It's that time of the year when you will be driving your street rod less and may find yourself contemplating changes. My dilemma revolves around changes for change sake; not because they are needed, required, or even make sense, but just because I can. That's a dangerous place to be. Generally speaking, this equates to too much imagination, too little time, and not nearly enough ability. "Why?" you say? 'Cause I will not work in the yard, clean up the garage, or for that matter, polish the aluminum on my roadster--all that just isn't fun!
For starters, I am already thinking about what I can do to my highboy during the downtime that's inevitable during the winter months. Well, I could change wheels. ... A harmless exercise other than there's absolutely nothing wrong with the present wheels. Hey, the roadster made it back and forth across country and the wheels worked fine, looked good, and, overall, performed flawlessly. So what?! In my mind I have conjured up the following: It's something that I can tinker with, will make a dramatic change to the appearance of the roadster, and in the end will give me something "fresh" to talk about come next summer.
Of course, it's never that simple; even changing wheels can take on a life of its own. Inevitably it will mean new tires. Cha ching! And then there's the mechanical aspect. Ah, here's where I get myself into enough trouble to turn a weekend affair into an affair to remember. Let's see, we (my dogs are at the ready as one sleeps on the creeper and the other is stretched out on the bench seat) will make sure we have the correct size (diameter and width), backspacing, and proper offset (positive or negative). Now you can see where I am going to get into trouble. Did I mention lug nuts?
I am pretty confident that I can count the number of lugs required to hold the wheels onto my roadster--five, right? See, that was simple. Except it isn't. To induce chest pains I have managed to install 1/2-20 RH axle studs in front and 7/16-inch studs in back. Don't ask! Oh yes, did I mention that at the same time the head size is 13/16-inch at one end and three-quarters at the other? Again, don't ask.
Of course this is only superseded by the bolt pattern (circle). It would seem simple enough to get correct. For reasons known only to a higher being, I managed to screw my roadster together with a Ford bolt pattern in front and Chevy in back! Hey, I told you there are some things that I shouldn't be allowed to attempt. I won't go into detail about how I got a drawer full of straight and rounded taper lug nuts while my wheels require flat-seat shank lug nuts! (Just so there's something of mechanical value to come out of this, it should be noted that flat-seat lug nuts with washers are used almost exclusively with aluminum wheels because the aluminum is too soft to withstand the frictional forces created by the taper and round-seat lug nuts.)
Now that brings us to backspacing and offset. Let me tell you, this is the area you had best be really careful with when ordering new wheels. Backspacing is the distance from the inside of the inside rim edge to the inside of the mounting face. The combination of backspacing and wheel offset determine where your wheel will "ride" and how close to the car's body the tire will rest. (Tire cross-section width is also a critical factor. Don't ask how I learned that lesson.) By the way, if you are ever trying to figure out the offset of your wheels, here's the mathematical formula to make things go simply:
Offset =
Back Spacing - Overall Wheel Width divided by 2
Example: Wheel = 15 x 6.5
Back Spacing = 4 inches
Overall Width = 7.5 inches
Positive Offset = +0.25 inch
Ah, there's positive and negative offset? Where did that come from? Well, as I found out, there's both, and they create vastly different situations. Either condition is determined by where the mounting surface is in relationship to the absolute center of the wheel. If the mounting surface is closer to the streetside of the wheel, you have negative offset, and closer to the curbside you have positive offset. Typically, we street rodders like our wheels with lots of negative offset as it yields that "deep dish" look we are all so fond of.
Modern, front-wheel-drive and sporty cars of today seem to like positive offset because of the necessary hub clearance within the wheel and, of course, proper suspension geometry is designed accordingly. The negative offset wheel is desirable in back (as on a street rod) because it improves stability and handling and can increase track. However, in front it can lead to excessive steering wheel kickback and places additional stress on wheel bearing and the vehicle's suspension. Rodders do not usually drive their cars that many miles, making this of lesser concern, but still something to be aware of.
Well, this is the short version, but as you can see, nothing is ever as simple as it first appears and it is always a good thing to do your homework before charging off into the sunset. Yep, only I could turn something as simple as installing a new set of wheels into a project that consumes all my time, money I didn't have, and make myself into a mockery in the process.
Now, before each of you laughs out loud for a prolonged period of time, think back to some of your "misalignments." Once you have done so, drop me a line so I can share these good intentions gone awry with the rest of us and get a real belly laugh ourselves!