Theory thread

[Highwayman]

This is a great thread.

[RocketManNINE]

While we are talking about theory. I am having a hard time wrapping my head around the fact that I can give my shock guy my shocks and he can smash them and give them back to me and I can go racing without ever putting my car on scales. Wouldn't there be a difference if one of my drivers is 225 lbs. and the other one is 165 lbs.? I am just having a hard time understanding how this is possible. Please help with the theory.

[fastford]

if you have consistent ride heights with the driver in the car , then it dont matter how much they weigh , when you send the shock man your shock length,s at ride height , he can put you on the numbers on the smasher , or at least mine can , its really about providing your shock guy with accurate info ......

[Kromulous]

I think the key as with all race car set up is to be consistent. Same fuel, same led, same, same, same etc etc. In the shop i even considered having set up tires, same set every time. I have been also looking at replacing the Driver, with led shot, 200 lbs worth just to be more consistent. Ive wondered as well, why even have the Driver weight in there? Same Driver all the time? then why mess with it. I did this for years with Modifieds, but changed with SLMs, not sure why LOL.


Here lately i have been making charts of the 4_link indexing effects on the shock length changes. Since running a limiter chain there is a impact when you move the 4 link rods around on how much shock drop you have. Sometimes upwards of an inch difference. That will make a big impact on the load numbers at full droop. My question now is do i want that increase or do i reset the load after i change bars locations ?

[RocketManNINE]

So let me put this theory into play. I scale the car and give my center to center measurements to my shock guy. Now by theory I do not have to put my car back on the scales the rest of the year. So now I go and run it and my chassis flexes (because by theory the biggest spring on the car is the flex of the chassis) so now how do I know that my bite has not changed? Also with all these steel left rear birdcages what are people doing to get the left side weight back down to a reasonable percentage without getting the overall weight to a high amount?

[Kromulous]

Good point, i think that is why CBR was putting new cars on a shaker and simulating 6 races. The mounting points will change from new i would imagine. Affecting all sorts of measurements.

[billetbirdcage]

So let me put this theory into play. I scale the car and give my center to center measurements to my shock guy. Now by theory I do not have to put my car back on the scales the rest of the year. So now I go and run it and my chassis flexes (because by theory the biggest spring on the car is the flex of the chassis) so now how do I know that my bite has not changed? Also with all these steel left rear birdcages what are people doing to get the left side weight back down to a reasonable percentage without getting the overall weight to a high amount?

You will change the LR bite if you:

1. Change stagger
2. Change stagger on front
3. Move a single bar on car, because most brackets on the LR are not at the right hieght.
4. Add or subtract fuel
5. You get the idea.....

That being said: If the car is moving around/flexing that much, then you have other problems. But putting on scales once in a while with a set of scale tires and everything the same will help you find issues for sure.

However you can just check the pin to pin measurements with the car on the ground (obviously everything has to be the same and on a level or same surface it was all set at. But if something is off then the pin to pin will be off with the correct smash numbers. Meaning if 17.5" on RF is the ride hieght with the smashed coilover on the car, then if it's off or any other corner of the car is off, then you have a problem or something bent.

As far as heavy LR components everyone is gonna be different but years ago when I started doing it, we measured the difference in left %. Meaning if I was 54.5% left and added 40# to LR axle, then the new % was 55.1%. At first we did not lower the %, because the car still see's the 54.5% left as dynamic roll. Some will lower the % and some won't, it's what works for you mostly.

[MasterSbilt_Racer]

While we are talking about theory. I am having a hard time wrapping my head around the fact that I can give my shock guy my shocks and he can smash them and give them back to me and I can go racing without ever putting my car on scales. Wouldn't there be a difference if one of my drivers is 225 lbs. and the other one is 165 lbs.? I am just having a hard time understanding how this is possible. Please help with the theory.

You cant fix left side percent no matter how much you twist on the shocks. The driver difference has to be adjusted with weight placement.

[MasterSbilt_Racer]

So let me put this theory into play. I scale the car and give my center to center measurements to my shock guy. Now by theory I do not have to put my car back on the scales the rest of the year. So now I go and run it and my chassis flexes (because by theory the biggest spring on the car is the flex of the chassis) so now how do I know that my bite has not changed? Also with all these steel left rear birdcages what are people doing to get the left side weight back down to a reasonable percentage without getting the overall weight to a high amount?

Some sanctions increased minimum weight by 50# since learning of the heavy lr trend.

[95shaw]

Was reading the bump steer guage post, and had a related question

Dou you set toe with the rf on the bumpstop? And lf on tether?

[Austin34471]

Was reading the bump steer guage post, and had a related question

Dou you set toe with the rf on the bumpstop? And lf on tether?

Do you race with the car there or at ride height?

[95shaw]

Do you race with the car there or at ride height?

So, can we say the need to check bump steer is effectively eliminated, as long as toe is optimized, on the bump, and near tether?

Maybe offer some insight on benefits of bump steer guage with this setup.

[billetbirdcage]

Lets say a few thing for the sake of discussion:

So if you set toe at .5" out statically like most measure it, then it is what it is at the dymanic. Lets say that this is at the ideal toe out of .75" (making up a number). Does it really matter whether which way you measure it, it's still at the ideal .75" toe out.

How much toe out is perfect? lets just say it's .75". What is or how much does the toe change when you steer? Is it still .75"? How much Ackerman the car has will effect how much this changes.

No matter how you measure it, it's a reference point. Sure knowing the dynamic toe out can be useful if you going to alter stuff to have a different toe's between static and dynamic and anything in between that the car see's. However if your just adjusting the toe without altering anything else that changes the toe curve or Akerman then you can just adjust the toe what ever amount you want from either state and see if it helps the car. But doing it from static is a hell of a lot easier.

Using my first paragraph dimensions which are the exact same thing just measured different ways and both will measure the same in the other state, so what did you gain by making it harder to measure by going to the dynamic state after you did it once just to know that number?

.5" out static wheels straight
.75" out dynamic wheels straight

if you alter either states measurement a 1/4" more out you still end up with this:

.75 static
1.0" dynamic

[Austin34471]

Lets say a few thing for the sake of discussion:

So if you set toe at .5" out statically like most measure it, then it is what it is at the dymanic. Lets say that this is at the ideal toe out of .75" (making up a number). Does it really matter whether which way you measure it, it's still at the ideal .75" toe out.

How much toe out is perfect? lets just say it's .75". What is or how much does the toe change when you steer? Is it still .75"? How much Ackerman the car has will effect how much this changes.

No matter how you measure it, it's a reference point. Sure knowing the dynamic toe out can be useful if you going to alter stuff to have a different toe's between static and dynamic and anything in between that the car see's. However if your just adjusting the toe without altering anything else that changes the toe curve or Akerman then you can just adjust the toe what ever amount you want from either state and see if it helps the car. But doing it from static is a hell of a lot easier.

Using my first paragraph dimensions which are the exact same thing just measured different ways and both will measure the same in the other state, so what did you gain by making it harder to measure by going to the dynamic state after you did it once just to know that number?

.5" out static wheels straight
.75" out dynamic wheels straight

if you alter either states measurement a 1/4" more out you still end up with this:

.75 static
1.0" dynamic

Agreed. As long as you know both static and dynamic at some point for reference. Another fun thing to think about is.. put say 700# on the RF wheel and turn it 20deg. Put say 200# on the LF and turn it 20 deg. (Weights replicating how much weight is on each corner on corner entry). Where are both of the contact patches actually pointed? 🤔 Some road course cars run anti Ackerman because the outside tires contact patch turns at such a delayed rate compared to the inside/less weighted tire.. and their tires are much less floppy than ours

[95shaw]

Agree with both above posts.

My point was , as long as the ideal toe is achieved dynamically, bump steer becomes largely irrelevant.
Provided the front suspension stays on the bump and tether.