wheel size, ordering tonight.
Thread Starter
JK Newbie
Joined: Feb 2008
Posts: 15
Likes: 0
From: columbia,sc
wheel size, ordering tonight.
hey guys, I am ordering a set of procomp 7005s in a few. I am a little concerned though. With the rough country 2.5BB it's recommended that I keep the backspacing at 4.5. If I order the 17x8's they are indeed 4.5" backspaced (0 offset). I am afraid that I need to order 17x9's, but the backspacing is 4.75" (-6mm). So do I need the 17x9's to accomodate the 35 12.50 17 mud grapplers that I have ordered. Maybe the offset corrects it, I am not sure how that all works.
JK Freak
Joined: Oct 2006
Posts: 556
Likes: 0
From: Mint Hill, NC
hey guys, I am ordering a set of procomp 7005s in a few. I am a little concerned though. With the rough country 2.5BB it's recommended that I keep the backspacing at 4.5. If I order the 17x8's they are indeed 4.5" backspaced (0 offset). I am afraid that I need to order 17x9's, but the backspacing is 4.75" (-6mm). So do I need the 17x9's to accomodate the 35 12.50 17 mud grapplers that I have ordered. Maybe the offset corrects it, I am not sure how that all works.
4.5 backspacing on 8" rim = 3.5" outside the jeep.
4.75 backspacing on 9" rim = 4.25" outside the jeep (but .25" more inside)
go with the 17x8s
JK Jedi
Joined: Oct 2007
Posts: 4,730
Likes: 3
From: BC
if you are running a 12.5 tire, you only need 8" wide rims (some are running on the stock rims 7.5", with spacers to change the stock backspacing.)
4.5 backspacing on 8" rim = 3.5" outside the jeep.
4.75 backspacing on 9" rim = 4.25" outside the jeep (but .25" more inside)
go with the 17x8s
4.5 backspacing on 8" rim = 3.5" outside the jeep.
4.75 backspacing on 9" rim = 4.25" outside the jeep (but .25" more inside)
go with the 17x8s
How come Toyo M/T's, Cooper STT's, Mickey Thompson MTZ's sized 33x12.5 or 35x12.5 require a 8.5" or wider rim in the book???
My tire dealer was not recommending that I place 33x12.5R17's on my aftermarket 17x8rim?? Thus, I am still looking at 285 or 295/70R17 tires.
JK Super Freak
Joined: Sep 2007
Posts: 1,623
Likes: 5
From: Lawrenceville, NJ
if you are running a 12.5 tire, you only need 8" wide rims (some are running on the stock rims 7.5", with spacers to change the stock backspacing.)
4.5 backspacing on 8" rim = 3.5" outside the jeep.
4.75 backspacing on 9" rim = 4.25" outside the jeep (but .25" more inside)
go with the 17x8s
4.5 backspacing on 8" rim = 3.5" outside the jeep.
4.75 backspacing on 9" rim = 4.25" outside the jeep (but .25" more inside)
go with the 17x8s
This BS explanation above is completely wrong btw...mostly because of #3 below I think...but, possibly 1 & 2, hard to say why the wrong answer was given from here...
Anyway - here's the clarification:
1. BS is measured from the INSIDE of the rim lip (Facing the wheel well/brakes...), to the hub face, NOT the outside.
2. BS DOESN'T change with the width of the rim, its from the lip, towards the middle of the rim, from te lip edge to the hub face....so a 3.5" BS on a 7" rim is EXACTLY the same as for a 10" rim, etc.
3. To confuse people, an 8" rim is 9" wide, and a 9" rim is 10" wide, ....as BS is measured from the rim's edge of the lip closest to the inboard side, whereas the NOMINAL rim size (What they list as the rim's "size") is measured IN-BETWEEN the rims lips, thus the 1" difference for that rims actual full size, vs its nominal size.
(So if you measure BS, and later try to figure out the offset, you'd go insane trying to figure out why the math didn't work, etc...)
So - ALL the math part is wrong - just do NOT want the newbies anymore confused than they already are. (Too late?)
The OFFSET is measured from the CENTERLINE of the width, so the 7" rim that's 8" wide would have a centerline 4" in from both side of the rim....and that would be called its ZERO Offset.
And, in case someone was NOT confused enough, they ALSO measure the offset in mm, and the BS in inches....because they really, really hate you. (1" = 25.4 mm if you have to convert...)
And for good measure, therefore, the OFFSET is related to the width of the rim....and measured how far off from the centerline it is to the hub face.
As for NOMINAL width...yeah, for a 12.5" section width, most people off roading use an 8" rim, or even a 7" rim, no problem off road.
For street people, a wider rim makes the tire less squirrelly and handle more precisely on the road.
For a 12.5" section width tire, about 1.5" less BS than the stock 6.25" has been working, so 4.75" or less BS should be fine
I hope that helps clarify things a bit.
Last edited by TEEJ; Mar 18, 2008 at 10:47 AM.
JK Jedi
Joined: Oct 2007
Posts: 4,730
Likes: 3
From: BC
This BS explanation above is completely wrong btw...mostly because of #3 below I think...but, possibly 1 & 2, hard to say why the wrong answer was given from here...
Anyway - here's the clarification:
1. BS is measured from the INSIDE of the rim lip (Facing the wheel well/brakes...), to the hub face, NOT the outside.
2. BS DOESN'T change with the width of the rim, its from the lip, towards the middle of the rim, from te lip edge to the hub face....so a 3.5" BS on a 7" rim is EXACTLY the same as for a 10" rim, etc.
3. To confuse people, an 8" rim is 9" wide, and a 9" rim is 10" wide, ....as BS is measured from the rim's edge of the lip closest to the inboard side, whereas the NOMINAL rim size (What they list as the rim's "size") is measured IN-BETWEEN the rims lips, thus the 1" difference for that rims actual full size, vs its nominal size.
(So if you measure BS, and later try to figure out the offset, you'd go insane trying to figure out why the math didn't work, etc...)
So - ALL the math part is wrong - just do NOT want the newbies anymore confused than they already are. (Too late?)
The OFFSET is measured from the CENTERLINE of the width, so the 7" rim that's 8" wide would have a centerline 4" in from both side of the rim....and that would be called its ZERO Offset.
And, in case someone was NOT confused enough, they ALSO measure the offset in mm, and the BS in inches....because they really, really hate you. (1" = 25.4 mm if you have to convert...)
And for good measure, therefore, the OFFSET is related to the width of the rim....and measured how far off from the centerline it is to the hub face.
As for NOMINAL width...yeah, for a 12.5" section width, most people off roading use an 8" rim, or even a 7" rim, no problem off road.
For street people, a wider rim makes the tire less squirrelly and handle more precisely on the road.
For a 12.5" section width tire, about 1.5" less BS than the stock 6.25" has been working, so 4.75" or less BS should be fine
I hope that helps clarify things a bit.
Anyway - here's the clarification:
1. BS is measured from the INSIDE of the rim lip (Facing the wheel well/brakes...), to the hub face, NOT the outside.
2. BS DOESN'T change with the width of the rim, its from the lip, towards the middle of the rim, from te lip edge to the hub face....so a 3.5" BS on a 7" rim is EXACTLY the same as for a 10" rim, etc.
3. To confuse people, an 8" rim is 9" wide, and a 9" rim is 10" wide, ....as BS is measured from the rim's edge of the lip closest to the inboard side, whereas the NOMINAL rim size (What they list as the rim's "size") is measured IN-BETWEEN the rims lips, thus the 1" difference for that rims actual full size, vs its nominal size.
(So if you measure BS, and later try to figure out the offset, you'd go insane trying to figure out why the math didn't work, etc...)
So - ALL the math part is wrong - just do NOT want the newbies anymore confused than they already are. (Too late?)
The OFFSET is measured from the CENTERLINE of the width, so the 7" rim that's 8" wide would have a centerline 4" in from both side of the rim....and that would be called its ZERO Offset.
And, in case someone was NOT confused enough, they ALSO measure the offset in mm, and the BS in inches....because they really, really hate you. (1" = 25.4 mm if you have to convert...)
And for good measure, therefore, the OFFSET is related to the width of the rim....and measured how far off from the centerline it is to the hub face.
As for NOMINAL width...yeah, for a 12.5" section width, most people off roading use an 8" rim, or even a 7" rim, no problem off road.
For street people, a wider rim makes the tire less squirrelly and handle more precisely on the road.
For a 12.5" section width tire, about 1.5" less BS than the stock 6.25" has been working, so 4.75" or less BS should be fine
I hope that helps clarify things a bit.
Great explaination on the BS issue. I was curious if you know why Toyo, Cooper and Mickey Thompson list 12.5" wide tires as requiring a minimum 8.5" rim? I love the look of the wider 33x12.5 Cooper STT.....However, my tire shop owner highly recommend I don't go with the 33.12.5R17 tire as my aftermarket wheel is only a 17x8 with a 4.5" BS. So, I am still on the fence about either going with a 285 or 295/70R17 tire or stick with my guns and get a 33x12.5R17 tire.
I know in the past I fit 33x12.5R17's Dick Cepek FC II's on my Diesel on a 17x7 stock rim with no real issues with the same tire owner. Is it a big issue?
Last edited by RevyJKU08; Mar 18, 2008 at 12:35 PM.