Hello all,
Last week I installed wheel spacers (15mm rear, 10mm frt) on my recently acquired 2008 C2. I was surprised how the steering feeling changed, something I had not seen mentioned in my prior research. The steering became very light on center and at very slight angles, almost as if it had a play, but very stiff thereafter. Turning at low speeds ie. parking lot required heavy steering wheel effort, like my first Audis from eighties. Done lots of research regarding this condition and going through, no kidding, hundreds of internet posts I have found just one. The poster describing exactly the same weird steering wheel feel after installing 10mm spacers on front wheels. On the other hand, there are posts and videos of people installing 15mm and not mentioning any changes in steering response. I understand that spacers increase the value of scrub radius, starting with negative will go toward zero and maybe beyond, starting with positive will increase SR. I think SR can be modified with adjustments of camber. Anyway, again I was unable to find any info regarding Porsche value of scrub radius. It is just my curiosity, since I have removed the front shims leaving just rear ones. Maybe in the future if I find what camber to set for 10mm spacers I would install them back. Strangely, the car does not look weird at all with only rear spacers. What say you?

 

I got an alignment after putting spacers on even though people said I didn't need one.
I also needed to torque my wheel bolts after every drive a few times before they stopped slightly loosening, which could have been a lot of different things but it seems worth mentioning. I had gotten new bolts in the correct length with the spacers from RSS, and since everything settled, I do not have to torque them so often.
Any time I have widened my track, I do feel like it adds some level of steering effort, whether is it wider wheels, wider tires, or adding spacers. Usually lowering and widening the track on all my cars has changed the steering radius for the worse as well.
My cousin had a 997.1 GT3 that came with 5mm rear spacers and no front spacers. There are a bunch of legends regarding this about Porsche engineers miscalculating the offset but IDK what the real reason is. The 997.2 rear wheels are exactly the size and offset of the 997.1 WITH 5mm spacers, so 🤔🤔🤔.
Right now I am using 997.1 GT3 wheels with 5mm spacers front and rear. IDK how that is relevant but it seemed like it at 1am.

 

Widening the front track isn't great.

Had 8.5 et53 wheels on my car and it drove great.

I put a set of 8.5 et42 front wheels on my car once and the stability was gone. It would dart over road crowns on the highway, wander around over 100 mph, and was very non confidence inspiring. Removed then after a month.

Bought custom 8.5 et50 and the rock solid stability was back.

On all 3 sets of wheels I ran the exact same make, model, and size of tire and never changed the alignment aettings. From my experience there is some offset number that throws the handling over the edge and it's somewhere in the low to mid 40s because 42 drives like crap and 50 is still fine.

 

Agreed. Correct torque is critical.

Interesting. I will mess around with offset(s) and see if a higher offset increases highspeed stability / tracking with my platform.

 

I suspect that Porsche, at least 997, has negative scrub radius setting. Therefore adding 10mm spacers changes SR to being at zero, but not enough to become positive value, creating this "weird" steering feel. BTW, I use ECS spacers which came with longer bolts and I do keep in mind, as mentioned, checking torque periodically.