I have not found a complete source of accurate information on this topic.
The 914 is listed as having a 108mm four bolt pattern. What measures 108mm?
The offset of my empi's are about 100mm. Is this the true specs?
I have read else where that offset is a incorrect term. My use of offset is the distance from the inner surface of the wheel to the edge of the wheel rim projected down to the center line. Is this correct?
Wheels are measured as 15 x 6.5. How do you measure the with of the rim? Is it from outer (curb surface) to outer or within the bead to bead? If you were to place your ruler on the rims, from what point to what point would you measure?
What bolt dia and length and thread patern are standard? Ebay has a set of bolts that are 2 3/8" or 60mm in length and 1 1/2 inch or 36mm thead length. This allows about 50mm engaged inside the rotor hubs. What length should the bolts be inside the rotor hubs to be safely secured?
Thanks,
L. MCChesney

108mm is the size of the imaginary circle that would cut throught the center of each lug.

Offset is the distance from the back face of the rim (surface that mates with the hub)to the center line of the rim.

Backspacing is the distance from the back face of the rim to the back edge of the rim.


The rim width is bead to bead (I think)

Can't answer the rest of the questions. I'm ignorant.


Andrew

I think the 4 bolt pattern is 4 X 130 mm, which is a little unnusual today. Offset and backspacing are also important. Empi (and other manufacturers) made a lot of wheels with 4 X 130 bolt pattern, but most had backspacing to fit a bug and the offset was wrong for the 914, particularly in the back.

I know because I have Empi 8 spokes on mine and the people who installed them before I knew better used a pry bar to bend the rear quarter panels out.
Seen from behind it gives it a nice wide stance though. Still it was not the right solution.

Dave

Phantom, is the 108, size of the imaginary circle. Do you mean the radius or diameter?
Dave, I have the Geoff not approved, 8 spoke Empi's as well with 205 on. Fit well when I had non flares. Now, Dave , you say it is a 4 x 130mm pattern. Is that 4 bolts, 130mm from center of hub to center of lug?
Thanks
L. Mcchesney

L.

It is diameter (commonly refered to as bolt circle). On a four bolt pattern, just measure from the midddle of one lug to the middle of the opposite lug. Since I know nothing about Porsches, I don't know if it is 108mm ( 4-1/4") or 130mm (almost 5-1/8").

Andrew

I think Dave is correct with 4 x 130.

130mm = 5.12", which you can see would be the diameter of the bolt circle as opposed to the radius.

Mike

Yes, it's 4x130mm. Measure from one bolt center to the opposite bolt center. (Works because we've got an even number of bolts.) You can also measure from the inside edge of the one to the outside edge of the other. Don't know where you picked up 108mm...

Offset, as mentioned, is the distance from the rim's centerline to the mounting pad where the rim sits against the hub. Backspacing is the distance from the plane of the inner lip of the rim to that of the mounting pad. (Note that you can calculate offset from backspacing if you know the rim width and can estimate the thickness of the rim lip.)

Rim width is bead-to-bead, so you'd put your ruler inside the rim, where the tire goes. (Easier to use a set of calipers with "inside" measuring jaws.) If you measure outside-to-outside, you will get results that are "about" a half-inch too large.

For alloy wheels, you need the long lug bolts. I recall they've got about 40mm worth of threads, but it doesn't all wind up on the inside of the hub.

Very few companies currently make wheels with the 4x130 bolt pattern. Fewer make ones with a 914-friendly backspacing, which is about 4.5".

--DD

108 millimeters = 4.2519685 in

4x108mm = 4x4-1/4in = Ford Mustang Rims

I got a full set Prime 4spoke (smooth) from my friend's 86 Saleen in my garage, anyone need a set for their Foxbody?



Sang

yep, can't stand those heavy Bug rims on a 914. If you want to get your boys involved , get them to help pick out some 4 bolt Fuchs, Mahles, or Pedrinis, or go to the 5 bolts for the windmills, cookies, etc. What ever goes with the wing.

Geoff

Thanks Guys,

Also, what is the bolt size, 14mm?

Geoff, great news! The guys have done exactly that. Their in the process of selling their scout uniforms and are trying to unload some cases of popcorn to come up with the money. They have done extensive research, considering strength, weight and artistic value and came up with these:
They are going with the Battle Ax spinners.
They wanna make you proud!

L. McChensey

Isn't that the rim Mike Mueller is putting on his car??? Nice, really nice.




Geoff

Geeze Geoff,
I was joking.
L. McC

yep, I'm putting rims similar to those on my 914, but I figured out a way to install brushless DC motors to keep the centers spinning when ever I want....when hooked up to the motor controller and G-Tech at the same time I can speedup or reverse the motors to aid in acceleration or brakeing...sorta like reverse intertia.....the hardest thing to figure out is should I make the centers spin at different RPMs while turning around a corner.....

once I get this design down, my next venture will be to make a device to change the air pressure in the tires to maximize the handling corner to corner

The other important specification to check is the Center Bore so the wheel will be hubcentric.
The 4x130 cars will need a 78.6 center bore while the 5x130 six cylinder and converted cars will need a 71.6 center bore.

The backspace dimension will vary dependent on wheel width and offset. For example, a 7" wide wheel with a 35mm positive offset will have a backspace dimension of 135mm, while a 6" wheel with the same offset will have a backspace dimension of 121mm. The backspace dimension may vary slightly with different makes of wheels due to differences in rim flange thicknesses and design, but it usually not by very much.

since you are running GT flares, you have a few more options for rims than the narrow bodied cars that are still 4x130.....you'd need to find a set of VW Bug wheels, 15x7 and 8's are semi-common in the used department, you might luck out and find some brand new in Hot VW mag or something similar.

another option is to run 4 to 4 adapters, some people don't like these, but if made correctly(hubcentric), they are perfectly safe...you choice now for rims is huge...and the cost of good quality rims is very reasonable....

a few of the GT flared cars that I know of, run 7's in the front with a 1" spacer (23mm rim, but with the spacer, it sorta cancels out the offset, so you could figure it to be a 7" wide rim with 0 offset or ~3.5" backspacing)

for the rear you can go wider...it's a matter of cost and wheter you need or just want wider tires and rims in the back

if you did go with the 4 to 4 adapters, a 4x4.5" bolt pattern would be a good choice,early Mustang 5.0 rims (factory or aftermarket)

if you like the look (they look great on Brett W's car) steel wheels can be had from Diamond Racing wheels in the 4x130 BC in a bunch of sizes and backspacings.

Thanks Mueller,
I agree and that is the reason for converting to GT flares. I have 9" flares in back and 7" in front. We have discussed using 255's in back and 225's in front. Thus, would be looking for 15 x 8 rims.
Would you explain more regarding the 4 to 4 adapters. Is this converting a 108 mm wheel to a 130mm hub?
Thanks,
L. MCChesney

What wheels are 108? Is it a typical FWD wheel?

For 15x8's, your best bet is datsun 240 or 260 series wheels, in fact Centerline has these on sale right now for about $80 a piece or 4x4.5 (mustang, which Centerline is also haveing a sale on)


You will not find many 15x8's in a 4 bolt pattern, but there are some for sure.


There are a few companies on eBay that make these adapters, of course they are not advertised exactly with these bolt circles, so you'll have to read the ads and contact them to make sure the can properly make them.

cost wise, I think they are about $150 per pair or something like that.

just a word of caution: it gets expensive and a PITA to be different with your wheel choice...I'm running 16x7's with a 4x100 bolt pattern, since I have no flares, I cannot run spacers or adapters so I re-drilled my hubs/rotors...I just picked up a set of 4 16x9's with the correct 4x130 bolt pattern, but I'd have to run 2" flares on the car and right now I don't want to touch the body.

Mueller,

108 millimeters = 4.2519685 in
4x108mm = 4x4-1/4in = Ford Mustang Rims


I have a set in my garage that a friend is trying to sell. I was thinking about puttin them on my 914, but damn, they're heavy!!!



Sang

Thanks Mueller,
It seems that I would be better served in seeking a VW aftermarket set.

God's speed,
L. McChesney