Spamby
Meat Product Toy
After a short while of being a member on this site I have answered quite a few questions regarding wheels and tires. I realized that wheel and tire mods are one of the, if not biggest, most done and anticipated mods of our cars, or any car for that matter.
Wheel and tire changes are done for various reasons such as performance, looks and necessity. However, it seems that there is some mystery regarding those all too common donuts under or fenders. Within this thread, I will attempt to take some of the mystery out of those round things so as to help others make more intelligent and informed decisions when buying your next set of bling for your whip.
In part one, I will attempt to cover the highlights of such things as wheels, wheel materials, finishes, manufacturing processes and all of those crazy dimensions and numbers you see.
In part two, I will also attempt to touch base on tires, tire types, tread design and sizes.
In part three, I will attempt to give you some pros and cons about wheel and tire changes, specifically how they may impact your driving experience.
This is a works in progress and I suspect that it always will be. Therefore, I encourage others to comment, adding suggestions where necessary and most importantly, pointing out unclear or nonfactual information.
Wheel tech 101:
Class is in session.
Wheels, rims, bling, mags, discs, what have you, are the usually metal things that mount to the hub of your vehicle. These hard and round objects are what your tires are mounted to. They are typically made of steel or aluminum and come in a plethora of diameters and widths. To complicated things, they also come in different offsets, backspacing, hub bores, stud bores and stud spacing. Throwing more salt into the wound, they can come in one piece, two and three piece configurations, the former either being pressed in, screwed or riveted.
With that said, onto the metal of it. Do you have the metal?
Wheel types and manufacturing processes.
Steel wheels:
These are low tech and have been around for ages. These used to be some of the most common wheels on the market. Cheap and easy to make and actually quite easy to repair when damaged.
These wheels were typically stamped and formed from steel and the hub holes, stud holes and center pattern cut or punched out.
Steel wheels are typically thin but heavy compared to alloy wheels. They are still used on autos today but are slowly being phased out. Most vehicles that use them still are either economy cars or light and heavy duty trucks.
Steel wheels are usually made from a two piece process. The barrel is one and the face is the another. The barrel is the rim and is sculpted into a round shape with a continuous bead and lip, formed on the inner and outer edge, to hold the tire on. The face is the pretty part. The face is stamped, punched or carved for the pretty pattern and the mounting points. The two are joined together, usually by welding.
Steel wheels are usually heavy and thus regarded as not a good option for our cars. A good thing is that custom steel wheels are easily made and if one were so inclined, you could enlist a manufacturer to build you a set.
Magnesium wheels:
Or simply mags. These wheels became popular during the 60’s. Peace, love and grass… oops wait must not trip… innagadadavida!!! Sorry.
These wheels as stated are simply made of a magnesium alloy. The properties of magnesium are very light but that’s about where the good ends. Mag wheels deteriorate very quickly, like almost immediately begin to pit and decay. Mag wheels also tend to crack easily. One nasty thing about mag wheels is that they burn, burn very hot!! Magnesium is used in things like road flares. Magnesium can burn underwater and in the presence of high CO2. Magnesium in its state as a wheel is pretty docile. But if your car were to catch fire and those puppies heated up? Whoosh!! You’ve got one helluva fireball and the firemen trying to put out that fire are going to be pissed!
With all of that fancy fire crap said, mag wheels are just not used very much today. They deteriorate quickly and have a tendency to crack. No bueno. This is due to the properties of magnesium and the low ductility of the material. (low ductility is rigid or brittle). For that, they are usually reserved for specific racing applications where aluminum or steel is too heavy.
Aluminum wheels:
Ahhh, finally we come to the most familiar wheel material most of us look at, aluminum. This stuff is awesome. It comes in various grades and can be formed with many different methods. It is strong and lightweight and relatively resistant to age and abuse.
Aluminum wheels can be made in one of four ways, low pressure casting (LPDC), high pressure casting (HPDE), gravity casting and forging. After casting or forging is done, hole drilling and final prep is performed to make the desired product.
LPDC is the act of placing the die over a crucible, or bowl, of molten metal and forcing the molten mass up into the die using air/gas.
HPDE is the act of smashing/hammering/squeezing the molten metal into a sealed die. Once the alloy has solidified then the die is opened.
Gravity casting is the act of pouring the metal into a mold, sand mold or permanent mold, and basically letting it cool to the shape of the mold.
Flow form is the act of pouring molten metal into a mold. Letting it cool to a basic form and then heating and spinning it at high speed while using rollers to pull and form the wheel into its final shape. The act of spinning, heating and pressure can create a wheel barrel with like strength as a forged unit.
Forging is the act of hammering or cutting the wheel from a heated solid or solid billet or hunk of metal until the desired shape is completed. Without going into another threads worth of discussion, forging, by its process, can create the strongest and lightest wheels today. With that said, comes a larger price tag.
**Note** Some wheel manufacturers such as BBS, O.Z., Rays and Alcoa have propriety casting techniques to make wheels. Some of theses casting methods can produce wheels with comparable strength, weight and designs as forging. O.Z. and BBS supply F1 cars with CAST WHEELS!!! These secretive methods are just that. Only a little information is to be had about their methods. Basically from what I have learned is that those methods they implore are most likely flow forming casting method and then backed with a heat treat.
All of these methods can produce good results in wheel strengths and characteristics but forging is arguably the best end product but the most expensive. Cast wheels depend on a lot of care to make a good product. But because of flow characteristics in the casting process, especially with gravity casting, voids, pinholes, cracks, impurities etc. can find there way into the product.
Heat treating, annealing, quenching and aging can also be performed on wheels to add strength. There are different applications of these processes and the grade of aluminum and desired effect would determine the method used. In short, heat is applied, held and either slow cooled or rapidly cooled. This changes the grain pattern of the metal and thus its properties. I.E. soft to hard or vice versa.
Heat treating step is a process I believe is a must. This is where a crappy cast wheel can turn into a very strong and quality wheel.
One piece, two and three?
A one piece wheel is just that. A wheel cast or forged in one piece.
A two piece wheel has two separately made parts. These parts are then joined together. One part is the barrel, the other the face. These parts are usually welded, glued, or riveted/screwed together. Two piece wheels allow for unique offsets and widths.
A three piece wheel has three parts. The face, one half of the barrel and another half of the barrel. These types of wheels are uber expensive and allow for very customizable construction.
Wheel finishes:
I won’t spend too much time on this one. Basically there are 5 types of finishes available.
1. Powder coating. A baked on and very durable finish. If damaged you can’t just touch it up. You will have to redo the entire piece.
2. Paint. With or without clear coat; gloss, flat, semi gloss, satin. The most common color application. This method is cheap and fairly easy to correct if damaged.
3. Polished/natural. With or without a coating. This is basically just raw aluminum polished to a specific luster. Uncoated, this is a pain to upkeep and requires constant attention.
4. Chrome. A very hard and durable finish. A tried and true method that has relatively easy care and maintenance. If damaged, the entire part needs to be refinished. No touch ups here.
5. Anodizing. This is the act of dropping the part into a chemical bath and a adding electrical current to sort of dye the item. Anodizing finishes can be very durable but this is not very common in wheels.
Enough, you say!! I just wanna know about the wheels themselves!! OK so here we go. Sheesh!
Wheel measurements and fitment:
When selecting wheels, there are six measurements that you want to pay attention to:
1. Diameter. This is the height of the wheel. I.E. 18”, 19” rolling on twenny fo’s, fo realz.
2. Width. This is the barrel width from lip to lip. 8”, 8.5”, 9.5” etc. Skinny to fatty.
3. Offset. This is the measurement of the mounting surface, or hub, in relation to the centerline of the wheel. Flush, inset, concave goodness and deep lips. The further out from the centerline (towards the face), the more positive the offset. The hub at centerline would be a zero offset. The hub further in from centerline (towards the car or inner lip) would be a negative offset.
4. Backspacing. This is similar to offset but is the measurement of the hub to the inside lip of the wheel. Sorta like 3.
5. Bolt pattern. The measurement of the stud mounting hole spacing and number of studs. 5x5, 5x4.5, 5x100, 5x114.3, 5x130... Blah, blah. So if I were to have a 5x130mm bolt pattern that would mean that I have five mounting studs and they are spaced 130mm from center of the stud to center of the opposite stud.
6. Hub bore diameter. Measurement of the center hole of the wheel. The hole in the middle of the bolt holes that mounts to the round thingy, hub, on your hub. 56mm bore, 73mm bore, 40mm bore., etc.
***hub centric means that this will fit your hub without the addition of hub rings.
Hopefully the illustrations will help you in seeing how the measurements are taken and how they effect wheel fitment.
So how does this apply to my Subaru and what wheels fit?
We have Brembo brakes. These brakes are large and have a huge impact on wheel fitment and choices. For the most part, wheel offsets will be fairly positive for our cars. This means that deep lips and deep concaved wheels are not seen too much.
OFFSET!!! A GR has a factory offset of positive 55mm. Or +55. Going more positive may not even be possible. The face would extend out beyond the outer lip and the barrel would sink in further towards the car running into suspension and chassis components. Going more negative would mean that for each millimeter less than 55 the wheel hub would extend inwards towards the car and thus the barrel of the wheel outwards. The face of the wheel usually would be more concave and/or a lip, with each negative mm, formed between the face and outer edge. This helps with fitment of wider wheels and thus wider tires. Basically, this is where you are going to get the flush look that so many desire. Paying close attention to offset is a must for fitment. Too negative and your looking at a lot of work to make that wheel fit.
A great example is diesel dully trucks. Look at the rear wheels. See how deep the rim is? This is an example of either a zero or negative offset. Now look at the front of the truck. See how the mounting hub or face protrudes out beyond the tire? This a great example of way positive offset.
Special considerations for the face have to be taken into account in order to clear the brakes. These design considerations, coupled with offset, can actually change the look of the wheel. One wheel at one offset and width may look a bit different than another wheel of the same type.
Hub centric means that the wheels hub bore will fit the hub ring/mounting flange of your car without the addition of hub rings. The use of larger hub bore wheels may need the use of hub rings to fit properly and/or to minimize vibrations and other undesirables. The use of hub rings is debatable. I myself have seen no difference when I do or don’t use them. When mounting wheels to the car, the practice of proper mounting may mitigate the need for hub rings. I.E. hand tighten the lugs in a crisscross pattern, each opposite lug and so on, then torquing incrementally, to the specified torque in that same crisscross pattern. This in effect should seat the wheel properly and centered.
GR specific general wheel fitments:
These are basic guidelines for wheel fitments on the GR chassis. Tire size will also contribute to fitment.
There are way too many variables to give a specific answer to what will fit on the STi. These are general rules with maximums and minimums as reference points only.
5x114.3 bolt pattern
56.1mm hub bore. Larger bores are ok and common. Use of hub centric rings may be needed.
Factory offset: positive or +55mm. Offsets as low as +38mm without work on the stock height suspension. Lower offsets than +38mm may need fender rolling, negative camber, fender pulling etc. especially on lowered suspensions. I would regard +38mm as the absolute max low offset on lowered STi’s before work is needed… more than just camber.
17”, 18” and 19” diameter wheels.
8”-10” wheel widths. Larger may require extensive work.
GD specific general wheel fitments:
These are basic guidelines for wheel fitment on the GD chassis. Tire size will also contribute to fitment.
Same as before, way too many variables for specifics other than hub bore and bolt patterns. I will say that the GD chassis and fenders limit wheel choices. The narrow fenders and different suspension design inhibit lower offset and wider wheels without running into issues and putting much work into making them fit. Basically the choices are less, in regards to wheels and tires, than the GR platform.
04 STi 5x100 bolt pattern
05+ 5x114.3 bolt pattern
Factory offset +53mm. Offsets to +42ish without work and depending on wheel width. +45mm seems the safe bet.
Hub bore 56.1mm
8”-9 or 9.5”. Strut rubbing issues can be had with wide wheels and tires, even at stock height.
****Please comment about GD fitments. I have only little experience with the older STi’s.
Cliff notes anyone?
There are several different wheel materials but aluminum is the king for us.
There are several different manufacturing processes but flow forming and forging are supreme. Add some heat treating and you have a very strong and lightweight wheel.
Wheel finishes are a toss up. No one seems better than the other. They all seem to have their own advantages and disadvantages.
Offset, offset, offset coupled with wheel width. This is your biggest thing to pay attention to. These will determine where the wheel sits in your fender, or not in some cases. Different width wheels with the same offset will sit differently in relation to a static point such as the fender lip or the mounting hub of the car.
I.E.: Scenario one: Your wheel is ten inches wide and has an offset of positive one inch. Given the centerline separates the wheel into 5 inch halves, you would have 6 inches of wheel inwards, from the mounting flange to the inner lip. Four inches of depth from outer lip to flange
Scenario two: Your wheel is 8 inches wide and has a positive offset of one inch. Given the centerline separates the wheel into equal 4 inch halves, you would have 5 inches of wheel inwards from the mounting flange to the inner lip. Three inches of depth from outer lip to flange.
Is your head spinning yet? Mine is rotating like Linda Blair’s in the Exorcist. A priest, anyone???
Wheel and tire changes are done for various reasons such as performance, looks and necessity. However, it seems that there is some mystery regarding those all too common donuts under or fenders. Within this thread, I will attempt to take some of the mystery out of those round things so as to help others make more intelligent and informed decisions when buying your next set of bling for your whip.
In part one, I will attempt to cover the highlights of such things as wheels, wheel materials, finishes, manufacturing processes and all of those crazy dimensions and numbers you see.
In part two, I will also attempt to touch base on tires, tire types, tread design and sizes.
In part three, I will attempt to give you some pros and cons about wheel and tire changes, specifically how they may impact your driving experience.
This is a works in progress and I suspect that it always will be. Therefore, I encourage others to comment, adding suggestions where necessary and most importantly, pointing out unclear or nonfactual information.
Wheel tech 101:
Class is in session.
Wheels, rims, bling, mags, discs, what have you, are the usually metal things that mount to the hub of your vehicle. These hard and round objects are what your tires are mounted to. They are typically made of steel or aluminum and come in a plethora of diameters and widths. To complicated things, they also come in different offsets, backspacing, hub bores, stud bores and stud spacing. Throwing more salt into the wound, they can come in one piece, two and three piece configurations, the former either being pressed in, screwed or riveted.
With that said, onto the metal of it. Do you have the metal?
Wheel types and manufacturing processes.
Steel wheels:
These are low tech and have been around for ages. These used to be some of the most common wheels on the market. Cheap and easy to make and actually quite easy to repair when damaged.
These wheels were typically stamped and formed from steel and the hub holes, stud holes and center pattern cut or punched out.
Steel wheels are typically thin but heavy compared to alloy wheels. They are still used on autos today but are slowly being phased out. Most vehicles that use them still are either economy cars or light and heavy duty trucks.
Steel wheels are usually made from a two piece process. The barrel is one and the face is the another. The barrel is the rim and is sculpted into a round shape with a continuous bead and lip, formed on the inner and outer edge, to hold the tire on. The face is the pretty part. The face is stamped, punched or carved for the pretty pattern and the mounting points. The two are joined together, usually by welding.
Steel wheels are usually heavy and thus regarded as not a good option for our cars. A good thing is that custom steel wheels are easily made and if one were so inclined, you could enlist a manufacturer to build you a set.
Magnesium wheels:
Or simply mags. These wheels became popular during the 60’s. Peace, love and grass… oops wait must not trip… innagadadavida!!! Sorry.
These wheels as stated are simply made of a magnesium alloy. The properties of magnesium are very light but that’s about where the good ends. Mag wheels deteriorate very quickly, like almost immediately begin to pit and decay. Mag wheels also tend to crack easily. One nasty thing about mag wheels is that they burn, burn very hot!! Magnesium is used in things like road flares. Magnesium can burn underwater and in the presence of high CO2. Magnesium in its state as a wheel is pretty docile. But if your car were to catch fire and those puppies heated up? Whoosh!! You’ve got one helluva fireball and the firemen trying to put out that fire are going to be pissed!
With all of that fancy fire crap said, mag wheels are just not used very much today. They deteriorate quickly and have a tendency to crack. No bueno. This is due to the properties of magnesium and the low ductility of the material. (low ductility is rigid or brittle). For that, they are usually reserved for specific racing applications where aluminum or steel is too heavy.
Aluminum wheels:
Ahhh, finally we come to the most familiar wheel material most of us look at, aluminum. This stuff is awesome. It comes in various grades and can be formed with many different methods. It is strong and lightweight and relatively resistant to age and abuse.
Aluminum wheels can be made in one of four ways, low pressure casting (LPDC), high pressure casting (HPDE), gravity casting and forging. After casting or forging is done, hole drilling and final prep is performed to make the desired product.
LPDC is the act of placing the die over a crucible, or bowl, of molten metal and forcing the molten mass up into the die using air/gas.
HPDE is the act of smashing/hammering/squeezing the molten metal into a sealed die. Once the alloy has solidified then the die is opened.
Gravity casting is the act of pouring the metal into a mold, sand mold or permanent mold, and basically letting it cool to the shape of the mold.
Flow form is the act of pouring molten metal into a mold. Letting it cool to a basic form and then heating and spinning it at high speed while using rollers to pull and form the wheel into its final shape. The act of spinning, heating and pressure can create a wheel barrel with like strength as a forged unit.
Forging is the act of hammering or cutting the wheel from a heated solid or solid billet or hunk of metal until the desired shape is completed. Without going into another threads worth of discussion, forging, by its process, can create the strongest and lightest wheels today. With that said, comes a larger price tag.
**Note** Some wheel manufacturers such as BBS, O.Z., Rays and Alcoa have propriety casting techniques to make wheels. Some of theses casting methods can produce wheels with comparable strength, weight and designs as forging. O.Z. and BBS supply F1 cars with CAST WHEELS!!! These secretive methods are just that. Only a little information is to be had about their methods. Basically from what I have learned is that those methods they implore are most likely flow forming casting method and then backed with a heat treat.
All of these methods can produce good results in wheel strengths and characteristics but forging is arguably the best end product but the most expensive. Cast wheels depend on a lot of care to make a good product. But because of flow characteristics in the casting process, especially with gravity casting, voids, pinholes, cracks, impurities etc. can find there way into the product.
Heat treating, annealing, quenching and aging can also be performed on wheels to add strength. There are different applications of these processes and the grade of aluminum and desired effect would determine the method used. In short, heat is applied, held and either slow cooled or rapidly cooled. This changes the grain pattern of the metal and thus its properties. I.E. soft to hard or vice versa.
Heat treating step is a process I believe is a must. This is where a crappy cast wheel can turn into a very strong and quality wheel.
One piece, two and three?
A one piece wheel is just that. A wheel cast or forged in one piece.
A two piece wheel has two separately made parts. These parts are then joined together. One part is the barrel, the other the face. These parts are usually welded, glued, or riveted/screwed together. Two piece wheels allow for unique offsets and widths.
A three piece wheel has three parts. The face, one half of the barrel and another half of the barrel. These types of wheels are uber expensive and allow for very customizable construction.
Wheel finishes:
I won’t spend too much time on this one. Basically there are 5 types of finishes available.
1. Powder coating. A baked on and very durable finish. If damaged you can’t just touch it up. You will have to redo the entire piece.
2. Paint. With or without clear coat; gloss, flat, semi gloss, satin. The most common color application. This method is cheap and fairly easy to correct if damaged.
3. Polished/natural. With or without a coating. This is basically just raw aluminum polished to a specific luster. Uncoated, this is a pain to upkeep and requires constant attention.
4. Chrome. A very hard and durable finish. A tried and true method that has relatively easy care and maintenance. If damaged, the entire part needs to be refinished. No touch ups here.
5. Anodizing. This is the act of dropping the part into a chemical bath and a adding electrical current to sort of dye the item. Anodizing finishes can be very durable but this is not very common in wheels.
Enough, you say!! I just wanna know about the wheels themselves!! OK so here we go. Sheesh!
Wheel measurements and fitment:
When selecting wheels, there are six measurements that you want to pay attention to:
1. Diameter. This is the height of the wheel. I.E. 18”, 19” rolling on twenny fo’s, fo realz.
2. Width. This is the barrel width from lip to lip. 8”, 8.5”, 9.5” etc. Skinny to fatty.
3. Offset. This is the measurement of the mounting surface, or hub, in relation to the centerline of the wheel. Flush, inset, concave goodness and deep lips. The further out from the centerline (towards the face), the more positive the offset. The hub at centerline would be a zero offset. The hub further in from centerline (towards the car or inner lip) would be a negative offset.
4. Backspacing. This is similar to offset but is the measurement of the hub to the inside lip of the wheel. Sorta like 3.
5. Bolt pattern. The measurement of the stud mounting hole spacing and number of studs. 5x5, 5x4.5, 5x100, 5x114.3, 5x130... Blah, blah. So if I were to have a 5x130mm bolt pattern that would mean that I have five mounting studs and they are spaced 130mm from center of the stud to center of the opposite stud.
6. Hub bore diameter. Measurement of the center hole of the wheel. The hole in the middle of the bolt holes that mounts to the round thingy, hub, on your hub. 56mm bore, 73mm bore, 40mm bore., etc.
***hub centric means that this will fit your hub without the addition of hub rings.
Hopefully the illustrations will help you in seeing how the measurements are taken and how they effect wheel fitment.
So how does this apply to my Subaru and what wheels fit?
We have Brembo brakes. These brakes are large and have a huge impact on wheel fitment and choices. For the most part, wheel offsets will be fairly positive for our cars. This means that deep lips and deep concaved wheels are not seen too much.
OFFSET!!! A GR has a factory offset of positive 55mm. Or +55. Going more positive may not even be possible. The face would extend out beyond the outer lip and the barrel would sink in further towards the car running into suspension and chassis components. Going more negative would mean that for each millimeter less than 55 the wheel hub would extend inwards towards the car and thus the barrel of the wheel outwards. The face of the wheel usually would be more concave and/or a lip, with each negative mm, formed between the face and outer edge. This helps with fitment of wider wheels and thus wider tires. Basically, this is where you are going to get the flush look that so many desire. Paying close attention to offset is a must for fitment. Too negative and your looking at a lot of work to make that wheel fit.
A great example is diesel dully trucks. Look at the rear wheels. See how deep the rim is? This is an example of either a zero or negative offset. Now look at the front of the truck. See how the mounting hub or face protrudes out beyond the tire? This a great example of way positive offset.
Special considerations for the face have to be taken into account in order to clear the brakes. These design considerations, coupled with offset, can actually change the look of the wheel. One wheel at one offset and width may look a bit different than another wheel of the same type.
Hub centric means that the wheels hub bore will fit the hub ring/mounting flange of your car without the addition of hub rings. The use of larger hub bore wheels may need the use of hub rings to fit properly and/or to minimize vibrations and other undesirables. The use of hub rings is debatable. I myself have seen no difference when I do or don’t use them. When mounting wheels to the car, the practice of proper mounting may mitigate the need for hub rings. I.E. hand tighten the lugs in a crisscross pattern, each opposite lug and so on, then torquing incrementally, to the specified torque in that same crisscross pattern. This in effect should seat the wheel properly and centered.
GR specific general wheel fitments:
These are basic guidelines for wheel fitments on the GR chassis. Tire size will also contribute to fitment.
There are way too many variables to give a specific answer to what will fit on the STi. These are general rules with maximums and minimums as reference points only.
5x114.3 bolt pattern
56.1mm hub bore. Larger bores are ok and common. Use of hub centric rings may be needed.
Factory offset: positive or +55mm. Offsets as low as +38mm without work on the stock height suspension. Lower offsets than +38mm may need fender rolling, negative camber, fender pulling etc. especially on lowered suspensions. I would regard +38mm as the absolute max low offset on lowered STi’s before work is needed… more than just camber.
17”, 18” and 19” diameter wheels.
8”-10” wheel widths. Larger may require extensive work.
GD specific general wheel fitments:
These are basic guidelines for wheel fitment on the GD chassis. Tire size will also contribute to fitment.
Same as before, way too many variables for specifics other than hub bore and bolt patterns. I will say that the GD chassis and fenders limit wheel choices. The narrow fenders and different suspension design inhibit lower offset and wider wheels without running into issues and putting much work into making them fit. Basically the choices are less, in regards to wheels and tires, than the GR platform.
04 STi 5x100 bolt pattern
05+ 5x114.3 bolt pattern
Factory offset +53mm. Offsets to +42ish without work and depending on wheel width. +45mm seems the safe bet.
Hub bore 56.1mm
8”-9 or 9.5”. Strut rubbing issues can be had with wide wheels and tires, even at stock height.
****Please comment about GD fitments. I have only little experience with the older STi’s.
Cliff notes anyone?
There are several different wheel materials but aluminum is the king for us.
There are several different manufacturing processes but flow forming and forging are supreme. Add some heat treating and you have a very strong and lightweight wheel.
Wheel finishes are a toss up. No one seems better than the other. They all seem to have their own advantages and disadvantages.
Offset, offset, offset coupled with wheel width. This is your biggest thing to pay attention to. These will determine where the wheel sits in your fender, or not in some cases. Different width wheels with the same offset will sit differently in relation to a static point such as the fender lip or the mounting hub of the car.
I.E.: Scenario one: Your wheel is ten inches wide and has an offset of positive one inch. Given the centerline separates the wheel into 5 inch halves, you would have 6 inches of wheel inwards, from the mounting flange to the inner lip. Four inches of depth from outer lip to flange
Scenario two: Your wheel is 8 inches wide and has a positive offset of one inch. Given the centerline separates the wheel into equal 4 inch halves, you would have 5 inches of wheel inwards from the mounting flange to the inner lip. Three inches of depth from outer lip to flange.
Is your head spinning yet? Mine is rotating like Linda Blair’s in the Exorcist. A priest, anyone???
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