Visit The Dirt Forum for More Information

Author Topic:   4 bar car question
OppendikeRacing29
Member
posted August 19, 2003 04:34 PM
what difference in angle do you run in the top bars on a 4 bar modified, i dont know what kinda car this is but just wondering the average. Dont most people stay with the same amount of angle in the lowers. This car has the springs in front of the axle


jdj9410
Member
posted August 19, 2003 07:29 PM
Right side upper 16-18 degrees, 14-15 degrees on left upper, lowers 2-5 degrees down. A little more up angle on the left side will tighteen car on dry but don't go over 17 degrees. Car will stand up on the bars and will be twitchy. The only one I ever change is the left upper. most of the time make changes needed for track condition with j-bar, right rear wheel offset and air pressures. Occasionally a shock change.


OppendikeRacing29
Member
posted August 19, 2003 09:36 PM
most of you guys run a little more angle in the right side upper bar then the left?


Wallydog9g
Member
posted August 20, 2003 12:30 AM
upper bars are for bite and lower bars are for rear steer
track is tacky-no rear steer
track is dry- rear steer
simple


OppendikeRacing29
Member
posted August 20, 2003 03:28 PM
so whats comon with the uppers, i thought the left normally had more bite then the right, when this car drives the right rear hikes up alot on the gas, as much as the left rear or more


Chad
Member
posted August 20, 2003 03:55 PM
Wallydog9g: I understand the upper bars control bite off the corner and the lowers control corner entry, but when adjusting the lower links, what position is necessary to limit (or, induce) rear steer. I'm assuming that when the lowers are angled downward (-5 degrees) this would limit rear steer, and the more angle that is added to the lowers (+3 or +5 degrees) increases roll steer. Is this correct???? Please explain how to adjust to control roll steer.

[This message has been edited by Chad (edited August 20, 2003).]

OppendikeRacing29
Member
posted August 20, 2003 05:40 PM
as i understand it, level would be no roll steer


OppendikeRacing29
Member
posted August 20, 2003 09:41 PM
lots of looks but no awnsers?


rocket36
Member
posted August 20, 2003 10:23 PM
a four link with the lower arms at 0 deg. (level) will still have roll steer. angle down for less rear steer (but still some)usually 5 deg. -ve and angle up for mor rear steer, mostly 5 deg +ve but some times more.
This will also change the birdcage indexing speed and amount.


Chad
Member
posted August 21, 2003 09:55 AM
Thanks for the info rocket36, your explanation was what I was thinking. The 4 link is new to me this year, and so far has been successful, but trying to understand how all the adjustments will effect the chassis.


Rick D
Member
posted August 21, 2003 12:28 PM
To get a better understanding of how your 4 link car works and what it is doing. Jack it up, take the springs out and drop some plum bobs from the hubs. It is really interesting to watch the affects that moving the bars from hole to hole have.



OppendikeRacing29
Member
posted August 21, 2003 06:16 PM
so whats the norm with the top bars


rocket36
Member
posted August 21, 2003 11:23 PM
to see the dynamic movement of a 4 bar: go to ozlatemodel.com then click on the links page. under the heading of manufacturers you will find a link to a 4 bar suspension simulator (its actually a product you can buy) but on there site there is a video clip of the simulator working - very intersting.


dirtracer14
Member
posted August 22, 2003 12:13 AM
You could also think of it this way hold a bar straight out then lower the outside of the bar as it drops it will get closer to you. Now if you get 4" of travel check from center down 4" now keep the 4" drop in it and drop it another 4" the lower the starting point the closer and faster it gets to you....same with the rear end....now if that was the top bar as you apply force to the rear wheel it pushs up on the bar and will as some point just be riding on the bars and will stay there untill you lift or the track runs out of bite.... I hope this helped some....Now with my z link i can set the bars to ride up on the bar and control the amount of steer wich helps when you need more lr to get out but need to keep it off the wall

[This message has been edited by dirtracer14 (edited August 22, 2003).]

OppendikeRacing29
Member
posted August 22, 2003 12:33 AM
thanks for the help but i have one more question. whats the norm with the top bars? What difference in angle do you run from the left to the right in the top bars?


rocket36
Member
posted August 22, 2003 02:34 AM
a good starting point is usually:
17deg up on the right top bar
15deg up on left top bar

so about 2 deg different to start with BUT
don't worry about it too much, just change one bar at a time and don't be concerned if you get the left bar angled more than the right on occassions, its normal.


Back to the Archives