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Author Topic:   LR 4 bar confusion ?
3kids
Dirt Roller

Total posts: 20
posted July 31, 2005 01:54 PM  
Do the top and bottom bars on the LR of a 4 bar car with the spring in front clamped to the housing on a weightjack bolt like a skyrocket or a hughes chassis and spring on top RR Z link do the same things as a late model with a floated spring behind?
What do these bars actually do with this setup? Does lowering the bottom bar still give you drive or does it now just remove roll steer?
Would you start the night on a tacky track with the bottom bar up and then work down for a dry slick track or just the opposite?
I get so many different oppions that I am getting confused.
Also would to much panhard angle in a short abr in front of the housing (12") drive the car loose off of the corners on a sweeping half mile?
Thanks so much for the help!!!! This site is a great place to get heads up answers!!

5tbone
Dirt Full Roller

Total posts: 58
posted July 31, 2005 02:45 PM  
this might help http://www.larryshaw.com/NModSetUp.htm

3kids
Dirt Roller

Total posts: 20
posted July 31, 2005 09:40 PM  
Come on people, I know someone has answers for this. Pleeeeeaaassee help!!!!!!!!!!!

rocket36
Dirt Freak

Total posts: 209
posted August 01, 2005 07:58 AM  
yes, they basically do the same thing. those bars push the car forward, and if angled upward they will push the car up and the wheel harder into the ground. because the bars swing in an arc, the left rear will move forward (adding bar angle - lift - traction). more the bars angle up, the harder the wheel is pushed into the ground and the further forward it will move.
clamping the spring in front and to the axle makes any reaction force (diff housing rotation) apply through the spring (often increasing traction on that wheel) where as the spring mounted behind and on the birdcage, relies on birdcage rotation (indexing) to apply force to the wheel (also adding traction.
hopefully that made sense.

irace74
Dirt Forum Racer

Total posts: 80
posted August 01, 2005 08:01 PM  
I think that the following link is the best discussion of 4 bar workings. http://www.afcoracing.com/tech_pages/4link.shtml

The bars combine to control rear steer and thrust. Generally speaking, the lower links are most effective at controlling rear steer. It is said that the upper links are most effective at controlling thrust angle. These generalizations are not exclusively true but, to the novice, they are effective. Oncce you learn more about 4 link suspensions, you will find that both link positions have an effect on rear steer and thrust. Wrenching around on them is generally not required once you find what works for you and your tracks. Significantly different tracks may require some adjustment.

jws
Dirt Maniac

Total posts: 115
posted August 02, 2005 09:02 AM  
This is a good question. It will be different with the spring clamped in front than with normal 4 bar sring behind on the cage. There are three things involved in 4 link adjustment, rear steer, indexing, and thrust angle. With the spring clamped indexing is not a factor. You are really only dealing with the thrust angle and the rear steer. Hard to say which has the greater affect since they are working against each other. I think that Shaw cars use that set up and maybe Hughes cars. You need to talk to one of those guys.

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