I have done some search re-search on our wheels. You all know the basics, 4 x 130 and 4 5/8 backspacing. On a thread somewhere I read for a 15 x 7 wheel the perfect offset would be 35mm to work with a stock fendered 914. Tire rack will custom drill the K1's for you.... Hmmmmm. Their blanks come in offsets of 12, 27, 38, 45mm. So with a spacer, and longer lug studs, or pressing in bolts to the hubs, one of these should work.

I keep getting the measurement of offset/backspace bassakwards. If I've got this right in my mind, the back spacing is from the back, or "inside" edge of the rim, measured to the mounting surface of the wheel hub. The off set would be the measurement from the front or "outside" edge of the rim, again measured to the mounting surface of the wheel hub.

So, if 35mm is correct as the optimum offset measurement, I'd want the 27mm blank and use a spacer, as this would initially put the "inside" edge of the rim to far in to the fenders, so the spacer would bring it back out, closer to the outer fender lip.

Have I got this right? Anyone contacted tire rack on this, or done it?

Oh yea, the big question, $$$. We have a tire rack dealer in our auto x club who basically sells at cost to members, he's checking in on $$$. The retail on that rim per add in GRM is $119-149, and another $30-40 for specialty maching, plus shipping. So cost for a 12.8-13.5 pound 15 x 7 wheel would be around 200 each. Cheeper than those fancy 3pc rims, less than panasports.... but still you'd have to mess with spacers and bolts/studs to get it all perfect.

sorry, those rims don't have a large enough diameter on the hub to make 4x130 bolt pattern rims....I think 115 or 120mm was the most they could do.........

offset is from the centerline of the rim measured to the inside of the lip, backspace is measured from the hub face to the outside of the lip

the thickness of the rim does not affect offset, yet it affects backspacing

If yer gonna screw with the studs....my modding them for longer length and such....just go with a standard pattern.

4x100 and get the wheels that fit with the offsett you need.....be advised each time ya munch a rotor or replace due to surfacing for a brake job, you have to make over the rotor AGAIN. Long term it gets expensive and to be a headache.

Or just do what's been found to be easiest, swap in a 911 front end.

Just spend a little time in the SCCA rule book; it looks like in Street Prepared you couldn’t pull off a 5 lug conversion. They say the diameter of the lugs themselves can be changed and bolts can be modified to accept lugs, but they make no mention of an allowance to change the bolt circle or the number of lugs.

Additionally, the stock brake caliper must be retained and conversion to a two piece hub/rotor is specifically prohibited.

So are we ready for a trip to Diamond Racing in Milwaukee?


David

Diamond Wheels are gud. and damn sexy.
15x8 is te narrowest. and the model will determine back space. Avengers 16 lbs 4 1/2" Pro 19 lbs and 5" back space.
pic your poison and go racing.


WONDER IF THEY WILL ENTERTAIN A GROUP BUY?
I want another set for the street....

Street prepared????? Screw that Street mod baby.

Street Mod is a scary place

David

Under that hood lies supercharged, water intercooled, 300 or hp motor in an 1800# car, he needs a full tank of gas to make min wt. Oh, and at the last event, that car and driver were 2 full seconds faster than the next fastest car w/fenders, and they beat an Fmod openwheeler. And this in a 110 car grid... scary place indeed!

Back to wheels, the diamonds sound sweet, but the 8's will never fit under the stock fenders, and if I was going to hack/bend/grind/mangle fenders I'd round them off and run some 13 x 9's and 245's.

What kind of backspace is needed to fit 7's under the fenders? I'd go so far as to cut or bend the inner fender return or lip for another 1/4 inch or so, but want to keep the stock look of the car...

Offset is CL of the rim to the mounting face.
Backspace is the inner edge of the rim to the mounting face.

I use backspace for about everything wheel related. 4.75-5.0 in is bout perfect for a 914. Most of the 4/5 lug Fuch we use are right around that.

Mueller is typically right on with his assessments. Even Keizer had some problems with their standard blanks when making my 10.0 lb race wheels to get the 4x130mm pattern and appropriate spacing.

As somone who has gone the custom wheel route there are a couple of things you need to watch out for beyond backspacing. If its a 74-76 car you will need to make sure you have proper hub centric bores in the wheels. Also the front caliper overhangs the plain of rotor hat where the wheel mounts. You need to make sure custom wheels clear the front caliper. In most cases that overhang wont be a problem as its only about 1/4 to 1/2 of an inch. Rear caliper doesnt overhang. Of course you could always go with a differnt backspacing and just use spacers and eliminate bot of these issues.

5" backspacing is a good number based on what I see with my wheels. clearence with inside fenderwell and suspension is good. My 15x8" wheels with 5" backspacing just required a bit of fender massaging. I do want to dispell the myth that you need to grind and cut etc to get 8" wheels to fit if you have proper backspacing. I'll have pictures soon. Biggest issue with 8" is you dont need them unless your running r comound 205/50 tires that can handle a 8" rim. Only reason why I'm running 8" is because the wheel guys made a mistake and I can get away with running an 8 inch wheel with DOT R compounds in the AX class I plan to drive in.