four link tubes

[440altered]

Is there an ideal length for four link tubes? if so does it vary with application and why? Sorry if it's a bit basic.
Thanks.

[David Lemmond]

I'm not sure there is an ideal length. Short bars are stronger but make a larger instant center change per adjustment, as they go down the track, with the car moving up and down around the rearend housing. Longer bars give up strength or have to use larger diameter and or thicker tubing to make up for being long. Longer bars have a more finie instant center change per adjustment.
The most common bar length used by Bickel, jones, and Mcamis is 23" from the center of the housing to the front rod end center.

[bigblue466]

I have seen some that have shorter tubes on top? Why is that?

[vanillagorilla]

From what I understand, the tube is shorter on top for packaging reasons. They still have to fit within the confines of a car's floor.

[BillyShope]

I have seen some that have shorter tubes on top? Why is that?

There is an optimum ratio, of upper and lower link lengths, for a given car. This is because, as the front of the car rises on launch, the link angles change and, consequently, the instant center moves. With the right length ratio, it's possible to maintain the same percent antisquat as the front rises.

There's a spreadsheet at my site to determine the optimum ratio for your car.
http://home.earthlink.net/~whshope
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