Music wire.

Not a direct answer – it may be worth trying an automotive brake specialist, likely to be cheaper than car dealership for such obscure items.

Jon link looks like instrument wire (piano, harpsichord) not solid piano wire as in spring steel. May be wrong and it's a trick of the camera pixels but worth a check.

My local model aeroplane shop sells piano wire in a range of sizes. Probably too thin for you, but I've bought stainless wire for making springs from dental technicians in the past

Edited By duncan webster on 08/12/2016 01:54:00

Piano wire is hardened by the drawing process, if you heat it you will destroy the temper and you will never get it back, many have tried and failed. It can and usually is bent cold. Do not hit the bend in order to complete it as that is a sure way to induce a crack. I would ask myself what have I got most of 'time or money' I feel sure your 60 seconds is very optimistic and it will take you far longer.

It may be possible to unwind a suitable coil spring for the material. Colin

I have used Tig stainless 316l for various applications it seems springy as I found when making those fishing lures.

As far as I am aware music wire is solid, comes ready hardened and tempered. Can be cold bent meaning it loses its memory and therefore not the greatest steel used but poor quality.
If heat it up guarantee problems ranging from collapsing to breakages and would be either hit and miss through trial and error.

It will easily take a 90 degree cold bend as a tag either end.
Make the coil first leave ends long, cut to length then bend the tags about 2 mins each on conservative side after a practice and setup.

Nick if you were making it correct you would harden and temper after!

How it behaves is material quality as in grade, hardening and tempering. Of which theres spring steel grades and theres spring steel grades of variable quality.
Just so happens this low grade spring steel used is not very hard or that springy compared to better quality and can only be hardened and tempered up to a limit hence it collapses past its yield. Fine for products that don't require much use or easy to make products without the necessity for harden and tempering which most will get wrong and come out anything from too soft to brittle.

Wondered why a brand new proper spring softens after a break in or first use?

Hmm, that comes as news to me, as technical director in a company that designs and makes many hundreds of thousands of springs every year for demanding automotive applications. Incidentally, you don't need to harden and temper materials to make springs from them. As long as you keep within their elastic limit they will work fine – and they don't even need to be made of "spring" steel.

I sympathise with the concern about the apparent cost of these springs, but this sounds very dodgy to me – do you have any parameters on these springs – under what conditions should they be able to work and so on? and to risk untested 'home-made' kit as part of the brakes on your car. Hope I don't live anywhere near this you. Bite the bullet and buy the correct parts, rather than take the risk.

Obviously you need to write in to Machinery's Handbook and complain that their extremely useful guides for mandrel sizes for winding compression and tension springs from piano wire have been misguiding engineers since 1914.

Alternatively you could buy a copy and learn how to wind some springs without heat treatment

There is a limit to the utility of some piano wire spring sizes but you should not be under the impression that winding soft and heat treating after is the only way to skin this cat, just because it's the only way familiar to you 😀

I make some gun springs from Piano Wire because they work better and last longer than OEM springs so this is by no means a simple subject and there is no one right way to make a spring without testing, 

– Nick

Edited By Nick Hulme on 17/01/2017 19:02:59