ETA 2824-2 Mainspring Dims

Good evening. Apologies if this is the wrong place to pitch this question which is not strictly omega specific, but I always get sensible answers on here. If it’s not allowed I’ll take it down , just say

I am buying a replacement mainspring for an ETA 2824-2 calibre, and the list of apparent right sizes is confusing. I cannot go by the existing as I know for sure it may not be original as it has been bodged onto the barrel and in poor shape.

My usual sources (cousins uk, EmmyWatch, and Generale Ressorts via watch guy) all give varying dimensions as follows:

1.23 x 0.132 x 400. Cousins
1.23 x 0.125 x 360. Generale Ressorts
1.25 x 0.125 x 360. Generale Ressorts
1.25 x 0.110 x 320. EmmyWatch
1.25 x 0.125 x ??? Current installation

Cousins are not likely to be wrong (supplied a zillion of these for such a popular movement ) but the addition thickness and length will increase stiffness - I don’t do this unless I absolutely have to

Which size would you guys run with, or which do you usually use without amplitude issues (too low or too high)

Kind regards,
Darren

does your barrel have the lid that opens from the top or side? the change was made to accommodate a longer mainspring to increase power reserve.

To be honest I never really paid that much attention I just ordered a spring to suit the 2824 from my local store and it passed all the tests, if amplitude is still low after a new mainspring I would usually be looking for something else that is causing a drop in amplitude.

Ah!! Thanks. That makes sense now as I recall seeing a YouTube video of 2824 with barrel parted through the height of the wall. This one is conventional barrel and lid. I’ve ordered the cousins uk spring and although marginally thicker than current spring, it’s less high. I’ll see how it goes, and will report back amplitude and and reserve for completeness of the question.

Thanks again for taking time to respond.

Kind regards, Darren

Thank you. I ordered my one from cousins on the premise that they sell thousands to professionals for services/ repairs. Not that is a guarantee, but I think if it were incorrectly sized, they would have been told by now. I will report back my findings upon completion of the service.

Once again thanks Erich🙂

Well I said I’d report back on this. The cousins part number for the ETA 2824-2 mainspring is G57162. Can confirm this works perfectly. I obtained 295 deg amplitude at full wind and 225-230 at 24hours post full wind. Will use this part number again in a 2824-2 service