A common weak point on mid-level gravel bikes is GRX drivetrains except a FSA crank. Mine has been under a heavy load, and developed intermittent clunks within 2000 miles and now has louder kerchunks and a lighter clank on the downbeat. The small chain ring appears to be wearing faster than my Sunrace cassette, so I think it's time to go full GRX. After getting a headache reading about BB "standards" and trying to figure out what my options are, I'm hoping someone with more knowledge of gravel BBs and cranks can help. Markings on mine say “MegaExo BB-4000” and “BC1.37" x 24T” It looks like different online vendors have Ultegra or Dura Ace BBs matching that spec mark, which I gather is English threading, but the GRX 10 speed site only lists the Tiagra BB is the threaded option. Will an Ultegra BB work or does it have to be Tiagra? Not having much luck finding the 2x10 GRX crank. Anyone know a reliable vendor that has these? Is there a real difference other than price and markings on 2x11? If i have to go that way?
You can use any Shimano BSA threaded 68mm external bottom bracket. Ultegra will work well. Ideally you want a 10 speed crankset. If you use an 11 speed crankset, for best shifting you’ll need to use an 11 speed chain and front derailleur (your 10 speed cassette and rear derailleur will work fine with an 11 speed chain).
Seems like the GRX crank availability is still pretty iffy, so unfortunately if you've already ruled out FSA, that's about all that is readily available with super or sub compact rings. FWIW I have not had any problems with a Gossamer sub compact that cost all of $50 over a couple thousand miles so far with an FSA T47 BB.
If you think the problem was related to high load / torque, you may indeed want to stick with the smaller 24mm Shimano spindle in a BSA BB because cranks with the larger 30mm spindles don't really have enough room for the correct bearings in that shell.
Another issue is that replacing the outer chain ring when it goes requires loosening a proprietary FSA lock ring that looks like a PITA and would require this $30 tool (more than an Ultegra BB) and a bench vise:
The FSA website doesn’t even list a replacement chain ring for their Omega gravel cranks, so I can’t fix the worn inner ring. Back to the search for GRX.
If they remade the Graduate this year, perhaps the advice to Dustin Hoffman’s character would be “Supply Chain” instead of “Plastics”!
With parts availability still iffy and not wanting to waste too much time I found quality 3rd party cranks like White to be an option, and I just did a whole bike with Ultegra. Some frames stated needing GRX over Ultegra for larger tires.
Maybe it's our weight - no one in the family more than 152 pounds - but a bike with FSA and White single speed crank and square taper bb have held up well.
I had more confidence with the Ultegra choice knowing some associates who use the 40t MTB cassette with it.
I would not fear anything Tiagra or Deore level. A friend with Tiagra and one of our bikes with Deore have proven how much your bike engine and some lube matter.
Completely agree. At my weight I opt for Ultegra over Dura-Ace, 10 spd over 11+. We did a couple of supported bike tours in Hawaii and Ireland, and the Irish tour was both very hilly with steep rollers and tons of rain—6 out of 7 days we rode. Both tour companies used Tiagra. From what I have learned, all Shimano road uses the same BB specs, and the cranks take care of the wider gravel chain line & Q factor.
Case closed. The folks at Competitive Cyclist emailed back and decided to sell me a crank they had set aside for their complete bike builds. I'll have it in a few days. They have really had great customer service for me a couple of times.
I called the LBS where I got the bike before I moved, and they said they were not having many issues with them, and recommended a bearing replacement, but I'm putting max bike load pressures on mine, and FSA doesn't have replacement inner rings available. My GRX Crank & Ultegra BB are here😍, and waiting for a rainy day to install. FSA should really think about the brand damage these low end cranks are doing to their higher end stuff that seems to work. These are more "Failure Seems Assured" than "Full Speed Ahead."
FSA is weird like that. Their high end stuff seems well thought out and very reasonable but their entry level cranks are loud and their wheels can leave you stranded.
