How much tire clearance does the 40mm extension actually give me?

40mm is enough for modest wheel upgrades and suspension drops without running into contact. Measure your current tire-to-fender gap and compare against your wheel and tire package specs to confirm fitment for your specific setup.

Will I need to drill holes or do any cutting to install these?

That depends on your vehicle's mounting point configuration. Check your OEM fender holes before installation — most factory points align with these flares, but minor adjustments to hole placement may be necessary on some vehicles.

What prep work does FRP need before painting?

Sand and prep the surface with appropriate grit to clean the primer coat and create adhesion for your chosen topcoat. Follow your paint system's prep recommendations for best results.