I am somewhat confused with backspacing on rims. Here is my delema. I have been searching for rims for a 2003 2500 4x4. Weld makes a rim 20x8. 5 with a 5. 125" backspace. I was told by a local rep that 20x9. 5 with a 6. 125" backspace would stick out approx 1. 5". would a 20x8. 5 with the 5. 125" backspace stick out the same distance. The rims are 1" narower and the backspace is 1" narower as well???? Please help
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question on rim backspacing
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Backspacing can get confusing. Offset is the number that is easiest to understand. A positive offset moves the tires in while a negative offest moves them out. The offset number is the distance of the hub surface from the centerline of the wheel. The 03's use a +40mm offset that is virtually unheardof in the industry. Most are 0 or negative.
Offset stays the same when wheel width changes, backspacing does not. So if you have a 8” rim with 40mm offset and 5” backspace, move up to a 10” wide rim with 40mm offset and you have 7” backspace.
-Scott
Offset stays the same when wheel width changes, backspacing does not. So if you have a 8” rim with 40mm offset and 5” backspace, move up to a 10” wide rim with 40mm offset and you have 7” backspace.
-Scott
Looks to me like they both will stick out 1. 375" more than stock or a little over 1 & 1/4"
One has a wider wheel but makes up for it in the back space to equal how far the wheel pokes out of the more narrow one.
That is based on the 6" back space my factory alloys have if I measured correctly.
What Weld wheel were you looking at?
A nice wheel with correct fit is this one, 18x8. 5 with 6. 125" back space.
#ad
That you can find here
One has a wider wheel but makes up for it in the back space to equal how far the wheel pokes out of the more narrow one.
That is based on the 6" back space my factory alloys have if I measured correctly.
What Weld wheel were you looking at?
A nice wheel with correct fit is this one, 18x8. 5 with 6. 125" back space.
#adThat you can find here
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SRadke said:
myself, i find the backspacing much easier to understand than offset [i can work with both, but backspacing is more clear to me]. i eventually want to get some 20x9 or 20x10 wheels for my truck, and i will need to have about 6. 5" backspacing on them to fit properly. that is for both the 9" or 10" width. now if we were talking offset, that would mean 2 different numbers for the offset i would need to remember. the 20x10 wheel would have +1. 5"/+38mm offset while the 20x9 would have +2"/+51mm. to me it's just much simpler to remember ±6. 5" backspacing
I have been looking at Weld Velocity 8 wheels 20". I have a bunch of estimates all over the 4k $$ range with 325 60 20 nitto grapplers. All wheels I was quoted had 6. 125 backspace but were 9. 5" wide. I found a awesome deal on ebay for a hardly used set of 4 with less than 1000 miles for 2k. They are 20x8. 5 with a 5. 125 backspace with 325 60 20 toyo A/T. (1" less backspace but also 1" narower) just wondering if they would stick out the same as a 6. 125" rim. seems they would be 1" shorter inward to the wheel well. Any help would be appreciated.
Another way to look at it is... the wider wheel is 1" wider but, the 1" more offset it has makes that 1" extra width all on the back side vs the 8. 5" wheel you are looking at.
Each rim should stick out the same, just one is more narrow on the back side.
That being said I would go with the width that best fits the tire.
Each rim should stick out the same, just one is more narrow on the back side.
That being said I would go with the width that best fits the tire.
with less backspacing, tires will rub
I was told that the rims with the 6. 125 backspace would rub on the control arms at full lock. why would rims with 1" less backspace rub? Its seems logical to me that they would be 1" further away from the control arms thus reduce the rubbing. I spoke with a tech at weld industries he told me that the 2 wheels mentioned above will stick out the same, but that they would stick inward 1" less. I am running a 2" RevTech leveling kit also. Is anyone else running this application or anything close?? Saving over 2k for 1" less backspace hope the will fit... ... ... ... ... ... .
If you run a wheel with 1" less backspace a 35" tire will rub on your fender. Front fender. If you compress your suspension while rubbing, CruNch!!!! I have factory stock cast wheels. I run Goodyear 37/12. 50/17 MT/R's. A huge agressive mud and sand tire. The only rub I have is when I turn hard to the right. Control arm. When I had the 35's on it. No rub. Another TDR member that I have become friends with, has 5 inch backspacing and 35's. He cannot run a KORE suspension or any lift due to rubbing. He has 35 inch tires.
IF you want to "use" your truck for anything spend the extr*****$ and get the right wheel. Fred Swanson had the 9 inch wheel with 5. 125" backspace. It stuck out 4 inches in the rear. Thats with a 35 inch tire. Plus you have to think seriously about the load on the bearing that the front hub has to deal with. If you move the leverage out 1 inch from stock, it might increase that load as much as 10 times. Somethings are better left to the engineers to figure out.
Greg
IF you want to "use" your truck for anything spend the extr*****$ and get the right wheel. Fred Swanson had the 9 inch wheel with 5. 125" backspace. It stuck out 4 inches in the rear. Thats with a 35 inch tire. Plus you have to think seriously about the load on the bearing that the front hub has to deal with. If you move the leverage out 1 inch from stock, it might increase that load as much as 10 times. Somethings are better left to the engineers to figure out.
Greg
Well I guess I'm royally confused now!! If the rims will stick out the same only difference is 1" less inward why would they rub the front fender? and stick out 4" in rear? Were just talking 1" difference? Stock is 6. 1 backspace so why would 1" difference be so off? thanks for all the help... ... ... ... ... ... ...
Gents,
As your steering and suspension cycles, many geometric changes occur in your truck's front end. There are four commonly-known dimensions that are related to the effects of wheel offset/backspacing. These are camber, caster, toe, and ackerman. There is also some black magic that has to do with the angles at which the counterbores for your ball joints are machined, the way the suspension can move independently side to side and variations in production tolerances. All of these static dimensions change as you sweep your steering side to side and the suspension cycles up and down. I don't have the time to describe what these dimensions are and how they affect these trucks. It would take a full dissertation to explain all this.
You can learn the same thing by doing this: Put your truck on a lift, take the springs and wheels and tires off but leave the shocks and bump stops in place and bump and droop your axle housing 100 times from middle pressure, 100 times from driver side pressure, 100 times from passenger side pressure and measure each cycle in 1/8" increments. Now do the same thing again with wheels and tires in place. Measure each 1/8" increment while sweeping the steering . 5 degrees at a time. Document all the data in an organized fashion and plug it into a computer on an Excel spreadsheet. Using this data, make a 3D model of the whole thing on CAD. Input various wheel/tire dimensions and computer analyze the repercussions, then you will begin to understand how complex the front of a 5 link actually is.
Suffice to say that if you use a wheel that is not exactly correct for your truck, you will start to mess things up. Your truck's steering and suspension will not work properly, performance will suffer and eventually something will fail.
This is not stupid marketing jargon and b. s. spewed forth just to sell stuff. It's simply the truth.
Now, I know someone will say, "I've been running such and such a wheel with 4. 5" backspacing for ten years and everything is still fine. " Maybe that's true if all you're using your truck for is picking up groceries for grandma.
I'll tell you this right now: Greg Boardman and I could put a 4. 5 or 5 inch backspaced, non-hubcentric wheel on one of our trucks and obliterate the front end in five minutes by driving "normally" through the desert.
Proper wheel dimensions are that critical for what we do - and for what anyone does - it just takes longer for the repercussions to appear.
Aside from the instant rubbing problems the wrong wheel will cause, the long-term effects can be grave. We can simply take five minutes in the desert to do what the average grocery-getter will do in five years.
Using a wide, off road tire on the proper wheel will not, aside from the greater stresses more weight and traction can impose, damage any OE components on your truck. However, wider tires may cause rubbing on the control arms - especially on the passesnger side of Dodge Rams that are up 2. 5" in front. With longer coils, the track bar causes the axle housing to move to the driver's side a bit. This places the larger tire closer to the passenger side control arms, causing a slight rub at full lock. Not all Dodge Rams manifest this problem. This inconsistancy has to do with the imprecise way in which the steering knuckle stops are machined at the factory. Older Rams had adjustable steering stops - a simple nut and bolt. On 3rd gen trucks a bit of rubbing at full-lock is a non-issue, since the control arms are boxed and smooth on the bottom. Second Gen control arms make a hideous noise when the large lugs of off road tires hit them because the arms are flanged outward and open on the bottom.
The cure for this is simple: drill a 1/4" hole in your steering knuckle and tap in a #12 U-Drive screw. This will limit your steering sweep by about 1. 5 degrees and usually solve your rubbing problem. You can do this on both sides if you want. Send a SASE padded envelope to KORE and I'll send you these parts free of charge. I don't care whose tire, wheel or lift you're running.
If you prefer, you can also simply drill and tap your steering stops and install a bolt and nut to adjust your steering sweep as you desire. This is a quick and easy retrofit.
Bottom line: If all you are concerned with is aesthetics, then it really doesn't matter what wheel you use. If you care about doing it the right way, and are concerned with the longevity of your components, use the right wheel.
It's not big rubber that will damage your truck; it's the wrong wheels.
Best Regards,
Kent Kroeker
KORE
As your steering and suspension cycles, many geometric changes occur in your truck's front end. There are four commonly-known dimensions that are related to the effects of wheel offset/backspacing. These are camber, caster, toe, and ackerman. There is also some black magic that has to do with the angles at which the counterbores for your ball joints are machined, the way the suspension can move independently side to side and variations in production tolerances. All of these static dimensions change as you sweep your steering side to side and the suspension cycles up and down. I don't have the time to describe what these dimensions are and how they affect these trucks. It would take a full dissertation to explain all this.
You can learn the same thing by doing this: Put your truck on a lift, take the springs and wheels and tires off but leave the shocks and bump stops in place and bump and droop your axle housing 100 times from middle pressure, 100 times from driver side pressure, 100 times from passenger side pressure and measure each cycle in 1/8" increments. Now do the same thing again with wheels and tires in place. Measure each 1/8" increment while sweeping the steering . 5 degrees at a time. Document all the data in an organized fashion and plug it into a computer on an Excel spreadsheet. Using this data, make a 3D model of the whole thing on CAD. Input various wheel/tire dimensions and computer analyze the repercussions, then you will begin to understand how complex the front of a 5 link actually is.
Suffice to say that if you use a wheel that is not exactly correct for your truck, you will start to mess things up. Your truck's steering and suspension will not work properly, performance will suffer and eventually something will fail.
This is not stupid marketing jargon and b. s. spewed forth just to sell stuff. It's simply the truth.
Now, I know someone will say, "I've been running such and such a wheel with 4. 5" backspacing for ten years and everything is still fine. " Maybe that's true if all you're using your truck for is picking up groceries for grandma.
I'll tell you this right now: Greg Boardman and I could put a 4. 5 or 5 inch backspaced, non-hubcentric wheel on one of our trucks and obliterate the front end in five minutes by driving "normally" through the desert.
Proper wheel dimensions are that critical for what we do - and for what anyone does - it just takes longer for the repercussions to appear.
Aside from the instant rubbing problems the wrong wheel will cause, the long-term effects can be grave. We can simply take five minutes in the desert to do what the average grocery-getter will do in five years.
Using a wide, off road tire on the proper wheel will not, aside from the greater stresses more weight and traction can impose, damage any OE components on your truck. However, wider tires may cause rubbing on the control arms - especially on the passesnger side of Dodge Rams that are up 2. 5" in front. With longer coils, the track bar causes the axle housing to move to the driver's side a bit. This places the larger tire closer to the passenger side control arms, causing a slight rub at full lock. Not all Dodge Rams manifest this problem. This inconsistancy has to do with the imprecise way in which the steering knuckle stops are machined at the factory. Older Rams had adjustable steering stops - a simple nut and bolt. On 3rd gen trucks a bit of rubbing at full-lock is a non-issue, since the control arms are boxed and smooth on the bottom. Second Gen control arms make a hideous noise when the large lugs of off road tires hit them because the arms are flanged outward and open on the bottom.
The cure for this is simple: drill a 1/4" hole in your steering knuckle and tap in a #12 U-Drive screw. This will limit your steering sweep by about 1. 5 degrees and usually solve your rubbing problem. You can do this on both sides if you want. Send a SASE padded envelope to KORE and I'll send you these parts free of charge. I don't care whose tire, wheel or lift you're running.
If you prefer, you can also simply drill and tap your steering stops and install a bolt and nut to adjust your steering sweep as you desire. This is a quick and easy retrofit.
Bottom line: If all you are concerned with is aesthetics, then it really doesn't matter what wheel you use. If you care about doing it the right way, and are concerned with the longevity of your components, use the right wheel.
It's not big rubber that will damage your truck; it's the wrong wheels.
Best Regards,
Kent Kroeker
KORE
Kent,
I understand what your saying but what I don't fully see is how going to a wheel that has LESS offest or even zero offset (which would be less backspacing on our trucks) would be harmful since it would be moving the wheel hub closer to center, not further. This I would think tend to put less leveraging stresses on the wheel and hub components would it not??
Also, is there any chance Weld will be making a 17" rim?? The tire selection in 18" off road tire is VERY limited. Why go bigger than you have to on the rim?
I understand what your saying but what I don't fully see is how going to a wheel that has LESS offest or even zero offset (which would be less backspacing on our trucks) would be harmful since it would be moving the wheel hub closer to center, not further. This I would think tend to put less leveraging stresses on the wheel and hub components would it not??
Also, is there any chance Weld will be making a 17" rim?? The tire selection in 18" off road tire is VERY limited. Why go bigger than you have to on the rim?
Last edited:
It's easy to visualize a 0 offset as ideal, being centered but its not.
The forces applied to the wheel bearings during cornering or hitting an object with the wheel turned is where things change.
A simple way to visualize how a deep back space is desirable is to take a small plastic or glass cup out of the cupboard, lay it on its side and get a pencil, insert it into the drinking end of the cup with the eraser at the bottom.
This is your deep back space wheel and axle, if you hold these together and sweep them through an outside corner- (the one getting all the weight) it is easy to see no "extra" force is applied at the eraser (base of the cup) where the bearing would be.
Next hold the pencil in the middle of the cup, this is your 0 offset wheel and do the same sweep. What you see is that the farther out you move the wheel the more "leverage" that tire/wheel can apply to the bearing during cornering when lots more load is applied. Taking a 35mph corner at 45 like many do puts way more load on the bearings than driving straight.
Kinda crude but fun to play with.
The forces applied to the wheel bearings during cornering or hitting an object with the wheel turned is where things change.
A simple way to visualize how a deep back space is desirable is to take a small plastic or glass cup out of the cupboard, lay it on its side and get a pencil, insert it into the drinking end of the cup with the eraser at the bottom.
This is your deep back space wheel and axle, if you hold these together and sweep them through an outside corner- (the one getting all the weight) it is easy to see no "extra" force is applied at the eraser (base of the cup) where the bearing would be.
Next hold the pencil in the middle of the cup, this is your 0 offset wheel and do the same sweep. What you see is that the farther out you move the wheel the more "leverage" that tire/wheel can apply to the bearing during cornering when lots more load is applied. Taking a 35mph corner at 45 like many do puts way more load on the bearings than driving straight.
Kinda crude but fun to play with.
Matt,
I thought about your example but I still don't see it. Maybe my engineering skills are rusty. The force applied to the wheel say from a bump can be roughly thought of as acting in the center of the wheel on average. If the wheel hub is inline with this you have the minimal stress being applied to both the wheel and axle hub. Move that center line away in either direction and you are then leveraging the applied force to act on the wheel hub and axle hub.
I thought about your example but I still don't see it. Maybe my engineering skills are rusty. The force applied to the wheel say from a bump can be roughly thought of as acting in the center of the wheel on average. If the wheel hub is inline with this you have the minimal stress being applied to both the wheel and axle hub. Move that center line away in either direction and you are then leveraging the applied force to act on the wheel hub and axle hub.
Maybe it will help to look at it this way...
Forget the wheel and lets talk about the tire, the farther out you move the rubber the more leverage can be applied to the bearing "during cornering" this is on the outside tire not the inside one that unloads weight in the corners.
Even a better way to visualize is an 8" wheel with 0 offset and a 10" wheel with 0 offset, surely you can see in that scenario the 10" well will give more leverage against the bearing during cornering.
Forget the wheel and lets talk about the tire, the farther out you move the rubber the more leverage can be applied to the bearing "during cornering" this is on the outside tire not the inside one that unloads weight in the corners.
Even a better way to visualize is an 8" wheel with 0 offset and a 10" wheel with 0 offset, surely you can see in that scenario the 10" well will give more leverage against the bearing during cornering.
I think you are just confusing the issue by comparing tires or different widths and talking about cornering. In cornering your mostly talking about forces parallel to the axle. It almost doesn't matter the tire width at all in that case (within some margin of reason, ignoring the vehicle leaning) if the offeset is zero the forces applied to the hub are the same.
Imagine a wheel with extreme offsets in either direction, all the way to the edge of the wheel. When applying a force to the wheel the hub is going to see the same forces acting on it regardless of which side of the hub the mass of the wheel is on.
I think it's safe to assume that if a manufacturer designs their stock system with any offset (plus or minus) it's safe purely from a component point of view to use a wheel that uses any offset from the stock offset to the opposite side (change sign from + to - or vice versa). In our case I think we can use a wheel with a -30mm (I think stock is +30??) offset which would over 2" more backspace.
Imagine a wheel with extreme offsets in either direction, all the way to the edge of the wheel. When applying a force to the wheel the hub is going to see the same forces acting on it regardless of which side of the hub the mass of the wheel is on.
I think it's safe to assume that if a manufacturer designs their stock system with any offset (plus or minus) it's safe purely from a component point of view to use a wheel that uses any offset from the stock offset to the opposite side (change sign from + to - or vice versa). In our case I think we can use a wheel with a -30mm (I think stock is +30??) offset which would over 2" more backspace.
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Subscribe
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