I get this question a lot, and while I don’t mind explaining to each customer how to do it, I know a lot of you guys are shy and don’t want to holla at a playa on the phone. So here goes, how to read a wheel sizing chart:
1. “Free Range” Offsets: These are sizing charts that allow you to choose from a “range” of offsets, rather than a preset number. Before all that though, you read the chart like any other table. As demonstrated by the purple arrow, this wheel is offered in an 18 inch (diameter) by 10 inch (width). If you look at the top of the chart, there are the following column headings: Taper Low Disk / Flat Low Disk / Flat High Disk. Each brand has a different name for its face choices, but for the most part, it will either go lowest to highest, or vice versa (obviously if it has “low” in the name, then you know it has LESS brake clearance in comparison to a “high” disk). Brake clearance and face choice is a whole other blog though. Let’s just take “Taper Low Disk,” which usually will be a rear wheel. As shown by the green arrow, you can get any offset -13 through +53. This means you can get any whole number offset, i.e -12, -11, +0, +1, and so on. The circled lip size I will be referring to is in light blue, i.e 77mm. Also, PCD = bolt pattern.
Lazy reader notes:
- Purple arrow: Wheel size - diameter (18″) by width (10″)
- Green arrow: Face choice + respective columns of available offsets
- Magenta square: PCD = bolt pattern of wheel
- Blue circle: “77″ is the wheel lip size in mm that is associated to +53 offset
- Taper Low Disk = least brake clearance (ideal for rear)
- Flat Low Disk = standard brake clearance (will clear most standard size front calipers)
- Flat High Disk = maximum brake clearance (ideal for BBK or big caliper)
2. “Preset” Offsets: These are sizing charts that allow you to choose from a “preset” offset, given to you by the sizing chart for that specific wheel. In this case, the 18×11.5 is offered in +5, -8, -16, and so on down the row. Each column represents the wheel faces that are offered, i.e “SL, NR, MD, HP.” Their respective meanings are color coded and shown below the chart. Again, it (SL, NR, MD, HP) goes from least amount of brake clearance (Super Low Disk) to maximum amount of brake clearance (Hyper Disk). At the top of the column, the 135mm refers to the lip size, and is the lip size for the 4 columns below it (i.e +5, -8, -16, and -26 all have 135mm lip size). Lip size is easy with presets, since you just figure out what diameter x width x offset you are running, and look at the column above. For example, an 18×11.5-26 (HP Face) has a 135mm lip, as well as an 18×11-14 (NR Face). An 18×12-1 (SL) has a 148mm lip, etc. Got it?
Lazy reader notes:
- Navy Blue square: Wheel size - diameter (18″) by width (11.5″) and corresponding offset choices
- Orange square: Lip sizing in mm, refers to the 4 columns of offset choices listed below it
- Magenta square: “HP” refers to the wheel face choice (i.e determines level of brake clearance), and offsets for that face choice are listed below it
- Lime green square: Usually where special notes are, in this case there are different color choices (which also can mean different prices). PCD = bolt pattern of wheel, and in this case, there are more bolt patterns possible, i.e you might be able to do a 5×120, 5×112, etc
- SL, NR, MD, HP: listed in order from least to most brake clearance
3. How to calculate lip size: First of all, you have to figure out what size wheel you want to go with. So if you take a look at the top most chart, let’s say you want a 18×10 with a +15 offset with a Taper Low Disk for your rear wheel. I had circled the number “77″ in blue, which is the lip size for an 18×10+53 Taper Low Disk wheel (this does not go for all 18×10 multipiece wheels, lip size is specific to EACH brand and model of wheel, so check the sizing chart always). So a +53 gives you 77mm of lip, which tells you that if you go to a +15, you will be getting MORE LIP (rule of thumb: lower the offset, the more the wheel sticks outward from the fender, and bigger the lip gets). So a (+53) minus (+15) = 38mm. Add 77mm + 38mm and you get 115mm, which is the lip size of a 18×10+15 Taper Low Disk.
“Logan you sound like the Charlie Brown teacher” Notes:
- Lower the offset, the more the wheel sticks outward from the fender
- Lower the offset, the lip size increases on a multipiece wheel
- 18×10+53 Taper Low Disk gives you 77mm lip
- 18×10+15 (if that’s the sizing you were trying to determine) gives you a 115mm lip
- You figure that out by subtracting 53-15, which equals 38. Add that to 77mm (because you are INCREASING LIP SIZE remember) and it gives you 115, which is the lip size in mm.
- For you Americans you can convert mm to inches with an online calculator.
4. Extra credit: let’s do one more: Let’s try doing another one. Again, top most chart: how about 18×9.5 offset -1 with a Flat High Disk. If you look at the chart, a -20 is equivalent to a 125mm lip. So this time it’s backward, but same idea. The offset -20 is a 19mm difference from -1. Yet if we use the rule of thumb (lower the offset, bigger the lip), you’ll then realize that a -20 has a bigger lip than a -1. So you have to subtract 19mm from 125mm, and you get a 106mm lip. So a 18×9.5-1 with a Flat High Disk has a 106mm lip.
“Logan I have no idea why you put a Nike shoe there” Notes:
- Lower the offset, the lip size increases on a multipiece wheel
- Even though an offset goes negative, the lower the offset rule of thumb still applies
- 18×9.5-20 Flat High Disk has a 125mm lip.
- 18×9.5-1 (if that’s the sizing you were trying to determine) gives you a 106mm lip
- You figure that out by subtracting (-20) minus (-1), which equals 19. SUBTRACT that from 125mm (because you are DECREASING LIP SIZE remember) and it gives you 106, which is the lip size in mm.
- For you Americans you can convert mm to inches with an online calculator.
Final note:
This may be common knowledge to some of you (especially industry folk), so my apologies if this is redundant info, but hopefully this helps those that were unclear about how to read and calculate wheel charts (I once had no clue either). Keep in mind that each wheel chart is different, so be aware when you go from brand to brand. Some companies don’t even give offsets or lip sizes (which I think is weak), but definitely do your research, since “offset is everything” (Hellaflush™ lol!)
P.S: I suck at math, and typing a long entry I might have made errors. So caveat emptor, but change the Latin to “let the reader beware.” LOL