Boxster Wheels/Tyre Sizing (Help Please)

[Verner]

Hi guys,

please forgive me for asking what is probably a very stupid question.
When it comes to Wheels/Tyres I have absolutely no idea.
I have a 2006 987S (Below):-

I am looking to purchase a new set of rims for her and have seen these "turbo" ones on Design 911 which I like,

The recommended Sizes are:-
Front 225/40/18
Rear 285/35/18

According to the tyres I am currently running they are:-
Front:- 235/40 ZR 18
Rear:- 265/40 ZR 18

I don't understand, does that mean I will need to get new Tyres for the new Rims, should I purchase them?
Does it mean these rims are the wrong size for my Boxster?
Once again, apologies for asking stupid questions, but as I mentioned before i am clueless.

Any advice would be greatly received,
Best wishes from North Yorkshire,

Verner

 

[AndrewCS]

Hi Verner,

See the attachment for the correct, original sizes.

Those in the advert do not match the Porsche data.

I`m not saying that they will not fit, just be mindful of having correctly matched offsets (ET in the ad / RO in the attachment), wheels and tyres

 

[Motorhead]

Verner,

Just to add to what Andrew has said, your Boxster has the correct tyres for the 18” rim. I think that your wheels are 8Jx18 ET57 and 9Jx18 ET43 (where J is the rim width and ET the offset) so the advertised wheels differ in a number of respects, the offsets in particular which may or may not be a problem for wheel arch clearance on front lock in particular.

Apparently the ideal tyre width for an 8J rim is 225 or 235mm and that for a 10J rim is 265 or 275mm so the advertised tyres are correct for those wheels.

I suspect that you’d be OK with those wheels and tyres but wouldn’t like to give you definitive advice. If you’re really keen then I suggest that you contact the supplier directly to verify the suitability of the wheels and tyres for you car.

Jeff

 

[Chappelle]

Verner

Don't do it, wheel sizes are wrong

Fronts wheels before after are okay (see above) as the wheel is the same diameter and width and would stick out by 7mm. This would be okay.

The rears are NOT suitable (in my opinion). I'll try to attach the calculations but in essence they would stick IN by 9mm but worse there would be 35mm less clearance inside the wheel arch and this is a no-no as it could well foul the suspension / brakes. Plus the car is going to look very odd with the front wheels sticking out relative to the original and the rears sticking in. In theory you could use wheel spacers to bring the rears out but I'd strongly advise against this as you'd still have wheels likely to foul the suspension


Your best solution is to look for wheels that match EXACTLY the dimensions of the standard wheels, ie 18 inch diameter 8J = 8 inches wide at front and 9J = 9 inches wide at the rear, but probably MOST IMPORTANTLY the correct offset as per Andrew's note of 57mm at the front and 43mm at the rear

 

[Chappelle]

Second calculation for the rears

 

[Chappelle]

Update: the wheels you have shown are for 911s not Boxsters. You might want to consider CODE: 458018081047 though thought would be needed if you wanted to keep your current tyres in particular the rears