I wondered if anyone has tried to run 17" turbo twwist wheels on their 914. The tires that came on the wheels are 205/50/17 fronts, and 255/40/17 rears. Wanting to go less "chunky" on the size, I was advised to go to a 195/40 front, and a 245/35 rear. Also, it looks like I need approx. a 20mm spacer for the rear, and about 13.5mm front. Any help is appreciated. Confused.

Boxter twists or turbo 911 twists (18's)?

I use the 9" rear boxster twists on the front of my car. and the 911 turbo rears on the rear..

We need to see what flares you have before any suggestions are really made... I have 1.5" of spacers up front and 3" of spacers in the rear.. But I have some decently wide flares.

Also need to know your wheel width.

Offset would help... along with width

Boxster twists (17 X 7 et 55) with 205's all around. rolled lips, not pulled. 1/2" spacer in rear and about 7/8" spacer in the front (I machined down a set of 1 inch). I would think the 205's on the front would be just fine, especially if you have flairs. I have 255's on my 928 (running the twists also like you have) and I think if you went narrower it would look funny on the rim.
Click to view attachment

I am running front offset with spacers (205/45-17) and rears with spacers (235/40-17). Offset per front is 55mm and rear 52mm since these are Cup II Non Twisted. With these tires I can run larger tires in the rear going to a higher diameter such as 245/45 or 50, 255/45 or 50 which does not present too much of a problem. The fronts are a little different and appear to have a problem in the front lower fiberglass flare. Yes, I am running different type rims than the twists and the width of the tires may be different: front 7in; rear 9in).

I am only commenting to give you an idea of what I have been used. The front lower lip is the problem I will have in determining larger series tires thus I will be modifying them accordingly. My main purpose is to put as large as series tire as possible under the car since my suspension is stiff, the sheet metal has been seam welded uncritical places, and I have used several of Tangerine Racing stress kits in the rear critical areas. I need a little more give in the front suspension since on very rough road surface I move laterally 2-4 inches. It has a very critical edge which I will be trying to setup a little softer, corner weighting and balancing, and very tight alignment.

Not to confuse you but this is to give you a whole picture of how I am developing my project.

Great responses. First and foremost, the pics are attached. Secondly, I have 7" front, and 9" rear fg flares. I have obviously converted to a 5 lug, and the rims are 17" boxster turbo twist. As pictured in the mostly green project. The sizes appear to be 17x7 front, 17X8.5 rear. Thaks for the info thus far. Click to view attachmentClick to view attachment

I think you need more spacers. I had to use 2" (52mm) on my early 911 and turbo twists.

I have a few sets of 21 mm spacers and some thicker ones. I think they are 1-1/4. Why not bolt up the wheels and see how they fit ?
It would give you a starting point. The studs required vary with the amount of spacer used. The lenght needed is 45 mm plus the spacer thickness.

You wont be able to bolt them up. You'll need at least a 1" spacer. What I would do is grab a big package of washers and start putting them on the threads until the rim fits like you want it on the fender. Then order the proper spacers.

Great practical advice. I have a bag o' washers and will be on it tomorroe. Many thanks.

Unless you have extra long studs in there now you can't get many washers on the studs and still install the lug nuts.