The heavier it is, the slower you are. That's only known.
it took me 49–51 seconds to run from the strip north gate to the free side door in t-51b power armour,and took me 37–39 seconds to run there in no apparel (i have the travel light perk on makes me 10% faster in light apparel or none) so add 10% of 38 on to 38 =41.8 so wearing heavy apparel proberly makes you 20% slower? :)
I did some testing myself (running back and forth in Freeside), and this is what I found out:
- No Armor - approx. 33.5 seconds
- Vault 34 Security (light armor) - approx. - 33.5 seconds
- Stealth Suit Mk II (medium armor) - approx 36.0 seconds
- T45-d Power Armor (heavy armor) - approx 38.5 seconds
My conclusion is this: Light armor does not slow you down. Medium armor adds 7.5% to your travel time. Heavy armor adds 15% to your travel time. Earlier tests proved Agility is of no factor (T45-d speed = T51-b speed // Stealth Suit Mk II speed = Combat Reinforced speed). Note: I have no movement speed affecting perks.