The level of grip on the track is the elephant in the room for the effects of roll center being inconsistent. For example, on carpet higher roll centers help remove grip as the car stays flat, that is until the traction of the surface is so high that the car begins to traction roll, then a lower roll center will help remove some initial grip to keep from rolling. A lot of touring car setup theory applies for offroad buggies when they are run on carpet.
I discovered this a few weeks ago on a club meet (on very high grip carpet) when I had to run my spare car in the final due to a mechanical issue... and that car was instantly 6 tenths a lap quicker. It had a softer shock / spring combo and a lower rear roll centre. The car looked 'wallowy' but I could absolutely throw it about without any worries about grip roll.
You have the right attitude in trying to tie things to basics physics , and seem generally happy to be corrected thus here are my 2 cents based on first hand experience on full scale vehicles (not all is translatable in RC but forced based explanations of the RC are very relatable to RC also) . iHMO need to start putting a lot of meat on the bone when trying to explain things although i do get that might involve more time from your side - you seem to have fire in your belly though so the effort put in will be worth in the end. Free body diagrams , balances of forces and moments (ie Undergraduate Engineering Statics level) is enough to start getting a grasp before moving to dynamics . Everything else being equal fewer shims will lower the roll center (a classic 2D diagram like one here will help you grasp it easier th-cam.com/video/WkZ7lrLivNg/w-d-xo.htmlfeature=shared) - so its the other way around @1:27 . All that being said higher/lower RC is still of relative importance - an unequal length wishbone suspension is a 4 bar linkage with 1 member (upright and wheel subassy) theoretically (momentarily for the shake of statics balance of forcess and moments) constrained with a spherical joint/hinge @ tyre patch contact point with the ground (repeat at the back end) .The forces acting on the CG of the car which is tied to the floating member of the 4 bar linkage are trying to push and pull through the wishbone and the top link and that will result in roll and pitch movements due to side forces at the same time .Specifics of the topology of the suspension from vehicle to vehicle , Kick ups , rideheight changes (resulting in a different stance of the 4 bar linkage etc at a given moment etc) will change the leverage ratios through the wishbone and top link resulting in different ammounts of induced roll and pitch movements).
Forgive me if I'm wrong. But I've been drawing diagrams. Is the top arm angle not the opposite to what you state? Lowering the inner link(more downward angle on arm) should lower the Roll centre down and vice versa?
It sucks that the RC change also changes camber gain on the upper link. Pills adjustments are probably better for learning what RC does without influence on camber change geometry.
Roll center is not something that works on its own. Jacking and moment arms are the key factors here along with the static roll center height. The absolute best and simplest way to look at this is a lower roll center means more force in roll is transfered through the shocks/springs and visa versa.
I totally agree, talking only about RC and not about roll couple and how they interact with each other is key. Most only speak of one CG of the car, but its more complicated than that. Typically the rear has a higher CG than the front (say you slice the car in 10 parts, every section has a CG, connect the dots and see the CG is higher in the rear) and matching the RC to this higher rear CG is important in tuning the car to many different variables. This guy just dont get it. th-cam.com/video/aG4KJ5ohsOo/w-d-xo.html&t
@@Ozzy3333333 yeah exactly, i talk about it in my videos as well how we could simplify the visualisation if we actually started focusing on the roll couple instead of just the rc. Also many forget to even consider that the front and rear end are connected.
had feelt before that roll center where some form of black magic but a year of testing things on my car and studdy all kinds of material and alot of JQ on roll centers i start to get a grip of it sort to speak. tested to tune others cars and for the astro track im mostly running on people tend to set the roll center to high and not enough camber so the cars feels stiff and sliding in corners or hooking abrupt and jacking force throw the car over.
I would add that changing washers under the inner upper ball has greater influence on camber gain than roll centers. So i think that most of the handling results are tied with the way the wheel gain or loose camber during its travel instead the effect of roll center. You can have a back proof running tests changing the high of lower arms pins without touching upper links inclination.
Hi there, this is a very interesting subject, one thing that most people find hard to solve is the grip roll situation. Can you add this as a future video. Cheers Neale
I might be a bit confused, but would adding spacers under the upper inner wishbones not raise the roll centre? Where as in the video its deacribed as lowering it?
The level of grip on the track is the elephant in the room for the effects of roll center being inconsistent. For example, on carpet higher roll centers help remove grip as the car stays flat, that is until the traction of the surface is so high that the car begins to traction roll, then a lower roll center will help remove some initial grip to keep from rolling. A lot of touring car setup theory applies for offroad buggies when they are run on carpet.
I discovered this a few weeks ago on a club meet (on very high grip carpet) when I had to run my spare car in the final due to a mechanical issue... and that car was instantly 6 tenths a lap quicker. It had a softer shock / spring combo and a lower rear roll centre. The car looked 'wallowy' but I could absolutely throw it about without any worries about grip roll.
You have the right attitude in trying to tie things to basics physics , and seem generally happy to be corrected thus here are my 2 cents based on first hand experience on full scale vehicles (not all is translatable in RC but forced based explanations of the RC are very relatable to RC also) . iHMO need to start putting a lot of meat on the bone when trying to explain things although i do get that might involve more time from your side - you seem to have fire in your belly though so the effort put in will be worth in the end. Free body diagrams , balances of forces and moments (ie Undergraduate Engineering Statics level) is enough to start getting a grasp before moving to dynamics . Everything else being equal fewer shims will lower the roll center (a classic 2D diagram like one here will help you grasp it easier th-cam.com/video/WkZ7lrLivNg/w-d-xo.htmlfeature=shared) - so its the other way around @1:27 . All that being said higher/lower RC is still of relative importance - an unequal length wishbone suspension is a 4 bar linkage with 1 member (upright and wheel subassy) theoretically (momentarily for the shake of statics balance of forcess and moments) constrained with a spherical joint/hinge @ tyre patch contact point with the ground (repeat at the back end) .The forces acting on the CG of the car which is tied to the floating member of the 4 bar linkage are trying to push and pull through the wishbone and the top link and that will result in roll and pitch movements due to side forces at the same time .Specifics of the topology of the suspension from vehicle to vehicle , Kick ups , rideheight changes (resulting in a different stance of the 4 bar linkage etc at a given moment etc) will change the leverage ratios through the wishbone and top link resulting in different ammounts of induced roll and pitch movements).
Forgive me if I'm wrong. But I've been drawing diagrams. Is the top arm angle not the opposite to what you state? Lowering the inner link(more downward angle on arm) should lower the Roll centre down and vice versa?
Just discovered your channel today and watched all videos. Very informative especially on the shock setup. Thank you guys
Perfect timing, almost done building a b6.2 street stock from scratch
love when you guys put out videos, thanks for the new drop!!!
Crystal clear explanation. Keep on going, i appreciate your passion and work. Bravi!
It sucks that the RC change also changes camber gain on the upper link. Pills adjustments are probably better for learning what RC does without influence on camber change geometry.
Roll center is not something that works on its own. Jacking and moment arms are the key factors here along with the static roll center height. The absolute best and simplest way to look at this is a lower roll center means more force in roll is transfered through the shocks/springs and visa versa.
I totally agree, talking only about RC and not about roll couple and how they interact with each other is key. Most only speak of one CG of the car, but its more complicated than that. Typically the rear has a higher CG than the front (say you slice the car in 10 parts, every section has a CG, connect the dots and see the CG is higher in the rear) and matching the RC to this higher rear CG is important in tuning the car to many different variables.
This guy just dont get it. th-cam.com/video/aG4KJ5ohsOo/w-d-xo.html&t
@@Ozzy3333333 yeah exactly, i talk about it in my videos as well how we could simplify the visualisation if we actually started focusing on the roll couple instead of just the rc. Also many forget to even consider that the front and rear end are connected.
had feelt before that roll center where some form of black magic but a year of testing things on my car and studdy all kinds of material and alot of JQ on roll centers i start to get a grip of it sort to speak.
tested to tune others cars and for the astro track im mostly running on people tend to set the roll center to high and not enough camber so the cars feels stiff and sliding in corners or hooking abrupt and jacking force throw the car over.
I would add that changing washers under the inner upper ball has greater influence on camber gain than roll centers. So i think that most of the handling results are tied with the way the wheel gain or loose camber during its travel instead the effect of roll center. You can have a back proof running tests changing the high of lower arms pins without touching upper links inclination.
Well put, sir. It depends on tyres, but also where you are in set-up land, as well as what the other end is doing.
Hi there, this is a very interesting subject, one thing that most people find hard to solve is the grip roll situation. Can you add this as a future video. Cheers Neale
Great video as always
I might be a bit confused, but would adding spacers under the upper inner wishbones not raise the roll centre? Where as in the video its deacribed as lowering it?
it is a lot of argument in hk about roll centre also
Do you guys not run the Fuzzbites overseas?
In Europe everone runs Schumacher tires, they outperform any others here (on Astroturf, that is)
@@sander89706 agreed, but I'm talking about carpet tires.