At track chassis tuning guides

[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.