Theory of height/rake of race car Need input
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Honda-Tech Member
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From: Luebeck, Schleswig-Holstein, Germany
Theory of height/rake/crossweight of race car Need input
Ok so over the past few weeks 2 very interesting tops have been brought up. both can be found here
https://honda-tech.com/zerothread/2372714
and
https://honda-tech.com/zerothread?id=2365405
Ok so from what people are mentioning that perfection is not possible. height of a car will never be even with a cross weighting and the ideal height may not even be even front to rear.
cross weighting can make the car uneven at all 4 corners and some people state that the rake of a car is important but to raise the front rather then the rear
by making the front of the car higher then the rear you load more weight on the front (from what people say on cross weighting) and that making the front heigher can help for lower spring rates to not bottom out the front end during braking and create a more level car during the turn(seems good idea in theory). Can this additional weight end up hurting a fwd 2 much by putting an additional stress on the front tires/brakes/suspension? is the ideal set-up a perfectly even dropped car with perfect cross weights and level rake?
is the only reason you adjust this out of the "ideal" range is so your height/weight distribution is set-up for your parts performance rather then perfetc performance.
Remember we are talking about Fwd not rwd car's (also take into consideration the difference in FWD and RWD, do these theories differ largely between the two drivetrains)
https://honda-tech.com/zerothread/2372714
and
https://honda-tech.com/zerothread?id=2365405
Ok so from what people are mentioning that perfection is not possible. height of a car will never be even with a cross weighting and the ideal height may not even be even front to rear.
cross weighting can make the car uneven at all 4 corners and some people state that the rake of a car is important but to raise the front rather then the rear
by making the front of the car higher then the rear you load more weight on the front (from what people say on cross weighting) and that making the front heigher can help for lower spring rates to not bottom out the front end during braking and create a more level car during the turn(seems good idea in theory). Can this additional weight end up hurting a fwd 2 much by putting an additional stress on the front tires/brakes/suspension? is the ideal set-up a perfectly even dropped car with perfect cross weights and level rake?
is the only reason you adjust this out of the "ideal" range is so your height/weight distribution is set-up for your parts performance rather then perfetc performance.
Remember we are talking about Fwd not rwd car's (also take into consideration the difference in FWD and RWD, do these theories differ largely between the two drivetrains)
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Joined: Sep 2003
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From: Scotts Valley, CA
Re: Theory of height/rake/crossweight of race car Need input (unrealwrc)
So many questions, I don't know where to begin...
Rake is important. It is not an effective way to shift the static load of the tires. These are the things I am thinking about when I am changing rake:
*changing suspension position changes your position on the toe/camber curves
*"raking" adjusts the inclination of the front and rear roll centers and inclination of the mass centroid, which can effect dynamic load transfer.
*aerodynamic benifits and consequences
So yeah, it's important. What specific problem are you trying to address?
Rake is important. It is not an effective way to shift the static load of the tires. These are the things I am thinking about when I am changing rake:
*changing suspension position changes your position on the toe/camber curves
*"raking" adjusts the inclination of the front and rear roll centers and inclination of the mass centroid, which can effect dynamic load transfer.
*aerodynamic benifits and consequences
So yeah, it's important. What specific problem are you trying to address?
Honda-Tech Member
Joined: Jan 2004
Posts: 2,350
Likes: 1
From: Cerritos, CA, USA
Re: Theory of height/rake/crossweight of race car Need input (gotocrx)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gotocrx »</TD></TR><TR><TD CLASS="quote">So many questions, I don't know where to begin...
Rake is important. It is not an effective way to shift the static load of the tires. These are the things I am thinking about when I am changing rake:
*changing suspension position changes your position on the toe/camber curves
*"raking" adjusts the inclination of the front and rear roll centers and inclination of the mass centroid, which can effect dynamic load transfer.
*aerodynamic benifits and consequences
So yeah, it's important. What specific problem are you trying to address?
</TD></TR></TABLE>
The mass centroid is a point, not something that can be aligned with some axis. The dynamic total load transfer during cornering, that is the amount of load that transfers from or to each tire is affected by the unsprung mass centroid perpendicular distance to the roll center neutral axis (the axis that joins the front and rear roll centers), front and rear roll stiffness, sprung mass, each unsprung mass and their distances to ground plane, lateral g's being applied to entire car, wheelbase, ect.
Rake is important. It is not an effective way to shift the static load of the tires. These are the things I am thinking about when I am changing rake:
*changing suspension position changes your position on the toe/camber curves
*"raking" adjusts the inclination of the front and rear roll centers and inclination of the mass centroid, which can effect dynamic load transfer.
*aerodynamic benifits and consequences
So yeah, it's important. What specific problem are you trying to address?
</TD></TR></TABLE>
The mass centroid is a point, not something that can be aligned with some axis. The dynamic total load transfer during cornering, that is the amount of load that transfers from or to each tire is affected by the unsprung mass centroid perpendicular distance to the roll center neutral axis (the axis that joins the front and rear roll centers), front and rear roll stiffness, sprung mass, each unsprung mass and their distances to ground plane, lateral g's being applied to entire car, wheelbase, ect.
Junior Member
Joined: Apr 2008
Posts: 149
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From: Tomball, Texas, USA
so my feedback isn't near as scientific as someof the other here, but I raised the front of my car 3/4" and lowered the rear 1/2 inch before my last track event. I had less tail-wagging under braking, and cornering was about the same. maybe a tad bit more mid-corner and exit (on-throttle) push than before.
anyway, my $.02
anyway, my $.02
Honda-Tech Member
Joined: Jan 2004
Posts: 2,350
Likes: 1
From: Cerritos, CA, USA
Re: (L8APX)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by L8APX »</TD></TR><TR><TD CLASS="quote">so my feedback isn't near as scientific as someof the other here, but I raised the front of my car 3/4" and lowered the rear 1/2 inch before my last track event. I had less tail-wagging under braking, and cornering was about the same. maybe a tad bit more mid-corner and exit (on-throttle) push than before.
anyway, my $.02</TD></TR></TABLE>
Well, raising the front of the car will add static camber (positive) and raise the CG a bit, both of which will help cause more push with the camber change causing most of the added push. In the rear, lowering the car will reduce camber and this will increase rear traction at the camber settings typically used. So overall, you have experienced that added understeer with your change in rake.
anyway, my $.02</TD></TR></TABLE>
Well, raising the front of the car will add static camber (positive) and raise the CG a bit, both of which will help cause more push with the camber change causing most of the added push. In the rear, lowering the car will reduce camber and this will increase rear traction at the camber settings typically used. So overall, you have experienced that added understeer with your change in rake.
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Joined: Jun 2004
Posts: 1,160
Likes: 1
From: Bay Area, CA, usa
Re: Theory of height/rake/crossweight of race car Need input (unrealwrc)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by unrealwrc »</TD></TR><TR><TD CLASS="quote">Ok so over the past few weeks 2 very interesting tops have been brought up. both can be found here
https://honda-tech.com/zerothread/2372714
and
https://honda-tech.com/zerothread?id=2365405
Ok so from what people are mentioning that perfection is not possible. height of a car will never be even with a cross weighting and the ideal height may not even be even front to rear.
cross weighting can make the car uneven at all 4 corners
## no, a car can be at most uneven at only one corner because the three other corners define a plane, and you can always tilt this plane to be parallel to the ground without affecting the cross weight. If all 4 corners aren't in a plane, well then your chassis is bent.
and some people state that the rake of a car is important but to raise the front rather then the rear
by making the front of the car higher then the rear you load more weight on the front
## rake negligibly affects front back weight balance, like 1-cos(theta) for small theta
</TD></TR></TABLE>
https://honda-tech.com/zerothread/2372714
and
https://honda-tech.com/zerothread?id=2365405
Ok so from what people are mentioning that perfection is not possible. height of a car will never be even with a cross weighting and the ideal height may not even be even front to rear.
cross weighting can make the car uneven at all 4 corners
## no, a car can be at most uneven at only one corner because the three other corners define a plane, and you can always tilt this plane to be parallel to the ground without affecting the cross weight. If all 4 corners aren't in a plane, well then your chassis is bent.
and some people state that the rake of a car is important but to raise the front rather then the rear
by making the front of the car higher then the rear you load more weight on the front
## rake negligibly affects front back weight balance, like 1-cos(theta) for small theta
</TD></TR></TABLE>
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Joined: May 2007
Posts: 1,298
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From: Binghamton, NY, US
Re: Theory of height/rake/crossweight of race car Need input (beanbag)
This is an awesome discution, from what i understand anyway. This is how I set up my car. I get a lot of hate from "tuners" who have their cars slamed, they say mine looks like a ralley car. Ha, it doesn't really but the front is by no means slamed. I don't have much experience with other setups, but this has definatly worked for me. The shop where i get the work done suggested this, bishop motorsports in CT. I think he can set up a honda pretty good, well at least give someone just getting started a good foundation to work off of.
When you say that raising the front, or having the front higher than the rear, will load the front tires more; do you mean durning weight transfer? I'm assuming you do because i thought this would take load off in a static state, and shift the cg rearward. Correct me if i'm wrong, i'm by no meaning of the word an expert on this.
When you say that raising the front, or having the front higher than the rear, will load the front tires more; do you mean durning weight transfer? I'm assuming you do because i thought this would take load off in a static state, and shift the cg rearward. Correct me if i'm wrong, i'm by no meaning of the word an expert on this.
Junior Member
Joined: Apr 2008
Posts: 149
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From: Tomball, Texas, USA
Re: (Johnny Mac)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnny Mac »</TD></TR><TR><TD CLASS="quote">
Well, raising the front of the car will add static camber (positive) and raise the CG a bit, both of which will help cause more push with the camber change causing most of the added push. In the rear, lowering the car will reduce camber and this will increase rear traction at the camber settings typically used. So overall, you have experienced that added understeer with your change in rake.
</TD></TR></TABLE>
I actually adjusted the camber back to what it was before the raising.
In the rear I did not, since the car was silly loose and I wanted a little more camber. Now the car is still pretty loose, but also pushes a wee bit more if I get on the gas too early. Could be that I am just getting on it earlier too, not sure.
So obviously my feedback is very subjective, but maybe it still helps a little.
I'll be raising the rear up a little before my next event to see how that affects things, and can come back to update this thread (hopefully I'll remember).
Well, raising the front of the car will add static camber (positive) and raise the CG a bit, both of which will help cause more push with the camber change causing most of the added push. In the rear, lowering the car will reduce camber and this will increase rear traction at the camber settings typically used. So overall, you have experienced that added understeer with your change in rake.
</TD></TR></TABLE>
I actually adjusted the camber back to what it was before the raising.
In the rear I did not, since the car was silly loose and I wanted a little more camber. Now the car is still pretty loose, but also pushes a wee bit more if I get on the gas too early. Could be that I am just getting on it earlier too, not sure.
So obviously my feedback is very subjective, but maybe it still helps a little.
I'll be raising the rear up a little before my next event to see how that affects things, and can come back to update this thread (hopefully I'll remember).
Honda-Tech Member
Joined: Jan 2004
Posts: 2,350
Likes: 1
From: Cerritos, CA, USA
Re: (L8APX)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by L8APX »</TD></TR><TR><TD CLASS="quote">
I actually adjusted the camber back to what it was before the raising.
In the rear I did not, since the car was silly loose and I wanted a little more camber. Now the car is still pretty loose, but also pushes a wee bit more if I get on the gas too early. Could be that I am just getting on it earlier too, not sure.
So obviously my feedback is very subjective, but maybe it still helps a little.
I'll be raising the rear up a little before my next event to see how that affects things, and can come back to update this thread (hopefully I'll remember).
</TD></TR></TABLE>
In a front wheel drive car, you really want to get your car straightened out as much as possible before getting on the gas. This is because your front tires are being asked to corner and accelerate the heaviest end of the car. And because the tire's traction circle dictates how much combined cornering and accelerating or decelerating, the more you are cornering the less available grip is available to accelerate out of the corner.
I actually adjusted the camber back to what it was before the raising.
In the rear I did not, since the car was silly loose and I wanted a little more camber. Now the car is still pretty loose, but also pushes a wee bit more if I get on the gas too early. Could be that I am just getting on it earlier too, not sure.
So obviously my feedback is very subjective, but maybe it still helps a little.
I'll be raising the rear up a little before my next event to see how that affects things, and can come back to update this thread (hopefully I'll remember).
</TD></TR></TABLE>
In a front wheel drive car, you really want to get your car straightened out as much as possible before getting on the gas. This is because your front tires are being asked to corner and accelerate the heaviest end of the car. And because the tire's traction circle dictates how much combined cornering and accelerating or decelerating, the more you are cornering the less available grip is available to accelerate out of the corner.
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Joined: Sep 2003
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From: Scotts Valley, CA
Re: Theory of height/rake/crossweight of race car Need input (Johnny Mac)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnny Mac »</TD></TR><TR><TD CLASS="quote">
The mass centroid is a point, not something that can be aligned with some axis. . </TD></TR></TABLE>
Sorry you're right. I used the wrong term. A centroid is a point. I was reffering to the imperfect line you get when you connect the centroids of you car once you divide it into n segments along the x axis. A car is not a uniformly dense object, after all.
Does the math simplify to where only the centroid matters, or does distrobution of mass not matter if center of mass is constant?
I have been taught that it mattered, but never did the math to figure it out myself.
The mass centroid is a point, not something that can be aligned with some axis. . </TD></TR></TABLE>
Sorry you're right. I used the wrong term. A centroid is a point. I was reffering to the imperfect line you get when you connect the centroids of you car once you divide it into n segments along the x axis. A car is not a uniformly dense object, after all.
Does the math simplify to where only the centroid matters, or does distrobution of mass not matter if center of mass is constant?
I have been taught that it mattered, but never did the math to figure it out myself.
Honda-Tech Member
Joined: Jun 2004
Posts: 1,160
Likes: 1
From: Bay Area, CA, usa
Re: Theory of height/rake/crossweight of race car Need input (gotocrx)
Distribution of mass matters for things that have 2nd or higher moments in the mass, such as moment of inertia mr^2. For example, how easily/quickly the car rolls, pitches, spins out. Which reminds me that I heard that MR2's rotate well because the engine is near the center of the car. For the same weight, it has a lower moment of inertia. Not sure if that actually matters...
Modified by beanbag at 11:40 PM 8/30/2008
Modified by beanbag at 11:40 PM 8/30/2008
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