Tying up the left front

[paul21]

How much drop do you put in the lf from ride height when you are tying the lf up with a cable? Thanks

[Matt49]

When do you want it to lift off the ground?
Just because the LR is ON the ground doesn't mean it is carrying a load or providing a steering advantage. Chaining/cabling it up isn't going to change anything except when it leaves the ground. It isn't going to hold the LR DOWN.
If you're looking to keep more load on your LF, chaining it to the chassis isn't going to help.
In other words...this isn't why Davenport is winning races.

[King1]

Sure made mine turn in better.

[MasterSbilt_Racer]

I have found it takes a little sidebite away and adds some drive. You will have to experiment to see what you like. I gave gone away from it.

[Dirtmod13]

A chassis builder told me one inch before spring unloads

[JustAddDirt]

When do you want it to lift off the ground?
Just because the LR is ON the ground doesn't mean it is carrying a load or providing a steering advantage. Chaining/cabling it up isn't going to change anything except when it leaves the ground. It isn't going to hold the LR DOWN.
If you're looking to keep more load on your LF, chaining it to the chassis isn't going to help.
In other words...this isn't why Davenport is winning races.


Matt49
have you ever done any work on a pull down rig?
there are advantages to limiting LF down travel, this is all I am at liberty to say.

[7uptruckracer]

We use it on asphalt quite alot it has merit. We just talked to rocket two weeks ago no mention of it call this week and ask them about it, oh yeah yeah buy this, do this and set it to this......

[paul21]

I didn't ask if davenport was doing this. Thanks

[paul21]

I didn't ask if Davenport was doing this. Thanks

[Matt49]

The only way that tying the LR suspension to the chassis will keep the left front wheel from coming off the ground sooner is if there is enough unsprung weight there to change the center of gravity of the entire car and/or prevent additional weight transfer from left to right.
That plays into what MBRacer said about less side bite and more drive. But aren't there a million other ways to do that? Just saying...

And the Davenport comment was a joke so lighten up. It you pay attention you'll see that a lot of recent threads seem to be taking stabs at figuring out what Rumley might be doing so I was having fun with it. Nothing personal.

Anyway, that's my best explanation of how tying the LF to the chassis might "work" but again I think there are better ways to accomplish the desired result without using logging equipment. Namely with shocks and front end geometry.

[JustAddDirt]

The only way that tying the LR suspension to the chassis will keep the left front wheel from coming off the ground sooner is if there is enough unsprung weight there to change the center of gravity of the entire car and/or prevent additional weight transfer from left to right.
That plays into what MBRacer said about less side bite and more drive. But aren't there a million other ways to do that? Just saying...

And the Davenport comment was a joke so lighten up. It you pay attention you'll see that a lot of recent threads seem to be taking stabs at figuring out what Rumley might be doing so I was having fun with it. Nothing personal.

Anyway, that's my best explanation of how tying the LF to the chassis might "work" but again I think there are better ways to accomplish the desired result without using logging equipment. Namely with shocks and front end geometry.

Not trying to start a pissing contest here but...

Do you have any data to support your explanation, or is it just how you believe it might work?
I have seen the data from a pull down rig. There is no denying hard data.
No log chains were harmed in the making of data...lol

[Matt49]

Not trying to start a pissing contest here but...

Do you have any data to support your explanation, or is it just how you believe it might work?
I have seen the data from a pull down rig. There is no denying hard data.
No log chains were harmed in the making of data...lol

No pissing contest here either. I really enjoy these discussions. There are certainly many ways to skin a cat.
That being said...
Does a pull down rig do anything that emulates lateral weight transfer? The answer to this (which is no) is the reason I've never been a fan of pull down rigs for vehicle dynamics analysis. It can help you in evaluating dynamic positioning (camber curves, roll centers, rakes, etc.) but not wheel loading. Emulating car attitude does not emulate wheel loading. It is impossible to emulate lateral forces on a race car with equipment in a shop. This is why data acquisition is coming into our sport. Because it is needed if you want to beat the guy that has the EXACT same car as you.

[Dirtmod13]

Was wondering if pull down rigs could tilt on 2 axis to load rt side and frt or rear then it may get interesting. Then they may be able to figure out the math to show centrifugal wt/gravity,depending on speed, corner circumference, approx wheel load/traction etc to get closer. But that just makes for more homework.

[JustAddDirt]

If you have data acquisition, and know were each of the 4 corners are at any point on the track, along with pull bar and or lift arm positioning, and pinion angle, you can simulate what the car is doing at those positions. then start changing things when the car is at attitude, you can simulate the wheel loading.

[Matt49]

You can get the attitude of the car where ever you think you're going to learn something on a pull down rig. What you can't do is emulate lateral weight transfer. How do you get weight to come OFF of the LR on a pull down rig to simulate corner entry? You don't.
How do you emulate the wheel rate changes that are introduced by anti-squat when the car is accelerating? You don't.
How do you emulate the wheel rate changes that are introduced by anti-dive when braking? You don't.
And perhaps the most fundamental place where a pull down rig fails to provide meaningful data is because the tires aren't rolling. Load at the contact patch is HEAVILY influenced by scrub and that can't be simulated on a pull down rig.

If you want to do some serious testing, something like this is the cream of the crop:
http://www.morsemeasurements.com/

[7uptruckracer]

I think the use a formula to determine lateral load but thats from my asphalt background and i haven't been around a rig in a few years

[#75GILLfan]

With as many wins and the resume JustAddDirt has you will have no arguments here.

[dirtdiggerracing]

Is it possible that they are tying LF up to stop it from having an effect on roll center movement ??

[MasterSbilt_Racer]

Is it possible that they are tying LF up to stop it from having an effect on roll center movement ??

If your LF is off the ground, what point is your front pivoting on?

[billetbirdcage]

When do you want it to lift off the ground?
Just because the LR is ON the ground doesn't mean it is carrying a load or providing a steering advantage. Chaining/cabling it up isn't going to change anything except when it leaves the ground. It isn't going to hold the LR DOWN.
If you're looking to keep more load on your LF, chaining it to the chassis isn't going to help.
In other words...this isn't why Davenport is winning races.

Ain't been on for a while: Did you mean LF on the first 2 "LR"s?

[25drtrkr]

Ain't been on for a while: Did you mean LF on the first 2 "LR"s?

What do ya think, bbc? Im with Matt on this one. The only thing I see is the spring stays more loaded, depending in the length of the cable, and wont catch on the spring cup. Is there something I'm missing?

[billetbirdcage]

What do ya think, bbc? Im with Matt on this one. The only thing I see is the spring stays more loaded, depending in the length of the cable, and wont catch on the spring cup. Is there something I'm missing?

I ain't sure what he said so I was asking? He kept typing LR and think he meant LF. I just wasn't sure what he meant as one post sounded one way and another sounded another and I didn't follow him at all.


However increasing/decreasing LF travel, can have a large effect on the car.

[Matt49]

I ain't sure what he said so I was asking? He kept typing LR and think he meant LF. I just wasn't sure what he meant as one post sounded one way and another sounded another and I didn't follow him at all.


However increasing/decreasing LF travel, can have a large effect on the car.

Two things:
1) I did mean LF on the first two LRs
2) My comment about changing the "center of gravity" was better described/illustrated by MBRacer. Roll center changes a bunch when LF comes off the ground so changing when that happens CAN be important. But again, I think there are better ways to do this and I stand by my comments that a pull down rig cannot simulate lateral load transfer.

[dirtdiggerracing]

It's not off the ground most of the time ? I am no expert I am just wanting to hear opinions! !

[Stede Bonnet]

What about the RR? I've heard guys tie down the RR, how much travel is good? Is it same rule, 1 inch before spring unloads? At ride height? Whats good for RR? I know this thread was started about the LF and I apologize for hijacking, but all this chaining/cabling has me thinking about its advantages, its Pro's & Con's. On the surface when I first heard about the Lf I thought it made no sense, but after reflecting on it, talking with Matt49 and considering everything effected I'm curious...

[JustAddDirt]

What about the RR? I've heard guys tie down the RR, how much travel is good? Is it same rule, 1 inch before spring unloads? At ride height? Whats good for RR? I know this thread was started about the LF and I apologize for hijacking, but all this chaining/cabling has me thinking about its advantages, its Pro's & Con's. On the surface when I first heard about the Lf I thought it made no sense, but after reflecting on it, talking with Matt49 and considering everything effected I'm curious...

Chaining the RR has a large difference on a modified with a pull bar. probably would a lift arm on a late model as well considering it s on the right side bell of the rear end. limiting the RR down travel and how much it would plant the RR under throttle. lets you play with more aggressive upper bar angles without the RR lifting up on the bars.

[Stede Bonnet]

Chaining the RR has a large difference on a modified with a pull bar. probably would a lift arm on a late model as well considering it s on the right side bell of the rear end. limiting the RR down travel and how much it would plant the RR under throttle. lets you play with more aggressive upper bar angles without the RR lifting up on the bars.

Oh yeah that makes sense on the bar angles. Does being on the RR spring help initial sidebite at entry? Like does the car land in the corner steadier with RR chained? Whats a good rule of thumb for limiting RR?

[JustAddDirt]

depending n track conditions I start 1" tight off ride height. RR spring still has tension on it. rough tracks you need to loosen it up or take it off.
the slicker the track gets the more I tighten to tight at ride height.

I also feel it keeps the RR spring tensioned, which certainly helps transition on entry. car does not fall till it hits spring (if spring is not tensioned at end of straightaway)
keeps tension on spring for more consistent corner entry

JMO though the seat of the pants feel.
I run a modified so with a pull bar this is a big deal.

[Stede Bonnet]

depending n track conditions I start 1" tight off ride height. RR spring still has tension on it. rough tracks you need to loosen it up or take it off.
the slicker the track gets the more I tighten to tight at ride height.

I also feel it keeps the RR spring tensioned, which certainly helps transition on entry. car does not fall till it hits spring (if spring is not tensioned at end of straightaway)
keeps tension on spring for more consistent corner entry

JMO though the seat of the pants feel.
I run a modified so with a pull bar this is a big deal.

Cool. No that's perfect I was gonna try it on a Rayburn swing arm w/pull-bar, so apples to apples. Thanks.

[JustAddDirt]

Stede
check your PM's

[Stede Bonnet]

Stede
check your PM's

Thanks! gotcha.