Looking for feedback: converting my Specialized Crosstrail 2019 into a Bike of Theseus
I've got a Specialized Crosstrail 2019 that is in desperate need of some TLC, and rather than buy a new bike I've decided to rebuild the entire damn thing and make a "Bike of Theseus" out of it, preserving the frame, wheels, and handlebars.
I'm gonna tackle two objections out of the gate here since I know they'll come up:
"This isn't economical. Just buy a new bike."
Yes, I know. I often DIY things for more than what the purchase price is, and treat it as a learning opportunity. In this case I will likely spend a few hundred more than what a "new" used bike would cost, but learn a heck of a lot about bike maintenance and building in the process. I already have most of the required tools, and already do all of my bike maintenance aside from wheel truing.
"You're building a bastardized bike that won't be great at anything and should just buy a XYZ category bike."
Also true, and yet not quite. My use case is a combination of city commuting (work is 7 minutes away by bike), gravel, and light trail riding. By light trail riding I mean hopping the occasional root, enjoying berms and rollers, and staying clear away from any jumps more than 1-2 feet in height.
With that out of the way, here's what needs work on the bike.
The brakes (Promax Solve) are, quite frankly, shit. I have replaced discs and pads but they just don't have enough stopping power; bleeding them is likewise a huge PITA as they don't have bleed ports.
The fork (Suntour NEX) is almost completely siezed, and was a cheap/shitty spring fork when new.
The drivetrain is Shimano Tourney/Altus. It works fine on the road but the derailleurs need to be re-adjusted after just a few hours of riding flow trails. The rear casette needs replacement ~2x per year as the 11T gear wears quickly and I'm hoping a higher end / better alloy can solve this.
So uh... Yeah. I'm replacing basically every mechanically important component. This is where the questions come in.
I'm replacing the brakes with a pair of Shimano 6100s I got on deep discount, and upgrading the discs to 180mm. The 6100s come with resin pads by default and I may swap to sintered metal if I decide I need even more stopping power. No questions here.
I'm having a hard time finding a replacement fork (not surprising, given the weird travel). The RockShox Paragon Gold RL is the closest thing I can find, with an extra 10mm of travel and otherwise matching dimensions. This listing has a straight 1 1/8" tube which I think is right for the bike, but I'm not 100% sure as Specialized doesn't detail the original fork beyond saying it's 1 1/8" diameter. Short of dropping the fork out, is there a way to easily confirm this?
I haven't researched the drivetrain heavily yet as my primary concern is having working shocks and brakes at the moment. If you have high-level comments or recommendations, I'd appreciate that. I'll note that I'm still wanting a large front chainring, but that a casette with more speeds in the back would definitely be nice. I'm concerned about the bottom bracket as square taper apparently is not that common any more (Specialized lists the spec as "68mm, square taper, 124.5mm length"); should I be worried about parts availability, can I get adapters, et cetera?
If you've made it this far, thanks. I appreciate any feedback you guys can give; while I can certainly flail about in the dark with my tools, bust a few knuckles, and get this built, I'd rather speed things up with as much good advice as I can get!