If you just switch the front wheels, you will never get the full wear from your tires. Besides the left front wearing in a different way than the right front, the fronts in general wear in a different way than the rears. By rotating so each tire spends 25% of its life in each corner (or 20% if you have a full size spare), you get the most out of your tires.

Besides, if you only replace the front tires and have the rear tires on for a long time, now you've got aged, UV-exposed possibly dry-rotted tires on the rear.

Oh, and the outside wear combined with pulling certainly sounds like a "toe in" misalignment.

it takes 10+ years for tires to get dryrotted (least thats around here)

alot less if thier not in the sun (if the cars parked make plywood cutouts to lean against the tires to keep the sun off them)

also use tireshine/protector, it soaks into the rubber preventing it from dryrotting

My spare has dryrotted out, it's surprising, it's the same age as other tires on there and it was holding full pressure fine, then all of a sudden, cracked all to hell and flat.... climate seems to eat rubber here... glass in Marvin has a small %age tint that's meant to cut UV too.

Rotating tires... From a fresh set installed on Marvin, (And every other FWD I've had has worn about like this too) they'll usually wear in this order, where 1st is most wear 4th is least.... Front Passenger, Front Driver, Rear Passenger, Rear Driver....

So how I swap them 1st time is FP gets RD, FD gets RP, RD gets FP and RP gets FD.... I guess that's an X pattern, but I write it like that to say FP always gets the best tire, FD 2nd best, RP 3rd best and RD 4th best... 5th best is in the trunk, but it will get switched in if any of the others get worse than it. So X pattern really only happens the first rotation, after that they get evaluated and switched accordingly, some corners might keep their tire through a rotation or two.

If I end up with different tires/tread patterns, they stay on the back, driven axle always gets matching pair, or when I'm really poor and have a heinz 57 mix, I match the two closest for the front. I don't "buy" the tire manufacturer/fitter advice of "if you only get 1 pair of snow tires, put them on the back" because half the time in icy winter driving, I'm TRYING to get the *** end to lose grip so I can haul it round to compensate for the front end understeering like hell (Yeah, I'm bad, I have my left foot on the brake and right foot on the gas in winter, steering it from both ends)

Reason for that is passenger side takes most of the weight on a crowned road, and gets most of the standing water, slush etc, so better tread on that side is good. Also IF either side is gonna "let go" first and slip, turning the car, I'd rather it be the driver's side, turning the car toward the shoulder rather than oncoming traffic, AND I feel more in control of a right hand skid than a left hand skid, due to better visibility of the road surface coming at you sideways from the drivers side allowing you much better perception for flicking it back out. You see the relative motion close to. In a left hand skid you're relying on "seat of the pants" feel and vision of relative movement wrt to objects much further away, and also can't see whether you're gonna catch a pothole or something within 15ft say, and flip the vehicle on it.

might check your ball joint(s) for wear as well. tho typically that would be inner tire wear.

Heh, yeah, whoops we missed that so far, you really should be looking closely at the suspension and steering for any problems, balljoints, tie rod ends, bushings, cracks in suspension members or front subframes, and loose strut or broken spring could also do it.

Check also whether it's pulling harder under acceleration or braking, that can tell you something. Like a loose tie rod end, may well be neutral under acceleration but go toe out that side and pull under braking. Listen for any clunks etc as you accelerate or brake or steer.

wow, thanks everyone! Well, I typically accelerate gently and brake moderately. I haven't noticed the pull change in these instances. The toe in mis alignment hypothesis seems reasonable to me. I plan to get an alignment next week. Thanks again! I think I'll swap right front to rear left and front left to rear right (x pattern as RW suggested) to balance things out and give the crappy Wal Mart $35 tires that are currently on the front a break.

Oh, there is one turn I take at speed fairly often that is a left hand turn--so that could also explain it (have to maintain some momentum for the hill, otherwise I'm starting out in 2nd and that's no fun)