What size wire and pipe for a 125A subpanel in an attached carport?
Most jurisdictions would allow 1/0 Al THWN or better wire rated at 120A (per 75°C terminations) to be rounded up to 125A protection, and a #4 Al ground if using non-conductive PVC conduit.
1.25&quot; minimum conduit would be needed with Sch40 PVC. Long sweeps are probably not necessary. If you use Sch80 PVC you would need to use 1.5&quot;.
LB's are fine, you may need to upsize LB's to 1.5&quot; with reducing bushings to accommodate the wire size used, consult the internal markings on the LB's.
You need to protect the feeder with a 125A breaker at the service, check the stab limits in your main panel, sometimes you can't install another breaker across from the 125A breaker.
Your subpanel needs to be rated 125A minimum. However, often for pennies more, you can get a big 200A panel with lots of extra breaker spaces, so do that if it can fit.