Alignment or Corner Balance first?
02-18-2009, 10:47 AM
#71
Registered User
Originally Posted by macr88,Feb 18 2009, 08:58 AM
Mike, I hope you don't mind the discussion, I just want to learn more and now I think I understand.
Forget about which knob you are twisting and look at the effects. In order to balance the cornerweights, you must change the height of the corners. The springs do NOT come in to play here, because the corner weight is defined at the static, resting position.
Now you can adjust this height by cranking down on the spring a bit, compressing it (or uncompressing it, if you go the other direction). This changes the static load on the spring, yes. But it also changes the ride height. Or, if you have another adjustment mechanism for coilover total length, you can change that instead, and that will also change the ride height. But either way, what the corner weights are reacting to is the ride height at the corners, not the load on the springs.
You could have a completely unsprung car, and if you adjust the ride heights you will adjust the corner weights. It really is like that four-legged table.
As a side note, for road course cars we usually want the diagonal corner weights to be equal. But for an oval track car, where you only turn in one direction, you usually don't want them to be equal. This is known as "wedge", and it's one of the prime methods available for adjusting the handling of an oval track car during the race.
02-18-2009, 10:51 AM
#72
Former Moderator
Originally Posted by Orthonormal,Feb 18 2009, 11:44 AM
If you think about it, having that threaded cup takes a chunk of length off the internal volume of the body, reducing the total range of motion. The cup may allow you to change the ride height while keeping the neutral position in the middle of the shock travel -- but you have less total travel available. By moving the seat height you are moving the neutral position closer to one extreme of travel, but in the end you may not be any closer to that extreme than with an adjustable-body shock because there is more travel available.
I don't think I'm explaining it right because of your response. What you said is right but not the question I was asking.
Mike adjusts his spring perch/ride height/preload adjuster for CB and I will continue to adjust the exact same thing he is adjusting to CB.
02-18-2009, 11:17 AM
#73
Former Moderator
Originally Posted by mikegarrison,Feb 18 2009, 12:47 PM
Forget about which knob you are twisting and look at the effects. In order to balance the cornerweights, you must change the height of the corners. The springs do NOT come in to play here, because the corner weight is defined at the static, resting position.
You could have a completely unsprung car, and if you adjust the ride heights you will adjust the corner weights. It really is like that four-legged table.
You could have a completely unsprung car, and if you adjust the ride heights you will adjust the corner weights. It really is like that four-legged table.
For the second paragragh
If I were to adjust my mechanical ride height then the four corners would be unequal when unsprung but you adjusting your ride height by way of spring perch yours stays equal when unsprung.
My spring perch adjustment is no different than yours in the effect so why adjust something different that would give me a short leg when unsprung but CB'd when at it's static resting point. I can adjust the exact same adjustment you're adjusting and have all 4 legs the same length and also be CB'd when at my static resting point.
02-18-2009, 12:00 PM
#74
Originally Posted by macr88,Feb 18 2009, 11:58 AM
Completely understood, but that is in regards to lowering the car or if you have clearence issues on bumps meaning a solid suspension component or tire is at it's end before the bump stop stops it.
Let me try a different approach. Lets say your spring is not exactly the same which they never are. You have 3 springs at 500lbs and one at 475lbs and you have a 2000lb car that was equally ballanced (500lbs in each corner). The 475lb spring is going to compress a bit more which will remove load on the opposite end and carry more load on the other two corners. Left rear/right front and right rear/left front.
So for all the springs to carry the same weight preload must be adjusted due to the softer spring, because that spring at 500lbs would have to compress a little over an inch where the others would be at 1 inch. I don't see difference between having the 500lb spring with more weight on it or the 475lb spring. You're just adjusting the springs resting point higher or lower.
I think adjusting mechanical ride height to corner balance came from the same people that think adjusting preload increases or decreases spring rate, it can only change the effectivess of the spring if your bottoming out. Ride height which is an effect of preload can change the ? Not sure what it's called but it's kind of like leverage which will effect how the car feels and may in fact make it feel stiffer or softer.
Mike, I hope you don't mind the discussion, I just want to learn more and now I think I understand.
Let me try a different approach. Lets say your spring is not exactly the same which they never are. You have 3 springs at 500lbs and one at 475lbs and you have a 2000lb car that was equally ballanced (500lbs in each corner). The 475lb spring is going to compress a bit more which will remove load on the opposite end and carry more load on the other two corners. Left rear/right front and right rear/left front.
So for all the springs to carry the same weight preload must be adjusted due to the softer spring, because that spring at 500lbs would have to compress a little over an inch where the others would be at 1 inch. I don't see difference between having the 500lb spring with more weight on it or the 475lb spring. You're just adjusting the springs resting point higher or lower.
I think adjusting mechanical ride height to corner balance came from the same people that think adjusting preload increases or decreases spring rate, it can only change the effectivess of the spring if your bottoming out. Ride height which is an effect of preload can change the ? Not sure what it's called but it's kind of like leverage which will effect how the car feels and may in fact make it feel stiffer or softer.
Mike, I hope you don't mind the discussion, I just want to learn more and now I think I understand.
475lb spring will not carry more load than the others just because it compresses more. Load transfer is a function of CG height and track width - nothing more. You could make the argument that because the 475lb spring compresses .25" more than the others that the CG will actually be lower in the corner and will transfer less load to that corner (but you really can't do that - there aren't individual CG heights at each corner, you have to consider load transfer across each axle pair from a front/rear view)
"Thinking out loud" a spring that is compressed 1" beyond its free length at full droop still has the same spring rate - it is preloading the upper bound of the shock by whatever its rate is - lets assume 500lbs. So you set the car down and it compresses another 1" (1000lbs total on that corner)- the preload on the upper bound of the shock is gone and the spring is compressed a total of 2". When that corner unweights - you will still have 500lbs of force on the upper bound of the shock - but the shock isn't moving so it doesn't matter. Someone take my circle of logic further - I need to do actual work now
02-18-2009, 12:13 PM
#75
Registered User
Originally Posted by TheNick,Feb 18 2009, 01:00 PM
475lb spring will not carry more load than the others just because it compresses more. Load transfer is a function of CG height and track width - nothing more.
(Again, that's assuming you don't actually shift ballast weight around, which will change the corner weights but is not typically what people mean when they talk about "corner weighting" the car.)
02-18-2009, 12:27 PM
#76
Former Moderator
Originally Posted by TheNick,Feb 18 2009, 02:00 PM
I haven't read the other responses after this one so if this has already been commented on - I'm sorry.
475lb spring will not carry more load than the others just because it compresses more. Load transfer is a function of CG height and track width - nothing more. You could make the argument that because the 475lb spring compresses .25" more than the others that the CG will actually be lower in the corner and will transfer less load to that corner (but you really can't do that - there aren't individual CG heights at each corner, you have to consider load transfer across each axle pair from a front/rear view)
"Thinking out loud" a spring that is compressed 1" beyond its free length at full droop still has the same spring rate - it is preloading the upper bound of the shock by whatever its rate is - lets assume 500lbs. So you set the car down and it compresses another 1" (1000lbs total on that corner)- the preload on the upper bound of the shock is gone and the spring is compressed a total of 2". When that corner unweights - you will still have 500lbs of force on the upper bound of the shock - but the shock isn't moving so it doesn't matter. Someone take my circle of logic further - I need to do actual work now
475lb spring will not carry more load than the others just because it compresses more. Load transfer is a function of CG height and track width - nothing more. You could make the argument that because the 475lb spring compresses .25" more than the others that the CG will actually be lower in the corner and will transfer less load to that corner (but you really can't do that - there aren't individual CG heights at each corner, you have to consider load transfer across each axle pair from a front/rear view)
"Thinking out loud" a spring that is compressed 1" beyond its free length at full droop still has the same spring rate - it is preloading the upper bound of the shock by whatever its rate is - lets assume 500lbs. So you set the car down and it compresses another 1" (1000lbs total on that corner)- the preload on the upper bound of the shock is gone and the spring is compressed a total of 2". When that corner unweights - you will still have 500lbs of force on the upper bound of the shock - but the shock isn't moving so it doesn't matter. Someone take my circle of logic further - I need to do actual work now
So the 475lb spring will compress more in an attempt to carry 500lbs with that happening more weight is distributed to the other two wheels.
02-18-2009, 12:35 PM
#77
Former Moderator
Just picture the table with the shorter leg as being the soft spring. 475lb spring with 500lbs will compress more than a 500lb spring. I'm only talking static and understand that other things will change when in motion.
02-18-2009, 12:39 PM
#78
Registered User
Sadly, you still don't understand. The corner weights are defined at the COMPRESSED ride height. It doesn't matter whether you got there by compressing a soft spring a lot or a stiff spring a little.
02-18-2009, 01:18 PM
#79
Former Moderator
Originally Posted by mikegarrison,Feb 18 2009, 02:39 PM
Sadly, you still don't understand. The corner weights are defined at the COMPRESSED ride height. It doesn't matter whether you got there by compressing a soft spring a lot or a stiff spring a little.
it's alright, like John said it doesn't matter anyways because it's such a small adjustment.
Thanks
Originally Posted by macr88,Feb 18 2009, 01:17 PM
Springs do come into play because that is what the car is resting on. And like you, adjusting my spring perch will raise the car and keep all four legs touching the ground evenly when fully extended or compressed just like yours would.
For the second paragragh
If I were to adjust my mechanical ride height then the four corners would be unequal when unsprung but you adjusting your ride height by way of spring perch yours stays equal when unsprung.
My spring perch adjustment is no different than yours in the effect so why adjust something different that would give me a short leg when unsprung but CB'd when at it's static resting point. I can adjust the exact same adjustment you're adjusting and have all 4 legs the same length and also be CB'd when at my static resting point.
For the second paragragh
If I were to adjust my mechanical ride height then the four corners would be unequal when unsprung but you adjusting your ride height by way of spring perch yours stays equal when unsprung.
My spring perch adjustment is no different than yours in the effect so why adjust something different that would give me a short leg when unsprung but CB'd when at it's static resting point. I can adjust the exact same adjustment you're adjusting and have all 4 legs the same length and also be CB'd when at my static resting point.
02-18-2009, 01:20 PM
#80
Former Moderator
Originally Posted by Orthonormal,Feb 18 2009, 11:44 AM
It's just funny that you're so adamant that it should be called preload, when it adjusts two things at once.