[Lotus99]

So let's say I run a 19" setup for the summer, and an 18" one for the winter. From a overall diameter point of view, there is no difference.

But my 19" wheels are 8.5" wide, and 38 offset, whereas the 18's are 8" wide and 43 offset. The wheel calculator says of my 18" setup:

Compared to your existing wheel, this new wheel will have an inner rim which is 1.3mm further away from the suspension strut. The outer rim will poke out 11.4mm less than before.

Based on that, if I was to get my alignment done on my 18 inch winter setup, would it be off slightly do you think when I move back to my 19 inch setup?

If you're wondering the context for all this, I want to get some Springs installed on the car now, after which I would do an alignment of course. But if the alignment will be off a bit when I go back to my summer setup -- which I run 8 months of the year -- I'm debating whether to put off getting my springs until I have my summer setup back on?

PS This is for my X3, in case you're wondering about the numbers above, but I figure the theory would be the same, so I'm asking you guys since I love you!
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[VTECaddict]

No, the alignment will not be affected.

[feuer]

Different rim width and offset will affect the scrub radius and camber, although minimal, with smaller offset the wheel will stick out further out and the car will sit lower. So yes, it affects alignment.

[mike-y]

No, the camber angle will not change. As said above, the scrub radius will be slightly different which may affect steering effort a bit, but your winter tires will probably affect that more.

in short, nothing to worry about.

[feuer]

I learn in theory that camber will not change but after doing so many alignments I have seen different reading on the alignment rack.

With wheels of 10mm less offset and 10mm smaller diameter I have seen increase of 0.1 to 0.2 in negative camber which I contribute to vehicle sitting lower.

I'm aware that is negligible and that I could have gotten 0.1 to 0.2 different reading even with the same wheels.

Camber changes is not something that one should be concern in this instance.

I would be worried about the scrub radius more.

[mike-y]

if the vehicle sits lower because of a different wheel/tire package, that is because the tires are not the same size, not because the alignment changes.

though it is possible that when you have the car lifted to swap tires, the springs don't settle properly when immediately set back down, and it could slightly alter static camber until the car is driven for a bit.

[feuer]

I agree with you, it could be because the suspension was not completely settled but I had to share my observations. Anyhow, is negligible difference. I'm not worried about it.

[Lotus99]

Thanks everyone. So it sounds like getting my lowering springs now with the winter setup, and having it aligned, won't change much when I switch over to my summer setup (which I run like 8 months of the year), so I don't need to put off that mod until the spring.

Right?

[mike-y]

correct!

[Lotus99]

And it all boils down to putting off modding is never a good idea!

[Three_thirty_I]

At the end of the day, if the alignment is correct for one of the sets of wheels, it will be fine for the other either way - it balances out if that makes sense. The slight difference that there will be is on all four corners, and it is to such a small amount that I reckon it would still be within alignment specs, or close. In practice, my 330i had the alignment last done in 2012 still when it had the normal style 159 17" square set on - I changed to style 188 17" staggered set and no issues. You may ask, why has the alignment not been done since. Simple - I have learnt over the years to only have the alignment checked and changed if there is a good enough reason to. So if there is a handling issue or tyre wear issue, otherwise, leave it alone and enjoy the ride - worst thing is to sit with a car that handled well, then had its alignment changed, and it's no longer handling properly. This has happened to me far too many times in the past!