Wheel Offsets, and My Attempt to Simplify Them

So you're trying to understand wheel offsets. Well, the good news is you've taken a huge step in the right direction! The truth is that the majority of wheel offset information is provided by people who knew it wasn't an exact science and spent countless hours scouring the internet. Truer still, you're likely to find out for yourself that the "trial and error" method still applies even when you attempt finalize your setup.

But no need to be scared, my goal is to provide a little insight as to what you're getting yourself into, and along the way I hope to teach you proper terminology and provide basic -and hopefully- over-simplified visuals for your understanding.

Sound good?

Let's start with the basics:

Wheels...Not 'Rims', and Why it's All About Them

Here's a wheel:

Wheels come in a series of measurements, typically by height (say, 18 inches) and width (8 inches). But more often than not they come in different fitments depending on the make and model of the car. We can classify them with the following terms:

Square: all four wheels are the same size (18x8 front, 18x8 rear)
Staggered: all four wheels are the same height, but two are different widths (18x8 front, 18x10 rear)
Double Staggered: two wheels are a different height and width than the other two (17x8.5 front, 18x9.5 rear)

We might also know that they come with various lug patterns, which are measured both in inches and millimeters. If we measure the distance as follows, like so:

we can determine the lug pattern of our wheels through simple conversion:

Lug pattern is essentially the specs of your hub (where the wheel mounts on your car). In order for the wheel to marry to the hub, you need to find a wheel with a matching lug pattern, or a means of cross-matching the wheel and hub together.

Lets take it a step further. Here's an image of a wheel broken down:

Wheels are manufactured either through a forging or casting process. Forged wheels have more dexterity at a molecular level, where-as cast wheels -although formed in a solid mold- tend to lack tactile strength (by comparison).

There are also various types of wheels, but we can generally classify them into simple groups:

OEM: Original Equipment Manufacturer; the factory wheels that came with a car
1 Piece: All the components are one solid piece
2 Piece: The face and the barrel are normally one solid piece, the outer lip is separate
3 Piece: The inner barrel, outer barrel and wheel face are three separate pieces
Aftermarket Forged
Aftermarket Cast Replica: a often a 1 piece wheel designed to look like a another 1 or 3 piece wheel
Aftermarket Cast


What's important to remember is that wheels take impact -- a lot of impact. If the wheels on your car were manufactured with poor materials, if the casting process was stream-lined for sake of sales, or to cut costs - well, there's a chance they're going to fail.

Replica wheels are notorious in this light:

But, bare in mind that wheel failure is not always a bad thing. High performance wheels are designed to give out at certain points. If the wheel were too dexterous, there's a chance of damage being transferred to the suspension, body or otherwise. Thus, one true sign of a well manufactured wheel is its ability to take impact and still hold air:

Offset is a Game of Millimeters, Not Inches!

Now that we're familiar on general wheel measurements, lets take a look at wheel offsets! Normally, stamped on the inside of the wheel (either in the barrel of the wheel, or recessed in the spokes) is the wheel's offset, or 'ET':

For the time being, let's just consider 'ET' to be synonymous with wheel offset.



ET or Wheel Offset is the measurement of the wheel in relation to its mounting point, in millimeters. It's important to know, because ET specifies the wheel's design specifications, and helps us determine wheel application.

Odds are, if you're looking at buying wheels, you'll inevitably see the following:

"FS: 18x8 all around, 5x114.3, ET35, $$$$ and etc.". These are all crucial details in determining whether or not the setup will work.

The Center Line is basically what it implies: it's the approximate center of the width of the wheel, and where the hub and measuring point of the wheel are constructed in relation to it. If you're confused, it's ok - referencing the Center Line is mostly left to determining clearance for brakes and independent suspensions, as with a positive offset.

Most wheels with a positive offset come from an older generation of manufacturers. Wheels with a positive offset naturally came with a lip, and the face of the wheel was recessed towards the centerline.

Imagine a wheel hanging on the side of a car. Although the barrel is stationary, you're given the ability to push the face of the wheel forward and back. If you push the face of the wheel towards the car, what's the first thing it might come into contact with? Odds are it's the brakes or suspension.

 

The most common offset measurement is the negative offset, which will be explained below.

 

Learn to Invert Your Frame of Thought

(This was the most difficult part for me to learn, and in light of that fact, I don't expect you to get it right away either.)

Recall this image:

We can identify the markings; the fact that it states "ET 35". However, what it should actually say is "ET-35". This is because most wheels now-a-days have more of a negative offset than positive.

Another way to think about it would be:

If you designate the mounting point of the wheel as 0 (or close to it), then +1mm would be away from it (or 1mm away from the car), and -1mm would be towards it (or -1mm towards the car) (but the majority of the time, it depends on where the mounting point lies). Therefore, ET35 actually translates to -35mm on a negative offset wheel.

Remember, ET35 implies the distance from the inner face of the wheel to the inner lip. Therefore, the inner lip of the wheel is -35mm from the inner face.

Here's an example of how we measure a negative offset:

 

Wheel ET CAN be modified, even on a one piece wheel. The right machine shop can shave millimeters from the hub, changing the wheel's negative offset from ET35 to ET39 (remember -35mm -4mm taken from the wheel hub of a negative offset wheel gives us -39mm)

 

 

While we can modify wheel characteristics through full out customization, we can also take the easy route by adding millimeters through the use of adapters and spacers.

 

Utilize All the Space!

 

 

Adapters take a lot of criticism from wheel enthusiasts. They claim everything from unnecessary load and weight causing wheel bearing failure to uneven tire wear -- some of which is true, but most of the time it's exaggerated. If they come from a reputable source who manufacturers them properly, you can avoid encountering these issues entirely.

 

What are adapters?

 

They're a solid piece of metal that mimics a wheel and hub. On the inner side, they have the car's factory bolt pattern. On the outer, they have the bolt pattern of the wheel. This enables us to cross lug patterns from 5x100 to 5x114.3 and so on.

 

 

 

 

There are essentially two different kinds: Hub-centric adapters, which are designed to marry to the hub of the wheel, and Non-hub-centric adapters, which -although less expensive- are not hub-specific, and can cause vibrations at high speeds and essentially all the problems listed above. 

Spacers are the same idea and feature the same details. The only exception is that the come with the factory bolt pattern in mind. Their purpose? To space the wheel further out from the car.

Both adapters and spacers are useful technology in this light. But the thing we need to consider is that while they have their own bolt pattern fitment, they also have their own offsets/ ET as well.

Protip: don't ever try to "space out an adapter", whereby placing a spacer on either side of an adapter. I will laugh, and you'll end up in someone's youtube fail compilation.

The minimum offset for an adapter is 15mm, but they range as high as 25mm, 30mm and so on. Consequently, that also means that the adapter must be at least 15mm long. Spacers on the other hand can be as small as 2mm and range as high as their counterpart.

http://bernardembden.com/xjs/hubcentric/

What to consider when you're applying an adapter or spacer is how they're going to affect the overall offset of your wheels.

For example, let's say the spacer shown above is 10mm long. We know the overall offset of our wheel is ET35. Since we're adding mass to the hub of the wheel, we take millimeters away from the offset. Therefore, the new distance from the spacer/ adapter to the inner lip of the wheel determines our new offset: ET25. We can streamline the process with simple math:

However, apart from measuring wheel ET, there's another type of offset to consider:

How Will It Sit?

Final ET, or how far the outer lip sits in relation to the car's fender.

Now that we know how to identify wheel offset, we have to determine how the wheel will look or "sit" on the car.

A good rule of thumb is that the lower the car gets, the further inward the wheel sits. It's not a lot, (no more than a few millimeters) but just enough to require the use of spacers/ adapters. And wheels will naturally camber roughly 1 degrees as well.

This is vitally important, because two cars can have the same offset, but depending on their ride height, the lip of one wheel might poke out, the lip of the other might tuck in the fender well.

ET1-10 might require the car be completely on the ground in order for the wheel fitment to work! It's that reason why the final ET will range based on ride height.

These are actually the Kerscher KCS wheels on my car. On the right, we were sitting at final ET28, on the left: final ET32. When we lowered the car a couple more millimeters we gained a few degrees of camber. It took a full afternoon with the fender roller before we acquired the desired look.

This is why we call it a game of millimeters!

However, most aftermarket manufacturers and enthusiasts have figured what specifications work best. We relate that to Natural ET.


Natural ET is the measurement which results in the outer lip of your car is sitting relatively flush with the fender.

We can say that the Audi featured above might've come with 16x7" ET45 wheels. However, trial and error proved that the proper fitment for the car was actually 18x8, ET35 (not just for sake of appearance, but performance). Inevitably, the guessing portion is virtually eliminated for most wheel fitments.

We still have to take ride height into account, however.

Assuming we lower the car to the extent that the wheels are nearly tucking inside the fender, provided a little wheel gap. The solution would be to add a 5mm spacer and achieve ET30. Essentially the look we're getting is the same as above, just predominately lower.

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And that's basically the essentials. I hope to add any additional info I can think of, but for now it's back to work!

If you have any questions, or would like to see anything featured, feel free to throw a comment or two below.

Thanks for reading!

The Manifold

I love projects like these.

When Derek at Exklusiv Motorsports brought up buying a manifold, I'll admit, it wasn't something I had in mind, especially when I associate manifolds and heads and big front mount intercoolers and big GT28 style turbos pushing 350whp in front wheel drive cars -- I'm not looking to generate that much power, nor do I like the look of a FMIC and it's piping. However, when Derek pointed out a small port ABD manifold on craigslist that promised an additional 12hp -at half the cost of retail- I had trouble saying no (right up until I started reading reviews).

 ABD Intake Manifold

007 Intake Manifold

The problem with manifolds is that while they claim to generate power through airflow (which is true), you need the right amount of air, the right amount of room, and the means to disperse it evenly. Many people have thrown aftermarket manifolds on their cars and noticed no particular gains with the stock turbo (in this instance, the KO3S). Once upgrading the turbo setup the modifiers noticed an increase of induction at an exponential rate, leading anywhere from 7 to 30 to 50hp depending on their compressor and setup. However, while they're "performing" better than stock, it doesn't mean every port is getting the right amount of air.

Here's two very common styles I've found:

Reading these mixed reviews put a bad taste in my mouth for a manifold project. I could see the point in generating better numbers, but not if it meant driving around with one cylinder's air/ fuel mixture enriched while the one on the opposite end is gasping. I needed to find an alternative, and here it is. Enter the Dual Plenum Intake Manifold:

 MR2 Gen 2 DPIM

The benefit of dual plenum lies in its cone shaped component. Air enters through the throttle body, into the cone and is spread out over all four runners.

The end result: controlled air velocity and even dispersal amongst all four runners:

But this didn't solve my problem. DPIM's are mostly custom projects, and none were available for me to buy. So after some brain storming, Derek came up with an AEB intake, which came off a Audi TT 1.8T. In the early 2000's, VW used a 1.8T motor which was also featured in the Audi TT. The exception being that Audi offered a 225 option which included larger ported exhaust and intake manifolds, bigger ports on the head (obviously) and a larger turbo. All these parts can be taken and swapped over to the VW model 1.8T, with modification.

Here's the stock AWP intake (top), and the AEB intake I purchased (bottom):

Apart from the runners being much longer, this size comparison shows a dramatic increase in port size between the two:

 

Jeff at Exklusiv custom-made manifolds for a living, and explained the process in detail. He would separate the runners from the plenum (already shown below), and the injector boss housings would be ground back to maximize airflow on the port end:

The 60mm 1.8T throttle body will be replaced with a 70mm R32 throttle body. You can read the comprehensive INA review here. Thanks AutoHaas LLC.!

Trumpet inlets on all four runners would be purchased and installed to ensure better air flow as well, via Nubwerks:

There's no room to build upward from the plenum in the engine bay (it could come in contact with the hood). The alternative would be to build the manifold with the dual plenum angled downward.

The only problem now is getting it to marry to the intercooler, and this is where it gets interesting.

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Not very long ago, I purchased a PWRhaus side mount intercooler and silicone kit, like this one:

While I'm still trying to convince every 1.8T owner that upgrading the silicone throttle body hose is paramount for the first string of engine mods, it still doesn't conceal the fact that its shape is arguably an issue for airflow. The pipe wiggles its way around engine components and all those bends do little to help get air from the intercooler to the throttle body, and hence to the intake manifold.

Here's the stock throttle body hose on the 1.8T side mount intercooler, which sits on the passenger side of the car, in front of the wheel (although oddly positioned in the photo).

The hose runs vertically from the intercooler and bends in a semi-"s" shape to couple the throttle body, as seen below:

I still say the $90 solution for better throttle response is best, even with the "s" style shape, but shortening the length of the silicone/ rubber piping even more - now that would be nice.

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Since Jeff will be relocating the inlet plenum and VR6 throttle body to the underside, it should decrease the distance between said inlet and the side mount. How short you ask?

You'll have to come back and find out.

I can leave you with the list of upgrades we're shooting for so far:

1.8T AWP motor (port matched to intake/ exhaust manifold)
1.8T AWP fuel rail
1.8T AEB dual plenum intake manifold
1.8T AEB exhaust manifold
.:R32 70mm throttle body
PWRhaus turbo inlet pipe
PWRhaus side mount intercooler
Snow Performance Stage 2 water methanol injection
Frankenturbo F23T KO4 Hybrid
Frankenturbo high pressure fuel pump
Siemen's 550cc injectors
Eurodyne maestro with 550 file

Project Respray

           I should start by saying what a terrible flip-flopper of ideas I am. I could never decide on wheels, I want things to look a utmost certain and specific way, and I know I've frustrated a lot of people in the process. (Oops).

           It's really one of the shortcomings I find with the MKIV and VW in general. When the 20AE came out, I was half way through highschool, and by the time I graduated, the MKIV had already become iconic in the import culture. Most people attribute that fact to the body lines, the OEM styling, and the fact that it's customizable in 100+ different ways. But for me, I think I was drawn to it because I was/ am so hypercritical. I had to look at the car from every angle and ask: "why is this working", "what's not working here", etc. I found myself surrounded by enthusiasts -- some of those who appreciated the early MKIII.5 and it's early stages, others who modeled their cars after Porsche's, and everyone that only bought OEM grade product. There was really no bad idea when it came to making it one's own.

           When it came to respraying the car, I admit I originally had no intention. A good friend of mine was going to correct the mix-matched Bora R bumper I previously had painted, and they brought up the point that T-Red was such an expensive color, "you might as well choose your own color and repaint the front end for a little more." That's something I wanted to avoid. Later on that night however, I went to the local car and coffee hang out, and found myself parked next to a red Porsche Boxter. It became obvious -- this color fails by comparison.

-I had the boser hood I always wanted, I had the R32 four door skirts, and I had the Bora R bumper and a spare set of marker-deleted fenders. Why couldn't I just find a rear bumper and paint the whole car once over? Yes, that would be nice, but instead I opted to paint each section at a time because, well, I'm on a budget.

           The color of choice became Calypso Coral, a 1965-71 Ford paint, which happens to be one of my all time favorite colors. It also coincides with the "if it ain't broken, don't fix it" ideology, I feel. Classic styling is often taken for granted. But especially now with the redux of modern muscle cars, we can look back at a 1970 Chevelle or Porsche 911 and appreciate their simplicity. Designers were obviously looking for the right shades of paint to reflect body lines, the right wheels and chrome accents to give the car curb appeal (which happens to stand out even a 1/2 century later). I believe if you can find the right template, the same process can be performed. Here's calypso coral on a 1969 Boss Mustang:

          This was an easy choice being that the exclusive VW paint series' for this generation were especially similar. Jazz Blue and Imola Yellow -although different in make-up, have similar qualities to that of the Ford orange. However, I'm beginning to realize I need to set limits on how much the GTI will transcend the Mustang qualities, for sure.









         Here are the fenders (side repeater light removed) and bumper (Bora R Line) with their fresh coat, along with the hood, which as you already know, has been extended and shaped: 

 

          The last component I needed was a rear bumper. I was hoping to find a votex series rear bumper, but unfortunately, the second I started shopping was the same time they were removed from the market. Something I also realized was that the closer I got to completion, the harder the decisions were to make. The last two pieces were wheels and the rear bumper, and with the shape of the R32, it's difficult to pull off the correct look without a large, monoblock style wheel or a three piece. Conventionality would simply not do in this instance.

          Ironically, however, this appeared in Canibeat a week later:

 
          Minus the extreme fender work, it made me realize I had never seen a fully shaved R32 bumper. It still maintained the right lines on the lower end, and combined with the solid red tail lights and shaved hatch, this would be a perfect example. But it still didn't solve my wheel problem. Here it is:

 

          So, when I think about wheels, I think of the countless hours I've spent scouring the internet for ideas. I looked at Rotiform BLQ's, Avante Garde Fuch's, solid faced steelies, and I'd find myself looking at Ford Mustangs as often as GTI's.

        Porsche styling also became a factor. Because I was hoping to limit the amount of chrome to the wheels and headlights, I began considering all possible color options between door handles, mirrors, wheel faces and roll cages.

        It finally took a suggestion from Derek to get the ball rolling. In 2004, one of Exklusiv Motorsport's customers picked up half a set of Kerscher KCS's. Derek sourced out the other two and had them ordered from Germany. A year later, they were on this 337 GTI on the cover of Eurotuner:

        When the car was parted out a few year after, the Kerscher's were picked up by a friend named Henry, who occasionally had them on his wagon. The KCS's seemed like a great idea, being that they could work in both yellow gold and black. They also have many of the similar qualities I'm looking for in order to marry the two (or rather now 3) ideas.

      And here they are:

 

  

 



          These KCS's are 18x8.5, ET31 and 18x10, ET28 and weigh well within the low 20's.

          The tires are no good to me, being that the original setup was a 205/40 for the 8.5 and a monster 255/40 for the rear -- that and the fact that they're more than five years old. If you look closely at the original picture, you'll see how low the front end of the GTI is sitting as a result. I think it'd be best to shoot for something to compliment the two.

          I'll be purchasing Yokohama S Drives, in 215/40 and 235/40. This shows a difference in size that's 200th's of an inch apart -- so the front and rear tire will look almost exactly alike. 

The last component to this process were a set of head lights. I really wanted to go with an OEM HID replica set, but I couldn't justify the price - especially when, in my opinion, they really don't sync up with the OEM styling. Solution:

 

 

Depo/ InPro/ Helix make a "joey-modded" matte black head light unit. I was afraid it was going to be a little on the nose, jumping back and forth between mustang and golf, but I can honestly say I have high hopes for these. 

 

This is also what I'm considering -- for this car, and most commonly for hatchbacks (I've surmised), much of the styling and many of the color combinations carry from head light to wheel and mirror caps, to roll bars and cages and vice versa. On the Golf, it's a little trickier.  

Bright sequential colors of these objects can easily contrast. But if you think in terms of textures, they're much more applicable. Glosses, mattes, satins, brushed and anodized textures/ patterns can be far more subtle and won't take away from the overall dynamic of the car. And as I've said with chrome, you want it in the background - hence, you'll always see it matched with black on this combo.