I was thinking of trying something fun. I have 9x flat AD Marks and 3x flat AD Quints and was thinking of running crit chance on my rune page.

9x crit chance marks = 8.37 (0.93 ea)
3x crit chance quints = 5.58 (1.86 ea)

9x flat ad marks = 8.55 (0.95 ea)
3x crit chance marks = 6.75 (2.25 ea)

6x crit chance marks = 5.58
3x flat ad quints/marks = 9.6

My main options would be:
1) 9.6 ad/5.58 crit chance
2) 8.55 ad/5.58 crit chance (This one isn't worth it)
3) 6.75 ad/8.37 crit chance
^(doesn't include the 1x flat ad glyph I currently use ofc)

I don't currently own the rune but the cheapest and best one seems to be the first option.
I currently run 9x flat ad marks, 3x flat ad quints, 1x flat ad glyph, 8x mr/level glyphs, 9x flat armor seals.

Can anybody help me out and tell me if this seams like a good idea to try out. It would help for when I rush IE and it would help me in lane since I harass a lot and could get lucky. I don't have a problem last hitting so less AD will only be a problem if my luck of critting is bad.

TL;DR: Are a few crit chance runes good on an AD Carry, also thinking about IE/Zeal.

Bump, still wondering.

They can be, and can net you more overall damage later in the game.

Problem is the inconsistency. Even going all crit runes and getting it to about 20% crit chance is still iffy. In any kind of serious play, you want to gauge your damage to see if you can win in fights or damage trades. With flat AD or armor pen runes, you for the most part know how much damage your going to do and thus know whether to fight or not. With crit, you mightttt do lots of damage... or you might not.

In addition, even though the crit chance can help you later in the game, you got to get to later in the game. Without that extra little boost in AD or armor pen, your likely to get muscled out of lane by the enemy that does have it and thus lose out on creep kills. Without a reliable early game, who knows when you'll be able to afford IE.

Yeah but I typically build for crit on my AD champs going 2x PD, IE, BT, Greaves, LW
This build with elixir of agility gives me 93% chance to crit, with 6% crit chance it would be 99% chance. I just want the better late game build and can still rely on winning trades w/o taking crit for chance since I only lose 6 AD by taking crit instead.

Edit: people downvote crit builds I guess

i have nothing but ad per level 30-40 ad at level 18 forgot how much

Your looking at it in an endgame build perspective. The crit will be weakest early game, essentially not good until you get an IE or at least a zeal. The enemy will take advantage of this and will shut you down in the lane and prevent you from reaching any of these items. This is why it's far too risky to invest in crit chance, and people opt for AD instead. The AD will help you get through early game and still benefit you to a lesser degree as the game goes on.

AD/level imo is never worth using because you won't win early trades with no armor and lower AD. It also makes it harder to cs.
I have every champ, 10 rune pages, lots of runes, extra IP to throw around and thought I would test this if it could be used efficiently. It could also work on critplank which I haven't played for the longest time.