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MG Midget and Sprite Technical - Stainless steel fixings

I wonder why manufacturers bother to zinc plate nuts and bolts. Within a year or so they are rusty and after a few more years the corrosion is rampant. I am just dismantling the front suspension which was rebuilt 8 years ago when I installed the disc brakes. I have to drill out the spring pan bolts as the nuts, new at the time, are so rusted they can't be gripped. This is very tricky with the spring under tension, and I can't quite see how I'll do it.

I would use stainless fixings, but they can stretch and loosen over time, and I wonder if that's safe on the running gear. What do you think?

Les
L B Rose

No, you shouldn’t use stainless on safety critical parts. Well, not the usual stainless you get from classic car fastener suppliers, it’s not usually strong enough. Maybe there are some better options from ARP or suchlike but not sure. Someone will be along soon with material specs etc, stuff I should know but have either forgotten or didn’t bother listening when being taught it!

I just use decent quality zinc plated nuts and bolts and cover them with copper grease then waxoyl. You will have to take the top trunnion apart (jack under wishbone/disc first!) and then you can remove the spring and grind/drill the heads off the pan bolts. Good luck!
John Payne

yes...what John says. SS is too brittle to use in very stressed situations. Use good quality steel fixings.
David Cox

I thought this stainless steel being too brittle had been disproved(?).

Definitely different qualities of stainless steel and in quality of nuts and bolts. A friend bought me some s/s setscrews and washers from a reliable local source and I was surprised to find that I need to nip then up after I'd done the usual nipping up and road testing nipping up. I discovered these weren't magnetic too so a pain to get out of the crevices they insist on dropping into.

Same as (unless I've forgot) I can't remember seeing anything to prove that split-washers actual give more grip.(?)

Nigel Atkins

Thanks guys. I got away without drilling the bolts out as 24 hours of WD40 did the trick. I managed to grip the nuts with the Mole wrench. New plated ones will go on, with copper grease and Waxoyl.

Les
L B Rose

I've always found letting the chemicals do the hard work and good dollops of patience get it done, though I'm not a big fan of ordinary WD40 as a penetrating/releasing fluid I prefer PlusGas or GT85 (sadly now owned by WD40).
Nigel Atkins

It ultimately comes down to price. Stainless are mega bucks in high tensile grades!

Do you want to pay 20p for a bolt or £2? If you are a manufacturer, building thousands a year the extra cost very quickly adds up to ruinous amounts!
Malcolm Le Chevalier

This thread was discussed between 17/04/2020 and 19/04/2020

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