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Unread 12-19-2013, 06:42 AM   #46
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Originally Posted by nickair544 View Post
Thanks Charlie, your post is just what I was interested in hearing feedback on. Do you have any advise on 15 inch wheel choices to clear the disc brakes on front and rear?
There are two problems.

The wheel dimensions specify 15 inch, but they don't tell you what the inside dimension is on the back side of the rim to fit around the caliper. That is why buying from a place that specs the vehicle on which you are putting he rim will keep you out of trouble. Of course, any OEM wheel from a disc brake Wrangler will work. Not all 15" rims 5x4.5 with a 5" backspace will fit around the caliper.

Second is the backspace (usually specified as "Offset"). 5" is ok.

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Unread 12-19-2013, 07:31 AM   #47
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Quote:
Originally Posted by wilson1010 View Post
Second is the backspace (usually specified as "Offset").
Aren't backspacing and offset different (although related) things?
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Unread 12-19-2013, 08:39 AM   #48
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Originally Posted by biffgnar View Post
Aren't backspacing and offset different (although related) things?
Absolutely. Most wheels are sold by the specification of offset. Offset is the distance in positive and negative numbers by which the part of the rim where the bolts seat, is in front of or behind the centerline of the wheel.

Back space is the distance from the inside plane of the rim to the part of the rim where the bolts seat.

A good discussion of this can be found here:

http://www.tirerack.com/wheels/tech/...jsp?techid=101

I said "usually specified as offset" because one rarely sees a wheel sold based on backspace, although the backspace can be found in the specifications. Typically 4.5 to 5.5 inches for Jeep rim. They are usually specified as offset in millimeters. So you will see a wheel that is 20mm offset offered. Backspace is important, however, because a narrow rim with 20mm of offset may not have room for every caliper. A 5" backspace is enough to accommodate any Jeep caliper.
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Unread 12-19-2013, 11:30 AM   #49
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I have never worried about offset in the thousands of tire/wheel combo's I have ran, Sold or otherwise unless its a car. If its a jeep, All you need to go off of is the backspacing you want and need to clear.
Offset is the last ****ing thing you need to worry about unless you want to run stockers. With most if not all, 3.75-4" is what you need so you don't have to adjust and reduce steering radius and rub on LCA's.
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Unread 12-19-2013, 11:35 AM   #50
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Originally Posted by KKiowaTJ View Post
I have never worried about offset in the thousands of tire/wheel combo's I have ran, Sold or otherwise unless its a car. If its a jeep, All you need to go off of is the backspacing you want and need to clear.
Offset is the last ****ing thing you need to worry about unless you want to run stockers. With most if not all, 3.75-4" is what you need so you don't have to adjust and reduce steering radius and rub on LCA's.

Offset and backspace measure the same thing on a specific width rim.
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Unread 12-19-2013, 11:57 AM   #51
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Originally Posted by wilson1010 View Post
Offset and backspace measure the same thing on a specific width rim.
They DO NOT measure the same thing.

Offset is a measurement of the wheel mounting surface in relation to the centerline of the wheel.

Backspacing is the measurement of the wheel mounting surface in relation to the back side of the wheel.

2 entirely different measurements.

Backspacing remains the same regardless of wheel width, while the offset varies with the width for a given backspacing.

You can disregard the offset as long as you get the proper backspacing.
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Unread 12-19-2013, 12:45 PM   #52
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They DO NOT measure the same thing.

Offset is a measurement of the wheel mounting surface in relation to the centerline of the wheel.

Backspacing is the measurement of the wheel mounting surface in relation to the back side of the wheel.

2 entirely different measurements.

Backspacing remains the same regardless of wheel width, while the offset varies with the width for a given backspacing.

You can disregard the offset as long as you get the proper backspacing.
Read my post more carefully before you jump into this.

I said as to a "specific width rim."

So, if the rim is 8" and the back space is 4" the offset is zero, right?

And, if the backspace is 5" the offset is 25.4mm, right?

They measure exactly the same thing on a particular wheel. Right? The location of the portion of the rim that bolts to the rotor assembly. Every 8" rim with a 5 inch backspace will have the same offset. they are both measurements of the location of the portion of the rim through which the bolts are inserted.

Now, if one was considering two different width rims, they could have the same backspace, but different offsets. So what? I wasn't talking about that.
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Unread 12-19-2013, 01:15 PM   #53
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Originally Posted by wilson1010 View Post
Read my post more carefully before you jump into this.

I said as to a "specific width rim."

So, if the rim is 8" and the back space is 4" the offset is zero, right?

And, if the backspace is 5" the offset is 25.4mm, right?

They measure exactly the same thing on a particular wheel. Right? The location of the portion of the rim that bolts to the rotor assembly. Every 8" rim with a 5 inch backspace will have the same offset. they are both measurements of the location of the portion of the rim through which the bolts are inserted.

Now, if one was considering two different width rims, they could have the same backspace, but different offsets. So what? I wasn't talking about that.

Read my post more carefully before you jump into this.... Or are you just contradicting yourself for the sake of argument....


They are two entirely different measurements... Plain and simple.

They do NOT " measure the same thing on a specific width rim". They measure 2 entirely different points/locations even on a specific width wheel.

Offset is the wheel mounting surface's relation to the centerline of the wheel....

Backspacing is the wheel mounting surface's relation to the backside of the wheel which also is a relation to the fitment on the vehicle.

You can determine one from the other but they are still 2 entirely different measurements.
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Unread 12-19-2013, 02:05 PM   #54
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Originally Posted by SLADE View Post
Read my post more carefully before you jump into this.... Or are you just contradicting yourself for the sake of argument....


They are two entirely different measurements... Plain and simple.

They do NOT " measure the same thing on a specific width rim". They measure 2 entirely different points/locations even on a specific width wheel.

Offset is the wheel mounting surface's relation to the centerline of the wheel....

Backspacing is the wheel mounting surface's relation to the backside of the wheel which also is a relation to the fitment on the vehicle.

You can determine one from the other but they are still 2 entirely different measurements.

Actually, they do. What they measure is where the rim's bolting surface is located. One expresses it in terms of the plane of the rim, the other in terms of the center line. Sort of like saying the 40 yard line on a football field is 60 yards from your end zone or 40 yards from mine. Or 10 yards from mid field.

In this case, the offset measures how far from mid field, the backspace is how far from your end zone. But, they are measuring exactly the same thing. The ball is on the 40 yard line.

A zero offset 8" rim will have a 4" backspace. And, a 4" backspace on an 8" rim will have zero offset. Right?


.
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Unread 12-19-2013, 10:07 PM   #55
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NickAir, this post is regarding your earlier questions about 33 x 10.5 R15 tires fitting your TJ.

Quote:
Originally Posted by wilson1010 View Post
The wheel dimensions specify 15 inch, but they don't tell you what the inside dimension is on the back side of the rim to fit around the caliper. That is why buying from a place that specs the vehicle on which you are putting he rim will keep you out of trouble. Of course, any OEM wheel from a disc brake Wrangler will work. Not all 15" rims 5x4.5 with a 5" backspace will fit around the caliper.
Wilson is correct on this topic. It's possible caliper clearance is not assured just by backspacing. I should have though to mention that.

However, I do know that my American Racing Ansen Sprint 15 x 8 with 4.5 BS had plenty of clearance for stock calipers. They even cleared the Vanco Big Brakes I later put on it.

So those 15 x 8 with 4.5 BS Ansen Sprint wheels work for sure. It's likely that a 15 x 8 wheel with 5" BS would also clear everything, including calipers, but no guarantees. I guess if in doubt do a test fitting of one wheel before buying.

Probably any 15 x 8 with 4.5 BS would clear calipers. Probably any 15 x 8 with 5" BS would clear. Stock Wrangler wheels are 15 x 8 with 5.5" BS and they clear calipers. So probably not a problem. However, there is a chance Wilson's concern might apply to some wheels.

Another thing I should have mentioned is when tire clearance is tight during turns, the stock swaybar usually rubs during turns before the LCAs will rub.

I didn't have to worry about rubbing stock swaybar because I had a Currie Antirock sway bar, which has more tire clearance.

Also, I had JKS round LCAs, which offer slightly more clearance than stock rectangular LCAs.

So NickAir, please keep those things in mind.
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Unread 12-20-2013, 04:04 AM   #56
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A zero offset 8" rim will have a 4" backspace. And, a 4" backspace on an 8" rim will have zero offset. Right?

Who gives a crap how they relate to each other.

The purpose of the two different measurements is not to determine how they relate to each other. Your just arguing a pointless observation.


There is a reason why tire fitment is based off of backspacing and not offset.
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Unread 12-20-2013, 04:48 AM   #57
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Who gives a crap how they relate to each other.

. . .

There is a reason why tire fitment is based off of backspacing and not offset.
Perhaps then you can convince the techies at Tire Rack to rename their article explaining all of this, "backspacing" instead of "offset."

Also, you might want to let the manufacturers of wheels know they should stamp the backspace on the inside of the rims instead of offset which is presently what they all do.
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Unread 12-20-2013, 11:12 AM   #58
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Originally Posted by wilson1010 View Post
Perhaps then you can convince the techies at Tire Rack to rename their article explaining all of this, "backspacing" instead of "offset."

Also, you might want to let the manufacturers of wheels know they should stamp the backspace on the inside of the rims instead of offset which is presently what they all do.

Is "Tire Rack" the only place you use to regurgitate information?

I don't need to convince them of anything. People use Backspacing, not offset to determine fit.

Lift manufacturers use backspacing when specifying tire fitment and Backspacing is specified when buying wheels (4 wheel parts for example). Out of all the wheels I've bought, sold, and used Ive never used Offset to determine fitment. Backspacing remains a constant and is easier to use regardless of wheel width.
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Unread 12-20-2013, 11:55 AM   #59
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Is "Tire Rack" the only place you use to regurgitate information?
No, I've actually looked on the inside rim of my aftermarket rims and . . . surprise . . there it is in millimeters, the amount of offset. I did look for the backspace, but could not find it. Do you think you could post up one of your rims with the backspace stamped into the metal? Or, do you carry a ruler and a level to measure each one as you look at them?
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Unread 12-20-2013, 11:57 AM   #60
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Backspacing remains a constant and is easier to use regardless of wheel width.
Yes, you're right.

Backspacing would be easier to use if you did not know the width of the rim you were buying and didn't care how far out to the fender it extended.
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