Baggage allowance for Economy leg on Business ticket. OW Saphire
 

We are flying with Latam from Frankfurt to Sao Paulo (Business), Sao Paulo to Buenos Aries (Business- Stopover), and Buenos Aries to Ushaia (Economy), and we are both British Airways Silver (OW Saphire), and then back on the same route (although Buenos Aries-Sao Paulo is Premium Economy, and stopover in Sao Paulo)

Our Eticket lists our baggage for the Economy legs as 23kg one way, and two bags the other way. LAN Argentina is carrier.

LAN website lists Economy as one bag 23kg. One World website says that for Domestic LAN services Saphire gets 2 bags 23kg total.

However I believe with the international segment on the tickets we get one extra bag.

We will have less than 2 x 23kg each but can’t work out if this is covered by the extra international sector (all on same PNR, but Eticket has six different numbers?)

Does anyone know if we’ll be OK with two x 23kg, or who we check with to confirm allowances?

You baggage allowance SHOULD be the Business allowance for your entire itinerary given you have everything on the same PNR. It's weird though that the e-ticket doesn't reflect that.

You could give LATAM (assuming you purchased the tickets from them) a call just to make sure, but AFAIR the rule is that you get the most permissive allowance within your itinerary for the whole trip

Spoke to British Airways (who sold me the ticket) and they didn't know the answer, so directed me to phone Latam (and gave me the different Latam PNR). Agent took all my details (including phone number) and tried to find out. Phone went quiet for about 5 minutes so I gave up as I wasn't sure what call was costing me! Never got a call back.
Now made contact via email form and I have a case number so I'll wait a while and see if anyone can tell me. Could be easier to confirm what I've paid for (or not!)

In the worse case you can carry a extra bag (2nd bag on domestic) up to 15 kilos, since that is the old Latam rule for OW.

I have seen now that they will use the same bagage rules for OW than for Latam pass, if it where that way you will get the extra bag with up to 23kg.

3 x 23kg for all flights
 

Thank you JLA Roulet and Pabloco for keeping my hopes up!
Got email confirmation this morning from Latam that the 3 x 23kg will apply to all flights.
Very impressed with the speed of the response which was less than 40h: Not bad considering it arrived in UK early Monday morning, so was possibly sent from South America late Sunday.
Shame the various websites can't make it clearer.

I have a similar question...

A friend of mine with no OW status and no FF miles accumulated will be flying CWB/GRU/JFK all on a single Economy class ticket on LATAM. He plans to stay in New York 3 days and then fly to SEA. I'm considering using my AA miles to buy him a F ticket JFK/SEA on AA metal, hoping to connect the PNR and, in turn, make the entire routing eligible for Business Class baggage allowance, including the normally very restrictive intra-Brazil 23kg limitation. Will this work?

Complicating things, does the exNYC airport need to be exclusively exJFK or could he depart from any NYC area airport and connect the tickets?

Could I book DL metal (767 vs AA's 738) instead of a OW Partner for the JFK/SEA leg and still connect the tickets and get the Business Class baggage allowance for the entire itin?

TIA

No. Buying a second ticket in F or J, on another airline, will not produce any changes in the CWB/GRU/JFK route that's already ticketed by Latam.

The rules, heavily summarized and simplified, are these:
1.- baggage allowance on a 100% Latam itinerary is the most permissive of all legs in the itinerary. This is not influenced by an ongoing flight on a different airline on a separate reservation

2.- if you have a multi-airline reservation, baggage allowance for the whole trip is determined by the most significant carrier as per IATA rules. In this case, assuming you did have CWB-GRU(Latam Y)/GRU-JFK(Latam Y)/JFK-SEA(American F) on the same reservation/same ticket, the baggage allowance for the whole roundtrip would be the one allocated by the GRU-JFK(Latam Y) segment as it's the first one that moves from an IATA sub-zone to another. Hence, your whole trip would allow 2x32kg

You cannot connect tickets from different airlines, purchased at different times, hence your plan is a little bit out of the question

Thanks, @jlarroulet. Years back, I booked a ridiculously complex R/T North America/ South America routing all on AA metal that covered a few weeks. IIRC, since one small leg was in F, it qualified the whole ticket for a hefty baggage allotment. Seems like much different circumstances here from my friend's Brazil itin across airlines. Too bad.

If everything was on the same reservation/ticket the above would still be true if you are flying everything on the same airline.
since in this case neither requirement (being in the same reservation and not "mixing" airlines), the whole set of rules that apply in this case are different (and, to my knowledge, have been different for a lot of years)