Rf wheel spacer

[hunterracing]

What would be affects of a 1 inch or 2 inch rf wheel spacer with convential shock and spring setup on rf

[Matt49]

What would be affects of a 1 inch or 2 inch rf wheel spacer with convential shock and spring setup on rf

All else being equal it would tighten the car all the way around. But all else won't be equal. You will likely see a decrease in static wedge. Front end geometry changes if that matters to you. This change also increases scrub radius which will change the weight jacking affect the RF provides with steering input.

[Kromulous]

More or less Matt49? i would think more but asking.

[hunterracing]

So more then likely throw how the car turns into the corner and not plant the rf? Would it affect how much the car rolls on rf since wheel and spring are farther apart?

[Mr.Kennedy777]

Increasing scrub radius reduces the jacking forces from the spindle.Decreasing scrub radius increases. Another way to look at it is this. If the top of the spindle is laid back towards the engine bay more, you will create more jacking forces along the radius the tire follows when you turn the wheel. The more upright it is, the less jacking force is created. If the spindle inclination is the same, and you move the wheel out further, you increase the scrub radius and what that means is you increase the path at which that jacking force is applied. The spindle will create the same force but it’s spread out over a bigger radius now, which results in a net decrease of that jacking effect at the wheel.

[Matt49]

Wheel and spring being further apart don't matter other than the motion ratio created by camber gain. This is, however, a common misconception. The static motion ratio is the distance from inner lower control arm to shock mount on the control arm, divided by the total length of the control arm. People think that moving the wheel way out lowers the wheel rate but it does not. You still have the upper control arm pushing back against the spindle that you are trying to move up. But it CAN lower the wheel rate due to the fact that camber gain becomes a negative weight jack due to the larger scrub radius.

[hunterracing]

So maybe putting a wheel spacer might be a bad idea then?

[Mr.Kennedy777]

Wheel and spring being further apart don't matter other than the motion ratio created by camber gain. This is, however, a common misconception. The static motion ratio is the distance from inner lower control arm to shock mount on the control arm, divided by the total length of the control arm. People think that moving the wheel way out lowers the wheel rate but it does not. You still have the upper control arm pushing back against the spindle that you are trying to move up. But it CAN lower the wheel rate due to the fact that camber gain becomes a negative weight jack due to the larger scrub radius. Not entirely true. Moving the wheel out doesn’t change the arm length but it changes the wheel length which changes wheel rate. Wheel Rate = Spring Rate * (Motion Ratio ^ 2) * Spring Angle Correction( the cosine of angle) Motion ratio = arm length/wheel length If the arm is 18” and the wheel is 20” then you have a 0.9 motion ratio of the arm to the wheel. Motion ratio of the coil over you would find by taking the shocks lower mounting point, and determining shock length. You would then take the shock length and divide that by the wheel length. In this case let’s say the shock was 14” from the inner pivot. This would mean that the shock has a 0.7” motion ratio to the wheel. You could also figure out the movement of the shock in relation to the ball joint, and this case it would be 0.77 repeated. But if your coil over is angled you need to apply the spring angle correction to get an accurate number. If your coil spring is inside the control arm, you could use the center of the spring seat as a rough guide although the inside and outside of a 5” spring do have quite different ratios especially if the inside of the spring is quite close to the attachment points. But as far as I have ever learned, THAT is how you calculate wheel rate.

[Mr.Kennedy777]

And as you have mentioned as well, camber curve also changes the movement of the wheel, and must also be factored in. But the change in the wheel spacing, doesn’t JUST effect the camber, it does provide a different motion ratio for the lower arm as well as wheel center line.

[Mr.Kennedy777]

And saying that, your motion ratio of the tire to the arm, is actually going to be different at different stages of travel depending on your arm configuration and what they’re doing not only under compression but also when the chassis rolls. You can’t determine actual wheel rate without combining the entire system together on one corner of an SLA suspension. And then all this is done assuming the tire is rigid. So that also changes things a bit on a guy.

[hunterracing]

Guess there’s a lot of factors to go into before bolting on and testing it

[Mr.Kennedy777]

I would say a 1” spacer would be alright to try. But sticking a 2” spacer on there is not that great a deal and might make everything move way more than it should.I’ve also heard it can be harder on the wheel bearing by creating too much a lever. If you’re looking for the wide front kinda deal I think changing mounts/links is the best way to do that.

[collateralDamage]

If you bolt a 1" or 2" or whatever spacer on the RF and do nothing else you will need more spring load to accomplish the same wheel load at the same travel, THAT'S ONLY ASSUMING you can generate the same wheel load to accomplish the same travel. In walks camber....

[hunterracing]

I can see more stress on the wheel bearing for sure

[fastford]

except maybe toe gain , i would think every aspect of geometry concerning the right front , would be effected going from static to dynamic conditions by moving the tire out.....Mr. kennedy , do you work for NASA ???? LOL.....

[Kromulous]

I have ran as much as 3" of offset, more than std., some cars like it, black front rockets for one.

Anyway its a tool in the box, track gets super slick in the summer, throw it on there and see if you like it.

What has me interested is the LF, if it reduces the jacking effect of counter steering i could see it being beneficial there, but you might have to add back in some spring rate. My knowledge of using it on the LF is it makes a car steer thru the center better.

Anyway seems like adding it to the LF on along with more spring, would really help on super slick to keep the car smoother on entry, no swings tight to loose entering. Anyone ever try it?

[Kromulous]

https://www.youtube.com/watch?v=SUDMEd1bMZI

This guy talks about the effects while breaking...

[Matt49]

Mr.Kennedy777,
Sorry but you're incorrect on this one. Wheel rate is not affected by the distance between the wheel and the spring on a double wishbone suspension. Again, NOT taking caber changed into account.
If you had a double wishbone suspension with equal length uppers and lowers (let's say 20 inches) and both at the same static angle, this would yield no dynamic camber change. Then let's say you put a 200 pound spring perpendicular to the ground at 10 inches between the frame and the ball joint on the lower control arm. The wheel rate is going to be 100 pounds. I don't care if the wheel is centered with the ball joint or the wheel is 500 feet away. The wheel rate will be 100 pounds. This is because the upward motion you try to place on the wheel is being pushed in two vectors. One is the top of the spindle pushing in on the upper control arm and the other is the lower control arm pushing up on the spring. If the upper control arm were a spring and not stiff, the distance to the wheel would matter, but it isn't so it doesn't. But don't take my word for it, go mock it up in your shop and test it yourself.

[Matt49]

And before you argue with me on this, pick up the phone and argue with the people at Koni and Hyperco, or the authors of any number of automotive engineering books the explain this clearer than I can.
http://www.truechoicekoniracingservices.com/worksheet.pdf

[fastford]

I guess im a little confused my self , I always considered wheel rate the weight or weight change at the wheel , if you put the car on the scales and move the wheel out 2 inches and nothing else , that wheel weight will lessen , which i assumed was wheel rate , of course we all know what assume does.........

[Matt49]

Static load is not wheel rate. The reason the wheel is lighter at static load is because you've moved it further from the center of gravity of the car.
You can't think of the spindle as a lever which is what confuses people on this. If it were a beam axle, the distance between the wheel and the spring mean everything. But all that matters on a double wishbone is the distance between the lower ball joint and the spring (assuming the spring is on the lower ball joint). All of the "leverage" that the spindle gives you, no matter how long the spindle is or where the wheel is mounted on it, is completely absorbed by the upper ball joint and and upper control arm. The spring only feels the wheel's ability to move the the lower ball joint UP. The wheel's ability to do so will never benefit by being placed further away.

[collateralDamage]

I understand the argument being made, and it's a really fun fact. Maybe there needs to be more clarity on the definition of "wheel rate" and "wheel load".

Unless the laws of physics have changed, there is no way that the upper control arm and the ball joint "absorbed the leverage". That force went somewhere.

We are all concerned with, and hopefully aware of, the load at the contact patch of the tire and how it contacts the track. There's just no way to ignore camber, distance from CG, etc. when it comes to how a wheel spacer affects load on the tire.

[Matt49]

I understand the argument being made, and it's a really fun fact. Maybe there needs to be more clarity on the definition of "wheel rate" and "wheel load".

Unless the laws of physics have changed, there is no way that the upper control arm and the ball joint "absorbed the leverage". That force went somewhere.

We are all concerned with, and hopefully aware of, the load at the contact patch of the tire and how it contacts the track. There's just no way to ignore camber, distance from CG, etc. when it comes to how a wheel spacer affects load on the tire.

Well, brush up on your physics because this is perfectly applied.
The force did go somewhere. It went into the upper control arm which is NOT a spring (at least not an easily measurable one) which is why it doesn't change the wheel rate.
When you push up on the spindle snout, all of that force is NOT going into the spring. Think about it. The only upward force the spring can possibly feel is what is being applied at the lower ball joint. The mechanical advantage being gained by distance between the wheel and the lower ball joint is being applied as force into the upper ball joint and control arm in a vector facing roughly perpendicular to the control arm which is NOT felt by the spring. Just take the upper control arm off and conduct this experiment and tell me what point matters as the spindles moves and the lower control arm doesn't move at all. How can the distance from the wheel to the lower ball joint come into play if you can't even move the lower ball joint WITHOUT the spindle being connected to the upper control arm.
These are the laws of physics and it's pretty tough to argue against them. I guess I'm going to have to mock this up and do a video to prove it.
It's easy to apply beam axle physics to double wishbone suspensions but it is WAY off. Easy, is why so many people do it.

[Matt49]

Wheel load - amount of weight on the tire contact patch
Wheel rate - weight required to move the tire contact patch one inch under compression suspension

[collateralDamage]

Everything you are referring to is concerning wheel rate. When you add a 1" spacer and do nothing else YOU WILL REDUCE WHEEL LOAD. The leverage of the spindle on the upper and the frame doesn't just vanish. Although maybe insignificant it goes into the frame and other wheel loads.

[hunterracing]

Has anyone tried it and felt diffence with or without it

[Matt49]

Everything you are referring to is concerning wheel rate. When you add a 1" spacer and do nothing else YOU WILL REDUCE WHEEL LOAD. The leverage of the spindle on the upper and the frame doesn't just vanish. Although maybe insignificant it goes into the frame and other wheel loads.

Yes, I explained why wheel load decreases when you move the RF wheel out. And why wheel rate does not change. Wheel load and wheel rate are two completely different things.

[collateralDamage]

If you reduce the WHEEL LOAD on the RF by putting on a wheel spacer, you will adjust the WHEEL RATE to maintain the WHEEL LOAD. Whether the WHEEL RATE changes IN THIS CASE or not doesn't matter. It's the change in WHEEL LOAD that matters.

That being said, the interesting fact that Matt49 is talking about, is good to keep in mind when determining HOW to change the WHEEL RATE.

If you do nothing more than bolt a RF wheel spacer on, the reduced wheel load should make the car feel tighter. If you make adjustments to maintain the wheel load you will change the way the front end "feels" to the driver and not necessarily change anything measurable on the stopwatch. Its not something I consider an at-the-track adjustment. You either set the car up to use a wheel spacer and you weld it on, or you leave it off -JMO

[matchbox]

What if my chassis has a option to move whole right front assembly out 1 inch. What will it do?

[Mr.Kennedy777]

And before you argue with me on this, pick up the phone and argue with the people at Koni and Hyperco, or the authors of any number of automotive engineering books the explain this clearer than I can.http://www.truechoicekoniracingservices.com/worksheet.pdf I don’t need to lol! Wheel rate that they talk about in that work sheet is actually ball joint rate, they use it to avoid having to complicate that work sheet to help guys get close enough. Anytime you have anything travelling a radius, extending it out further on that radius, while creating the same degrees of movement, you will experience more motion. If the point of rotation is 1” away from the ball joint, 1 degree change isn’t very big. If you’re 36 feet away, one degree is quite a bit. Even on a beam axle wheel spacing changes wheel rate.

[Mr.Kennedy777]

When both wheels are in compression it’s 1:1, but one wheel bumps and roll, it’s different.

[Mr.Kennedy777]

Checking wheel rate at a ball joint is not accurately measuring wheel rate. It can give you simple motion ratios to give you an idea roughly how much stuff is moving with what and approximate load at the ball joint, but there are way more calculations that need to be considered to get wheel rate. One of which includes measuring the distance of the wheel compared to distance of the lower ball joint.

[Matt49]

Okay...so, like I've said 100 times, taking camber gain OUT of the equation. Grab the end of a spindle and move it up one inch. How far did the spring compress? Now imagine the spindle is 50 feet long and that is where the wheel is. Move the wheel up one inch and how far did the spring compress? The EXACT same amount as when the wheel was right next to the ball joint! Therefore the exact same wheel rate. The distance from the wheel to the lower ball joint makes ZERO difference on the wheel rate on a dual wishbone suspension. Even if you put camber gain back into the equation, you would have to move the wheel a great distance out for it to significantly impact wheel rate. People seem to be stuck with thinking that the distance from the wheel to the lower ball joint gives the wheel some mechanical advantage on the spring but that simply isn't true. The spring only moves as far as the motion ratio to the lower ball joint dictates. Where the wheel is doesn't change that in any way.

[fastford]

Checking wheel rate at a ball joint is not accurately measuring wheel rate. It can give you simple motion ratios to give you an idea roughly how much stuff is moving with what and approximate load at the ball joint, but there are way more calculations that need to be considered to get wheel rate. One of which includes measuring the distance of the wheel compared to distance of the lower ball joint.

this is the way i have always considered wheel rate as well , there is no doubt , both you guys are smart , but to me , wheel location has to play a role in wheel rate...

[Kromulous]

Matt49 i agree with you, but would some of the force get reduce by the leverage of the wheel location to the ball joint if if it was excessive? It would be small but you are introducing a moment there, correct?

I think you talked about that before, some of the load getting transferred thru the upper ball joint, but just making sure.

[dirtrace09]

The distance the wheel is from the spring does have an effect on the wheel rate. We use this idea constantly in the hydraulic world. The movement of 1 inch is still 1 inch no matter the distance. However; the rate at which you can and will move that wheel, bucket, claw, etc... is changed due to leverage from the distance. Is it major for a race car? Not seriously significant but can be at a different location.

[Mr.Kennedy777]

Taking the wheel out of the picture yes, but then you’re just getting BALL JOINT RATE. You can’t take camber change out of the picture because if you have zero camber change during bump, you’ll have camber change in roll, if you have zero camber change from roll, you have camber change during bump. If you split the difference for bump, roll and pitch then you’re getting less overall camber change for that total motion but for each individual motion you must be gaining and losing camber which changes the wheel rate in bump, roll and pitch differently. Moving the tire away from the spindle changes wheel rate because it changes the angle of the line of action the tire has that is connected to the intersection of the lines of action of upper and lower control arms and tie rod as well as the forces of the into the spindle. Therefore wheel rate is changed. The force at the wheel does change, and the spring motion may not be affected greatly in relationship to the ball joint of the lower control arm because that length always stays the same, but when you put a spindle and upper into the picture and a tie rod, the amount the wheel center moves compared to the lower and upper ball joint changes way more, and that’s why I am saying what you’re measuring at the end of the lower control arm is ball joint rate, not wheel rate. As you have mentioned before moving the wheel further away from the car changes the weight on it because it’s further away from the center of mass concentration. This changes lateral weight transfer amount not motion ratio. To get the same weight on the wheel as before you need a stiffer spring to even out the lateral load distribution. That’s not what I am talking about right now though. What I am saying is that the wheel movement at the wheel center, to the lower ball joint is changed greatest when a spacer is put on because both the lower and the upper both travel in a radius. The motion ratio of ball joint movement to the spring movement isn’t changed no. But the movement of the wheel center, the axis of the rotation of the tire, does change, And that’s why wheel rate cannot be accurately measured at the ball joint.

[Mr.Kennedy777]

And when I’m talking about axis of rotation, I’m taking about the axis the wheel rotates about the hub when rolling, not the rotation of the tire on its camber curve from a front view.

[swingarm4life]

We use to do this all the time back in the day on the Rayburns for obvious reasons. Never had any problems with bearings. We would put the 1" on the LR when the track started blowing, then later in the night we would move it to the RF and put a 2" on LR.

[Kromulous]

I'm not sure about now, maybe somebody can say but back in the day LOL (2003 ish) we used to work with rim offsets all the time running mods. It was a nice easy way to tune a car. I am not real sure why its not used more in SLMs.

Just like swingarm said, RF & LR would be a good adjustment for the feature.

[collateralDamage]

Matt49 i agree with you, but would some of the force get reduce by the leverage of the wheel location to the ball joint if if it was excessive? It would be small but you are introducing a moment there, correct?

I think you talked about that before, some of the load getting transferred thru the upper ball joint, but just making sure.

No, I'm pretty sure Matt49 stated that the force is "completely absorbed" by the upper ball joint/upper control arm.

[Matt49]

No, I'm pretty sure Matt49 stated that the force is "completely absorbed" by the upper ball joint/upper control arm.

That's right. The wheel is pushing up on the spindle snout and the force that goes into the spring is not on a solid beam. It has a point of articulation (the lower ball joint) so some of the upward force on the spindle snout goes into stress on the upper control arm and ball joint. Just take the upper control arm off and see how that works. There is NO mechanical advantage gained by lifting up on the spindle further from the ball joint. Again...other than the VERY small amount of motion ratio gained by the affect that camber gain may have on the distance the end of the snout can travel without moving the spring the same amount. But on a setup without camber gain, if the end of the snout moves up one inch, the ball joint moves up one inch. Therefore the spring moved the exact same amount. Motion ratio the same means rate is the same. It doesn't get any simpler than that.
Now I realize that we ALL have camber gain in our suspension geometry. But the point that I've been trying to make is that the distance between the wheel and the ball joint has no affect on motion ration OTHER than the camber gain factor of it. There is no leverage being gained by the distance but it isn't a solid "lever" like a beam axle. All of the upward motion is at the lower ball joint. So moving the wheel out two inches is not going to have any noticeable impact on wheel rate. Wheel load? Yes. Wheel rate? No.

[fastford]

if the ball joint moves up 1 inch and the spring is mounted in board of the ball joint , how can the spring travel the exact same distance?

[Matt49]

if the ball joint moves up 1 inch and the spring is mounted in board of the ball joint , how can the spring travel the exact same distance?

That's not what I'm saying. I'm saying if the ball joint moves up one inch and the wheel moves up one inch, the spring will travel some distance (call it X) depending on it's location on the LCA and that will dictate wheel rate. Moving the location of the wheel away from the ball joint doesn't change the distance that the ball joint travels relative to the travel of the wheel therefore it does not change wheel rate.
If there were no camber gain, the wheel could be 10 feet from the ball joint and it would take the same amount of force to move it up one inch because you still have to move the ball joint up one inch to compress the spring X amount. You don't have any leverage on the spring by moving the wheel out which is why moving it out doesn't change wheel rate. It is NOT a beam axle and people seem to be stuck in the mindset of treating it like one.
Camber gain would generate a certain amount of motion ratio change but only a very minute amount at the distances we're talking about moving the wheel.

[fastford]

i guess im still confused , if the wheel travels 1 inch up , then you move it out 5 inches and it moves up 1 inch , the ball joint is not gone travel up as much as it did to begin with before you moved the wheel out , this is what i would consider a change of rate at that wheel....

[billetbirdcage]

i guess im still confused , if the wheel travels 1 inch up , then you move it out 5 inches and it moves up 1 inch , the ball joint is not gone travel up as much as it did to begin with before you moved the wheel out , this is what i would consider a change of rate at that wheel....

https://i.imgur.com/NEWzotN.png


If you raise the ball joint 1" the spring will compress 1/2 that distance, since that crappy drawing I did has basically no camber gain the tire (blue or green) will still only move up that 1" regardless of which one you choose.

Now change the suspension so it has camber gain and you will see a difference.

[Austin34471]

https://i.imgur.com/NEWzotN.png


If you raise the ball joint 1" the spring will compress 1/2 that distance, since that crappy drawing I did has basically no camber gain the tire (blue or green) will still only move up that 1" regardless of which one you choose.

Now change the suspension so it has camber gain and you will see a difference.

Billet is that Solidworks you are using for your 3d modeling?

[matchbox]

So if I move my mounting points out one inch. What does that do?

[fastford]

https://i.imgur.com/NEWzotN.png


If you raise the ball joint 1" the spring will compress 1/2 that distance, since that crappy drawing I did has basically no camber gain the tire (blue or green) will still only move up that 1" regardless of which one you choose.

Now change the suspension so it has camber gain and you will see a difference.

so in your drawing , your saying if the ball joint travels up 1 inch , the blue tire is going to travel the same as the green tire? how can that be with it out 6 inches more than the other?

[billetbirdcage]

so in your drawing , your saying if the ball joint travels up 1 inch , the blue tire is going to travel the same as the green tire? how can that be with it out 6 inches more than the other?

The spindle never changes camber (snout will always be level as it is in the drawing), so it moves the same whether the tire is right at end of snout or 100 foot away from the snout.

*Note: This is with parallel and equal length control arms which a LM usually never has. I was only showing this because it shows what matt was saying with "no camber gain".

https://i.imgur.com/va5jpdG.png

[fastford]

ok , i guess im not looking at it with both upper and lowers being identical in mounting points and length as with your drawing above.....

[Matt49]

Thank you billet for explaining what I was trying to explain so unsuccessfully.
As the old saying goes, a picture is worth a thousand words.

[Ghopper]

This tread got entertaining. More or less because it got heated in rhetoric. It is not good to be overly idealistic as the point can be lost and people mislead. I have been wrong many times because of simplifying the problem.

Wheel rate is vertical spring rate at the wheel center. All our current used suspensions have resulting camber components so it is a waste of time to not consider that. You guys can point physics fingers all you want at that....

A 1" wheel spacer on the RF of an XR1 will change the wheel rate ~10lbs/in. My example is with a linear 300lb/in primary spring. Wheel rate moves from ~103lb/in to ~94lb/in within the 3in of travel range. Tracking and steering influences will be easily noticed by the driver. I suggest you make this change only on a test track so you can back to back the resulting observation.

[billetbirdcage]

This tread got entertaining. More or less because it got heated in rhetoric. It is not good to be overly idealistic as the point can be lost and people mislead. I have been wrong many times because of simplifying the problem.

Wheel rate is vertical spring rate at the wheel center. All our current used suspensions have resulting camber components so it is a waste of time to not consider that. You guys can point physics fingers all you want at that....

A 1" wheel spacer on the RF of an XR1 will change the wheel rate ~10lbs/in. My example is with a linear 300lb/in primary spring. Wheel rate moves from ~103lb/in to ~94lb/in within the 3in of travel range. Tracking and steering influences will be easily noticed by the driver. I suggest you make this change only on a test track so you can back to back the resulting observation.

Long time no see, nerd! (grins)

Good to see you have a little time to race now and then, hope is all good.

[Matt49]

Nice CAD work ghopper. I've been working on simulating some front end stuff in Fusion 360 but have been encountering some challenges that may simply be finding the limits of what it can do. What did you use for this?

[fastford]

dont know about the " heated rhetoric " thing , if you do not question things , then you may never know if your right or wrong. I have gained a lot of knowledge from you guy,s and I appreciate it......what Ghopper has explained is what I was trying to say concerning wheel rate , just did not know how....

[Ghopper]

Nice CAD work ghopper. I've been working on simulating some front end stuff in Fusion 360 but have been encountering some challenges that may simply be finding the limits of what it can do. What did you use for this?

Siemens PLM Software's Simcenter 3D Motion. It is based on an NX CAD platform. I drew out some cars to get practice after being based in Dassault Catia V5 for a long time. Lots of holiday time with the wife sarcastically asking if I was drawing her pictures.

https://www.plm.automation.siemens.com/global/en/products/simcenter/simcenter-3d.html

Billet - It can be years between looking at this site. I should be at a race track a few times this year. Will probably be rusty as ever behind the wheel.

[Mr.Kennedy777]

This tread got entertaining. More or less because it got heated in rhetoric. It is not good to be overly idealistic as the point can be lost and people mislead. I have been wrong many times because of simplifying the problem.Wheel rate is vertical spring rate at the wheel center. All our current used suspensions have resulting camber components so it is a waste of time to not consider that. You guys can point physics fingers all you want at that....A 1" wheel spacer on the RF of an XR1 will change the wheel rate ~10lbs/in. My example is with a linear 300lb/in primary spring. Wheel rate moves from ~103lb/in to ~94lb/in within the 3in of travel range. Tracking and steering influences will be easily noticed by the driver. I suggest you make this change only on a test track so you can back to back the resulting observation. That’s beautiful man. Lol. I’ve been using performance trends to map out the front, a little pre historic compared to that nice cad work, but it does tell a guy the same stuff. It’s nice they finally added a pitch setting and improved the four link aspect of their system a bit. Still do all the four bar and birdcage stuff on paper with separate drawings and then kinda mix it all together that way, so I’m always dealing with a certain amount of error based on scaling from iso paper to actual size. Need to invest in some new software lol.

[fastford]

dam , i may as well give up with my old school technology , i use strings and chalk and plum bobs , and a 4 ft by 8 ft white slick bathroom wall board to scale my front end out on , oh well........

[Matt49]

I agree, fastford. Some of this stuff is very difficult to explain through words alone. I think we all just get frustrated trying to get technical thoughts out in plain English. There is a reason why all college-level physics classes typically have a lab class married to them. It takes really doing it to understand sometimes.
Pretty much all of the regular posters on here have contributed quite a bit of valuable information over the years. Obviously not many of us are pros at this but this is FREE information and there a great many people out there that use it to help their racing program. And I learn stuff on here all the time.

[Ghopper]

Whoa. We also all start from the same place - zero knowledge. The state of the art is continuously growing and expanding. A growing knowledge gap every year that new racers will need to overcome. That is the same knowledge race we have been battling on the track for decades....knowledge to make the car better.

Just for perspective; I repeated terminology found in $10-50 books and standardized in industry for nearly 75yrs or longer.

For proper "old school" testing: It is easy to constrain the chassis, build a special wheel that has a lift point at the wheel center (2in from hub face for a 5in backspace wheel, near spindle snout end), measure with tapes, jacks and load cell (wheel scales). Or build a pull down rig for $500. I live 30hrs from my shop today, so I needed virtual models to answer questions for my extremely limited time in my shop (7 shop days this year before I go to a national event as my first race).

The track change of this wheel spacer is harder to explain, and doesn't matter as much as the driver actually knowing the feel of a wheel spacer change. In conclusion, I would be less likely to make this adjustment has it has a significant change of CG position relative to RF tire contact patch.

[Ghopper]

FYI - Ride Rate is the spring rate of the suspension measured from the tire contact patch. Basically the Wheel Rate plus geometrical effect of the wheel transformation from wheel center to contact patch with compliance (spring rate) of the tire. This is what you are measuring on a Pull Down rig and you are extrapolating to get much else off of a quasi-static rig.

Your chassis builder should provide you with the necessary information to compete. Partner with a group that helps you. That is their job. If they don't, another builder will.

[fastford]

i have to admit , i do have one of the early programs , done by performance trends , that i use from time to time to see the effects of changing things on the front end , but you still have to use old school methods to get the initial info to put in , I also have some tie downs in one bay of my shop , that was originally used for body repair , to use as a crude way of pulling the car down , but i have mentioned on here before , we learned more by taking the chassis with all the suspension in place and solid rods in place of shocks and set in the dynamic state , best i could , and pulled it through the turns with a 4 wheeler , you would be amazed at what you can see and find.......