Revival discussion

[Jking24]

Man this section is dying. Their used to be alot of good conversation in here and some very smart people. I feel like many are still here their just tired of bickering with the keyboard warriors. So I'm gonna try a new thread. Has anyone in here built or had access to and experience with any type of pull down fixture. If so what do you feel were the biggest take aways from examining the car in attitude ? Having been through it what are some keys things you would recommend doing if given the opportunity? Do you feel it actually helped your program ? What would you recommend based on your actual experiences to someone who is building one ?

[Jking24]

Man this section is dying. Their used to be alot of good conversation in here and some very smart people. I feel like many are still here their just tired of bickering with the keyboard warriors. So I'm gonna try a new thread. Has anyone in here built or had access to and experience with any type of pull down fixture. If so what do you feel were the biggest take aways from examining the car in attitude ? Having been through it what are some keys things you would recommend doing if given the opportunity? Do you feel it actually helped your program ? What would you recommend based on your actual experiences to someone who is building one ?

Ok since 45 people have looked at this post and not one reply. Either nobody likes me lol or theirs low too minimal experience on the subject matter. So ill shift it a little. Has anyone made up some "dynaimic" ride sticks or spring and shock set to attempt to examine the car in a simulated dynamic state? Particularly Camber caster toe etc... Or even just dumped the rf. If so what did you learn or notice ? Was their anything surprising ? Someone has to have some experiences

[LRtireCHANGER]

Jking24, I saw your post this morning. I drive a petroleum delivery semi all day, and I hate posting stuff while I am using my phone. I have working man sausage fingers, and I can't see up close anymore. I love this board, and I feel that this board is dead. My new project is helping a guy with a 2012 Barry Wright, he/we is gonna run it at the local dirt track in the CRUSA weekly series. We bought the car in November, and we have removed the body and engine, and we painted the frame 2 weeks ago. The engine is about ready to go back in, and I am about to start pulling measurements on rf travel. I have never ran CRUSA weekly late models, and last week I sent an email to the technical director of CRUSA, and I asked him 3 questions. The questions were: 1a. Are bump stops allowed? 1b. What corners of the car are they allowed on?

2. Are stacked springs allowed? His response was: You can run stacked springs and as mini bump stops as you want only in 604 late modols

I have been told by others that bump stops are only legal on the rf.......His response is not very coherent to me. I am and edumacated truck driver, but me no understand. I have read the 2026 rules, and the rules do not mention stacked springs at all, nor do they mention bump stops or bump springs.

[billetbirdcage]

LRtireCHANGER unless something has changed you are allowed to run stack springs and bumps anywhere you like.

[billetbirdcage]

Jking24 I been planning a writing a responsebut to give a decent one will take more time then I currently have at the moment. Long story short how much you gain or learn is gonna boil down to level you're at and the level of the team and if your doing development work. My opinion is generally speaking for most people it is going to be a waste of money to either build one or take a car to rig more then once a year (again unless you're doing development work or have a non up to date car or one with little development work done on them.

[Jking24]

One more try to get some meaningful discussion going. I get that not that many people have been on or built any sorta pull down fixture so let's bring it down a few notches to good ol fashion shop time. Let's talk about total toe out. Basically static toe +bump steer. Bump steer settings aswell as toe settings seem to be all over the place these days. Not having much experience with other chassis brands im left to guess our assume that most manufacturers land around the same total toe out at full attitude. They all just have different theories on the best way to get their. With that being said what are people running for total toe ? What's to much ? What isn't enough. Why do you think this ? I have a funny story about a conversation between two pretty well known guys in the industry several years ago. Im not gonna waste my time typing it out though unless theirs some decent engagement.

[billetbirdcage]

Let’s start with stating some basic general guidelines of a current LM:

1. Operating range of front suspension travels a typical LM will see on the track is approximately as follows:

The LF will typically be in a range of 1.5” of compression and 2” of rebound from ride height (again can be less or more but as a general rule that’s somewhat close). The RF once down will typically stay within an inch and half of max travel, the more grip a track has and the more power the engine has the more it will pull the RF up before the next corner. This means a crate car may only come is as little as 3/8” from max travel at turn in from turn 1 to turn in at turn 3, while an open engine under the right conditions can almost instantly pull the RF up 1.5 when they stab the gas. (These numbers are shock travels NOT wheel travel).

2. Wheel travel vs shock travel: Every car is somewhat different and can be fairly linear or very non linear in ratio. This can easily be 1” of wheel travel or ½” of shock travel, so when checking bumpsteer most bump plates have around 6” or 7” of travel on the plates (typically marked with 3, 2, 1, 0, 1, 2, 3). So if you start at ride height at the very top of the plate and run thru the full travel available on the plate, you are likely only getting to 3.0” to 3.5” of actual shock travel. This is closer to the highest the RF typically works in so you aren’t checking the bump in the range the RF sees on the track. Also if you check bump in that 0 to 3” range and it’s really close to zero bump, the part you’re missing is (typically with a short upper with a lot of angle) that beyond 3 to 3.5” the RF will start toeing out at a fast rate (like .200 per ½” of shock travel). NOTE: keep in mind this is with the wheels straight ahead.

A. It’s extremely difficult to actually get the RF bumpsteer close to zero over the full travel of 4.5” to 5” from ride height. You will either have to have the RF toe in from 0 to 3.5 and let it come back out to 4.5 and still be more toed out then it was from ride. Or you stay close to zero from 0 to 3.5 and let it toe out a bunch by 4.5”.

B. Typically these days the general idea is to keep bump close between the range it sees on the track (3.0 to 5.0) and not worry about the static toe. You adjust the toe so it what you want at the dynamic state.

3. Now you get to the real problem, Toe change when steering. Setting all the static and bump toe changes aside, what the front end does under steering conditions is going to have a large effect on how much dynamic toe you run when wheels are straight a head.

A. I’ve seen one front end that when set to ½” toe out in dynamic attitude (RF at -4.5” and LF at +1.5”) with wheels straight and turn the wheels 15 to 20 degrees right and it toe goes from the ½” OUT to ¾” toed IN. This is likely why they recommend 2” of toe out static at ride height.

4. The next question should be, where are the wheels pointed on average and do we actually ever turn left? Keep in mind that will rollsteer and the car dog tracking crocked that the wheels are typically pointed 5 to 7 degrees right from dead straight just to go straight with the car hiked up, HMMM

[doyle hargraves]

I had a conversation with Cj Rayburn about toe many years ago. He told me to set the static toe at 1 inch and I thought that was quite the jump from the old school 3/8 that was used many years ago. He told me to think about the actual difference in the contact patch of the tire instead of where we measure it at. 1 inch seemed more reasonable

[doyle hargraves]

I have been noticing that on the newer cars the anti dive is way different on the left front. I have a rocket xr1.2 and the left front upper arm is pretty much level front to back. Also noticed on the longhorns that it looks to be running down hill to the front. What are they doing here ?

[doyle hargraves]

Another question I have is that why didn’t the reverse right front strut deal work out ? I noticed that a few years ago longhorns were set up to be run either forward or reverse strut but every one I looked at was being run forward. I also see capital has went back to forward strut. I realize the forward mounting point probably has more travel at I given suspension movement but not sure how this affects the geometry of the suspension through its travel

[Jking24]

Let’s start with stating some basic general guidelines of a current LM:

1. Operating range of front suspension travels a typical LM will see on the track is approximately as follows:

The LF will typically be in a range of 1.5” of compression and 2” of rebound from ride height (again can be less or more but as a general rule that’s somewhat close). The RF once down will typically stay within an inch and half of max travel, the more grip a track has and the more power the engine has the more it will pull the RF up before the next corner. This means a crate car may only come is as little as 3/8” from max travel at turn in from turn 1 to turn in at turn 3, while an open engine under the right conditions can almost instantly pull the RF up 1.5 when they stab the gas. (These numbers are shock travels NOT wheel travel).

2. Wheel travel vs shock travel: Every car is somewhat different and can be fairly linear or very non linear in ratio. This can easily be 1” of wheel travel or ½” of shock travel, so when checking bumpsteer most bump plates have around 6” or 7” of travel on the plates (typically marked with 3, 2, 1, 0, 1, 2, 3). So if you start at ride height at the very top of the plate and run thru the full travel available on the plate, you are likely only getting to 3.0” to 3.5” of actual shock travel. This is closer to the highest the RF typically works in so you aren’t checking the bump in the range the RF sees on the track. Also if you check bump in that 0 to 3” range and it’s really close to zero bump, the part you’re missing is (typically with a short upper with a lot of angle) that beyond 3 to 3.5” the RF will start toeing out at a fast rate (like .200 per ½” of shock travel). NOTE: keep in mind this is with the wheels straight ahead.

A. It’s extremely difficult to actually get the RF bumpsteer close to zero over the full travel of 4.5” to 5” from ride height. You will either have to have the RF toe in from 0 to 3.5 and let it come back out to 4.5 and still be more toed out then it was from ride. Or you stay close to zero from 0 to 3.5 and let it toe out a bunch by 4.5”.

B. Typically these days the general idea is to keep bump close between the range it sees on the track (3.0 to 5.0) and not worry about the static toe. You adjust the toe so it what you want at the dynamic state.

3. Now you get to the real problem, Toe change when steering. Setting all the static and bump toe changes aside, what the front end does under steering conditions is going to have a large effect on how much dynamic toe you run when wheels are straight a head.

A. I’ve seen one front end that when set to ½” toe out in dynamic attitude (RF at -4.5” and LF at +1.5”) with wheels straight and turn the wheels 15 to 20 degrees right and it toe goes from the ½” OUT to ¾” toed IN. This is likely why they recommend 2” of toe out static at ride height.

4. The next question should be, where are the wheels pointed on average and do we actually ever turn left? Keep in mind that will rollsteer and the car dog tracking crocked that the wheels are typically pointed 5 to 7 degrees right from dead straight just to go straight with the car hiked up, HMMM

Good info and thorough response as always billet. I have also seen the results you referenced about dramatic toe change during steering change. I guess that's the double edge sword of aggressive or at least considerably different Ackerman from left to right. I honestly never gave it much thought until seeing this. We/ i always think about the effects of Ackerman specificaly shortening/ changing the lf steering arm to help the car turn in. But as with Everything and possibly more important in this instance it has a opposite effect when back steering. Im also glad to see you mention the bump steer challenges. Despite the fact that we don't race their the old school racer in me has had alot of trouble with that. It was beat into my head for years that in regards to toe and bump the hard rule above Everthing else is "never in" lol.

[billetbirdcage]

Another question I have is that why didn’t the reverse right front strut deal work out ? I noticed that a few years ago longhorns were set up to be run either forward or reverse strut but every one I looked at was being run forward. I also see capital has went back to forward strut. I realize the forward mounting point probably has more travel at I given suspension movement but not sure how this affects the geometry of the suspension through its travel

If you're looking from the top of the car, the rear strut should be inline with the bolt for the lower arm at the crossmember. Meaning if you stuck a long rod thru it instead of a bolt it should line up with the strut's rodend. This puts the mount almost into the oil pan so many of the car with reverse struts end up with the strut too far right which causes caster gain under compression.

Next issue is the rear strut ends up hitting the tire when turned right so you end up with an S shape to it to make it clear and its weak.

[billetbirdcage]

I have been noticing that on the newer cars the anti dive is way different on the left front. I have a rocket xr1.2 and the left front upper arm is pretty much level front to back. Also noticed on the longhorns that it looks to be running down hill to the front. What are they doing here ?

Even with a fair amount of angle in the upper arm mounts, many cars still have PRO DIVE not anti dive due to the lower front strut raised a bunch to keep it out of the ground. Remember anti/pro dive is the difference between the upper and lower, so if the lower has 10 degrees to it and the upper has the old standardish of 5* then it has PRO dive.

[billetbirdcage]

Good info and thorough response as always billet. I have also seen the results you referenced about dramatic toe change during steering change. I guess that's the double edge sword of aggressive or at least considerably different Ackerman from left to right. I honestly never gave it much thought until seeing this. We/ i always think about the effects of Ackerman specificaly shortening/ changing the lf steering arm to help the car turn in. But as with Everything and possibly more important in this instance it has a opposite effect when back steering. Im also glad to see you mention the bump steer challenges. Despite the fact that we don't race their the old school racer in me has had alot of trouble with that. It was beat into my head for years that in regards to toe and bump the hard rule above Everthing else is "never in" lol.

This is where a pull down rig can be handy IMO, since most can measure toe during dynamic movement. Why I said depends on what your doing, but I find most of the other info from one is not very accurate on load numbers at the wheels especially the left side numbers and with the torque arm activated. If you ever seen those numbers you'll know what I mean.

You can do the front end stuff without a pull down rig, it just take more time and a little ingenuity to get accurate numbers.

[Jking24]

This is where a pull down rig can be handy IMO, since most can measure toe during dynamic movement. Why I said depends on what your doing, but I find most of the other info from one is not very accurate on load numbers at the wheels especially the left side numbers and with the torque arm activated. If you ever seen those numbers you'll know what I mean.

You can do the front end stuff without a pull down rig, it just take more time and a little ingenuity to get accurate numbers.

It's the front end stuff aswell as wheel base and rear steer that I'm most interested in. I have a set of ride height sticks that simulate dynamic travel. I don't have any data info to support my center to centers their basically an educated guess but my thought process is even if their not exactly correct they give me a consiistent point to guage from and adjust accordingly. Do you have any advice or information and recommendations on rear travel numbers similar to what you gave on front travel numbers. Kinda a what and where particular travel numbers are at given points on the track.