Could anyone explain the armor rating cap to me?
The wiki says this:
Damage reduction is capped at 80%. If you are wearing all four pieces of armor, this occurs at 567 displayed armor rating. If you have 100 skill and all relevant armor perks, this requires a smithed armor rating of about 135. You can increase your smithed armor rating by 1 roughly every 2 points of Smithing with the appropriate perk, or every 4 without. Therefore, at 100 Smithing you will need 85 base armor with the appropriate perk, which is not achievable with Light Armor (though Dragonscale comes close at 82 for the set) and requires at least a Steel Plate set for Heavy Armor. With Fortify Smithing apparel you can boost Smithing even further, which can potentially allow any material for which a Smithing perk exists to reach the cap. At the extreme end, you will need about 126 Smithing to make Steel Armor hit the cap, and about 154 Smithing for an Elven set. Unfortunately, Fur, Hide, Studded, Leather, and Iron armors are not affected by any Smithing perks and so cannot be improved as much.
Spells and the Lord Stone can reduce the base armor required to hit the cap even further, but these require more management.
What would seem to be the best you could do with iron? Also, is this not taking into account alchemy? And isn't the Lord Stone just a flat boost to armor rating and magic resistance?