Sway Bar Rates

[Track Junky]

Thats what I was thinking. When I talked to Speedway Engineering they told me that they twist one side 5*. Global West told me they did it the same way. I'm going to have to get more information on Monday.

[David Pozzi]

They are using different methods of calculating rate.
Here is a free online calculator: http://www.auto-ware.com/calcs/swaybar.htm
The Hotchkis hollow bar is .156" wall, Hellwig hollow is .188" OD is 1.125 but the powder coat can add .020" which you don't want to count.

I recall Speedway rates with a flat 5deg twist which will be 1" with an arm length of 11 3/16" only, the other arm lengths listed are useless numbers. 1st gen Camaros have a very short arm. Some calculators use 1" arm movement on each arm, so your calculated rate is double. It's best to take the dimensions and re-calculate them using one formula or online calculator. The bent hollow bars are not Chrome Molly steel, the Hellwig solid is and so is the Speedway hollow. I think the Modulus of elasticity is different between the two but most online calculators have the modulus Pre-entered so you can't change it.

[Track Junky]

Dave, Standard OEM bar shape tough to figure how to measure. When I measure length of bar on the Global West and DSE bar do I measure from outside to outside of straight or take it to the outside of the 22.5* bends.

[David Pozzi]

I use the inside of bend to inside of bend. I don't think of bar rate as an accurate number, just as a way to compare one bar to another. There are too many unknowns, like bar mount flex, end link flex, frame flex. Then the bar has a motion ratio that translates to wheel rate, so the bar rate at the wheel is maybe half.
changing from splined bar to splined bar is easier to compare. The Global West and DSE numbers might be inch pounds per degree or per 5 degrees, hard to say.

I can tell you I have used the Hotchkis hollow and it's about right, the Hellwig is one step stiffer but it will take more rear bar to get the car balanced assuming a front tire if 275 & rear if 335. If tires are more equal the Hellwig works OK.

Try using this HTML sway bar calculator. The original web calculator is no longer active but I saved a copy of it and it works pretty well. Great for comparisons. I would reload the page when entering new bar dimensions, it sometimes can give wrong results if you jump in and change the numbers, but I'm on a Mac with Firefox, so maybe it's my computer.
Note keep the slider for motion ratio to the right at 1 to 1 unless you know your sway bar motion ratio. http://www.mediafire.com/?jteoqxvspc4ozq0
This is a free download hosting site, so it will have popups, sorry.

[Track Junky]

Thanks Dave. I agree the numbers are ball park but none of those numbers make sense to me.

I have a Global West bar and a DSE bar. I did feel like I got a touch loose going to the hollow DSE bar but still not sure what to make of it.
If I were to take Global Wests and DSE's numbers seriously I'd have to say going to a bar with more lbs/in up front made me lose which means I got more grip up front with more weight transfer.

[Dave@Hellwig]

Track Junky. I think we talked last week about rates. We use SAE formulas to calculate the spring rates we give out. The rate I gave you includes a 20% reduction to account for compliance in bushings, end links and frame mounts. This factor has correlated fairly well between real world testing and calculated rates. The rate of our 1-1/8" tubular bar without any loss is 750 lb/in.

[Track Junky]

Thanks Dave@hellwig. I do remember us discussing the compensation for reduction. Your input was very informative and I appreciate your help.