Porsche 991 wheels - will they fit my 987?

[Andy L]

Wondering if anyone can help me out with this question. I'm looking at a set of 991 wheels, but I'm not sure if they'll fit my Gen 1 987 Cayman S. The wheel diameter is the same as on my current rims (19 inch lobster claw), and the fronts are the same tyre width 235 albeit with a slightly deeper side wall 40 as opposed to 35. The rear tyres are 285 as opposed to my current 265, but I'm running 15mm spacers on the rear and there is still plenty of room inside the arch so I'm assuming that's ok. Sidewall depth on the rears are 35 which is the same as my current setup. What I'm worried about is the offsets though. I'm clueless on this topic... The full spec of the wheels/tyres is:

 

Rear 11J/19 ET69 - 285 35 19
Front 8.5J/19 ET54 - 235/40 19

 

Any advice gratefully received!

 

Thanks,
Andy

[Rob63]

http://www.alloywheelsdirect.net/information/fitting_chart/porsche

 

Any use?

[Andy L]

Thanks Rob, but I'm not sure it does. My understanding is my current wheels have an offset of ET57 front and ET67rear which would say my current wheels won't fit according to this chart. I could be wrong though if the 987 uses the same wheels as the C4/C4S.

[Bushman]

there is a lad at work with a 987 Boxster who has 911 19 inch rims and boots on it. he has 295 35 19s at the rear. you have to use spacers to clear the rear struts. there is a delicate balance between clearing the strut and hitting the arches if you go too big with spacers.. he has 245s on the front but dropped down to 30 profile tyres to stop them dragging on the wheel arch liners. this car also has a hefty roll cage so was probably set up as a track day special. I will try and find out more if he is about next week

[PorscheGT4]

it the rear offset which is the issue.

[DJMC]

... and your insurer's permission also...?

[Andy L]

Thanks all for your input. I had meant to post and update on this, but I've been distracted over the last couple weeks looking for a new car for my wife. Managed to get that sorted over the weekend so I now have my life back...

 

After seeing Rob's post on the 27th I spent a fair amount of time scouring the internet in an attempt to get my head around wheel sizing and offsets. First thing I realised was that the information I'd originally been fed about  911 wheels and Cayman wheels being the exactly the same across each series (e.g. 9x6, 9x7, 9x1) is complete bull. Yes the fronts are the same but the Cayman rear wheels (on the 987 at least) are closer in offset to the 997 4S wheels. Another useful bit of information I found was that genuine Porsche alloys have the width and offset stamped into the wheel either side of the valve stem.

 

Armed with factual information I then came across a great website  http://www.willtheyfit.com . Here you simply enter in your current wheel, tyre and offset data along with the same data from the wheels you are considering. You then get a breakdown of all the relevant data as well as a visual representation of how the new wheel will sit in relation to the current set up. Turns out the wheels I was considering would be 18mm further in from the wheel arch than my current wheels but critically over 40mm closer to the strut. to get the outside edge of the wheel anywhere close to where my current wheels sit with the 15mm spacers I'm running would have meant using 30mm+ spacers on each side. Even then I wasn't sure that gave me enough clearance strut side. In addition to the clearance concern I was also worried about the potential impact on handling of adding 60mm+ of spacers across the rear axle along with an additional 40mm of rubber...

 

Taking all of this into consideration I decided to stick with my current set-up.