Thanks for the help so far - I have another quick(ish) question. I'm trying to get up to speed with all the BB maintenance stuff, so please bear with me:

I suspect I (LBS) may need to do some bottom bracket maintenance. When spinning the cranks without the chain on it sounds a bit "sandy" and doesn't spin for long. I tried to read a bit about the bottom brackets on the first gen SC 9s and it seems like it is BB90? As I said, I'm not particularly well versed in BB tech, but I saw quite a lot of mixed reviews about the BB90 set-up, e.g. lots of grit and dirt getting in, particularly via the non-drive side. Has any solution to that been found? Aftermarket seal or something? What is the recommended long term maintenance strategy for prolonging the life of the bearings and frame?

If I do need to replace the bearings - are there any particular brands/types that people recommend for replacing these particular bearings? Would I just need to buy any 2x BB90 bearings, but not the sleeve (or anything else)? ...or is there a specific Trek BB90 that I have to get?

Thanks for any help, it's much appreciated!