinth (which I can't find listed anymore for my 1275), or is it mounted direct to the rear panel?
M Weller

It was directly on the panel. It didn't need much reach, as I had a stick-on number plate.

I'm wondering if I have a plinth somewhere?
Dave O'Neill 2

OK thanks. I'm thinking of bumperless / stick on plates, and have an old lucas 467 lying around. Tell me, how was the interface between rear of lamp unit and curvature of panel?
M Weller

I don't recall having an issue with the curvature, there is a rubber gasket on the back of the lamp.
Dave O'Neill 2

This thread was discussed between 26/10/2016 and 30/10/2016

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