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Post by ambonci21b on Sept 16, 2013 5:26:43 GMT -6
Have a 07for Hoffman 4link LR 2 link rr. Left side wheel base is 1 1/2 shorter than right. My question is will that affect left side bars as far as making car tight on throttle. 29 degrees in upper bar. Car bites awesome but to tight in traffic. If we don't move that bar to that angle car is loose and has lot less forward bite.
Thanks
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Post by smithmod on Sept 16, 2013 8:58:44 GMT -6
without knowing any other data on your car... here is my initial thought....
I think you have two things going on here that is making the car fight against itself. with the LR 1 1/2" in front of the RR you are starting with "loose rear stear" so you are making up for that loose condition with increased LR bar angles puting more "bite" or drive in the LR thus making it tighter. If you take the lead out of the LR and set bar angles down a little you should feel a much more comfortable car. It is probably pretty radical right now, I think the car will settle down and be much more forgiving after making these changes. Now, here is the question... is the RR back or the LR forward that far??
Most IMCA type modified chassis are designed so that the rear end is set back 72" (center of rearend) from the front of the engine midplate. I would set the RR at that 72" and then square the rearend by putting a tape measure on the grease zirk on the bottom a arm and measure to the rearend using a framing square against the housing and the floor. measure both sides and set swedge tube lenths off of this. It may require different swedge tubes to do this. Also set the bar angles each down a few holes on LR and up one on the RR. it is my experience on the 4/2 (at least it was for our cars) that the LR likes a lot more angle than the conventional 4link bars.
this is just my opinion but I feel you are chasing yourself in a circle with what information you have given us. Could you post other bar angles, spring rates, and scale info also???
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Post by ambonci21b on Sept 16, 2013 10:26:08 GMT -6
We measured from hub to hub and LR was further forward. The car is evil if not driven hard. Just wants to push. I can't remember exact spring rates I believe 600lf 650rf 225lr 200rr. Spring in front LR ontop rr. 45 lbs LR without driver. 57.8 rear %. We ran a 50/30 shock on rf Friday and car was absolutely terrible.
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rickd39
Fourth Place
www.duricaracing.com
Posts: 54 
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Post by rickd39 on Sept 16, 2013 17:01:03 GMT -6
First, before you start moving things, you have to know why the wheel base is like that.
Not knowing what type of frame that is built on here are some things to check.
#1 Do you have the same type of lower control arms on both sides?
#2 Is the front clip built with any amount of lead in the front tires?
#2A Some cars are built square from the motor plate, not the lower control arms
Like Smithmod said, measure your car
Measure from the lower grease fittings to the front of the motor plate, the grease fittings to the rear-end, from the front of the motor plate to the rear end and see where everything is.
My buddy bought a metric framed modified that the guy had a metric lower on the R/F and Nova lower on the L/F, that made the L side wheel base over 1" longer
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Post by washeduptoo on Sept 16, 2013 22:01:25 GMT -6
I would think that the car can be squared off the tubing that runs side to side by bottom brackets. Call Hoffman to verify that. Also that 2 link rr is usually going to be tight. Does this happen when track is heavy or slick? We used to have to run less fuel with that set up on heavy track.
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Post by ukblue on Sept 17, 2013 4:28:54 GMT -6
What lenghth bars do you have on the left and right also what are the angles is you right rear being pulled foward
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rickd39
Fourth Place
www.duricaracing.com
Posts: 54
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Post by rickd39 on Sept 18, 2013 8:41:05 GMT -6
Check the Jet Modified website, they have their modified set-up manual and it explains how to square up the rear end
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Post by ambonci21b on Sept 18, 2013 15:25:30 GMT -6
Any suggestions if we left it for last race as it is? As far as making it looser?
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Post by ljsracing on Sept 18, 2013 16:28:36 GMT -6
Soften RF spring.. help the car roll onto the RF.. Can you raise the RR bar a hole? What about putting 1/8" trail in the rr? maybe 1/4" (im going to assume that your rearend is square see next part)
Im with Rick on the wheel base. My guess is the stub is turned. So your rearend should be square to the midplate but your wheel base wont be the same.. Not familiar with Hoffmans but most newer cars you set the bar length at what they tell you and thats square..
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Post by flipflopoo1oo on Mar 2, 2014 10:02:52 GMT -6
Lower bars for steer and upper for traction and yes they do both but this is a good understanding of long and short bars! More angle more bite and steer! We run a negative left lower to help control too much positive in the corner with all right side angles more than left but yet even under full roll and acceleration for a smooth exit! With enough even traction and steer to roll open yet run the rear end closed 3/8 for a low exit if needed! Some chassis designs are made to only work there way it seems by the locations of things making strange ride heights come into play! Driver beware if you will to the new guys with 6" of steer on 3 wheels that are making it work!
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