EVE New Citizens Q&A

Basically, Overtanked is a much more nebulous concept, but it is possible to tank too much for the situation at hand, especially in PvE where all the variables are known.

You are often making a choice between Tank and Gank when you fit a ship, and trying to find a balance between those. In missions, its possible to know the DPS coming in on you. If you have enough modules to deal with that incoming damage, then you are tanked as much as you need to be for the mission. If you add more modules, you are reducing your ships damage or other potential capabilities to deal with a threat that isnt really there.

PvP is more tricky because its not really possible to say you are 'overtanked', since you wont know what sort of situations you are coming up against, but if you have (for example) a drake where all its lows are taken up by shield recharge modules, and no missile damage modules, you could have a ship that is more tanked than it should be, and you might not have the damage to kill the enemy before they kill you.

Confirming above.

Simply, you're over tanked if you could have fitted another damage module (heat sink, gyro, mag stab, or even a tracking computer) and still be fine.

Thanks for the replies guys, Still one to answer (unless Im to dim and have missed if).
How do I know when my ship is "over tanked"??

If your defenses are rock-solid and your weapons aren't doing much more than scorching the paint of whatever you're shooting at, that's the time to start sacrificing tank for gank. It's a balancing act, and subjective to how defensive or offensive minded you are; for solo PVE work, people aim to improve their ISK earned per hour, so the faster they kill rats, the faster they earn money, but the higher the risk that something will go sideways on them (drones aggressing the wrong target and bringing down insane aggro, for example) and they'll lose their ship, which rips into profit pretty badly.

There's no bright line for when you're overtanked; it depends on your play style.

For squad work and PVP, it depends on what role you're playing in the squadron - sometimes people will bring over-tanked ships simply to draw the attention of hostiles and survive long enough for squadmates to sneak up and hammer them with gank-heavy ships (and jammers, tacklers, and what have you). In PVP, folks are smart enough to watch out for it, so if they see a Drake swanning about on its own, they may hesitate to engage because the Drake may be sporting a brick tank which could survive long enough for a few Hurricanes to jump in, warp in, and shred the attackers.

I guess I'm saying that whether a ship is overtanked also depends on the role it's playing.