LR Bar Adjustment???

[DirtRacer9x]

What would having a 14-15" LRU do? Also for more drive would I move LRU bar down and let strap out or just move LRU bar up and leave same strap? What overall LRU bar angle should I not exceed? Will exceeding a certain degree cause a hop in rear end?

[DirtRacer9x]

I see that I may not be the only one in the dark on this...

[MM90]

45 degrees is max bar angle at drop. 4-5" drop from ride height is common regardless of where your upper bar angle is. But like everything, there are exceptions to the rule. What works for one car and or driver won't work for you and vice versu.

[DirtRacer9x]

45 degrees is max bar angle at drop. 4-5" drop from ride height is common regardless of where your upper bar angle is. But like everything, there are exceptions to the rule. What works for one car and or driver won't work for you and vice versu.

Can anyone answer as to why 45* is the magic number and also anymore on the original question?

[fohne mod 21]

To answer why 45* is the norm for most cars. If you run over 45....let's say 50 the probability of your LR bird cage over indexing is great. If you have too much angle and as the car hikes there needs be to less than 180* from your rod to your bird cage mount otherwise te bird cage will over center and the car will never relax off of the bars. To answer the other question about lowing the bar and lengthening the strap....the reason you start with 24* or so static angle is so that you can achieve the correct ride height and at the 4-4.5" (45*) drop of the rearend you still have some travel in your shock and coil before bottoming the shafts out. The front of the bird cage that the shock mounts to travels more than just the 4 inches of drop of the rearend due to the bar forcing the cage to rotate. By the time the movement is amplified the shock shaft moves about 85% of its capability and then risk the change of damage from bottoming out

[DirtRacer9x]

Now I understand the bottoming and over Indexing but I have been to 52* and it was close to over Indexing but never did. Just was seeing if there was more of a reason as to why 45* is the number. What about upper bar length? 14-15"?

[Lizardracing]

45' is a general rule of thumb. You risk "overcentering" if the plane between chassis mount, upper AND lower BC mount line up.

For example, if the lower BC mount is forward of the axle center line at ride height you will be able to get more angle out of the upper bar before the chassis, upper and lower mounts line up. Again for most cars 45' is about where everything lines up but the mount locations are the contributing factors.

[langdonracing48]

Idk what running a shorter top 4 bar would do, but most of the fast cars up here in Michigan/Indiana have a bracket bolted to their factory bottom 4 link mount to allow them to run a very short left rear bottom 4 bar. 10" center to center on heims. Makes the car react much quicker, but without as much hike it seems. Gives it more "instant" traction.

[DirtRacer9x]

Idk what running a shorter top 4 bar would do, but most of the fast cars up here in Michigan/Indiana have a bracket bolted to their factory bottom 4 link mount to allow them to run a very short left rear bottom 4 bar. 10" center to center on heims. Makes the car react much quicker, but without as much hike it seems. Gives it more "instant" traction.

That's interesting to know. I've never seen a 10" eye to eye yet but makes sense as to what's trying to be accomplished. I was thinking a shorter upper link would do the same as well but not sure. Currently our car is 15" LU 14" LL 18" RU 16" RL but have other holes to lengthen or shorten. Anything on dropping RU bar down on birdcage as to what it does? Mine is all the way down on BSB cages. Thanks for your response.

[MasterSbilt_Racer]

Idk what running a shorter top 4 bar would do, but most of the fast cars up here in Michigan/Indiana have a bracket bolted to their factory bottom 4 link mount to allow them to run a very short left rear bottom 4 bar. 10" center to center on heims. Makes the car react much quicker, but without as much hike it seems. Gives it more "instant" traction.

That would take index out of the cage as the car hikes. Should kill drive on lr spring behind axle setup.

[MasterSbilt_Racer]

What would having a 14-15" LRU do? Also for more drive would I move LRU bar down and let strap out or just move LRU bar up and leave same strap? What overall LRU bar angle should I not exceed? Will exceeding a certain degree cause a hop in rear end?

As with most things, it depends, there is no one correct answer.

The higher the lr corner gets, the more weight it has on it.

The higher your bar angle is, the more load the tire receives as the car is accelerating off the corner.

Too little bar angle or tire loading will not allow the lr corner to lift the chassis.

Any time you increase angles or drop, you increase axle steer if everything else stays the same.

Those are absolute truths. The trick is to figure out what you need at various points on the track and use the above truths to improve your car.

[DirtRacer9x]

That would take index out of the cage as the car hikes. Should kill drive on lr spring behind axle setup.

A short upper or lower?

[MasterSbilt_Racer]

A short upper or lower?

Short lower

[DirtRacer9x]

Short lower

What about short upper? Does height of slider mounted on lr birdcage from centerline change anything. Meaning I can change mounting location up or down on the actual birdcage? What's recommended?

[MasterSbilt_Racer]

What about short upper? Does height of slider mounted on lr birdcage from centerline change anything. Meaning I can change mounting location up or down on the actual birdcage? What's recommended?

Shortening the upper has the opposite effect to wheel rate and indexing. Yes. Distance from axle centerline to lower spring mount effects the car as well.