Type Three Tuning Page -- Rims

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Answers by Jim Adney from the Type 3 email list:
> A while ago I asked how one tells the proper wheel. Someone replied that
> between two lug holes [on the rim] would be 15x41/2J. The spare in the square I just bought
> has 4Jx15, the one that I took off a junked square has 41/2Jx15, and the one I took
> of the T3 Ghia I junked has 51/2x15 . Aside from the scrambling of the order of
> the numbers how much difference does this make?

These could all be real VW wheels, except maybe the 5-1/2". I'm not sure if VW ever sold that size on one of their cars, so it may be aftermarket or from a late beetle. If these are all 4-bolt wheels then only the 4-1/2 could actually be a type 3 wheel.

OE VW wheels have VW stamped into them with the month and year, the offset, diameter, profile, and width. There are 4 raised flat sections between the 4 lug bolt holes. Examine each of them for stampings. You should find a VW logo, a size (type 3s say 4-1/2 x 15J) a date code stamp (year and month in a circle) and a 2 digit number. The 2 digit number is the offset which for type 3s is 46mm. Sometimes this says ET46. Scrape or wire brush these surfaces to find the info. If you can't find anything there, find a straightedge that is about 12-14" long. Place it against the circular ridge that the hubcap goes around and then slide one end outwards until it hits the rim. If it hits right in that area where the balancing weights fit, then it is a type 3 wheel.

If it is a Type 3 wheel it will say 15 J 4-1/2 AND 46 somewhere (sometimes prefixed with ET). If it has an number other than 46 it is a beetle wheel. ET stands for Einpress Tiefe, which is German for Offset. One can loosely translate it to "Pressed Depth". These are all on the OUTSIDE, the side that faces outwards when the wheel is mounted on the car.

For every tire size the tire manufacturer has a recommended range of rim widths that will work correctly with this tire. 4-1/2 is the right width for a 165 tire while 4 is correct for a 155 tire. A 5-1/2 rim would probably be good for a 185 or 195 tire, but way too wide for a 165.

> What are these numbers measurements of anyway?

4-1/2 is the inside measurement (in inches between the rims) that tell how far apart the bead of the tire will be allowed to spread.

J is a designation of a certain kind of rim profile. J rims were introduced in about '66 to use with tubeless tires and have the "hump" just inboard of the bead seating area on each side. Non-J rims should always be used with tubes, otherwise there is danger of sudden loss of inflation on hard cornering.

15 is the diameter of the rim where the bead seats, in inches.

46 is the offset (from the rim centerline to the mounting plane) in millimeters (mm).

Thus, the correct offset for a T3 rim is 46mm and the rim should be a 15x4/12J.

Offset Image Backspacing/Offset Explained by John Jaranson
"Backspacing" and "offset" are two different dimensions on a wheel. They are often used interchangeable in conversation, but are unique. It is also important to know the difference and to check with your wheel supplier when ordering to find out which measurement they are using.

Backspacing is the distance measured from the mounting surface of the wheel to the inside rim edge. Backspacing will always be a positive number, unless you have a VERY strange wheel.

Offset is the distance measured from the mounting surface of the wheel to the centerline of the wheel. Offset can be either positive or negative. Deep dish wheels will have a negative offset. Most production wheels have positive offset, including the T3 wheel.

Here's a little exercise to help:
15"x5.5" rim should have an offset of what?

a = Stock offset = 43.0mm
b = Stock width = 114.3mm ( = 4.5" x 25.4mm )
c = New width = 139.7mm ( = 5.5" x 25.4mm )
d = New offset = ??.?mm
e = Stock Backspacing
f = New Backspacing

You have to decide what your goal is.

a) Do you want the load on the bearing to be the same? The preferred method as it saves your bearings.
b) Do you want the inside edge of the rim to be the same distance from the inner fender well?
c) Do you want the outside edge of the rim to be the same distance from the fender?

The solution is different for each goal.
a)Here the extra width is split evenly inside and outside.
a = d = 43mm
e = (b/2)+a = 100.2mm
f = (c/2)+d = 112.9mm

b)Here the extra width is all on the outside.
d = a-((c-b)/2) = 30.3mm
e = (b/2)+a = 100.2mm
f = (c/2)+d = 100.2mm

c) Here the extra width is all on the inside.
d = a+((c-b)/2) = 55.7mm
e = (b/2)+a = 100.2mm
f = (c/2)+d = 125.6mm

Both a) and c) move the inside edge of the rim and tire in towards the inner fender well. a) moves it in 12.7mm and b) moves it in 25.4 mm. Both of these will probably cause rubbing on the inner fender well when you corner. b) keeps the inside edge of the wheel/tire in the same relative position and moves the outside edge outward. You have to watch the wheel well opening on the fender with this one.

There is no free lunch. Hope this is clear. Take a look at http://www.tirerack.com in the Wheel Tech section for additional help.

I have mounted the following wheel/tire combos successfully on type 3s. by Brian Fye
Mahle 4 lug G/B: 195/60/15 front, 195/70/15 rear--required 3/8 spacers
Centerline: 145R15 front, 185/65 rear
EMPI 8 spoke: 145R15 front, 165R15 rear--barely tucked
Eagle centerline knock offs: 195/60/15 front, 195/70/15 rear
Original Rivieras: 195/60/15 front and rear
Current Rivieras w/ flat panel on each spoke: 145R15 front, 165R15 rear--again, barely fit.
2.0 Fuchs: 195/50-15. Petri 1971 Notch O. C. L.