For the Second Generation Trans Ams, there were quite a few different wheel and rim combinations that you could order. I will try to cover a few of these here and give you some examples of different styles and sizes. The rims changed sizes, shapes, and colors depending on the year and what options you ordered on your car. There were really 4 main types of rims for the Second Generation Pontiac Trans Am. There was the Rally and Rally II rims, the Honeycomb rims, the Snowflake rims, and the Turbo rims. I will try to touch on each one of these in a little detail to show you some of the differences.
The Rally and Rally II rims came across the widest band of Firebirds from 1967 all the way up to 1981. The Rally I rims were used up only to about 1970, then it was the Rally II rims. They were considered by most to be the "basic" rim used on the Firebirds and Trans Ams. They came in varying sizes like 14x6, 14x7, 15x6 and 15x7 and most of the time had a trim ring and centercap installed. They had a "two-tone" paint scheme used and were typically painted gray, but also could be painted to match the body color of the car. They were also available in gold for the Special Edition Trans Ams when N67 code was ordered.
The honeycomb rims made their debut in 1971 and lasted until 1976 when they were replaced by the snowflake rims. Unlike the Rally rims, the honeycombs rims really only came in two sizes and two colors. They had the 14x7 and the 15x7 honeycomb rim. And the colors... well, you could order them in silver (called magnesium) and.... well, that was about it. Just like the rally rims, the honeycomb rims came with trim rings and centercap. The honeycomb did also come in gold for the 1976 50th Anniversary, but you could not get them in gold for any other Firebird or Trans Am.
The snowflake rims made their debut in 1977 on the Pontiac models and continued until 1981. They were most popular on the Firebird and Trans Am, but you could also order them on other Pontiac models like the Grand Prix and Sunbird. The snowflake rims in 1977 came in a 14x6 inch and a 15x7 inch. The 14x6 inch you could not order on the Firebird models, only the 15x7 inch size. At the start, the snowflake rims were available in different colors such as white, grey, blue, gold, and red. Now, due to the popularity of the snowflake rims and trouble in production to meet the demand, the snowflakes were canceled for the other Pontiac models. They were canceled "due to limited supply". Also because of the limited supply, the white, red and blue colors were canceled and you could only get the grey (technically called "argent") or the gold snowflake rims. Here are some shots of the Distribution Bulletins regarding the snowflakes: Rim Bulletin. Now, the "specialty" Firebirds like the Sky Bird, the Red Bird, and the Yellow Bird still came with the painted rims to match the body color of the car, but this was the only exception. In 1980 and 1981, you could also order "natural" which was a bare aluminum rim as well.
The 15x7 inch snowflae rims came in two different variations. Both were 15x7 inches in size, but there was a second design released in 1979 that was a thinner/lighter snowflake rim. Most people do not know the difference, but when you put them side by side, you can definitely see the difference. Here you can see the difference between the 15x7 inch snowflakes for 1979-81 (left) and 1977-81 (right). You can tell from far away by the inner most circle has edges on the right and not the left. Also, the outer most circle has openings on the left, but not on the right. Now as far as which rims were used on which cars and why they still had both styles in 1979 to 1981 is still left to be determined.
So, if you are looking to purchase a set of rims off of someone from the Internet, make sure you look closely at the photos to make sure the rims you are purchasing are all the same "style". I have seen plenty of auction on Ebay or ads for rims for sale where there is a mismatch of rims for sale. So study the photos closely and you will be able to tell if all fours trims that you are purchasing are the same.
In 1978, Pontiac came out with the WS6 handling package which included new 15x8 inch snowflake rims. They do look similar in nature, but are definitely different sizes as you can see in the photo below. The 15x8 inch snowflakes (shown on the right) had a 1 inch lip surrounding the outside edge of the rim that gave it the extra 1 inch depth.
Now again, just like in 1977, these rims could only be ordered in the agrent (grey) or gold colors. The gold rim was typically used on the Special Edition Trans Ams, but you could order gold 15x8 inch snowflake rims and any Trans Am from 1978 to 1981 with the WS6 handling package.
In 1978 when the gold rims first came out, they were painted all gold except for the outer lip of the rims. Typically you see this style of gold rim on the Y88 Gold Special Edition rim, but this was also true for any gold rim ordered in early 1978. As you can see from the photo below, the rim on the left was the all gold rim used in early 1978 that was painted except for the outer lip, and the gold rim on the right used late 1978 through 1981 is painted gold only in the recessed areas of the rim.
Like was said above, these gold rims were typically seen on the Y88 Gold Special Edition Trans Ams, but they could also be ordered on any Trans Am with the WS6 handling package. Now when they made the change from the all painted gold rims to the machined edged gold rims is anyone's guess right now. My research has shown that it happened sometime in 1978, but when and why they made the change has yet to be seen. We do know in 1979 the all painted gold rims were gone and they were all the machined edge for the gold rims. The argent (grey) rims never had this type of a paint scheme or change, it was only the gold rims.
There are also differences in the 15x8 inch rims as well. As you can see in the photos below, the edges are different on different rims. The 15x8 rims from early 1978 had sharp corners around the edges and the ones from late 1978 and later had more of a rounded edge. The spokes in the middle are also different. The early style had 1/4 inch thick spokes in the center, the later style had 3/8 inch spokes in the center. It isn't by much, but you can definitely see a difference. Also, there is more even in the later style rims. You can't really notice because they look almost exactly alike but some I have seen are 5/16 inch thick spokes, and the others are 3/8 inch spokes. I have found at least 4 different variations on the 15x8 snowflake rim (maybe 5). So, if you are looking to buy or replace just one or two wheels, make sure you get the right ones.
Some people point out that you can also tell the difference by the location of the lug hole in relation to the valve stem. If you notice in the photos below, the rims have different locations of the lugnut holes. Some are to the right of the valve stem, and some are to the left of the valve stem.
If you also look at the backs of the rims, the names, dates, and codes are also listed in different areas of the rim.
The turbo rims were introduced first 1979 and came only on the 10th Anniversary Y89 Trans Am. The Turbo rims for 1980 and 1981 for the Turbo Trans Ams came in two sizes and also three colors. They were finished in a natural color and had a machined face with silver painted inside the fins like on 10th Anniversary Trans Ams. They also came in gold for the Special Edition Turbo Trans Am in 1980 and 1981 which could also be ordered for a non-Special Edition as well. And lastly they came in white for the 1980 and 1981 Y85 Turbo Pace Cars.
There are slight differences between the 15x7 Turbo Rims and the WS6 15x8 Turbo Rims. It is hardly noticeable but when you line the two up together, you can definitely see the difference. From the top looking down at the Turbo rims, it is hard to tell. In the photo below you can't even really see a difference can you? Ok, besides one is real shinny and the other one is real dull.
The difference between the rims really comes in the depth of the front dish. The rims are real close in height. They are both 16 inches across, but the 15x7 Turbo rim is only 8 1/2 inches tall whereas the 15x8 Turbo rim is 9 inches tall.
The difference come in the front dish depth of the rim. They both have a 4 1/2 inch back spacing to them, but the front spacing is different. The 15x7 Turbo only has about a 3 1/4 inch depth and the 15x8 Turbo has about a 3 3/4 inch depth. It is really noticeable when you look closely at them.
So, if some one is selling you a set of Turbo rims and you need the 15x8 inch ones for 10th Anniversary cars, then ask them the EXACT measurements on the height of the rim. Some people measure them and see that they are 8 1/2 inches tall, so they figure they have 15x8 inch Turbo Rims... Well, they aren't. Don't take round numbers like "Well, its about 9 inches...", ask them the EXACT height.
The last thing to take a look at is the measurements for the rims. I get alot of questions on people who want to change rims and ask what other type of rim will fit. Well, it would be too long of a list to list every type/style/manufacturer of rim that would fit the Trans Ams and Firebirds. So what I will cover is how to measure the rims to know if the rim will even fit the car. The first thing to take a look at is the lug pattern. The GM cars like the Firebird and Trans Am used the 5 on 4 3/4" lug pattern. What does this mean? It means there were 5 lugs that held the rim on and they were spaced at 4 and 3/4 inches apart. So looking at the rim, you can easily tell if it has 5 lugs or not. But the correct spacing for measuring the lug pattern is done by measuring from the back on one hole to the center of the hole diagonal to it (shown below). So, on all of the snowflakes, honeycombs, turbo, and rally rims, the measurement was a 5 lug pattern spaced at 4 3/4 inches apart.
The next thing to take a look at is the offset and backspacing for the rims. The backspacing is easy to measure. Place one of your rims up on its edge and take a measuring tape and place the end of it flush to the back inside of the rim where the lug nuts would attach (where it would sit flush against the hub or drum of the car). Then take a look straight down the edge of the rim and see where the edge of the rims line up and take your measurement (shown below). As you see in the photos below, this rim has a 4 3/4 inch backspacing.
The las item to take a look at when thinking about changing rims on your car is the offset of the rim. The off set whether it be positive or negative does make a difference on how the car handles. To determine the offset of the rims, you first need to measure the width of the rim from edge to edge. Divide that in half to get the centerline of the rim. Now take your backspacing and subtract the measurement of the centerline of the rim from it to get your offset. So, in the example shown below of a 15x8 snowflake rim, you see that the rim is 9" from edge to edge which means the centerline is 4 1/2". Take the backspacing of 4 1/2" and subtract the centerline measurement of 4 1/2" and it gives you an offset of + 0". So, the simple math is: offset = backspacing - (width of rim /2).
So, once you know the lug pattern, the backspacing, and the offset of the rims, then you can determine what rim you would be able to fit on your car. The measurements of the stock rims on the Firebirds and Trans Ams are as follows:
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