Rear Roll Resistance Never Needed
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problemchild
- Posts: 901
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Re: Rear Roll Resistance Never Needed
I think the "world is flat" analogy is poor. A better analogy would be those nuts that claim the holocaust did in fact not happen ..... their "facts" and discussion are just to gain some spotlight and mess with people.
Greg Rice
"Happy 50th Birthday"
"Happy 50th Birthday"
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hardingfv32-1
- Posts: 1014
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Re: Rear Roll Resistance Never Needed
The World is flat is a perfect analogy. The droop limiter represents the edge of the know World.
Are you smart enough to ask a logical engineering or scientific based question to challenge my statements? To date all that has been stated is that bad things will happen if we go beyond the edge of the FV World or that anyone who says the World is round is evil.
I challenge you to carry on an intelligent discussion on this subject.
Brian
Are you smart enough to ask a logical engineering or scientific based question to challenge my statements? To date all that has been stated is that bad things will happen if we go beyond the edge of the FV World or that anyone who says the World is round is evil.
I challenge you to carry on an intelligent discussion on this subject.
Brian
Re: Rear Roll Resistance Never Needed
Okay, let's just assume for a moment, for the sake of moving this discussion forward, that you don't need a droop limiter. So what? What does that tell me? What does that have to do with why I would not want to more evenly distribute the roll resistance of a car?
Stephen Saslow
FV 09 NWR
FV 09 NWR
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hardingfv32-1
- Posts: 1014
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Re: Rear Roll Resistance Never Needed
1) We have moved on from the roll resistance topic. Droop control has nothing to do with roll resistance. If you want restart the topic then reread the thread and post an appropriate question. We can pickup from there.
2) You are being intellectually LAZY to just assume that we do not need a droop limiter. The whole learning experience is to determine WHY it is possible. I don't know what answering this question might tell you personally. The point is to build a base of knowledge to better base future decisions about your FV's suspension. It is more cost effective to resolve issues in our heads than to test them on a car.
Brian
2) You are being intellectually LAZY to just assume that we do not need a droop limiter. The whole learning experience is to determine WHY it is possible. I don't know what answering this question might tell you personally. The point is to build a base of knowledge to better base future decisions about your FV's suspension. It is more cost effective to resolve issues in our heads than to test them on a car.
Brian
Re: Rear Roll Resistance Never Needed
Let's assume a smooth, flat track according to Brian's request.
Let me say that I don't see that anyone here is suggesting that people blindly remove their droop limiters - we are discussing whether a rear suspension could function properly without needing to bump up against a limiter.
Maybe the question should be…
What would we have to do or have so that we don’t bump up against the limiter during hard cornering?
When and if we can answer that, the next question is…
Would that new suspension be better performance-wise?
There are two setups that are possible (and a million more). But the two of interest for this discussion are the following.
1) Rear suspensions designed to work with a droop limiter:
In this case the spring rate is low and the car will rise up high during hard cornering due to jacking force if there is no limiter. That's what a soft spring does - it doesn't change force much as it stretches - so a lot of jacking with little force change if it's not contained in some other way! With this setup, the droop limiter must be in place to limit how far the rear of the car rises. My car is set up like this and I can't remove that droop limiter without changing something else. Greg's right, this would be dangerous.
2) Rear suspensions designed to work with a droop limiter, but do not hit the shock limit during a typical lap:
In this case the spring rate must be high enough to reduce spring force faster than the force added due to jacking. The reason Brian's car doesn't go past 2 degrees is because his spring rate is high enough. If he put in a softer spring it would raise up more. Don't forget, the spring rates we are talking about are the effective spring rates at the wheel. What spring you run on your coil-over depends on the suspension geometry.
In the force calculation that Brian mentioned, the question was how do jacking forces enter in and how does that interact with the spring. This leads to a specific choice of spring rate to hit the targets of how much the car raises without a limiter. Every car in existence with jacking - like our daily drivers - work like this and are designed with a specific rate and do not need to hit a limiter to contain the jacking. The Vees jack more easily it seems and require different spring rates to combat this.
Please let me know if either of the above situations are not possible or correctly described. I'll correct them if they're not right.
John
Let me say that I don't see that anyone here is suggesting that people blindly remove their droop limiters - we are discussing whether a rear suspension could function properly without needing to bump up against a limiter.
Maybe the question should be…
What would we have to do or have so that we don’t bump up against the limiter during hard cornering?
When and if we can answer that, the next question is…
Would that new suspension be better performance-wise?
There are two setups that are possible (and a million more). But the two of interest for this discussion are the following.
1) Rear suspensions designed to work with a droop limiter:
In this case the spring rate is low and the car will rise up high during hard cornering due to jacking force if there is no limiter. That's what a soft spring does - it doesn't change force much as it stretches - so a lot of jacking with little force change if it's not contained in some other way! With this setup, the droop limiter must be in place to limit how far the rear of the car rises. My car is set up like this and I can't remove that droop limiter without changing something else. Greg's right, this would be dangerous.
2) Rear suspensions designed to work with a droop limiter, but do not hit the shock limit during a typical lap:
In this case the spring rate must be high enough to reduce spring force faster than the force added due to jacking. The reason Brian's car doesn't go past 2 degrees is because his spring rate is high enough. If he put in a softer spring it would raise up more. Don't forget, the spring rates we are talking about are the effective spring rates at the wheel. What spring you run on your coil-over depends on the suspension geometry.
In the force calculation that Brian mentioned, the question was how do jacking forces enter in and how does that interact with the spring. This leads to a specific choice of spring rate to hit the targets of how much the car raises without a limiter. Every car in existence with jacking - like our daily drivers - work like this and are designed with a specific rate and do not need to hit a limiter to contain the jacking. The Vees jack more easily it seems and require different spring rates to combat this.
Please let me know if either of the above situations are not possible or correctly described. I'll correct them if they're not right.
John
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hardingfv32-1
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Re: Rear Roll Resistance Never Needed
John
That seams like a reasonable explanation.
Brian
That seams like a reasonable explanation.
Brian
Re: Rear Roll Resistance Never Needed
Brian, thanks. I was trying to focus the discussion after reading a lot of input and viewpoints from folks. Those was helpful - got me thinking - not always a good thing, though.
I think if we can focus on those two situations I brought up, perhaps sharpen them to make the concepts more well defined or palatable, and then not stray off topic, then we can move perhaps understand them better, and eventually move on to discussing how they might affect handling behavior one way or another. John
I think if we can focus on those two situations I brought up, perhaps sharpen them to make the concepts more well defined or palatable, and then not stray off topic, then we can move perhaps understand them better, and eventually move on to discussing how they might affect handling behavior one way or another. John
Re: Rear Roll Resistance Never Needed
The world is flat.
See you on the track.
See you on the track.
Stephen Saslow
FV 09 NWR
FV 09 NWR
Re: Rear Roll Resistance Never Needed
I'm really missing something. A spring pushes against the suspension and raises the car. If I put a stiffer spring on my car, and change nothing else, the car will loose camber and rise. When a vee undergoes jacking, it looses camber and the ride height is increased right? How does a stiffer spring act as a limiter to jacking if both have the same effect on the chassis.
Frankly, I don't care what shape the world is in, I'm just trying to understand what's being said.
Frankly, I don't care what shape the world is in, I'm just trying to understand what's being said.
Last edited by brian on October 29th, 2010, 2:51 pm, edited 1 time in total.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
Re: Rear Roll Resistance Never Needed
So Brian,
If you are looking for an answer for why you can get your zero roll system to work I think John almost noticed it but as I was reading the latest posts this morning before I came to work I think I know what you might be doing but not how. If the spring that holds the chassis of the ground can reach its limit of resistance (travel) before you reach you limiter (shock length) then it is possible that you can not be using the limiter to stop from going to positive camber and stop the jacking and stay at you desired max. droop. This also assumes that you can keep the jacking effect on the tire from continuing to rase the chassis up (someone mentioned this as the reason for jacking because of the leaverage effect on the axle due to cornering) and needing to engage the limiter to keep the chassis from continuing to rise. On my car the spring is soft and without the limiter it will keep pushing until it runs out of length way into positive so the limiter is required because of this. Without a lot of thought I don't know if it would be possible on my zero roll because of the geometry and needed length of spring to make it work.
For those of us that have met you in person and talked to you, we know that you are a creative and think person and even though some on this board take shots at you I know you constantly think outside the box, sometimes way outside.
Like I said I don't know how you are doing this but it might be the answer to this excersise that you have had us thinking about. So unless I have time this afternoon before I leave work to check any responses to this I won't be able to reply untill I get back to work on Monday since I seem unable to log onto the forum to post from home for some reason.
Ed
If you are looking for an answer for why you can get your zero roll system to work I think John almost noticed it but as I was reading the latest posts this morning before I came to work I think I know what you might be doing but not how. If the spring that holds the chassis of the ground can reach its limit of resistance (travel) before you reach you limiter (shock length) then it is possible that you can not be using the limiter to stop from going to positive camber and stop the jacking and stay at you desired max. droop. This also assumes that you can keep the jacking effect on the tire from continuing to rase the chassis up (someone mentioned this as the reason for jacking because of the leaverage effect on the axle due to cornering) and needing to engage the limiter to keep the chassis from continuing to rise. On my car the spring is soft and without the limiter it will keep pushing until it runs out of length way into positive so the limiter is required because of this. Without a lot of thought I don't know if it would be possible on my zero roll because of the geometry and needed length of spring to make it work.
For those of us that have met you in person and talked to you, we know that you are a creative and think person and even though some on this board take shots at you I know you constantly think outside the box, sometimes way outside.
Like I said I don't know how you are doing this but it might be the answer to this excersise that you have had us thinking about. So unless I have time this afternoon before I leave work to check any responses to this I won't be able to reply untill I get back to work on Monday since I seem unable to log onto the forum to post from home for some reason.
Ed
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CitationFV21
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Re: Rear Roll Resistance Never Needed
Okay, I will throw another thought out there.
If the outside tire is causing jacking, I put it that the inside tire is doing the reverse.....
There is a force acting down on the transmission on the inside that is fighting the roll.
Since the car cannot roll on it's normal axis with the force on the transmission there is a tendency to squat, which works against the jacking force on the outside tire.
The softer the spring the greater the squat, which would result in more negative camber. So the spring has nothing to so with increasing jacking, but the softer spring would work better in allowing more negative camber. If the shock is valved correctly for bump ( so the tires do not come off the ground when they hit a bum), then the rebound would control the roll and camber change during initial turn in.
For another variable, leading arm cars may not lower the roll center, but trailing arm cars might. This could explain why the Citations, Lynx and D-13s are considered good handling cars. (Add the VDF to that?) I am trying to find some information on calculating roll centers with different types of suspensions, but since no one cares about FV, they are hard to come by.
What do you think of them apples?
ChrisZ
If the outside tire is causing jacking, I put it that the inside tire is doing the reverse.....
There is a force acting down on the transmission on the inside that is fighting the roll.
Since the car cannot roll on it's normal axis with the force on the transmission there is a tendency to squat, which works against the jacking force on the outside tire.
The softer the spring the greater the squat, which would result in more negative camber. So the spring has nothing to so with increasing jacking, but the softer spring would work better in allowing more negative camber. If the shock is valved correctly for bump ( so the tires do not come off the ground when they hit a bum), then the rebound would control the roll and camber change during initial turn in.
For another variable, leading arm cars may not lower the roll center, but trailing arm cars might. This could explain why the Citations, Lynx and D-13s are considered good handling cars. (Add the VDF to that?) I am trying to find some information on calculating roll centers with different types of suspensions, but since no one cares about FV, they are hard to come by.
What do you think of them apples?
ChrisZ
Re: Rear Roll Resistance Never Needed
Chris, we need to talk - where can meet?
I think I can agree with everything up to "So the spring has nothing to do with increasing jacking...", and then...
Forgetting about dampers for the moment, static attitude of any suspension system is a result of the forces acting on the suspension (axles in the case of a vee) and the springs. So, the springs have everything to do with increased or decreased jacking.
The roll center is essentially defined by the swing axles and tires. Leading vs. trailing arms can have a small effect, but make little difference (if any) in locating the roll center. Just like you showed in your diagrams the other day. That was it.
Maybe we can meet up apple picking. John
I think I can agree with everything up to "So the spring has nothing to do with increasing jacking...", and then...
Forgetting about dampers for the moment, static attitude of any suspension system is a result of the forces acting on the suspension (axles in the case of a vee) and the springs. So, the springs have everything to do with increased or decreased jacking.
The roll center is essentially defined by the swing axles and tires. Leading vs. trailing arms can have a small effect, but make little difference (if any) in locating the roll center. Just like you showed in your diagrams the other day. That was it.
Maybe we can meet up apple picking. John
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problemchild
- Posts: 901
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Re: Rear Roll Resistance Never Needed
You guys are getting lost in all these theories and engineering terms and missing the basic dynamics that VW, Corvair, and FV enthusiasts learned in the 60s.
When a swing axle car enters a corner and lifts off the gas ..... weight transfers from the rear and the chassis begins to roll. There is nothing to keep the rear from lifting. Because the outside wheel is loaded, it acts as the pivot and the entire rear lifts and rolls on that point. As that happens, the inside wheel just drops. The rear of the car cannot stabilize because that inner wheel is down and positive. It rolls more, the inside wheel drops more .... it just keeps getting worse and the rear end literally ratchets itself higher until the car spins out.
The process is less severe without the "lifting off the gas" but the inside wheel is still trying to drop when the car rolls.
Starting with more static camber helps because it takes longer for the jacking to get too bad that the driver gets back in the gas and the rear stabilizes. Adding droop control is just limiting the amount and/or rate that the inside wheel can drop. It also acts to slow/reduce longitudenal weight transfer which is desirable. A softer rear spring rate may help reduce jacking but will compromise other situations like bump control and slow corner exit dynamics.
Rear roll resistance (back to the topic) would only be used by people who have a surplus of rear grip. People running without rear droop limiters (or people claiming not to need them but using their shock as a droop limiter set at zero for safety purposes only) would not have surplus rear grip and no need to use that surplus to improve the front grip.
PS .... go ahead and point out my incorrect terminology and minor theoretical mistakes .... but this is absolutely what is happening and why controlling rear droop is absolutely required. Where I live, the world is flat, and that is all that concerns me.
When a swing axle car enters a corner and lifts off the gas ..... weight transfers from the rear and the chassis begins to roll. There is nothing to keep the rear from lifting. Because the outside wheel is loaded, it acts as the pivot and the entire rear lifts and rolls on that point. As that happens, the inside wheel just drops. The rear of the car cannot stabilize because that inner wheel is down and positive. It rolls more, the inside wheel drops more .... it just keeps getting worse and the rear end literally ratchets itself higher until the car spins out.
The process is less severe without the "lifting off the gas" but the inside wheel is still trying to drop when the car rolls.
Starting with more static camber helps because it takes longer for the jacking to get too bad that the driver gets back in the gas and the rear stabilizes. Adding droop control is just limiting the amount and/or rate that the inside wheel can drop. It also acts to slow/reduce longitudenal weight transfer which is desirable. A softer rear spring rate may help reduce jacking but will compromise other situations like bump control and slow corner exit dynamics.
Rear roll resistance (back to the topic) would only be used by people who have a surplus of rear grip. People running without rear droop limiters (or people claiming not to need them but using their shock as a droop limiter set at zero for safety purposes only) would not have surplus rear grip and no need to use that surplus to improve the front grip.
PS .... go ahead and point out my incorrect terminology and minor theoretical mistakes .... but this is absolutely what is happening and why controlling rear droop is absolutely required. Where I live, the world is flat, and that is all that concerns me.
Greg Rice
"Happy 50th Birthday"
"Happy 50th Birthday"
Re: Rear Roll Resistance Never Needed
Greg,
That was an excellent post. Without pointing out your minor errors, what you described very well is very complete and describes the status quo for suspension designs and thinking in FV. It's exactly why we are doing what we're doing today, and why we make the adjustments we do to tune the car's handling.
The good thing is that your desciption agrees with our "theories". It probably has too because those theories are just basic concepts. So, we're all on the same page as you, and perhaps as lost as it appears. John
That was an excellent post. Without pointing out your minor errors, what you described very well is very complete and describes the status quo for suspension designs and thinking in FV. It's exactly why we are doing what we're doing today, and why we make the adjustments we do to tune the car's handling.
The good thing is that your desciption agrees with our "theories". It probably has too because those theories are just basic concepts. So, we're all on the same page as you, and perhaps as lost as it appears. John
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CitationFV21
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Re: Rear Roll Resistance Never Needed
The fact that we are at 90 posts and this is the first time the word "manifold" has been said is amazing in itself! 
I think threads like this are fun as they challenge conventional wisdom and exercise our brains.
Greg - I totally agree with you that fundamental setup is essential, but we are talking fantasy here. With very few exceptions, is anyone going to redesign his car based on these discussions?
But what I would like to get to, when this thread dies out, is a better understanding of how cars work. For example:
A driver comes to me and is complaining about snap oversteer. I go over his settings and decide he is not running enough camber in the rear and too little (too negative) droop. He makes the changes and the car handles better. Now he had the same car I did - would the same go for a different make?
Another driver is bottoming in the Uphill at Lime Rock. Needs stiffer springs right? But what else does he have to do? Revalve his shock? Change the pushrod length? Or was it all shock in the first place? Should he have a bump stop on the shock?
Back to Brian's original thought. Turns that are constant radius, you enter at a relatively constant speed (so transitions are not a factor).
I know 2. maybe 3.
1. West Bend at Lime Rock
2. The Carousel at RA
3. Maybe the last LH (turn #??) at Watkins Glen.
(I was going to put the 1st turn at New Hampshire on the list, if you run the bottom, else the banking is a variable.
Now, If you believe in active droop limiting, once the car is fully on the limiter (not just touching it) any increase in cornering (jacking) should reduce traction on the inside tire. Since we don't run limited slips, the inside tire should spin/slip. Anyone seeing this in their cars?
Or does the decrease in handling result in an oversteer condition which reduces the load. In which case why not try more (going toward positive) droop and see what happens?
ChrisZ
I think threads like this are fun as they challenge conventional wisdom and exercise our brains.
Greg - I totally agree with you that fundamental setup is essential, but we are talking fantasy here. With very few exceptions, is anyone going to redesign his car based on these discussions?
But what I would like to get to, when this thread dies out, is a better understanding of how cars work. For example:
A driver comes to me and is complaining about snap oversteer. I go over his settings and decide he is not running enough camber in the rear and too little (too negative) droop. He makes the changes and the car handles better. Now he had the same car I did - would the same go for a different make?
Another driver is bottoming in the Uphill at Lime Rock. Needs stiffer springs right? But what else does he have to do? Revalve his shock? Change the pushrod length? Or was it all shock in the first place? Should he have a bump stop on the shock?
Back to Brian's original thought. Turns that are constant radius, you enter at a relatively constant speed (so transitions are not a factor).
I know 2. maybe 3.
1. West Bend at Lime Rock
2. The Carousel at RA
3. Maybe the last LH (turn #??) at Watkins Glen.
(I was going to put the 1st turn at New Hampshire on the list, if you run the bottom, else the banking is a variable.
Now, If you believe in active droop limiting, once the car is fully on the limiter (not just touching it) any increase in cornering (jacking) should reduce traction on the inside tire. Since we don't run limited slips, the inside tire should spin/slip. Anyone seeing this in their cars?
Or does the decrease in handling result in an oversteer condition which reduces the load. In which case why not try more (going toward positive) droop and see what happens?
ChrisZ
Re: Rear Roll Resistance Never Needed
If I get wheel spin, and i have, i increase droop since a wheel off the ground is always worse than any camber. At a track like Sears Point, oops Infineon, i have had the rear wheels come off the ground with too much droop control or z bar preload.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
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problemchild
- Posts: 901
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Re: Rear Roll Resistance Never Needed
Chris,
All those corners are different. As I tried to explain to you before ... the carousel at RA is not even a corner in a decent FV.
Sorry that I cannot relate to this hypothetical situation but I consider it just a game for Harding. His premise that FVs are naturally balanced is only facilitated because he is running his droop limiter at zero. Of course he has poor rear grip! When people (like Bruce or Scott) tell him to totally remove the droop limiter ..... he does not reply. When I tell him to put on a limiter at 2-3 N degrees .... like most FVs use ..... again he goes quiet. After you and John reintroduce some other theoretical banter, he then posts again and ignores the logical solutions or questions to his wacky premise. The only conclusion is that he is getting his jollies by messing with the people on this forum. We are dealing with technology that is a minimum of 50 yrs old. The only new technology that affects this design was the introduction of quality dampers that are well into their 3rd decade. There is nothing new. These are exactly the same issues that early FV people delt with in the 60s. Nothing has changed .... which is why we are all running variations of zero-roll developed 40 years ago.
Cheers!
All those corners are different. As I tried to explain to you before ... the carousel at RA is not even a corner in a decent FV.
Sorry that I cannot relate to this hypothetical situation but I consider it just a game for Harding. His premise that FVs are naturally balanced is only facilitated because he is running his droop limiter at zero. Of course he has poor rear grip! When people (like Bruce or Scott) tell him to totally remove the droop limiter ..... he does not reply. When I tell him to put on a limiter at 2-3 N degrees .... like most FVs use ..... again he goes quiet. After you and John reintroduce some other theoretical banter, he then posts again and ignores the logical solutions or questions to his wacky premise. The only conclusion is that he is getting his jollies by messing with the people on this forum. We are dealing with technology that is a minimum of 50 yrs old. The only new technology that affects this design was the introduction of quality dampers that are well into their 3rd decade. There is nothing new. These are exactly the same issues that early FV people delt with in the 60s. Nothing has changed .... which is why we are all running variations of zero-roll developed 40 years ago.
Cheers!
Greg Rice
"Happy 50th Birthday"
"Happy 50th Birthday"
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hardingfv32-1
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Re: Rear Roll Resistance Never Needed
Brian... Yes, my spring is so stiff that it almost come off the perch at max jacking point. It does not have anymore rebound travel.
Ed... Your summary of what I'm doing is correct. That is NOT to say that it is by design. I like using VERY stiff springs. This thread is teaching me that the stiff springs are effecting how I get to max jacking. This was NOT part of the design criteria. Still processing the implications.
Chris and Brian... You bring up the issue of lose of traction with the inside rear tire. ASSUMING smooth operating zero roll with NO rear roll resistance why would the inside wheel loose traction? I know the weight is not equal because of weight transfer, but why isn't this weight relationship between sides maintained? I can't say I have seen this issue on my car.
Brian... When you modify you droop for the above situation, are the rest of the turns effected by the change in droop? Are you in fact making a compromise?
Brian
Ed... Your summary of what I'm doing is correct. That is NOT to say that it is by design. I like using VERY stiff springs. This thread is teaching me that the stiff springs are effecting how I get to max jacking. This was NOT part of the design criteria. Still processing the implications.
Chris and Brian... You bring up the issue of lose of traction with the inside rear tire. ASSUMING smooth operating zero roll with NO rear roll resistance why would the inside wheel loose traction? I know the weight is not equal because of weight transfer, but why isn't this weight relationship between sides maintained? I can't say I have seen this issue on my car.
Brian... When you modify you droop for the above situation, are the rest of the turns effected by the change in droop? Are you in fact making a compromise?
Brian
Re: Rear Roll Resistance Never Needed
I wonder if it's just the attitude of the inside tire (rolling on the inner edge) that makes it give-up first? Take a look at Chris' picture of the rear of his car.hardingfv32-1 wrote:... You bring up the issue of lose of traction with the inside rear tire. ASSUMING smooth operating zero roll with NO rear roll resistance why would the inside wheel loose traction? I know the weight is not equal because of weight transfer, but why isn't this weight relationship between sides maintained? I can't say I have seen this issue on my car.
Brian
Bill Roché
Citation XTC41
Team FootShoot partner
Citation XTC41
Team FootShoot partner
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hardingfv32-1
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Re: Rear Roll Resistance Never Needed
I'm assuming it takes a special situation like a turn cresting a hill to cause this situation. In theory the loads should stay at the same proportions side to side. That said, we know the outside has more load in the turn. Maybe the cresting action is causing unjacking and poor rear camber. With this poor camber we are very close to loosing traction and the inside tire having less load is the first to show signs of loss of traction.
So yes, your thought could be correct. We are close, but not over the limit yet when both tires lose traction.
Question answered, thanks
Brian
So yes, your thought could be correct. We are close, but not over the limit yet when both tires lose traction.
Question answered, thanks
Brian
Re: Rear Roll Resistance Never Needed
Brian, the loss of traction is not just on the inside. If I have too much droop, or a lot of rebound control in the shock, I can feel both tires comming off the ground on the rise leading into the Carousel at Sears. Generally speaking, any adjustment will be a comprimise but I generally don't feel minor changes to droop. Like you I'm always trying to figure out the whys of what we do. I've noticed some slowing in my data and I'm trying to figure out if Father time is catching up to me or have I went the wrong direction with my car. Lap times are still very good but that's mostly motor I think. Keep the discussion going.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
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hardingfv32-1
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Re: Rear Roll Resistance Never Needed
Chris asked:
"A driver comes to me and is complaining about snap oversteer. I go over his settings and decide he is not running enough camber in the rear and too little (too negative) droop. He makes the changes and the car handles better. Now he had the same car I did - would the same go for a different make?"
Based on info from this thread, it would seem that static camber is NOT relevant for the std FV rear suspension for mid turn performance. You are going to get into the limiter no matter what, so the droop setting is really your relevant camber setting for best cornering performance. In your example, we can we be sure what side of perfect droop you are on, too much or too little camber? My take away from this thread is that the main rear suspension adjustment is droop. Is this wrong?
Whether you apply your adjustments between chassis might be clouded by the rocker and spring systems used by each. A complexity we have avoided to this point in our discussions.
Do you think that adding the word "snap" could imply something more complex? For most older drivers, any movement in the rear could be described as a "snap".
Brian
"A driver comes to me and is complaining about snap oversteer. I go over his settings and decide he is not running enough camber in the rear and too little (too negative) droop. He makes the changes and the car handles better. Now he had the same car I did - would the same go for a different make?"
Based on info from this thread, it would seem that static camber is NOT relevant for the std FV rear suspension for mid turn performance. You are going to get into the limiter no matter what, so the droop setting is really your relevant camber setting for best cornering performance. In your example, we can we be sure what side of perfect droop you are on, too much or too little camber? My take away from this thread is that the main rear suspension adjustment is droop. Is this wrong?
Whether you apply your adjustments between chassis might be clouded by the rocker and spring systems used by each. A complexity we have avoided to this point in our discussions.
Do you think that adding the word "snap" could imply something more complex? For most older drivers, any movement in the rear could be described as a "snap".
Brian
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tiagosantos
- Posts: 389
- Joined: June 20th, 2010, 12:10 am
Re: Rear Roll Resistance Never Needed
hardingfv32-1 wrote: For most older drivers, any movement in the rear could be described as a "snap".
Re: Rear Roll Resistance Never Needed
Guys - excellent posts!
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CitationFV21
- Posts: 272
- Joined: July 6th, 2006, 10:49 pm
Re: Rear Roll Resistance Never Needed
Sorry, I have been away.
If we agree to certain parameters as being constant from car to car. Weight, Weight distribution, track F & R and wheelbase, Center of gravity, etc., then every car would start with the same amount of negative camber in the rear and would end up with a droop limit of the same relative amount, That is because for a given radius turn, the forces acting on a car would result in the same camber change due to roll and jacking.
But we don't all run the same amount because our cars are not the same. Going back to theoretical, you would want the outside rear to end up around 1- 2 degrees negative and the inside wheel could be 0 - 1 positive. Now the problem is we don't have that much control in the rear (any maybe less in the front).
The outside tire goes too negative and the droop stop actually hurts us by keeping the inside tire too negative. If on Brian's car, he could set his droop at zero, and through a combination of spring rate, pickup points and roll, he ends up with the outside tire at a good camber, then the inside tire dropping to a more positive camber actually could increase handling. The D-13 has dual droop stops, and I have to look at how they work in this scenario.
However; there is a compromise. With increased travel comes increased chance of toe change and rear steering. Also in quick transitions the extra travel means the car may not take an immediate set (the "corkscrew" at New Hampshire or the bus stop at the Glen.) So you are looking for a compromise between quick reaction (stiff spring/shock and active droop) and and more controllable car at a higher limit.
If we had really spec cars this discussion would be easier - but there are many variables so that two different cars could have two different setups.
ChrisZ
PS -- Radial racing tires would help handling because they can adjust for bad camber angles - but the breakaway would be sudden. The bias ply we use probably makes the car easier to drive.
If we agree to certain parameters as being constant from car to car. Weight, Weight distribution, track F & R and wheelbase, Center of gravity, etc., then every car would start with the same amount of negative camber in the rear and would end up with a droop limit of the same relative amount, That is because for a given radius turn, the forces acting on a car would result in the same camber change due to roll and jacking.
But we don't all run the same amount because our cars are not the same. Going back to theoretical, you would want the outside rear to end up around 1- 2 degrees negative and the inside wheel could be 0 - 1 positive. Now the problem is we don't have that much control in the rear (any maybe less in the front).
The outside tire goes too negative and the droop stop actually hurts us by keeping the inside tire too negative. If on Brian's car, he could set his droop at zero, and through a combination of spring rate, pickup points and roll, he ends up with the outside tire at a good camber, then the inside tire dropping to a more positive camber actually could increase handling. The D-13 has dual droop stops, and I have to look at how they work in this scenario.
However; there is a compromise. With increased travel comes increased chance of toe change and rear steering. Also in quick transitions the extra travel means the car may not take an immediate set (the "corkscrew" at New Hampshire or the bus stop at the Glen.) So you are looking for a compromise between quick reaction (stiff spring/shock and active droop) and and more controllable car at a higher limit.
If we had really spec cars this discussion would be easier - but there are many variables so that two different cars could have two different setups.
ChrisZ
PS -- Radial racing tires would help handling because they can adjust for bad camber angles - but the breakaway would be sudden. The bias ply we use probably makes the car easier to drive.