Posted: Wed Mar 14, 2012 4:10 pm Post subject: Offset rim vs stock, will these fit?
So- I need new rims- instead of steelie's for the winter tire. I thought about buying new rims for the summer and keep the stock LS rims for the winter tires.
According to http://www.naioa.com/v2/module.....mp;start=0, which references mypoltpattern.com, My question is more towards the backspacing. What is it for our 2005 imp? OR is that the same as Offset: 42mm?
See below for rims I would like to buy. Will these fit a 100% stock impala with 225/60-16's?
Offset is measured from the centerline of the barrel of the wheel to the hub mounting surface. If that hub mounting surface were in the exact center of the barrel of the wheel the offset would be “0". If the mounting surface is away from the center of the wheel the offset is measured in millimeters. There are 25.4 millimeters to an inch. So if the mounting surface is 12mm from the centerline of the wheel it has a 12mm offset. That would also mean that it is about ½ inch. If the mounting surface is moved away from the vehicle that is a positive offset. The picture shows a wheel with the positive offset. A positive offset will cause the wheel to set in or tuck into the vehicle. Originally you found positive offsets on just front wheel vehicles. Due to that some people refer to positive offset wheels as front wheel drive offsets. Currently there are many rear wheel drive cars and trucks with positive offsets. The higher the positive offset the less it sticks out from the vehicle and it will have a higher Backspace. If the mounting surface is moved in toward the vehicle past the centerline, that is a negative offset. A high negative offset will produce a lower Backspace. Once again the measurement in millimeters is how far away from the centerline the mounting surface is. A -24mm offset means that the mounting surface is located 24mm or 1 inch from the centerline toward the vehicle. The wheel will come out farther from the vehicle and will have that deep dish look.
Back spacing is measured from the inner edge of the wheel to the hub mounting surface. It is a convenient measurement in that, as long as the back spacing remains the same, the clearance to the suspension also remains the same. If you know the width of the wheel and the offset you can compute the backspacing. For example if you have an 8 inch wheel with a +24mm offset. An 8 inch wheel is actually 9 inches wide so if the offset were 0 the mounting surface would be right on the centerline and the backspacing would be 4.5 inches. With a positive offset the mounting surface moves off center 24mm or 1 inch toward the outer edge of the wheel. This will make the inner edge go more inside which will result in a 5.5 inch backspacing.
So when purchasing aftermarket rims, what is the range of off set you should have?
high offset, somewhere in the 38-45 range should be fine. Make sure you also get the right bolt pattern. The Impala uses 5x115. Dont let anyone or the shop tell you that 5x114.3 will work. A lot of people think it doesnt matter, but its been proven time and time again by members breaking wheel studs due to the improper bolt pattern.
Think of it this way, if it didnt matter, or was acceptable, why would wheel manufacturers spend all that $$ to make both patterns available if they were simply interchangeable.
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