Originally Posted by
raqball
I went with the GRX 810 calipers because I found them on sale and was able to combine the sale price with a coupon code.
XT would not work unless you used an adapter to convert from post mount to flat. The FX Sport uses flat mount calipers. I *think* XT and XTR are all post mount.
The bike came with BH59 brake lines and they were just re-used for the upgrade.
Love this ^^^^ ... your project! FWIW, new XT (and XTR) calipers are now available in a flat-mount variant:
https://bike.shimano.com/en-EU/produ.../BR-M8110.html . I have them on my Sirrus X Carbon Comp. It was a long wait, but worth it.