i changed my tires to P215/45/17 dunlop FM901... not the stickiest rubber around but still A LOT better than stock. I've had these tires for about a year now and both left and right bearings had to be changed this week... the wheels would make a ticktick sound when turning at low speed. old bearings where very loose... could these tires be a little harder on the bearings' life?

hmmmmm interesting post. No doubt worth a few flames as soon as some people get into it. Everyone will have opinions on this, .... and me too! Have you changed the offset of your wheels? That will have some effect, of course.
I would think that YES, if you have increased the grip of the car in corners, especially if it is enough that you can feel it, that you have increased the effective load being handled by those very same bearings. After all, they are the sole means of transferring up and down, forward and back, and sideways movement to the suspension from the tire. Nothing else substitutes. So if you have made the car 'more responsive' then something is 'trying' harder for that to happen; at least harder than the stock, original setup. So my vote is that you have in fact shortened their life by pushing them a bit harder. Not a bad thing I suppose as long as you keep on top of it.
NOW: if you DON"T drive the car in a spirited fashion? If you simply change the tires (using the same offset wheels). Will the bearings life be shorter SOLELY due to the tire change? (Is it really objectively fair to say you won't drive it harder?........ ) That would be interesting. I suppose a 1/2 year or one year test might be in order. A lot is going to depend on what has happened - if anything - to the scrub radius you have. Is it worse now with the wheel change? That is a major issue. So a few items to add in to your thread maybe.
interesting.

The tire change itself is not a measurable difference to bearings.

What you put the tires on and how you drive is a huge difference.

Rolling resistance, the torque created by wider wheels, and alot of G forces will affect the front end, and not just the bearings.

If your bearings are clicking, replace both. If you want to drive with alot of aggression on the corners, expect more brake, tire, shock, and suspension wear and tear. Simple.

Arn

i did change the offset of the wheels, and i do drive quite hard.... so... would it be possible to get stronger bearings that would fit the fiero hub? anyway, i'll check for use regularely and keep you posted if they wear prematurely... let the long term test begin!!

back in the dark ages, we would change offset on vw by reversing the wheels, wheel bearing life dropped to under a year per set. offsetting changes the angle of pressure on the bearing causind uneven pressure and wear.

just for a bit of perspective on sizes; and also to say that when I first took the fiero bearings apart, the outer has got to be the smallest I can remember seeing!

I have made a bunch of mods to mine and I am now using camaro bearings (long story; don't ask) but the SMALLer camaro bearing (the outer one) is almost the same size as the INNER fiero bearing (the larger one)

So of course the inner camaro bearing is HUGE by comparison to the fiero bearings and I am suspecting that I won't have any probs with them....... for a long time, anyway