The best and easiest way to upgrade your Classic Volkswagen is to go with a different wheel set up but you will need to do one of three things.
Install adapters (Not recommended)
Change over to disc brakes with the bolt pattern you need
Purchase blank drums and drill and stud them to the pattern you need
Close your eyes and think of the ultimate wheel for your ride. You are
going to need some specifics of that wheel. Bolt pattern being one of
them. To measure bolt patterns check out this video.
The next spec you will need is the offset or backspacing. To figure out what back spacing you need.
For example we will start with the popular
17" diameter 7" width wheel. This particular wheel has a back spacing of
4.50". What does that mean? It means that from the back face of the
wheel where it would touch the drum or rotors to the back edge of the
wheel measures out to 4.50". If you take a 7" wheel and minus 4.50 " you
have 2.50" that will need to go towards the outside of the car.
Back Spacing = 4.50"
Front Offset = 2.50"
Those two measurements equal the width of the wheel. So you need at least 2.50" of gap between the rotor and the inner fender lip for that particular wheel to fit.
So you go out and measure your front offset and you come up with 2.00". That means the wheel will stick out 1/2" on each side. Does that work? The answer is no and yes. It will not work with the configuration you have now but you can now narrow your beam to compensate for the amount needed. So if you install a 2" narrowed beam you would be tucking under the fenders by 1/2" on each side.
For all pre-66 Beetles in stock configuration you usually have about 2" of front spacing in the front and 2" in the rear. But this is just an estimation. To get an accurate measurement you will need a carpenters square or something similar to verify what the front offset or "B" is.
These particular pictures are from our Project 73 Super Beetle. It had 3" front spacing or "B" and 5.250" back spacing or "A" in the rear with stock fenders. We put 17x7" wheels on it that had that a 2" front spacing and they fit like a glove.
The keys to being able to put any set of wheels you want on your ride come down to these products.
Bolt Pattern (Disc brakes or Drilled Drums)
Any collaboration of those could be needed to make your dream wheel fit on your ride.
Just a note of caution, rule of thumb here at Airkewld, keep the width of the wheel to 7" - 7.5" and the diameter no larger then 18". Anything larger can and will damage or wear out your chassis components faster than you can imagine.
So I have come up with a new formula to figure it out.
The Gap -
A - The distance from your rotor or drum to the inner fender lip of the top of the fender
The Width -
B - The width of the wheel you want to use
The Back Spacing - C - From the back pad of the wheel to the back edge of the wheel
Track Adders - Drop Spindles = .375" (3/8) -
D - Disc Brakes .375" (3/8) - E
EXAMPLE - 17x7" Wheel with a 5.00" Back Spacing. Our 58' Beetle has a 2" fender gap and we plan on installing drop spindles and disc brakes on it. Will our wheels fit? Let's do the math!
Back Spacing 5.00" - C
Wheel Width * 7.50" - B
Fender Gap 2.00" - A
Drop Spindles .375" - D
Disc Brakes .375" - E
Front Offset of the wheel - X
Track Adder's Added up - Y
Modified Fender Gap - Z
Narrowed Beam Needed - Q
Real Time Offset - RTO
Back Spacing - BS
Additional Offset - *
(B - C = X) ((A - (D + E = Y) = Z
X Y Z
(7.5 - 5 = 2.50) (( 2" - (.375 + .375 = .750 or 3/4") = 1.25" Fender Gap))
Now we need 1.25" of narrowed track on each side giving us a total measurement of 2.50" narrowed beam. If we would like it flush to the out side edge or tucked further in we can use a narrower beam to give us the added look and effect.
(Option 1) ((X - Z) = RTO) x 2 = Q
((2.50"-1.25") =1.25") x 2 = 2.50"
Option 2 = X - If we have 1.25" of (MFG) and the rim width is 7" we subtract our MFG from the wheel width to give us our back spacing needed to fit wheel on the car. That would give us 5.750" back spacing needed to fit. If this was not confusing yet here is the confusing part. When you see a wheel list as a 17 x 7 wheel it is actually a (* 17x7.5") because wheels are measured from the inside edge of the bead to the outer edge. So any time you try to do the math always add .500 (1/2") to the back spacing as a rule of thumb.
(Option 2) ((B - Z = BS) + * = RTO
(7" - 1.25 = 5.750") + .500" = 6.250 RTO
If this math has confused you I still do not believe I actually wrote it out. This is why a majority of clients ask me for this info because it is this difficult. But after a while it is common knowledge. I hope this helps.