How to Adjust Droop to control Rear Steer

After reading the stagger threads, i was curious to how someone could come up with a good way to control the rear steer in a car according to the cornering of a track. The stagger thread used wheel spin ratios and corner radius to dictate correct stagger for maximum tire patch use. How does the rear steer come into play. and we often adjust the droop to let the car jack up or hold it down, and track the bar angles at dynamic state and the rear steer movement. but really dont have any idea in a geometry way to explain what works better. For example what works better in certain situiations. More rear steer when?? Any comments on this.

also kinda curious on this. we typically took rear steer out as the night went on (track slicked), but didn't always improve a whole lot. of course we also made other changes as well, and I'm not sure if this was just a crutch, or an unnecessary change that caused other problems. towards the end we were trying more static and dynamic rear steer, but not having much noticeable difference.

Well first and foremost, you should use a chain (or something similar) connected to the axle tube to control your LR droop (travel). Many people rely on the shock in front for this which (no offense to anyone that does it) is just plain stupid. For one, it WILL eventually destroy your shock. And for two, the amount of travel allowed will change with static bar angle changes due to the change in indexing of the birdcage.
That being said, use a chain from the frame to the axle tube to limit your LR travel.
Generally speaking, you don't want your top LR bar to exceed 45 degrees of angle at full travel. A lot of guys will start the evening with their chain set to allow them about 38 degrees and then move toward 45 as the track slicks off through the night. Not by changing the static bar angle but by changing the length of the chain. The thinking being that more bar angle will provide a tighter overall race car. That is true (in general) but you are also allowing for more rear steer which is somewhat counteracting (making the car loose) the tightness that you gain from the increased dynamic bar angle. Net-net, the result is still probably a tighter car. BUT if you really wanted to increase your travel and not change your rear steer (as much) you could simply lower your left BOTTOM bar on the frame as you increased your travel limit. This will settle the rear steer down quite a bit and it will provide some added drive just by itself. Spend some time in the shop doing the homework with your car on jackstands with the shocks and springs off just to see what the bar changes and chain length changes are doing to rear steer and you'll have a much better appreciation for it. A jack, a marker, a tape measure, a plumb bob, a case of beer, and a few hours of time are all you need.

Don't forget, this used to be a large problem, not as much anymore, but many drivers like to go up on bar angle and rear steer for slick, then they think the car is extremely tight.
Really the rear end is trying to rotate around, so you turn the front on corner exit, and now all four walk for the wall, so the car drifts out toward the wall hard and some drivers count this has tight, it's a fake tight, be sure your not falling in this trap. Older 2002-2006 mods with extremely short bars show this to an extreme, the driver thinks its tight, and is on the gas but not going forward hard.

That is exactly what i did. We went to the races real early one day and i spent the whole time tracking every movement from bar angle to rear steer and chain length. and wrote down how it all effected each other.

well matt, many shows have been won with no chain! maybe you just didnt know how to keep it from tearing itself up..stupid in latemodel racing, is not keeping an open mind..i think your in violation..

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Originally Posted by huntingrip

well matt, many shows have been won with no chain! maybe you just didnt know how to keep it from tearing itself up..stupid in latemodel racing, is not keeping an open mind..i think your in violation..

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The chain takes nothing away from the setup, so why would anyone not want to be safe instead of sorry?

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Originally Posted by huntingrip

well matt, many shows have been won with no chain! maybe you just didnt know how to keep it from tearing itself up..stupid in latemodel racing, is not keeping an open mind..i think your in violation..

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Yup...and races have also been won on flat tires, bent spindles, broken axle tubes, motors with no oil pressure, etc. But it doesn't make any of them practical or the right way to do things now does it?
In my post, did I not say "no offense to anyone"??? I was simply trying to make a point which you clearly didn't get. I am in fact very open minded. So much so that I would like you to enlighten me on the proper way to use the shock as a travel limiter without abusing it. Also please explain to all of us how you are keeping the max travel the same (when using said shock as a travel limiter) when a bar changed is made which makes the birdcage index differently. I'm REALLY interested in hearing that.
If you can't provide good explanations for both, I'm going to keep using a chain if that's okay with you - closed minded as that may be.
And I promise not to make any comment about any idea being stupid ever again.
I guess even comments on 4m.net have to be politically correct these days.

Matt, That was a good explanation of chain use beyond a limiter. Don't let em troll ya :)

I still haven't seen a real solid answer, though, on if you need to change rear steer based on conditions, try to control it when changing bar angles/chain length, or if it's something you settle in on based track size and line and try to keep the same.

It seemed in the stagger discussions, that most seemed to agree that there was an ideal stagger to use all night for your track, based on corner diameter/banking. So i'm curious if, as with stagger, there's an ideal amount of rear steer to try and hit for a track, and any changes made should be to try and effect bite while keeping rear/roll steer close to the same.

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Originally Posted by MasterSbilt_Racer

The chain takes nothing away from the setup, so why would anyone not want to be safe instead of sorry?

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when a car is on the chain, you may as well take the coilover off on the left rear cause its doing nothing.

So, why do the Rockets generally have the spacer that mounts on the underslung which controls the droop instead of the chain. Ive heard a few different reasons, but we use the chain setup while most Rockets use the spacer that can rotate and change the gap where the rear end hits the underslung. Why??

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Originally Posted by fastford

when a car is on the chain, you may as well take the coilover off on the left rear cause its doing nothing.

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Not exactly...
Taking the chain off won't put the car back down on the spring. You'd be off the spring with or without the chain (hence the term "on the bars").
The spring is critical in getting it to transition up on the bars through the corner. Just because the spring ends up unseated doesn't mean it didn't play a role in getting it that way.
The LR spring is playing a key roll and how much weight gets unloaded from the LR to the RR and how easily the car can hike up with throttle application which generates the bar angle (thrust angle) that you need to get LR drive. A softer LR spring promotes this which is why a softer LR spring (behind the birdcage that is) will typically make the car tighter from center off.
So the chain is only limiting the potential bar angle and potential rear steer. It isn't really doing anything to the affects the LR spring has on the setup in of itself.

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Originally Posted by fastford

when a car is on the chain, you may as well take the coilover off on the left rear cause its doing nothing.

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At that point it is doing nothing. The spring is also doing nothing when your shock is fully extended and the spring is unloaded.

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Originally Posted by dualdj1

Matt, That was a good explanation of chain use beyond a limiter. Don't let em troll ya :)

I still haven't seen a real solid answer, though, on if you need to change rear steer based on conditions, try to control it when changing bar angles/chain length, or if it's something you settle in on based track size and line and try to keep the same.

It seemed in the stagger discussions, that most seemed to agree that there was an ideal stagger to use all night for your track, based on corner diameter/banking. So i'm curious if, as with stagger, there's an ideal amount of rear steer to try and hit for a track, and any changes made should be to try and effect bite while keeping rear/roll steer close to the same.

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As far as rear steer for track conditions...
Consider this, the most common issue people have on heavy/tacky race tracks is getting the car to turn on entry. That being said, I know of some people (can't say I'm one of them at the moment) that increase their compression and gas pressure on their LR shocks so that the car maintains more rear steer on entry (doesn't fall off the bars as hard) and turns easier. Just food for thought.
On the other hand, I can tell you that we have increased chain length as the track slicks in an effort to increase upper bar angle potential. While it does also increase rear steer we find the net result to be tighter corner exit.
There are also some that are of the school of though that more rear steer can actually help you roll through the center of the corner on a slick track without having to get the car sideways.
A lot of stuff to think about.

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Originally Posted by Matt49

As far as rear steer for track conditions...
Consider this, the most common issue people have on heavy/tacky race tracks is getting the car to turn on entry. That being said, I know of some people (can't say I'm one of them at the moment) that increase their compression and gas pressure on their LR shocks so that the car maintains more rear steer on entry (doesn't fall off the bars as hard) and turns easier. Just food for thought.
On the other hand, I can tell you that we have increased chain length as the track slicks in an effort to increase upper bar angle potential. While it does also increase rear steer we find the net result to be tighter corner exit.
There are also some that are of the school of though that more rear steer can actually help you roll through the center of the corner on a slick track without having to get the car sideways.
A lot of stuff to think about.

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I like workin with a limiter chain on RR so as you can't extend that RR side shock, or drop over an inch and a half longer than ride height at very most can control rearend movement and seems to help drive off. JMHO. As for being PC, ain't happening.

We have tried alot of different combinations. We have let the chain open up to an extreme allowing for excessive bar angle, than to get the rear steer out we lengthen the arms. We have tried holding the car down so it limits the travel, than moving the bar angles to where we need them at dynamic, and shortening arms. Holding the car down seems to me that you keep the car more balanced and more weight available toward the back of the car. Any comments? Cuz when you hold the car down you dont have as much travel or as much rear end movement. What do you think about what setups work best with oval tracks vs. tight corner-long straight away tracks. Seems like less rear steer is better for longer straight away as it keeps wheels in line. and oval tracks might need more rear steer as your turning the whole time. thoughts??

This theory is what i am questioning from another?

"That being said, I know of some people (can't say I'm one of them at the moment) that increase their compression and gas pressure on their LR shocks so that the car maintains more rear steer on entry (doesn't fall off the bars as hard) and turns easier. Just food for thought"

i see some conflicting info on this theory. First what can help turn the car on entry is the left rear spring rate. As the car comes down on the spring, doesnt this help turn the car, which is why generally you stiffen LR to loosen entry. Also, one observation is ask yourself which way the rear is pointed when you want to enter the corner if you keep the rear steer in it. Out and toward the wall. I actually think that if you let the rear end settle before entry you will have a better entry as the rearend is inline with the track. Also, if you add rear steer for dryslick to maintain patch contact. The hardest concept i think to grasp is you actually want less rear steer on a tacky track as you need the tires to be able to break the contact patch in order for the car to turn. I see alot of people adding rear steer on tacky tracks. Any experience with these thoughts?

Axle drop or limit (on either side) determines the dynamic wedge of the car. In the corner there is little time that the car is not at the limit of LR travel.

The 4-bars will determine rear steer at limit and a portion of the dynamic wedge during the transition between static ride height and full limit. The absolute dynamic wedge limit is set by the hard stop (chain, damper, underrail)......................combined with the spring rate/mechanical stiffness of the other corners of our 3 legged tables :)


...now I need to go back to work preparing for a trip to China (for auto customers), so I can make money for my Belgian employer, so they keep paying skilled workers in the USA.....that spend it all on dirt cars and taxes


Ghopper

The whole thing with using the high rebound and high gas pressure LR shocks to hold up the car and generate rear steer on corner entry for a tacky track was suggested to me by a very reputable shock and setup guy. So I have no doubt that it works given the right conditions (meaning track conditions and driving style). But I can't say I've tried it yet as we don't typically have issues with tight corner entry on heavy tracks. We HAVE had issues with tight from center off on heavy tracks and we have found ways to deal with that (more top RR bar angle, less RR shock rebound, etc.)
That being said, we're probably treading into the territory of "what works for some won't work for others". Many other variables here including the aforementioned track configuration. The biggest variable still is probably the nut between the seat and the steering wheel. A "throw and go" type driver is going to be on a completely different setup than a guy that likes to drive the car straighter on entry then needs it to rotate more in the center. Both driving styles can work in any track condition (to an extent) but the setup needs to match what the driver is trying to do. That or convince your driver to change his style...good luck with that, right :-)

Something to consider on this subject as the track slows down and the driver starts driving the car straighter, feathering the throttle more etc... the car is going to naturally generate less rear steer on its own or at least at a slower pace.