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Author Topic:   straight bar vs. j bar
dirtracr
Member
posted July 16, 2001 08:44 PM
One reason you may lose shock travel is that with a J-bar the chassis roll is being transfered on a shorter arch so the same amount of lift moves the rearend over to one side more with the straight bar which I assume is longer. I hate to assume things because when you do it makes an *** out of u and me. Other factors include center of gravity- roll centers- and dynamic movement. With rebound or up travel LR what is the rearend doing in relation to the car's center line? Are you pushing the rr into the track or is the opposite true- think of the side bite. With out knowing other factors such as spring rates, rear roll center,and ballast placement it is impossible to make an accurate picture of what is really happening. By changing this one thing it affects several others in how they interact as a suspension unit.


wfoondirt
Member
posted July 17, 2001 01:58 PM
are you talking about a long straight bar or a short one mounted to the pinion?


dirtracr
Member
posted July 17, 2001 05:09 PM
I'm not a big advocate of the short panhard bar. I ran one about 4 years ago and was never real happy with the effects, granted in some cases it helps with off the corner but other wise i think it hurts the handling, but thats personal opinion.

Here are the typical effects of switching to the short bar. For one it moves the roll center more to the left and usually higher because of packaging constraints. also depending upon the angle it moves the rearend more laterally through ride/roll than a j-bar or long bar.

What happens with the short bar is that as the car rolls it will jack wedge into the car which will typically loosen entry and tighten exit. This is probably the reason for the changes in shock travel.
Another consideration in loosing rr shock travel is suspension bind, the short bar moves the rearend ALOT more that a long bar so be sure nothing is binding as the chassis moves.


dirtracr
Member
posted July 18, 2001 08:48 PM
How long are your trailing arms? The new Dirt Works have blocks for 7inch trailing arms this hooks up faster and hav much more roll. Look closely at your competition I bet they have other differences like the lr underslung is curved or has a dip to provide more roll without the rearend banging the frame rail. The only time I would run the short bar is on a smooth super dry track.


dirtracr
Member
posted July 19, 2001 05:00 PM
like the guy said earlier the shorty jacks wedge in the car , no longer is the car simply rolling over in the turns it is actually raising the lr thus reducing the downward travel on rr. jl


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