Can anyone tell me what the proper wheel offset is for the 15x7 rally wheel for the 1969 camaro? Is this offset number measured from the back of the wheel at the lug point, to the inside bead?

 

Wheel spacing can be measured two different ways. The more common reference pointis the backspacing, which is the measurement from thewheels mounting surface out to the outer rim of the back side of the wheel. Offset is the measurement from the wheels mounting surface to the centerline of the wheel. The 15x7 rally originally had a 4" offset.

 

"The 15X7 rally originaly had a 4" OFFSET"

I think you ment backspacing.

 

OOPS, did I say that? That would make for a very flat wheel, wouldn't it?

 

If you want the car to handle correct you need to take into account the diameter of the tire when calculating offset. I know most people just do not want the tire to rub and that is the most important thing. But if you want the car to hand well you want to maintain the SAI (Steering Axis Inclination). What is SAI you ask. If you stand in front of the car with the wheel off draw a pretend line through both ball joints continue the line to the floor chalk mark the floor. Mount up the tire and the center of thetire should be right over the chalk mark. Most of the pro builders get the rims custom made with the correct SAI for that car and the tire size they want then make the adjustment for clearance. Since we do not have that kind of resources I thought I would just let you know so you can keep an eye onit and do not let it get to out of control.

I find it funny when guys go out and spend hundreds for dollars on performancesuspension parts andthe wheel offset is so far offnot only is the SAI way off but its so far off the correct Ackerman angles are long gone. These two angles are what make a car track around a corner.

 

are you just trying to sound important to people that don't know much about cars? because that sounds like some of the biggest bunch of technical double talk that I have ever heard on ANY forum.

if someone did what you just said, then they would get all kinds of different figures. a lifted car will totally change the "imaginary" line to the ground as the suspensionis loaded up. caster and camber are what makes a car track properly

 

Sorry if I sounded pompus but the topic is someone asking about wheel offsets I thought I would explain what was important. Caster Camber and toe in are important for alignment but they are adjustable and are not effected much by rim offsets. Riding height effects every aspect of you supension. I did make the assumpsion people had enough sense to know that they would get different measurement if they had the car jacked up, just like with caster, camber and to in.

I am not just throwing out double talk of stuff I read in a magazine. Iwas GM ans ASE certified Master Tech who used to build race cars and yes I have done many 4 wheel alignment back in the day. I have explained how to figure out the rim offset to many people the normal reaction I get is "Hey thanks for explaining it to me". Anyone with a mechanical background could put "Steering Axis Inclination" and "Ackerman angles" in "The Google" and with about an hours worth a research never have to ask "what offsets do I need" on any car ever. If that kind of information is not wanted on these forum then I am wasting my time.

BTW:
There is another test you could do to test your SAI on a car. Throw a layer of fine saw dust on the floor drive your car so one of the front tires are on the dust. With the car sitting still turn the stearing wheel as far as it will go towards the side of the car you are testing. Do not turn it back. Now jack up the car and move it.Look at the swirl pattern. Is the center of the swirl in the center of the tires? If it is then SAI is correct. I never tried this test but it should work. The reason I never try it is because Iused aself centering turn tables that show center of rotation.