Overton's rr

[ZERO25]

Its quite a bit lower in dynamic than the others. I talked to two other national LH drivers, they said they see it but cant figure it out!

[MasterSbilt_Racer]

If all you do is lower the rr, car gonna wheelie.

[95shaw]

The real needed information needed is the contact patch pressure at all 4 wheels at a specific dynamic point in question.

Travel needed to provide those weights can be achieved by any number of methods.

Is this actually better because of the method used to achieve this attitude?

[Austin34471]

The real needed information needed is the contact patch pressure at all 4 wheels at a specific dynamic point in question.

Travel needed to provide those weights can be achieved by any number of methods.

Is this actually better because of the method used to achieve this attitude?

This is very very much not how it works. With the tools we have, it impossible to calculate how much weight is on all 4 tires. Maybe Ghopper is getting close to simulating it, but linear shock positions tell you very little about how much weight is on said tire.

[95shaw]

This is very very much not how it works. With the tools we have, it impossible to calculate how much weight is on all 4 tires. Maybe Ghopper is getting close to simulating it, but linear shock positions tell you very little about how much weight is on said tire.

That was my point. There is no way of knowing the weights on the tires by simply looking at the attitude of the car.

Any mix of springs j bar settings, control arm positions, etc, can alter the actual dynamic weight seen by the contact patch.
Trying to equate attitude with some specific handling characteristics is fruitless.

[Austin34471]

That was my point. There is no way of knowing the weights on the tires by simply looking at the attitude of the car.

Any mix of springs j bar settings, control arm positions, etc, can alter the actual dynamic weight seen by the contact patch.
Trying to equate attitude with some specific handling characteristics is fruitless.

I see. I thought you were saying that spring loads at certain positions were representative of how much weight was on the tire. Your last paragraph is spot on.

[billetbirdcage]

This is very very much not how it works. With the tools we have, it impossible to calculate how much weight is on all 4 tires. Maybe Ghopper is getting close to simulating it, but linear shock positions tell you very little about how much weight is on said tire.


Blasphemy

You mean if I increase the droop load on my LR shock at full extention by 200#, I'm not adding 200# more to the LR tire while going around the track?

Hmmm, who would of thunk . . . next your gonna say that LR weight highly varies with the banking of the track too I suppose.

^all sarcasm^

[ZERO25]

Trying to equate attitude with some specific handling characteristics is fruitless.

So you dont agree that Overtons car has more rear aero downforce?

[95shaw]

Trying to equate attitude with some specific handling characteristics is fruitless.

So you dont agree that Overtons car has more rear aero downforce?

I'm saying I can set the rr bars and bury the right quarter panel of the body into the track.

Does that mean there is more aero downforce?
I'm not feeling it

[Ghopper]

Better description: "more body roll, less body pitch compared to other generally fast Longhorn cars."

This helps you look past the narrowly focused discussion about RR components and move on to system level response....that includes the resulting LF response and a few parts in between.

[95shaw]

Better description: "more body roll, less body pitch compared to other generally fast Longhorn cars."

This helps you look past the narrowly focused discussion about RR components and move on to system level response....that includes the resulting LF response and a few parts in between.

I think I understand what you are saying.

I know the RR tire is loaded by not only the RR spring and bars, but also the LR spring and bars, the j bar, and the lift arm. Any aero loads are applied to the contact patch through these routes.
Not knowing if the setup is exactly the same as the other cars, there is no way to know the contact patch pressure on any of the tires.

I realize that geometry changes loading as well, so travel at other corners has a bearing in relation to timing of weight transfer, making the LF important, especially at turn in, which sets up the whole corner.

I cannot see how blindly assessing visual cues can deliver useful data without knowing more of the picture.

[MasterSbilt_Racer]

I think I understand what you are saying.

I know the RR tire is loaded by not only the RR spring and bars, but also the LR spring and bars, the j bar, and the lift arm. Any aero loads are applied to the contact patch through these routes.
Not knowing if the setup is exactly the same as the other cars, there is no way to know the contact patch pressure on any of the tires.

I realize that geometry changes loading as well, so travel at other corners has a bearing in relation to timing of weight transfer, making the LF important, especially at turn in, which sets up the whole corner.

I cannot see how blindly assessing visual cues can deliver useful data without knowing more of the picture.

He's just better articulating what I said with my one sentence earlier in the thread (post2). Looking at the rr is like looking at an average height tree in the forest. It isn't half the story, nor do I think it's even much of the story. The pitch comment is the key to the whole analysis, IMO. I didn't want to go as far as to directly point that out.

[ZERO25]

He's just better articulating what I said with my one sentence earlier in the thread (post2). Looking at the rr is like looking at an average height tree in the forest. It isn't half the story, nor do I think it's even much of the story. The pitch comment is the key to the whole analysis, IMO. I didn't want to go as far as to directly point that out.

Rumley must not have a degree in forestry!

[95shaw]

Rumley's most notorious achievement came before the cars were on bump stops on the rf, and chain limiters on the lr.
As was indicated in a couple posts before, rr height is mostly dictated by chain length and stop rubber spring rate and height.
With both of these at their physical limits the car teeters toward lf or rr.
Lift arm and j bar can affect which of these car teeters toward. CG height and position as well as rr and lf spring rates also have an effect.
I guess we should throw tethers in there as well.

I'm not certain aero plays as much of a factor as some would let on

[MasterSbilt_Racer]

Rumley's most notorious achievement came before the cars were on bump stops on the rf, and chain limiters on the lr.
As was indicated in a couple posts before, rr height is mostly dictated by chain length and stop rubber spring rate and height.
With both of these at their physical limits the car teeters toward lf or rr.
Lift arm and j bar can affect which of these car teeters toward. CG height and position as well as rr and lf spring rates also have an effect.
I guess we should throw tethers in there as well.

I'm not certain aero plays as much of a factor as some would let on

Hold on. Guys been running bumps for like 15 to 20 years, depending on what percentage of the field makes it count.

The car doesn't have to teeter between any two points. Most do teeter lf to rr, however.

[95shaw]

If you can achieve desired wheel weights in dynamic, bumps and limiters are not needed. Might be what Rumley achieved with his "device".
Near as I know, current setups use these as most means to arrive at those desired wheel weights have been outlawed.

Dirt late model racing is headed to a formula type arrangement.

[95shaw]

As a side note, karting is able to reach those dynamic numbers without separate suspensions.
They effectively teeter as well.

[MasterSbilt_Racer]

If you can achieve desired wheel weights in dynamic, bumps and limiters are not needed. Might be what Rumley achieved with his "device".
Near as I know, current setups use these as most means to arrive at those desired wheel weights have been outlawed.

Dirt late model racing is headed to a formula type arrangement.

Modern dlm suspension makes actual suspension function compromises to aid aero attack angle. Due to the fact we have lost every rule the suppressed aero downforce, the strategy is effective. That's where it is like formula.

It's not really about mechanical wheel loading. It's about producing the correct thrust vector from the rear tires at the right time. This means there are plenty of load and alignment combinations that will achieve the same result for the driver.

Rumley device, in short, was acknowledgement that the suspension works in both the compression and rebound directions and only looking at "getting up on the bars" means you may be screwing a lot of other stuff up.

[95shaw]

Please do tell.

How are you achieving torque thrust vectors without mechanically loading the tires?

The tires are the only contact with the track surface.
Mechanical linkages are the only connection between chassis and tires.
Yes, aero surfaces can help aim the chassis around the track. But is intimately connected to track by tires
.
I concede there are various ways to get the car around the track, but can still not see how visual cues give indication of how chassis is working the tires.

[MasterSbilt_Racer]

Please do tell.

How are you achieving torque thrust vectors without mechanically loading the tires?

The tires are the only contact with the track surface.
Mechanical linkages are the only connection between chassis and tires.


I never said tires were not loaded. I said there wasn't one magical set of numbers for the 4 wheels. The alignment of the front and rear axles changes the ideal load division.

I'm also going to say running on a stop, either in compression or rebound, leaves the suspension less able to handle surface irregularities than a suspension that is still working.

I'm also gonna say a car with a lower rr dynamic ride height and the lf off the ground will be beaten by a car with the same rr dynamic ride and the lf still aiding steering, all else being somewhat equal.

[ZERO25]

Since his lf is on the ground, whats your best guess how he's keeping it there?

[MasterSbilt_Racer]

Since his lf is on the ground, whats your best guess how he's keeping it there?

It doesn't share dynamic roll centers with the other cars. You can work on either end of the car, or both to achieve that.

His lf still comes up, just not as bad as it should.

[JustAddDirt]

Since his lf is on the ground, whats your best guess how he's keeping it there?

heavy suspension parts, heavy tie down/limiter.

[95shaw]

More rf travel. Less lr travel.
More left weight. Different spring rates.

Pretty long list of things can change chassis attitude.

[MasterSbilt_Racer]

More rf travel. Less lr travel.
More left weight. Different spring rates.

Pretty long list of things can change chassis attitude.

If speaking in generalities, yes. Ghopper has already narrowed it down.

[ZERO25]

More rf travel. Less lr travel.
More left weight. Different spring rates.

Pretty long list of things can change chassis attitude.

So, how has Overton figured out how to get more rf travel than the other top LH cars?

[MasterSbilt_Racer]

So, how has Overton figured out how to get more rf travel than the other top LH cars?

He hasn't. Getting the rf lower just moves one end of the roll axis lower. You can always move what hits and get more travel, but that's not it.

[ZERO25]

He hasn't. Getting the rf lower just moves one end of the roll axis lower. You can always move what hits and get more travel, but that's not it.

How do you know he hasnt?

[MasterSbilt_Racer]

How do you know he hasnt?

Doesn't look like it me me. If he did, it doesn't explain the way the chassis works.

[Ltemodel]

I'm thinking Overton is looking at ways to get around the droop rule and get more aero angle on the deck.
I think the biggest question on my mind is, did he move his RR bars up to compensate for the difference in push point angle?
The smash loads we are seeing on these smashers are nothing more than we used to adjust on scales except, if done right and we know the finished height the car is running at, we can closely predict the spring load on the tire.
To keep the LF on the ground we can do a bunch of different things.
As far as RF compression now, I think our new stopping point is the rack.
I already saw in Florida, a couple of teams cutting their bumpers back and putting more spring steel holding the RF nose up, only to let it collapse as it hits the ground. This would get us around any RF nose height rule by just letting the RF self adjust to any height it wants.

[crownman25]

well its got to be something that gets softer but thinks its still stiff sooo Thats what you got to figure out....maybe he is running a z link on the rr they use to have that look about them I know weaver use to run a z link on the rr...