Rear Axle Position (Not Lead)

R

race760

Member
We have a JR2 driver running a big tube RIVAL. We mainly very low bite tracks. Currently the rear axle is square and in the stock position. Would there be any improvement to moving both side of the axle forward (closer to the driver)? Again not talking about moving one side but moving the entire axle forward.

We typically fight a loose in condition and we have been through several adjustments with front stagger, RF camber, nose weight, etc. Most of these have helped some but I was just thinking a shorter wheelbase on a JR driver would transfer a little better and maybe get off the RF a little sooner on corner entry.

It is not an adjustment I want to reverse at the track so wanted to gather some feedback before messing with it.

Thanks
 
Try moving his seatback up, how far off the axle are you now? I went through the opposite of you, always fighting a push with my Jr2 driver and JR Curtis from UMax told me to drop my seat from 15" off the axle to 11-12" and it instantly loosened us up.
 
The push was caused by too much weight transfer at the rear, overloading the RR and underloading the RF. Lowering the seat caused less weight transfer to the RR and more at the RF causing the RF to have more grip and the RR to have less grip. That higher seat height created a much higher VCG than the lower seat height.

Race760, I believe you need different setup numbers. In most cases there are rules with the wheelbase. If you are loose then you need to preload the RR more. Maybe less cross, a higher seat height. I see it all the time, way too many parents have the seat too laid back on Jrs.

Msquared - Understanding Chassis Theory and Dynamics
 
Copied from No Goats


Loose entering corner
Oversteer - Too much front end grip Rear is loose
Decrease nose weight in 1/2% -
1% increments Increase rear weight
Increase cross weight
Decrease left side weight Decrease left front camber (more
negative)
Less right front camber (more
positive)
Decrease left front caster
Increase right front stagger Decrease rear stagger in 1/8” - 1/4”
increments
Move right front wheel out
Move left front wheel in
Move right rear wheel in
Move left rear wheel out
Move rear track to left
Move seat back
Raise center of gravity
Harder right front tire compound Decrease right rear tire pressure Softer right rear compound Narrower right rear wheel
Stiffen front of chassis
Check toe out
 
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