At track chassis tuning guides

[joedoozer]

I have a feeling that this thread might get out of hand......but here goes, lol.

I am still learning the workings of the 4 link. Finally getting the handle on a good base line to take to the track. I have had a pretty good track record of adjusting the car to changing track conditions. I have 2 "cheat sheets" I use to decide what to change on the car, I don't have the confidence to make a change without confirming it at this point lol.

This one
http://www.larryshaw.com/printablesetupsheet.pdf

and this one (kind of big)
http://www.afabcorp.com/exp/files/resourcesmodule/@random440610d5778ca/1168265974_circle_tuning.pdf

For the most part I use the Afco one, but I like the format of the Shaw one, it's easier to look through and compare changes. But there are differences in both guides. Wedge for example and LLB too. Is the Afco guide more accurate? Should I stop referring to the Shaw one?

On another note. I am just bouncing ideas around in my head here. Generally speaking increased bar angles means increased load to that tire. On Left Side bars the increased angle increases the load on the LR, and also roll steers the LR forward. Is it safe to assume the forward drive added to the LR out weighs the added roll steer? I have made a LUB adjustment before to tighten the car on exit before. That means more load to the LR. And the added roll steer wasn't enough to cause a loose condition.

I keep notes on how the adjustments effect the car. But I like having the guide to turn to when I need it. I am just wondering what one is correct and what one should I take out of my book.

[joedoozer]

Raising the LLB on the frame would add more roll steer than the upper bar, because it's shorter. That would loosen the car. Maybe I answered one of my questions myself haha.

[MasterSbilt_Racer]

Raising the LLB on the frame would add more roll steer than the upper bar, because it's shorter. That would loosen the car. Maybe I answered one of my questions myself haha.

The effect to the spring rate is the bigger deal here. It effectively stiffens a spring behind.

[MasterSbilt_Racer]

None of these guides can always be right. Style of track, style of driver, car's attitude before adjustment, and many other variables come into play. You really have to understand vehicle dynamics to get it right most of the time. I say most, because sometimes a change may cause the car to take an entirely different attitude than expected and you will then be wrong.

[joedoozer]

The effect to the spring rate is the bigger deal here. It effectively stiffens a spring behind.

I thought the more the B/C indexed the more it effectively stiffens the spring. I can't seem to picture a bottom bar doing that if you raised it on the chassis. Not if the spring is behind. Maybe I am seeing it wrong in my head.

[MasterSbilt_Racer]

I thought the more the B/C indexed the more it effectively stiffens the spring. I can't seem to picture a bottom bar doing that if you raised it on the chassis. Not if the spring is behind. Maybe I am seeing it wrong in my head.

When you compress the lr below ride height, a more-angled lr lower will cause the birdcage to rotate more counter-clockwise. This loads the spring more for a given wheel movement. This means the wheel rate will be stiffer.

[MasterSbilt_Racer]

Or if you look at the lr during droop travel, it causes the birdcage to rotate more clockwise. This unloads the rear spring faster. A spring that unloads quickly during a small amount of travel is stiffer than one that takes a lot of movement to unload.

[joedoozer]

When you compress the lr below ride height, a more-angled lr lower will cause the birdcage to rotate more counter-clockwise. This loads the spring more for a given wheel movement. This means the wheel rate will be stiffer.

hmmm going to have to think about this somemore.

[TALON75]

doozie- never forget K.I.S.S. ! I make bar adjustments based on a simple concept that the lower bars=steer bars, upper bars=drive bars. If you need more steer raise either lower bar(conditions will sometimes determine which side it should be), if you need more drive raise the bar on which side you need to drive more, reading tires really helps to determine this, BUT... gotta also understand what the driver is doing to the car, ie. sliding too sideways on entry, spinning them on exit,ect. Also I believe the Shaw guide is all you really need at the track, simple basic ideas for quickly tuning the car, the Afco one is for studying during the week to better understand the complete package of how the car needs to work, but a bit complicated for quick reference . Good Luck !

[joedoozer]

doozie- never forget K.I.S.S. ! I make bar adjustments based on a simple concept that the lower bars=steer bars, upper bars=drive bars. If you need more steer raise either lower bar(conditions will sometimes determine which side it should be), if you need more drive raise the bar on which side you need to drive more, reading tires really helps to determine this, BUT... gotta also understand what the driver is doing to the car, ie. sliding too sideways on entry, spinning them on exit,ect. Also I believe the Shaw guide is all you really need at the track, simple basic ideas for quickly tuning the car, the Afco one is for studying during the week to better understand the complete package of how the car needs to work, but a bit complicated for quick reference . Good Luck !

My main concern was the differences between the 2 guides. Afco says decreasing bite will loosen the car, Shaw says that will tighten entry. Is it because Afco lists it under the "on throttle" sections, and Shaw is assuming you are off throttle on corner entry?

[MasterSbilt_Racer]

My main concern was the differences between the 2 guides. Afco says decreasing bite will loosen the car, Shaw says that will tighten entry. Is it because Afco lists it under the "on throttle" sections, and Shaw is assuming you are off throttle on corner entry?

That is correct. Talon's assertations are also okay as long as you are talking about a traditional setup with lr behind on floater and rr ahead on floater. You wil usually get the correct answer, but sometimes for the wrong reasons. The reason raising the lower and raising the upper are different is because of what they do to the spring rate. They effect the thrust angles the same.

[joedoozer]

That is correct. Talon's assertations are also okay as long as you are talking about a traditional setup with lr behind on floater and rr ahead on floater. You wil usually get the correct answer, but sometimes for the wrong reasons. The reason raising the lower and raising the upper are different is because of what they do to the spring rate. They effect the thrust angles the same.

Traditional set ups right now. Nothing clamped, stacked or bumped. Good to know that the Shaw guide assumes you are off throttle on corner entry. I think that clears up any confusion in the 2 guides.

[sj valley dave]

We learned that after dealing with corner entry! After a few conversations with Skip Arp and Joe Garrison we finally got it figured out that bite and corner entry totally depended if we were on throttle or off throttle...Now the driver is getting in more in an "on throttle" deal so we can adjust accordingly..We are on a traditional setup also, so like Talon posted, bottom bars are "steering" upper bars are "drive" ...

[jedclampit]

One to make you boys think.....use your guides, wisely!
OK, you have a car that is up all the way on bars thru mid corner and off , all lr travel/drop is used, will raising the lr upper bar @ frame make the car tighter or looser off corner,with same drop? Why?
MBR save your reply for later!

[drtrkr244]

One to make you boys think.....use your guides, wisely!
OK, you have a car that is up all the way on bars thru mid corner and off , all lr travel/drop is used, will raising the lr upper bar @ frame make the car tighter or looser off corner,with same drop? Why?
MBR save your reply for later!

Every car that I have worked on inc, Mastersbilt, Rockets, Warriors, Snow Bros., raising the LUB always increased forward bite.

Put your car on scales , raise LUB, and look at the change, and thats in a static state!

[sj valley dave]

We have raced our DLM on pavement and even when we chained down the LR to keep rear steer out, which you do not want on pavement to the degree we do on clay, when we added LUB angle we increased the drive off the LR tire...

[MasterSbilt_Racer]

One to make you boys think.....use your guides, wisely!
OK, you have a car that is up all the way on bars thru mid corner and off , all lr travel/drop is used, will raising the lr upper bar @ frame make the car tighter or looser off corner,with same drop? Why?
MBR save your reply for later!

I will stay out. I see where you are going with this. But I am not sure it would come into play unless I was helping Don O'Neal.

[TALON75]

I say tighter, you are increasing drive angle on the lr even if the drop is staying the same that will increase load on the lr . You will also index more into the spring, but you said it is always on the bars so at that point the spring has little to no effect( at least on the one I work on!) , you also do get a little steer out of it but not as much as raising the lower that is why I say the lowers are for steer and the uppers are for drive, they both do both jobs really but with different affects .

[jason29a]

The Afco guide is written by Mark Bush... And it really gets in to detail. But he will tell you that when adjusting your car you have to think of when, where, and what. On the throttle and off the throttle and braking are two differnent things. LRU bar angle will increase loose roll steer and may require an extra adjustment to counter act it. But your on the right track with your thinking. No matter what adjustment you are making always think of what its doing to the car at the tires and how its affecting the contact patch.

PS... Kevin Shaw and Mark Bush are thinking alike, there just explaining different

[jedclampit]

Handling will be looser, more steer no increase in drive angle. Very useful on fast, momentum tracks.
Increased angle will help get/keep car up, but once up against limiter, more angle adds steer, therefore looser handling.

[MasterSbilt_Racer]

Handling will be looser, more steer no increase in drive angle. Very useful on fast, momentum tracks.
Increased angle will help get/keep car up, but once up against limiter, more angle adds steer, therefore looser handling.

Yep. Once you have reached the limiter device, the upward force in the bars equals the downward force on the chain. The bars only add thrust downforce while lifting the chassis. After that, it is only about the dynamic ride height and accelerations (lateral and fore to aft) acting on the chassis.

[drtrkr244]

Yep. Once you have reached the limiter device, the upward force in the bars equals the downward force on the chain. The bars only add thrust downforce while lifting the chassis. After that, it is only about the dynamic ride height and accelerations (lateral and fore to aft) acting on the chassis.

I respectfully disagree due to the fact, that once the limiting device is maxxed out, the rearend cannot move any farther forward. Thus, the thrust of the left rear is increased. Also, every dlm ive worked on, the limiting device is always maxxed out on acceleration. If that is the case, then every dlm lub adjustment and every adj. guide would be wrong. Maybe it is your particular track condition that is causing this.

[sj valley dave]

Don't forget that you can also lower the LLB to the bottom hole and if you work through a mock up that will show how it will help kill the excess rear steer that having the LUB up high on the chassis will cause...

[MasterSbilt_Racer]

I respectfully disagree due to the fact, that once the limiting device is maxxed out, the rearend cannot move any farther forward. Thus, the thrust of the left rear is increased. Also, every dlm ive worked on, the limiting device is always maxxed out on acceleration. If that is the case, then every dlm lub adjustment and every adj. guide would be wrong. Maybe it is your particular track condition that is causing this.

The chain is almost NEVER maxed out at the point the driver applies the throttle. That is why the chassis raises when the driver gets in the gas.

Typically, the limiter is tight once the car is going in a straight line.

The fact the rear is not moving is proof positive that the forces balance out. When forces don't balance out on an object, it moves.

Jed's example is not typical for average saturday night hacks, but he is correct when the situation arises.

It is an example of why tuning guides cannot always be right now matter how hard they try to cover every scenario. The AFCO guide correctly leaves out the lr spring when discussing tightening exit handling. This is because an extreme stop and go track and a momentum track will yield different results when you stiffen the lr spring.

[drtrkr244]

The chain is almost NEVER maxed out at the point the driver applies the throttle. That is why the chassis raises when the driver gets in the gas.

Typically, the limiter is tight once the car is going in a straight line.

The fact the rear is not moving is proof positive that the forces balance out. When forces don't balance out on an object, it moves.

Jed's example is not typical for average saturday night hacks, but he is correct when the situation arises.

It is an example of why tuning guides cannot always be right now matter how hard they try to cover every scenario. The AFCO guide correctly leaves out the lr spring when discussing tightening exit handling. This is because an extreme stop and go track and a momentum track will yield different results when you stiffen the lr spring.




Maybe, we're talking about something different. The dlm's at the tracks i go to are full throttle at the apex or shortly thereafter.The rearend is not moving forward and the body is not lifting ie., the chain must be tight. I know a driver who wins his fair share of races who adjusts the chain length to increase forward bite.

[MasterSbilt_Racer]

Maybe, we're talking about something different. The dlm's at the tracks i go to are full throttle at the apex or shortly thereafter.The rearend is not moving forward and the body is not lifting ie., the chain must be tight. I know a driver who wins his fair share of races who adjusts the chain length to increase forward bite.

Adjusting the chain will effect the lr drive coming off the corner. I didn't say it wouldn't.

Jed is also correct that keeping the chain the same and increasing the bar angle will give you more steer when the chain is tight.

[drtrkr244]

Adjusting the chain will effect the lr drive coming off the corner. I didn't say it wouldn't.

Jed is also correct that keeping the chain the same and increasing the bar angle will give you more steer when the chain is tight.

Yes, i agree that u will get more roll steer.

But its been my experience that the increase in bar angle gave more drive, not less.

[MasterSbilt_Racer]

Yes, i agree that u will get more roll steer.

But its been my experience that the increase in bar angle gave more drive, not less.

Depends on car's attitude when the gas is applied. Most cars are not at full extension when the driver gases up. Even if it looks like it is.

[jedclampit]

My point was when you get enuff drive angle to max out the lr travel adding more will loosen the car with increased angle in left upper bar for a set drop.
No doubt, more angle will still get you there faster and keep you maxed out as long as rear tires have traction and chassis has roll.

[jason29a]

This is simple really.... More angle equals more drive. It also equals more loose roll steer. Its a balance between the two. Sometimes you have to cournter with another adjustment to acheive your balance.

[MasterSbilt_Racer]

This is simple really.... More angle equals more drive. It also equals more loose roll steer. Its a balance between the two. Sometimes you have to cournter with another adjustment to acheive your balance.

Well...

That is somewhat safe thinking, but not correct. It is more drive until you reach maximum lift. When you reach maximum lift makes all the difference. Once you reach a limiting device, the sum of all forces acting on the axle tube equal zero. The bars are pushing down as much as the undersling bar, chain, shock, whatever, is lifting the wheel. I think that best sums up this whole discussion.

[drtrkr244]

This is simple really.... More angle equals more drive. It also equals more loose roll steer. Its a balance between the two. Sometimes you have to cournter with another adjustment to acheive your balance.

AGREE, The balance you're referring to is matching your left rear tire to the track condition.

The only times I've seen the incresed LUB angle not induce more drive is when a too soft of tire was chosen. That is a mistake I see quite often.

[jason29a]

not to be misunderstood as any amount of increased angle.