This statement is also incorrect. A solid bar is slightly stiffer than a hollow bar of the same outside diameter. The solid bar's stiffness is the same as the stiffness of the hollow bar, plus the stiffness of a bar that fills the hole in the hollow bar.

Because the stiffness is proportional to the 4th power of the radius (or the diameter ;-)) the bar that fills the hole is not very stiff compared to the solid bar. So the difference between solid and hollow is small in terms of stiffness.

The torsional strength will have the same relationship, because that is based on the region of maximum shear stress, which is on the outside surface of the bar.

 

4th power, 5th power, nth power are all geometric relationships (x^n). Exponential (n^x) is in another class. It grows a lot faster in the long run than a geometric relationship.

 

We shouldn't muddle this guy's thread up with a discussion of math, but there is no difference when comparing sway bars between using diameter and radius as long as you use the same one with both bars. Since radius is diameter divided by 2, if you take it to the fourth power you get radius^4 = 1/16 * diameter ^4. No matter what the diameter is, it's always 1/16 multiplied by it, so it's not an exponential difference.

So if you use radius the number will be 1/16 times the number you'd get if you'd used the diameter. For both of them. So when you divide one by the other the 1/16 cancels out. So the comparison will still be valid.

For example say you were comparing 1.25" diameter to 1" diameter with everything else the same so you're just comparing the size to get stiffness.
1.25" ^ 4 = 2.441
1" ^ 4 = 1

So the 1.25" bar is 2.441/1 (equals 2.441) times as stiff as the 1" bar.

Using radius:
(1.25/2)^4 = 0.1525
(1/2)^4 = .0625

So then the 1.25" bar is .1525/.0625 (equals 2.441) times as stiff as the 1" bar

Obviously the example is with solid bars but the same thing will happen with a hollow bar for the same reason.

 

Another way to show the equivalence:
[CODE] S

 

So I ended up ordering the Whiteline bar. Now my question is, will it be okat to run OEM endlinks with it? My endlinks have over 127k miles on them. I don't want to run the risk of them breaking due to the extra added stress but if I'm okay to run them then I will just use what I have.

 

If your OEM endlinks are loose or make noise, replace them. Otherwise just keep using them.

 

I'm assuming I will know this while its on the car? Should I try to shake it see about the noise or to see if its loose?

 

So I got the bar in and I love it so far. The only problem is now after the install I have a popping noise from the F/R section of the car. I think its the endlinks but don't know for sure. Anyone have any input on this?

 

If you plan on tracking the car at some point and having it setup properly this would include corner weighing the car. If this is in your plan you need to get adjustable end links so the bar will not be preloaded and throw off your corner weights.

When corner weighing the car you disconnect the link on one side then corner weigh the car then with the car on a level surface as you corner weighed it you reconnect the link by adjusting it so it slides in the hole without any tension on the bar.

You can get by with just one adjustable end link on the front bar and one on the rear bar to do this.

 

^^