Wheels and offset

[M/bikertom]

So set of wheels

Front 18 x 8.5 et 57

Rear 18 x 10 et 40

 

Original

18 x 8 et 57

18 x 9 et 43

 

Proposed wheels will sit inside the front wheel arch by 6mm and 10mm more at the rear, being closer to the wheel arch by 6mm front and 16mm at rear though tyres I'm fitting will be the same 235 and 265's.

 

On a standard Cayman, no "S" can anyone see any issues fitting these without spacers?  

 

Many Thanks

 

Tom

 

 

 

 

 

 

 

 

Edited August 1, 2016 by M/bikertom

[Beanoir™]

Which wheels are they Tom, from another Porsche? 

 

Mine are 19" 8.5"and 10", rear offset is 42 I think, so should fit, they'll be closer to the outside of the car, but should be ok, about 15mm - given people fit spacers wider than that on the rear.  

 

 

Edited August 1, 2016 by Beanoir

[CaymanDave]

Big difference on the rear! Spacers will shift it even closer to edge of wheel arch..

 

 

 

[DKR_77]

I don't think protruding towards the arch is the issue general on the rear, especially with standard ride height (non PASM or Sports Suspension) it's normally how close it sits on the inside of the arch and proximity to the other components, suspension strut etc. 

 

 

[Red5]

They might need to be squared up with some spacers, to get them the same front / rear!

 

Are they aftermarket? Do you have any plans for TPMS sensors? 

[Highland Fling]

A very interesting graphic on the wheel offsets CaymanDave. 

 

Can you explain where the ET value is measured from. For example, the lower the number, say ET40 compared to ET43, the greater the offset from hub to rim giving more of a dished effect.

 

The reason I'm asking is that I have a set of 19" X 8.5", 19" X 10" Spyder alloys, the rears are ET42, the fronts are ET55, which I am retaining for occasional fitting on my forthcoming new 718 Cayman S. This new car will have the 20" Carrera Sport optional alloys fitted. I am currently seeking the ET offset values of these new optional wheels so I can verify wheel arch and suspension strut clearances.

 

I am interested in finding out where the ET values are measured from.   

 

Brian          

[Highland Fling]

As a postscript to the above, I have now discovered the offsets of the 718 optional Carrera Sport alloys.

 

20" X 8.5" ET57

20" X10.5" ET47

 

I am now even more puzzled.

 

Going by the photos of the press Miami Blue 718 Cayman S with these 20" optional wheels fitted, the dished effect of the rears look very similar to my current 19" Spyder alloys.

 

These ET values are quite confusing.

 

Can anyone explain please.

 

Brian   

[Trickle]

Does the overall width of the wheel not play a part in this too Brian? So an offset of ET47 would be a different distance from hub to run on a 9" wheel compared to a 10" wheel...or is it a constant?

[bcr5784]

Offset is measured from centre line of the  wheel.  So a wider wheel with the same offset as a narrower one will protrude both inboard and outboard of the hub by half the extra wheel width more.

[Highland Fling]

Thanks guys, for your info on the ET values. I did suspect the measurements were from the centre line of the wheel through to the hub flange. It's a tricky thing to measure.

 

My thinking is that my 19" X 10" and 19" X 8.5" Spyder alloys will successfully fit my new 718 Cayman S without clearance problems.

 

Brian