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Discussion Starter #1 (Edited)
My new fitment questions are not getting much traction in the Wheels section, so hopefully more experience here with this sort of stuff. To start with I've rounded up a set of '10-'14 CTS 18"x 8 1/2" and Conti Extreme Contact DWS06:






In trying to clear the skirt skirt tabs without going overboard too far inboard I've been going through offset calcs for the spacer adapters. I had seen different offset numbers given for the oem Fleetwood 15x7 wheels: -6mm, 0" and +6 have been listed in search and online. Then I came across this from here, showing +10 offset:
https://www.wheel-size.com/size/cadillac/fleetwood/1996/#trim-57i-lt1-usdm-255







I first worked up the comparison below between the stockers and new setup just as an exercise. Then I figure the most valid numbers are below that by comparing the closer size (and more familiar to me) Impala SS 17x8 1/2" wheels I ran for years with 255/55:
oem Cady FWB v. CTS




SS Wheel v. CTS:


I tried a mockup of the wheel/tire in the well at riding ht. For reference the existing lugs project 1.1" from the rear drum, and with the mounting face of the CTS wheel tight to the "end" of all the lugnuts I get about 1/2" from skirt tab to sidewall (even before modding the tab at all), and the same 1/2" from sidewall to frame. Us Fleetwooders know you can pick up a 1/2" more clearance to the skirt just by slicing off part of the unneeded top of the lever plastic pocket.

The best size spacer might be 1.25". I'm just looking for extra eyes-on with the math, and especially any experience from anyone with similar setup that I can take into discussion with Motorsport-tech/Adaptec next week for a spacer-adapter order.

It's of course going to be tighter with this setup, so really interested just how thick a spacer can be used in the rear BEFORE it interferes with the tire getting past the fender. lol
 

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You should be able to run either a 1.25 inch or 1.5 inch spacer and be safe. I have run an 18x9 inch wheel with a 5 inch back space no problem.
 

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Does the CTS and Bbody have the same bolt pattern?


I ask because I have both a CTS and a Bbody. I find it hard to find rims for my CTS as they say its a special size. Just curious.
 

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Discussion Starter #4
They are NOT the same. B-/D- body are 5x5 (127mm), and CTS is 5x120. Most CTS wheels have very high offset compared to the +6mm or so on B- and +10 on a D-. I am working with Lenny at MotorSport Tech on a set. Will post upon final configuration, and working with numbers close to what Neil mentions.
 

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Discussion Starter #5 (Edited)
Those Vogue Octavos & Gold Stripes

GOING



GONE ! !



Recapping: CTS 18x8 1/2 48mm offset, with 255/55 Continental Extreme Contact DWS06. Note original FE1 coils with 1/3 coil cut off fronts, which gives 1" drop. No air in the Airlifts. Much improved ride. The little 15s were bald, and 18s with new rubber sure ride quieter and less clunky. I'm guessing about 100% of you guys would like another 1" drop in the front to get me back to before the +1" tires. I'll have to settle for 5# in the airbladders for now. A little rub on the stab bar and rear of the opposing LCA at full lock but that's expected v. stock.

The spacers for the back were easy enough. After measuring at ride ht. I decided on 1.3", but for other's benefit you can add almost 1/2" to that if shaving the forward skirt tab. Mind you all this is +48mm offset wheels. With mock-ups, lots of measurements and sketches it took several back-n-forth with Lenny Jr. at Motorsport Tech. to revise from the rears to work on the fronts. I will say he is great to work with. First, the hubcentric lip and part of collar had to be shaved to clear the hub:









The diciest part turned out making sure the spacer is thick enough so the grease cap clears the little wheel centercap. I didn't want too thick and lose all bearing on the hub to positively center the wheel. I settled on the same 34mm thickness all 4 corners. I lucked out - the note hub is proud of spacer a bit over 1/4":




Now I'm off to rebuilding the opti (again) and try to finally lose the 0336 code to pass inspection. If no luck then I'll have it programmed out with the rest of a tune. And there's a new catback laying in the garage. I'm already planning new paint - another monochrome scheme.

 
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