Im new on this forum and I have little or no knowledge of Jeep mechanics. The most I have done is change a bumper. I have a JK 2008 with 2" lifts. My 15" tires are just too small, want to go to 17" but do not understand the lugs size 5X5, 4.5, etc. Does anyone have the knowlegde to tell me the right lug set sizes and 7.5, 8, 8.5, 9.0 ??? I am confused, please help!

I am absolutely not an expert...there are those who will give you much more knowledgable replies than I can. But until they chime in, I'll see if I can help a little.

Wheels
There a variety of important numbers:
the 15" and 17" dimension you refer to are the diameter of the wheel itself.
the 7.5" 8.5" 10" dimension is the width of the wheel at the outer edge (Bead) where the tire makes contact with the wheel.
The 5x5, 5x4.5 dimension yo mentioned is the Lug configuration. 5lugs x 4.5" spacing between the NEAREST lug....that means measuring from one lug hole to the one right next to it. and I believe 5x4.5 is the standard Jeep configuraltion and is shared by several other auto manufactures...but Im not sure which ones.
Another important number to consider is Back-Spacing which is the distance from the rim of the wheel to the back of the mounting plate (the surface of the wheel that makes contact with the hub. Lay a board accross the back of the wheel...measure from the bottom of the board to the back of the lug hole...thats your "Back space". The more back space....means the wheel (and the tire) fit further UNDER the fender. Less Back-space means the wheel and the tire stick out further away from the hub.

TIRES:
Also a bunch of important numbers:
First, the type you will hear most about, high floatation tires. While it sounds like floating like a boat, its intended to mean that they are wide enough to disperce seurface area and thus surface pressure so they they can cross loose, uneven, or soft terrain without "Diggin in" (think: snow shoes)
High floatation tires will have dimensions like 33x12.5x16
this means that the tire is ROUGHLY 33" tall. ROUGHLY 12.5" wide and fits on a 16" wheel.
I believe the 33x12.5x___ is the largest tire that will fit on the JK without a lift. I left the wheel size blank because it doesnt have much effect on the over-all dimensions of the HIGH FLOATATION tires and because some 15" wheels will fit on a JK and some will not. This is a function of the architecture on individual designs of the wheel (how it is laid out). Lets re-visit the subject of wheels for just a sec...

Some 15" wheel designs will interfere with the brakes...some will fit without problems. Apparently, as the wheel diameter increases, there are fewer and fewer instances of interferance. It is natural to assume, there-fore, that it makes sense to go bigger and bigger with the wheel diameter....not the case. First...the factor that effects everyone is that wheels with larger diameter requires tires that are TYPICALLY more expensive than wheels with smaller diameters. for example, a 33x12.5x18 is significanly more expensive than a 33x12.5x16 of the same manufacture and design. this is primarily because more 15" are produced than 18"....simple supply and demand economics. Another factor for deciding on wheel size is YOUR intended usage. Serious offroaders seem to prefer smaller wheels because it allows them to deflate their tires slightly so that the surface of the tire becomes more plyable and can "grip" terrain and obsticals (think climbing a tree with your hands instead of your fists). And apparently smaller WHEEL diameters allow the TIRES to be deflated more without the tire losing its "bead" (the air-tight seal which keep the TIRE on the WHEEL. (these folks usually carry an air compresser with them so that they can RE-inflate the tires when they are done "crawling").

Now back to TIRES:
Then you have the P-Metric sizing for tires. IE: 305/70r16 This is where it gets REALLY bizarre....
In this case 305 is the width of the tread....305mm if you divide that by 25mm/inch you get 12.2" wide.
Then the 60 referrs to the side wall height (the distance from the rim of the wheel to the ground) in this case, 70 means that the side-wall is 70% of the width of the tire. Soooo....70% of 12.2" = 8.54" of side-wall.
And of course the last set of numbers 16 tells you that its for a 16" wheel.
And thats all it tells you....now you take the 8.54" of sidewall at the bottom of the tire, add 16" of wheel, and then add 8.54" of sidewall at the top of the tire and you get a TIRE that is roughly 33" tall.
sooooo....
33" x 12.5" x 16"wheel
305mm x 70% x 16"wheel
are ROUGHLY the same size.

Then you get into load ratings (how much weight they can take without popping), sidewall construction, Tread design (Mud or Snow or all-terrain or highway) and all sorts of other variables that long ago made me give-up trying to make my own educated choices for what is right for me and to simply see what's working for others and just copy them....no need to re-invent the wheel (no pun intended).

When all else fails...seek out any posting from a forum-member named "Discount Tire" ...AWESOME fella. At the bottom of all of his posts are several links which will take you to a site which will tell you all you want to know about tires and wheels and has a variety or useful calculators and other cool stuff. Best of all....HE HAS PICS!!!!! worth a thousand words.

__________________ Threads wander aimlessly....always refer back to post #1
2012 Black Unlimited Sahara (mine)
2011 Black Corvette 3LT (wife's)
2005 Black Suzuki C50T (ours)
"Hope" is NOT a strategy

I am absolutely not an expert...there are those who will give you much more knowledgable replies than I can. But until they chime in, I'll see if I can help a little.

Wheels
There a variety of important numbers:
the 15" and 17" dimension you refer to are the diameter of the wheel itself.
the 7.5" 8.5" 10" dimension is the width of the wheel at the outer edge (Bead) where the tire makes contact with the wheel.
The 5x5, 5x4.5 dimension yo mentioned is the Lug configuration. 5lugs x 4.5" spacing between the NEAREST lug....that means measuring from one lug hole to the one right next to it. and I believe 5x4.5 is the standard Jeep configuraltion and is shared by several other auto manufactures...but Im not sure which ones.
Another important number to consider is Back-Spacing which is the distance from the rim of the wheel to the back of the mounting plate (the surface of the wheel that makes contact with the hub. Lay a board accross the back of the wheel...measure from the bottom of the board to the back of the lug hole...thats your "Back space". The more back space....means the wheel (and the tire) fit further UNDER the fender. Less Back-space means the wheel and the tire stick out further away from the hub.

TIRES:
Also a bunch of important numbers:
First, the type you will hear most about, high floatation tires. While it sounds like floating like a boat, its intended to mean that they are wide enough to disperce seurface area and thus surface pressure so they they can cross loose, uneven, or soft terrain without "Diggin in" (think: snow shoes)
High floatation tires will have dimensions like 33x12.5x16
this means that the tire is ROUGHLY 33" tall. ROUGHLY 12.5" wide and fits on a 16" wheel.
I believe the 33x12.5x___ is the largest tire that will fit on the JK without a lift. I left the wheel size blank because it doesnt have much effect on the over-all dimensions of the HIGH FLOATATION tires and because some 15" wheels will fit on a JK and some will not. This is a function of the architecture on individual designs of the wheel (how it is laid out). Lets re-visit the subject of wheels for just a sec...

Some 15" wheel designs will interfere with the brakes...some will fit without problems. Apparently, as the wheel diameter increases, there are fewer and fewer instances of interferance. It is natural to assume, there-fore, that it makes sense to go bigger and bigger with the wheel diameter....not the case. First...the factor that effects everyone is that wheels with larger diameter requires tires that are TYPICALLY more expensive than wheels with smaller diameters. for example, a 33x12.5x18 is significanly more expensive than a 33x12.5x16 of the same manufacture and design. this is primarily because more 15" are produced than 18"....simple supply and demand economics. Another factor for deciding on wheel size is YOUR intended usage. Serious offroaders seem to prefer smaller wheels because it allows them to deflate their tires slightly so that the surface of the tire becomes more plyable and can "grip" terrain and obsticals (think climbing a tree with your hands instead of your fists). And apparently smaller WHEEL diameters allow the TIRES to be deflated more without the tire losing its "bead" (the air-tight seal which keep the TIRE on the WHEEL. (these folks usually carry an air compresser with them so that they can RE-inflate the tires when they are done "crawling").

Now back to TIRES:
Then you have the P-Metric sizing for tires. IE: 305/70r16 This is where it gets REALLY bizarre....
In this case 305 is the width of the tread....305mm if you divide that by 25mm/inch you get 12.2" wide.
Then the 60 referrs to the side wall height (the distance from the rim of the wheel to the ground) in this case, 70 means that the side-wall is 70% of the width of the tire. Soooo....70% of 12.2" = 8.54" of side-wall.
And of course the last set of numbers 16 tells you that its for a 16" wheel.
And thats all it tells you....now you take the 8.54" of sidewall at the bottom of the tire, add 16" of wheel, and then add 8.54" of sidewall at the top of the tire and you get a TIRE that is roughly 33" tall.
sooooo....
33" x 12.5" x 16"wheel
305mm x 70% x 16"wheel
are ROUGHLY the same size.

Then you get into load ratings (how much weight they can take without popping), sidewall construction, Tread design (Mud or Snow or all-terrain or highway) and all sorts of other variables that long ago made me give-up trying to make my own educated choices for what is right for me and to simply see what's working for others and just copy them....no need to re-invent the wheel (no pun intended).

When all else fails...seek out any posting from a forum-member named "Discount Tire" ...AWESOME fella. At the bottom of all of his posts are several links which will take you to a site which will tell you all you want to know about tires and wheels and has a variety or useful calculators and other cool stuff. Best of all....HE HAS PICS!!!!! worth a thousand words.

I am absolutely not an expert...there are those who will give you much more knowledgable replies than I can. But until they chime in, I'll see if I can help a little.

Wheels
There a variety of important numbers:
the 15" and 17" dimension you refer to are the diameter of the wheel itself.
the 7.5" 8.5" 10" dimension is the width of the wheel at the outer edge (Bead) where the tire makes contact with the wheel.
The 5x5, 5x4.5 dimension yo mentioned is the Lug configuration. 5lugs x 4.5" spacing between the NEAREST lug....that means measuring from one lug hole to the one right next to it. and I believe 5x4.5 is the standard Jeep configuraltion and is shared by several other auto manufactures...but Im not sure which ones.
Another important number to consider is Back-Spacing which is the distance from the rim of the wheel to the back of the mounting plate (the surface of the wheel that makes contact with the hub. Lay a board accross the back of the wheel...measure from the bottom of the board to the back of the lug hole...thats your "Back space". The more back space....means the wheel (and the tire) fit further UNDER the fender. Less Back-space means the wheel and the tire stick out further away from the hub.

TIRES:
Also a bunch of important numbers:
First, the type you will hear most about, high floatation tires. While it sounds like floating like a boat, its intended to mean that they are wide enough to disperce seurface area and thus surface pressure so they they can cross loose, uneven, or soft terrain without "Diggin in" (think: snow shoes)
High floatation tires will have dimensions like 33x12.5x16
this means that the tire is ROUGHLY 33" tall. ROUGHLY 12.5" wide and fits on a 16" wheel.
I believe the 33x12.5x___ is the largest tire that will fit on the JK without a lift. I left the wheel size blank because it doesnt have much effect on the over-all dimensions of the HIGH FLOATATION tires and because some 15" wheels will fit on a JK and some will not. This is a function of the architecture on individual designs of the wheel (how it is laid out). Lets re-visit the subject of wheels for just a sec...

Some 15" wheel designs will interfere with the brakes...some will fit without problems. Apparently, as the wheel diameter increases, there are fewer and fewer instances of interferance. It is natural to assume, there-fore, that it makes sense to go bigger and bigger with the wheel diameter....not the case. First...the factor that effects everyone is that wheels with larger diameter requires tires that are TYPICALLY more expensive than wheels with smaller diameters. for example, a 33x12.5x18 is significanly more expensive than a 33x12.5x16 of the same manufacture and design. this is primarily because more 15" are produced than 18"....simple supply and demand economics. Another factor for deciding on wheel size is YOUR intended usage. Serious offroaders seem to prefer smaller wheels because it allows them to deflate their tires slightly so that the surface of the tire becomes more plyable and can "grip" terrain and obsticals (think climbing a tree with your hands instead of your fists). And apparently smaller WHEEL diameters allow the TIRES to be deflated more without the tire losing its "bead" (the air-tight seal which keep the TIRE on the WHEEL. (these folks usually carry an air compresser with them so that they can RE-inflate the tires when they are done "crawling").

Now back to TIRES:
Then you have the P-Metric sizing for tires. IE: 305/70r16 This is where it gets REALLY bizarre....
In this case 305 is the width of the tread....305mm if you divide that by 25mm/inch you get 12.2" wide.
Then the 60 referrs to the side wall height (the distance from the rim of the wheel to the ground) in this case, 70 means that the side-wall is 70% of the width of the tire. Soooo....70% of 12.2" = 8.54" of side-wall.
And of course the last set of numbers 16 tells you that its for a 16" wheel.
And thats all it tells you....now you take the 8.54" of sidewall at the bottom of the tire, add 16" of wheel, and then add 8.54" of sidewall at the top of the tire and you get a TIRE that is roughly 33" tall.
sooooo....
33" x 12.5" x 16"wheel
305mm x 70% x 16"wheel
are ROUGHLY the same size.

Then you get into load ratings (how much weight they can take without popping), sidewall construction, Tread design (Mud or Snow or all-terrain or highway) and all sorts of other variables that long ago made me give-up trying to make my own educated choices for what is right for me and to simply see what's working for others and just copy them....no need to re-invent the wheel (no pun intended).

When all else fails...seek out any posting from a forum-member named "Discount Tire" ...AWESOME fella. At the bottom of all of his posts are several links which will take you to a site which will tell you all you want to know about tires and wheels and has a variety or useful calculators and other cool stuff. Best of all....HE HAS PICS!!!!! worth a thousand words.

I'd be shocked if that didn't involve stimulants.

__________________

"What we see depends mainly on what we look for."
—John Lubbock

I just realized a minor mistake I made with my wheel/tire combo. My wheels (already ordered) are Black Rock Yuma 17x8. The tires I want to use are treadright guard dogs 315/70r17. I was looking at them again and it states wheel width between 8.5-10.5. I've not purchased tires yet, but will that .5 inch be an issue? I'd appreciate any input! Jeep is a 2012 JKU R, 2.5 inch BB lift.

I just realized a minor mistake I made with my wheel/tire combo. My wheels (already ordered) are Black Rock Yuma 17x8. The tires I want to use are treadright guard dogs 315/70r17. I was looking at them again and it states wheel width between 8.5-10.5. I've not purchased tires yet, but will that .5 inch be an issue? I'd appreciate any input! Jeep is a 2012 JKU R, 2.5 inch BB lift.

You won't have a problem putting the 315 on the 8" wheel. Many folks run 315s on the stock wheels and they are only 7.5" wide.

__________________
-Jeff-
'11 JKU Sport - TF Leveling Kit - 16" Strike 5s on 33s

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