Breadfan

I have a Tiagra 4700 50/34, 170mm crankset on my Niner RLT. My framespace/hubs are 142, my cassette is 11-34. I want to get a 46/30 with a 24mm spindle crankset with a chainline that matches closely with my current cranks, which is 43.5mm. I was gonna go with the GRX FC-RX600-10 but the chanline is 47mm and I'd also have to get the GRX FD. I'm already at my limit with what I have as far as cross chaining so 47mm seems like too much. My chain rubs just a a little the way it is when I am in the big chainring on the front and the 34 on the back. Anymore would rub and I like to stay in the big chainring on the front for everything but the thick stuff. The Cues is even more at almost 49mm. I have found the Samox G3 46.30, and at 45mm (chainline) and a 24mm spindle, it fits the bill. I don't know much about them but I have seen some good reviews. Now, I am not hard on my bike, I ride mostly sitting down and I don't get up much. The worst terrain I go through is plowed dirt and mud, no mountains around here. I've looked at Easton, they look good but they are a little pricey for what I need. FSA has a lot but I don't see any of them with 24mm spindles. They seem to withhold a lot of info on their website. I really want to stick to replacing just the crankset. Any help in pointing me in the right direction would be much appreciated.

Polaris OBark

I have a GRX crankset with an otherwise Ultegra drive train. I did not have to change either the front or back derailleur, but just made a small adjustment of the H-limit screw on the front. This is by far the least expensive/invasive solution, so it is worth a try.

(If for some reason that doesn't work on your setup, you can salvage the investment with a < $50 GRX front derailleur.)

shelbyfv

I too suggest you get the GRX crank and maybe FD, call it done. It was designed for bikes like yours with 142 spacing. Jillions of people use it happily.

t2p

some have gone with a FSA crank -

FSA Gossamer Pro Modular
AGX+ Crankset
46-30

on my Topstone Tiagra 4700 (4725) 10 speed bike I installed a RX810 48-31 crank and RX810 FD (with SM-AD91 front band adapter)

shelbyfv

Yes, my Topstone came with an FSA crank. While I don't have any specific complaints, I wouldn't buy one if Shimano was available.

Mtracer

Another vote for the GRX crankset and FD if needed. I'm pretty sure every GRX crankset in use is on a 142 mm hub. Or at least that is going to be the most common. I know I have had one setup with a 105 FD without any problem, both with an FSA Omega (?) 46/30 crankset and the GRX 800 48/31. This too was on a Topstone.

FD setup is always a bit finicky, but I've been able to get it to work without any FD cage rubbing, even when crossed-chained big-big. Though I'm a taller rider and therefore ride larger frames. So, I know this makes my chain angles a little less extreme because of longer chain stays.

Remember you can play with the FD angle a little as another variable to adjust. Also, how much time are you really in big-big. I get using that for a moment to avoid shifting the front just to crest a hill or similar. No big deal in that case if it rubs for a few moments.

Breadfan

Thanks for the insight, folks. You've helped me a lot.