The answer is I don't really know the maximum but I can set a floor.
So I rode over to my nearby beer store. This is what I bought...
It comes to:
- 8 x 750ml Avec Les Bon Voeux
- 6 x 12oz Bear Republic Racer 5 IPA
- 6 x 12oz Ballast Point Sculpin cans
- 4 x 16oz Golden Roads Wolf in the Weeds IPA
- 1 x 750ml spoiled grape juice (a/k/a "Wine")
- 1 x 26oz distilled grain spirits (a/k/a "Booze")
It doesn't look like much in the cart, but it is a a fair amount to transport on a bicycle.
I didn't plan well enough -- I meant to bring some newspaper to wrap the bottles. We have a paper bag law and one use paper bags are 10 cents. I knew that went for grocery stores but didn't realize it was for bottle bags as well. The store gave me some cardboard inserts and using my jacket and a cloth bag I managed to get it all in and wrapped.
This was the first time I had a real load in the front basket and it worked OK. I am usually pretty good at balancing the bike with little or no forward motion but not with a load. So long as I got a good push off it went fine. The disk brakes stopped with no issues.
It's less than two miles to the store, so it wasn't a distance test, but I am happy with how it worked. With a little better planning I could carry more but I wouldn't want to double the load.