18" Wheels Speedo Calibration on '01 Boxster S

[chriscase200]

Might sound like a silly question but i want to put 18" wheels on my Boxster 'S' and i want to know how to recalibrate my speedo, does this have to be done by porsche or can i do it myself

[2 Smokin Barrels]

Are the profiles on the tyres reduced, the circumference therefore being the same?

[chriscase200]

Never thought of that
Its just an idea at the moment, can you recommend some tyres that will match the circumference. of a 17" wheel with standard tyres

[The Undertaker]

You shouldnt have to recalibrate unless you have gone well under/over the standard tyre sizes.
To go from the standard 17'' diameter 205/50 fronts and 255/40 rears to an 18'' wheel the sizes of tyres as a standard upgrade are 225/40 and 265/35 and do not require you to recalibrate the speedo.
Hope this helps

[chriscase200]

Yeah, it helps a lot!!! , You've just made my decision for me...i'll do it!
Thanks Undertaker
Chris

[The Undertaker]

Theres some more info on this thread.
www.pistonheads.com/gassing/topic.asp?t=187295&f=137&h=0

Just remember if you use 10J rears with spacers you will need correspondingly longer wheel bolts.