Changing to 18" from 17" rims, issues?

[UppNer]

Hi all,

I have a 986 -00 base with 17" rims today.
Yesterday I bought 18" 997 rims which I guess (hope) will fit my car.

But, how will I for sure know that they´ll fit my car, is there somekind of table or calculator that can tell me this?
Do I maybe need spacers or do some other mods?

The new rims are - Front: 8Jx18H2 ET 57 and Back: 10Jx18H2-ET58

Is this enough information or do I need more?

I mean, just because they fit in the wheelhouse standing still, what happens when I start to drive on a bumpy road, in corners etc?

How shall I think?

Thankful for all input on this, BIG thanks in advance!

[ike84]

Check out willtheyfit.com. They have a great tool to show you differences between setups. If they're closer than your stock setup, you may need spacers.

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[PaulE]

This table from the Boxster Owner's Manual (not sure what year) may help in picking a spacer size. Since 10 inch rears for a Boxster have a 47mm offset and your 997 rear wheels have a 58mm offset, a 10 or 11mm spacer may work on the rear. And on the front, the 8 inch Boxster wheel has a 50mm offset and the 997 wheels have a 57mm offset, so maybe a 7mm spacer. You will also need to change your lug bolts to longer ones to account for the spacers. They might also fit without spacers, but you would have to mount tires and check clearances. The handbrake cables may also need to be ziptied away from the tires.