They probably debated about whether to just call it the Beijing Tweed Run and then decided that tweed was too British or too obscure for local tastes. For the participants, however, the look was most definitely tweedy. I had no idea that there was quite this much check, argyle and houndstooth in wardrobes around the city.
From the 700bike site, here are pics of just about all the attendees. Also, for comparison, their site has some very nice photos of tweed runs in London, Tokyo, and Moscow, which is oddly one of the most stylish assemblies of men I have ever seen.