Razor1973

To make a long story short, I bought my front tires online and got the wrong size (245/45-18) and never realized until I installed them (I'm an idiot). I am still not sure whether it was my error or the seller's and that's something I'm trying to work out right now, but the point is the tires have been mounted for almost 2 months now and I just realized when I bought and got my rears tires (the right size this time).

My question is... Is this a huge deal? What consequences could this have on my driving experience, wear, etc.? I honestly haven't been able to tell because I've also needed balancing and maybe an alignment, cause my car hasn't been driving the same as before. Maybe it's the tires, maybe it's in my mind, which is why I wanted to ask the experts.

Also, if I were to keep these tires or at least for whatever long I have them, how much should I inflate them? Same as the standard ones?

Thank you in advance!

By the way, I also have two other questions I've posted in different threads here and here.

crypto

Huge deal? no .. especially if you fit them on and have had no problems - they are just a bit higher than the normal size. I'd just google the inflation settings.. I've always found people run a pretty good degree of varying PSI levels for both the front and back in most of these threads. If your gas mileage seems fine, you're within spec, and you're not having any ride issues then you're probably fine. This is a tire size you hear about more as a winter tire though.

Razor1973

I'm in Miami, so I definitely have no need for winter tires.

My car has felt shaky and more disconnected from the road, but I can't tell whether this is because of the wrong tire size, lack of balancing or misalignment.

I am currently working with TireRack and will consider this purchase a $411 loss if they can give me a substantial discount on their Continental ExtremeContact DW 245/40-18's, which are currently actually on sale. I'd be paying $316 including shipping. Maybe I can sell the slightly used ones.

Thanks a lot for your advise! I'd love to read others as well.

SilberGrauE60

Using this calculator, Tire Height Calculator, your 45 aspect tires are 1 inch taller overall (26.7 inch vs. 25.7 inch) than the OEM 40 aspect tires. Doubt this alone would produce any noticeable difference in feel. You don't say what brand/condition the rear tires are compared to the new fronts, but if different make/model, this is more likely the source the the feel.

Razor1973

The tires were the same make & model (Continental ExtremeContact DW), but the rear ones weren't in the best shape. That's until this past weekend that I had those replaced as well (same make & model). The car does feel a lot better now, although it's still shaking at higher speeds. Balancing, I'm guessing, right?

Thanks for your feedback, guys!

SilberGrauE60

I just put 4 Michelin PS2s on mine, and it was recommended by the M6Board to do a full, four-wheel alignment at the time of the tire change. I'm glad I did. Before, I was having some steering wheel shake/vibration, and now it is all gone. I guess I have been converted to this practice, on these BMWs at least.

Razor1973

How much are those approximately? I may do that.

SilberGrauE60

If you mean the cost of a four-wheel alignment, it was approx. $150 at the dealership. One of the additional things I asked for was to take out as much negative camber as possible to improve the tire wear. I had cord showing on the inside edges of the fronts while the main section was still visibly above the wear bars. You did not say if you have Sport Package or not, but 18s indicate you might have it (even staggered, if not xDrive), and these are typically set up with a good amount of negative camber, wearing the inside edges well ahead of the main section. Negative camber helps with high-speed stability, i.e., cruising the autobahn at 100 mph or higher, so if you don't need it, it's safe to dial some out.

Razor1973

Sport, no xDrive. That's a good idea. I'll probably ask the same if I have an alignment done, which sounds like I will. Thanks!