Drag Racing Tech - How does pinion angle affect traction and launch?

2 weeks ago I went racing with a non adjustable torque arm. I was under the car hundereds of times but never actually measured pinion angle.. I could have sworn it was near or at 0.. At least no visible angle..

I cut 1.40 60's stock internals NA.. pulling big air.. shocks 1 all around

2 weekends ago I cut many 1.3 60's all dead hooking.. Even cut a 1.31 60.. All getting mad air.. front shocks at 1 rears at 4. I dead hooked every pass.

So I blew up the torque arm that day.. and with a very VERY big + pinion angle I was still able to hook a low 1.4..

So I put in a new adjustable torque arm.. adjusted it to -2.. Now I cannot hook for crap.. Went last weekend and didn't hook the car once. I spun off the t-brake every single time.

My rear end does not move at all on launch.. Everything is so light and stiff I find it hard to believe the pinion angle really moves so I am thinking about putting it back to 0.

It is real frustrating to have no traction problems with the car ever.. and then put a new torque arm in, adjust it to -2 and all of a sudden not be able to hook the car.

I race on a 28x10.5x15 ET Drag at 13psi hot. I should be hooking!!!

so how does pinion angle affect traction and launch?

kinda wondering myself, im just typing so that if you get a response from brian on this one i can find it quicker :)

my car has a spoohn tq arm i think at about -2 or so the car dead hooks with stock shocks and springs and stuff, but from what ive been told is to keep going negative till the car hooks than go bakc just a bit till it hooks with the least amount of negative pinion angle

Whose arm did you put on the car MAGNUS.??? Does this one mount different than your old one??

Pinion angle on a t/a car is usually set at 2.5 to 3 degrees down. I think the problem on Magnus's car is instant center.

I set the pinion angle with my old combo at -3.5 degrees per Steve Spohn.I hooked really well,mid 1.40's in a heavy stick car.

Hmmm, I have mine set at -1.5, hooked amazing on stock shocks, but then I got hals, and ever since, i've been having issues gettin her to hook up, would the shocks make a diff in where the pinion angle needs to be set? Cuz I did testing when I was on the stock one's, set it at -1, then went to -1.5, then went to -2, from -1 to -1.5, the 60' got better by .04, and from -1.5 to -2, it got worse by .02, so I put her back to -1.5 and have left it there ever since. I heard between negative 1 and negative 2 is where you want it on an auto car, but now i'm not sure, should I try goin more negative when I get the car running again?

I have heard -2 is basically the standard for autos.

I actually need to adjust my pinion angle after TH400 install. anyone have the formula for doing this or the link to that one guys pictorial/instructional?

Ken

If all you changed is the trans then you dont need to reset pinion angle.

Anytime you change a suspension part you have to test until you find the setting the car wants. The best thing to do is go to the track make a pass, then make ONE change. See if it helped or hindered. Then try something else. You might have to make 20 passes to find your combo.

If all you changed is the trans then you dont need to reset pinion angle.

Anytime you change a suspension part you have to test until you find the setting the car wants. The best thing to do is go to the track make a pass, then make ONE change. See if it helped or hindered. Then try something else. You might have to make 20 passes to find your combo.

Yeah, that's what I figured, guess i'm gonna have to get out to bradenton one of these days after I get her back up and running to test everything out, cuz moroso never hooks consistently for me to feel confident that it was the setting that caused the worse 60' and not the track!

come up to bradenton devon, no doubt 1.4s will be yours there.

come up to bradenton devon, no doubt 1.4s will be yours there.

Shit, i'm lookin for 1.3's!!!! I've actually already pulled 1.4's, cut a 1.47 at moroso, was my best 60' ever there!!! And she was initially hooking and then unloading the rear and blowin the tires off, so hopefully that'll be taken care of with the new rear swaybar and lca relocate brackets I got, and maybe i'll even be able to hook some 1.3's at moroso, that would be badass!!! I just gotta get my new motor together, still waitin on parts to come in! :cry: And i'm sure i'll make my way up to bradenton after she's together so I can get the suspension all tuned in!

Whose arm did you put on the car MAGNUS.??? Does this one mount different than your old one??

Pinion angle on a t/a car is usually set at 2.5 to 3 degrees down. I think the problem on Magnus's car is instant center.

I went from the MAC/Jegs torque arm which is non adjustable to the Alston torque arm that is adjustable.

I used the same center style tunnel mount. It has a yoke that sticks out that the torque arm slips over.. I didn't have to change that at all.

I just put on the new torque arm and adjusted it.. The torque arms look identical but the Alston has an extra brace and is adjustable..

I go from dead hooking my car EVERY PASS to not dead hooking the car at ALL.

It feels like with the torque arm set at -2, the front just doesn't want to lift up.. Before, the front end of the car would lift up easily and the car always hooked.

I need the front to lift more. :(

I had the same problem after changing to an adj. torque arm. After It was installed it seemed like my rearend was pushed farther back in the car. I didn't have adjustable lca's at the time so I couldn't verify that was the problem.

How does pinion angle affect how a car hooks at all? it doesn't affect instant center does it? I thought it was set negative so that when the car launches the u joints are more in a straight line to keep them from self destructing? :confused:

How does pinion angle affect how a car hooks at all? it doesn't affect instant center does it? I thought it was set negative so that when the car launches the u joints are more in a straight line to keep them from self destructing? :confused:

Adding pinion angle in excess from O degrees (neg. pinion angle) causes pinion bind and slows the rate of movement of the housing as power hits the tire. Idealy the pinion angle should be set to acheive 0 degree when the car is moving. So, ideal pinion angle would be the angle at rest being the amount of angel needed to bring the angular distance between the drive shaft center line and the center line for the axle pinion to netural angle under power with the car in motion.
A lot of us racers have used pinion bind as a tool to add or remove hook but like any other "bind" it is damaging to parts... a little bind= little damage, big bind = big damage... just part of racing!!

Have you set it back to 0 yet? From what I understand, adjusting it negative is only to counteract the pinion moving during launch? I may be wrong there...but what Maggie wrote makes me think I'm right. Still...simple answer is move it back and see what happens.

I plan on moving it back to 0 and probably just leaving it there.

When my car launches, the rear end does not move at all.. Everything is so siff back there and the car is so light.. Even when I wheelie huge the wheel gap is the same..

I find it hard to believe the pinion angle is changing.

Seems like I lost a couple MPH as well with a -2 pinion angle vs 0.. :(

You said you reused the front mount from the Jegster set up, could that have gotten tweaked when the other TA bent/broke?
Would it be worth putting the Alston front mount on the car and check?

I find it hard to believe the pinion angle is changing.

Seems like I lost a couple MPH as well with a -2 pinion angle vs 0.. :(

That's what I'm saying. The neg. angle is to counter-act counterproductive suspension/weight movement, but your car is stiff and REALLY light. Go back to zero...or buy a Madman TA like you should have in the first place ;)

The jegster mount didn't get tweaked.. I must have spent 10+ hours under the car with the torque arm debackle.. The whole mount looked fine.

Not sure how a madman torque arm would differ than the alston... The alston style is exactly what I want, it bolts to the inside of the upper trans tunnel allowing full clearance for duals and anything else..

oh well.. :(

Are you sure you are adjusting it the right way?

As an example:


My driveshaft points down towards my pinion 2 degrees (-2 degrees). In order for my pinion angle to be 0 (at rest) I would have to point the pinion up 2 degrees to meet the -2 (-2+2=0) degrees of the driveshaft. If I want 0 degrees under load I would have to set the pinion to 0 degrees and as the rear rises 2 degrees under load my pinion angle would return to 0.

John

Not sure I follow ..

My driveshaft and pinion make a V with an angle of 2 degrees.

I guess the theory for most cars is that under load the rear end will move or there may be some give in suspension components which causes the pinion to "twist" upward more making the V into a -- with a 0 degree angle..

Are you sure you are adjusting it the right way?

As an example:


My driveshaft points down towards my pinion 2 degrees (-2 degrees). In order for my pinion angle to be 0 (at rest) it would have to point the pinion up 2 degrees to meet the -2 degrees of the driveshaft. If I want 0 degrees under load I would have to set the pinion to 0 degrees and as the rear rises 2 degrees under load my pinion angle would be 0.

John

Is it ok to have higher numbers? Cuz to get mine to -1.5, the angle on my driveshaft is -3.5 and the angle on my rearend is *edit* (I meant +2).

Aren't we just measing the angle between the driveshaft and the pinion?

Ground reference is not required afaik.

Aren't we just measing the angle between the driveshaft and the pinion?

Ground reference is not required afaik.

All I know is the car is supposed to be on the ground in running position (or on a driveon lift) and then you take the difference between the angle on the driveshaft and the angle on the rear t/a mounting plate or something and you want the number to come out negative and the number on the driveshaft should be bigger than on the rear and set it to whatever negative angle ur lookin for. That's my understanding of how to set it, is that correct? :confused:

Aren't we just measing the angle between the driveshaft and the pinion?

Ground reference is not required afaik.


Correct .

Both of the links below do a good job of explaining the process.

http://www.streetissuecustoms.com/pinionangle.html

http://www.carcraft.com/howto/91758/




:drive:

Rossler trans had a good write up about setting pinion angle and I thought it did not actually measure the DS angle, but the angle that the tailshaft was and the bottom (flat part) of the pinion on the rear end.
And I can see how the trans could be one angle and the DS being a different one since their is a slip yoke and the U-joint on that side along with the U on the pinion side.

In my LT1 A4 car I did the measurement on the front of the DS where it went into the trans and the pinion area and set it at -2 but I think I was lucky,the car didnt make a lot of power and launched softly for some reason....never hit hard....unlike most of you guys.

I use the flat part on the bottom of the rear as my plane for the rear end as well.

I'm just going to set it at 0 and be done with it. I find it hard to believe it moves at all in my car... however, I could be wrong as I am no expert.

madman is the expert here. :) what is istant center???!!! Share your wisdom o wise one.

Magnus are you coming to Atlanta????

Instant center is where the suspension is lifting the front end and planting the rear.

I know that there are alot of different ideas on pinion angle and what it does. The proper way that works for me is disregard the driveshaft AND the ttrans. Measure off the pinion(NOTHING ELSE) and set your pinion angle.

Magnus another possibility is now the car is actually hooking and bogging the motor. Why not trying to add air in the rear tires.

I agree with Mad man 100%, but would like add a little about instant centers.
Instant centers are unseen points in a moving suspension that can be drawn and scaled for blueprinting suspensions. They are called "instant" because they could be anywhere due to the dynamics of the suspension... When the suspension moves the component moves: Thereby, the movement can be plotted.
When we apply instant center to the rear suspension, Instant Center refers to the center of the arc that the rear housing makes as it moves through it's verticle movement, hence, instant center is an effective lifting point...The higher the instant certer the greater the load transfer and harder the car hits the tire.
When the front of the Torque arm is moved, even in very small amounts, the the pinion angle MUST remain the same. If the instant center is changed even a small amount the pinion angle will need adjustment.
The closer the pinion angle is to 0 the better the total efficiency of the combo. Pinion bind uses up power but is sometimes necessary to launch effectively... It is ALL just tools of the racer.

I've always took the difference of the DS angle vs the pinion angle.

My car has always dead hooked. Hell, I even run my shocks @ 6 in the front,7 in
the rear.

Sean, you run a mans tire while I'm still on a girlish 28x10.5x15 ET Drag...

I kinda understand the "theory".. but not enough to make sense of it.

What I do know is this.. My car is now not hooking beacuse its too hard for the front end to come up. I have enough seat time in the car to know what is exactly happening at launch.. and beacuse the front end is very "heavy" the tires just slip a little... Before the front end came up much easier taking some load off of the torque arm and thus shocking the tires a little less..

I'm gonna go back to 0 and just see how that works. The way my torque arm mounts will make my pinion angle the same at any small variance in height in the back..

I set our car up with -3 since it has poly bushings everywhere. If we get some more track time I'd like to mess around with it a little more as the car since we bought it as a roller has only made maybe 20 passes total (only 3-4 were cam-only, never had a chance to tune the setup). Best 60' cam-only was a 1.38 but it did seem the suspension unloaded a little. I 'think' it hits the tires too hard off the line to where it unloads the suspension after the car gets moving though.

If I'm understanding right Instant center can also be controlled by lower control arms if relocated to where there is an upward plane from F-R, and not just torque arm itself?

Well I used to hook a 27x11.5(10" tread) DOT Hoosier to 1.46's consistantly.
I consider myself lucky to never have done much suspension tuning.

set the pinion to zero, drop the tire pressure a 1/4# at a time.
You hooked a 1.37 that day, so you are probably on the ragged edge of traction.

It shouldn't take much to dial it back in.

REMEMBER- SMALL CHANGES!

If I'm understanding right Instant center can also be controlled by lower control arms if relocated to where there is an upward plane from F-R, and not just torque arm itself?

Instant center can be changed or "influenced" by any of the seperate components of (in this case) the rear suspension.
But keep in mind, to fully understand IC, you have to realize that each seperate component of the suspention that moves through an arc has it's own IC.
Think of it this way, If we have a long skinny triangle on it's long side and we anchor the bottom of the short side of the triangle so that it can only move in an arc around its anchor point. Then, if we push on the short side of the triangle it will move the long end of the triangle in a downward arc because the force of motion is above the anchor point. if we move the anchor point up higher on the short side of the triangle so that when we push on the short side a greater amount of force will be applied below the anchor point the long end of the triangle will be pushed up creating "lift".
Now, if we were to put a rod from the rear left connecting point of the lower controll arm to the rear right lower controll arm connecting point and mark a point directly under the torque arm that mark would represent the bottom of the short side of our triangle. The top of the torque arm would represent the top of the short side and the snout of the torque arm would be the long end of our triangle.
Hmm. maybe I better quit before I get everyone really confussed!

if someone can get me dimensions and a sketch of a stock suspension I can draw it up in 3-D using CAD software. I can do motion, although I have never really used it......yet.

Frank :)

Instant center can be changed or "influenced" by any of the seperate components of (in this case) the rear suspension.
But keep in mind, to fully understand IC, you have to realize that each seperate component of the suspention that moves through an arc has it's own IC.
Think of it this way, If we have a long skinny triangle on it's long side and we anchor the bottom of the short side of the triangle so that it can only move in an arc around its anchor point. Then, if we push on the short side of the triangle it will move the long end of the triangle in a downward arc because the force of motion is above the anchor point. if we move the anchor point up higher on the short side of the triangle so that when we push on the short side a greater amount of force will be applied below the anchor point the long end of the triangle will be pushed up creating "lift".
Now, if we were to put a rod from the rear left connecting point of the lower controll arm to the rear right lower controll arm connecting point and mark a point directly under the torque arm that mark would represent the bottom of the short side of our triangle. The top of the torque arm would represent the top of the short side and the snout of the torque arm would be the long end of our triangle.
Hmm. maybe I better quit before I get everyone really confussed!

Too late, i'm already confused as all hell!!! :bang: :(

OK Maggie this is getting fun.What Would moving the front of the t/a up do???

I love this stuff!!!!
Keep it going!

I think I got the jist of the first part, see the pics and let me know if they illustrate what you're refering to. I am assuming something is connected to the lower "short side" of the triangle? Lower torque arm mounting point?

I labeled each edge so that it can be better explained.

Still working on the second part....

This isn't rocket science, guys. What you want is the pinion to be parallel to the crank/trans mainshaft under load. The goal is to have the same angle on the ujoints at the front and the back of the drive shaft. This generally requires a little downward bias on the pinion so that as the rear suspension flexes the pinion becomes parallel to the mainshaft.

Pinion angle won't make you hook better or any such nonsense. It can break parts if incorrect.

Instant center has a major impact on hooking, along with the shocks and springs, and you get much closer to rocket science here. The normal F-Body setup with lower control arms and torque arm fixed at the axle and pivoted at the front is a bit strange. You will not find an example like it in the literature on rear end setups, and I haven't seen it in any suspension software. It does not act like a four link at all. It acts more like the lift bars Ford invented for the Thunderbolts, but those LCAs are a kicker. The angle of the LCA has a much greater impact on the lift/squat characteristic than the torque arm does. The torque arm provides no longitudinal moment to the chassis - only vertical. The LCAs put in a combination of horizontal and vertical that varies with the angle of the LCAs with repsect to the ground. (The pictures I've seen of Madmans TA show it to be different. It is fixed at the front end and does provide longitudinal force input to the chassis, but binds because it is fixed at the rear). I am not convinced that the instant center applies to us (or in what manner it might) since I didn't take the math far enough yet. If it does apply, then the instant center will move forwards as the car squats and rearward as the rear rises. If you try to compute an instant center on a stock F-Body, you would come up with close to infinity, or at least way out in front of the car. Some upward angle on the LCAs would bring that back closer to the car, but it would take maybe 30* upward on the LCAs to bring that "instant center" anywhere near the CG of the chassis. I think 30* would cause the rear end to hop off the ground though.

Back to your regularly scheduled programming ...

So basically, most torque arms lift up, while LCA's can lift forward and up. On the few stock eliminator cars I've seen, they has stock type LCA's in as much as I can visually tell in stock type locations, ie no relocation brackets, but had the 'madman' style torque arm (much lower rear mounts compared to conventional). One more thing I noticed was the rear had mini upper control arms, which tied from the top of the rear axle housing to about the middle of the LCA.

What I'm curious is knowing is if the torque arm setup can bite too hard with the LCA's relocated and what the fix would be for that? (I think I know already) I have the LCA's at the lowest point now, and the car gets wheelie happy no matter what the shocks are set to. I'd like it to push forward more and not as high.

I'm kinda lucky the car has done decent for just throwing a bunch of off-the-shelf parts at it and not knowing exactly why its working.

You guys are getting close keep going.

It seems confusing.I always that it was the v between the driveshaft and the pinion but the of the 2 links,one says rear seal to pinion and the other says the v approach with a rear trans seal/drivetrain as a bonus.I have 1* up on the trans and 1* down on the pinion,so is that -2 degrees or 0? Do I need to have 3 degrees total down on the pinion so that it would be 0 under power? That sounds right...............

Damnit, you guys all confused me, I can't remember my numbers or how I calculated the pinion angle anymore and the car is apart, so I can't even go look!!!! Now i'm gonna have a hard time remembering what's supposed to be done, I used the bmr directions, but now I just read them and am confused, I shouldn't have read this post, hehe!!!! :(

So basically, most torque arms lift up, while LCA's can lift forward and up. Exactly correct. And the ratio of up to forward depends on the angle of the LCA.
On the few stock eliminator cars I've seen, they has stock type LCA's in as much as I can visually tell in stock type locations, ie no relocation brackets, but had the 'madman' style torque arm (much lower rear mounts compared to conventional). Lower or higher mount to the rear end won't make any difference.
One more thing I noticed was the rear had mini upper control arms, which tied from the top of the rear axle housing to about the middle of the LCA. That has the effect of changing the LCA into a very short Thunderbolt style lift bar and would need very stiff rear shocks to keep the car from hopping.


What I'm curious is knowing is if the torque arm setup can bite too hard with the LCA's relocated and what the fix would be for that? (I think I know already) I have the LCA's at the lowest point now, and the car gets wheelie happy no matter what the shocks are set to. I'd like it to push forward more and not as high. Move the rear of the LCAs up a hole or two. That should help.

The other thing to do is to drop the car. Wheelies a pretty simple physics. The center of gravity of the car is above ground level, where the tires react again the earth. Push hard enough there and you overcome the force of gravity pulling down in the CG. If the CG were at ground level (impossible, I know) it would be impossbile to make it wheelie. If the CG was over the axle, it would be impossible to move without a wheelie. The torque of the axle can also contribute, but it's contribution is much less than simple interia until you get into high power/weight ratio vehicles.


I'm kinda lucky the car has done decent for just throwing a bunch of off-the-shelf parts at it and not knowing exactly why its working. Sometimes that happens ;)

It seems confusing.I always that it was the v between the driveshaft and the pinion but the of the 2 links,one says rear seal to pinion and the other says the v approach with a rear trans seal/drivetrain as a bonus.I have 1* up on the trans and 1* down on the pinion,so is that -2 degrees or 0? There is a lot of misinformation floating around on this subject. I recently saw an article where they made the point that the mainshaft and pinion should be parallel under load and ran tests that showed no significant change in ET or short times with pinion angle change. Sorry, I can't remember where it was. Mabye someone else saw it too.
Do I need to have 3 degrees total down on the pinion so that it would be 0 under power? That sounds right............... 3 degrees down compared to what? The mainshaft? No, that is too much.

Here is another thing to consider. If this is a street car, changing the pinion angle down will wear out ujoints and can cause vibration at highway speeds if you change it enough. The idea with this pinion angle thing is to make the pinion parallel to the mainshaft under load for drag racing, which requires a little negative alignment under static conditions. But this applies only to drag racing, not to streeet cars, not to autoXers. You want it parallel under static conditions for those.

You will not find an example like it in the literature on rear end setups, and I haven't seen it in any suspension software.

check your PMs :drive:

Heres one to really confuse everyone

I have a 2000 Firebird PROMOD car that was built by Jerry Bickel in the shop right now. The pinion angle is set at 2 degrees down. With the car at ride height and thru out the arc of the suspension travel the pinion stays at 2 degrees down. This car has a 4 link and is a full tube chassis so I dont see much flex. Now this being the case and more pinion doesnt help and less takes 60ft away AND the driveshaft never comes in a straight line or 0 degrees as everyone thinks why would you measure the driveshaft or tailshaft in reference to the pinion???????

Heres one to really confuse everyone

I have a 2000 Firebird PROMOD car that was built by Jerry Bickel in the shop right now. The pinion angle is set at 2 degrees down. With the car at ride height and thru out the arc of the suspension travel the pinion stays at 2 degrees down. This car has a 4 link and is a full tube chassis so I dont see much flex. Now this being the case and more pinion doesnt help and less takes 60ft away AND the driveshaft never comes in a straight line I would suggest that whatever you change that affects the short time is not pinion angle per se, but that pinion angle is a side effect.
or 0 degrees as everyone thinks why would you measure the driveshaft or tailshaft in reference to the pinion??????? I doubt that much 4 link wisdom transfers to stockish F-Bodys, but the driveshaft doesn't matter. All you want is the pinion to be more or less parallel to the crank/trans mainshaft. The job of the universal joints in the drive shaft is to make up for the fact that those two centerlines are not one (and obviously can't be). When a ujoint runs at an angle, the angular velocity of one side or the other changes. If both joints run at the same angle, the driveshaft absorbs this without much complaint. If they don't, some of that angular velocity difference is passed forward and backward into the trans/engine and rear end via the ujoints, which is why missalignment shortens their life. The trans/engine and rear end are not particularly happy about it either.

You are right 4link tuning versus ladder bar versus t/a suspensions all tune differently. The point is that pinion angle is exactly what it says "PINION ANGLE". It has no bearing on the crackshaft centerline or the tailshaft or the driveshaft.

On this same car the crank shaft is lower than the pinion in the car. The driveshaft runs uphill to the pinion. If we put 2 degrees in with your method or the driveshaft method the pinion would be way down.

On this same car the crank shaft is lower than the pinion in the car. The driveshaft runs uphill to the pinion. If we put 2 degrees in with your method or the driveshaft method the pinion would be way down.

The crankshaft being lower has no meaning in and of itself. Only the angle of the crankshaft does. Since the goal is not to point the pinion at the crankshaft, only to put the centerlines parallel.

Is the crankshaft level? Or is the front or the rear lower in this case? By about how much?

The motor is level in the car. The crank is 10" from the ground. The pinion is 15" from the ground.

Exactly correct. And the ratio of up to forward depends on the angle of the LCA.



So the lower the LCA's are the more the car would want to wheelie?


I need some relocation brkts :) (tryin to rip the bumper off) :devil:

You are right 4link tuning versus ladder bar versus t/a suspensions all tune differently. The point is that pinion angle is exactly what it says "PINION ANGLE". It has no bearing on the crackshaft centerline or the tailshaft or the driveshaft.

On this same car the crank shaft is lower than the pinion in the car. The driveshaft runs uphill to the pinion. If we put 2 degrees in with your method or the driveshaft method the pinion would be way down.



If the crankshaft points up at 5 degrees towards the pinion then the pinion must point down 5 degrees to keep the driveline in line. If you wanted to account for any upward pinion movement under load (say 2 degrees) then the pinion would have to point down 7 degrees in relationship to the crankshaft.
And yes in this case the pinion would be pointing down in relation to the level ground.

The crank is at "0" degrees at ride height in relation to the ground.

The driveshaft must be pointing up at some degree (say +5 degrees) to meet the pinion. Whatever that angle is the pinion must be pointing down at that same angle (-5 degrees) to meet up with it if you want the driveline to be in line.
You do not have to run it that way but if you want it in line you do.

Excatly JNorris. You have proved my point. You are trying to set "driveline angle" not "pinion angle.

Exactly correct. And the ratio of up to forward depends on the angle of the LCA.

Move the rear of the LCAs up a hole or two. That should help.


Carl, thats what I had planned next time I get to a decent track, racing at 5000DA on our local tracks suck. Its not a big issue currently being cam-only, but when I put the S/R engine back in is when I need it to work its best and/or if we put the bottle on it someday. Like I said, havn't had much time to make adjustments other than QA1 settings.

What about the location of the front torque arm mount? Does torque arm length come into play as much as we would think it does? Lifting in the stock type location -vs- lifting more towards the rear such as the BMR/Spohn designs. :judge:

Height plays a big part of the chassis setup. Height is what changes instant center. The length is not as important if you can move the height of the front mount.

Excatly JNorris. You have proved my point. You are trying to set "driveline angle" not "pinion angle.


Pinion angle is part of driveline alignment.
The goal of having your pinion angle set is to have your driveline in line. Correct?


John

No. Pinion angle is exactly what it says. Getting your driveline in line is something different.

Height plays a big part of the chassis setup. Height is what changes instant center. The length is not as important if you can move the height of the front mount.

So what's better, higher or lower? Cuz I have a little area to play with where I mount my torque arm on my th-400 crossmember, right now I kind of have it in the middle of it, so I could go either up or down.

Up hits the tire hard and then tends to unload the tire farther out. Lower tends to plant the tire and keep it planted down track.

Up hits the tire hard and then tends to unload the tire farther out. Lower tends to plant the tire and keep it planted down track.

Cool, thanks a lot man, i'll try and move it down a little and see what happens when I get back together! Hey, are you at ur shop by any chance, just wonderin if I could call to order the oh shit bars while it's on my mind?

I just got home. I will be there in the morning at 5.00am if you are up. I have 10 sets ready to ship.

Up hits the tire hard and then tends to unload the tire farther out. Lower tends to plant the tire and keep it planted down track.
so if im unloading almost instantly and my front is at the top of the adjustment on the bmr relocation k-member and my pinion is at say -2, you are saying i should bring it down a lil in the front which would give me say -4 or so then readjust the bottom rear adjustment together more to move the rear back up to get my -2 back without moving the torque arm. hence i still have the same pinion angle but now the front of the torque arm is much lower? am i starting to get this?

I just got home. I will be there in the morning at 5.00am if you are up. I have 10 sets ready to ship.

Sweet, i'm off work tomorrow and will probably be pullin my motor after I get up at the ass crack of dawn to go do my turn-in at the office, so i'll give ya a call on the way, probably around 7ish am florida time, hehe!!!

so if im unloading almost instantly and my front is at the top of the adjustment on the bmr relocation k-member and my pinion is at say -2, you are saying i should bring it down a lil in the front which would give me say -4 or so then readjust the bottom rear adjustment together more to move the rear back up to get my -2 back without moving the torque arm. hence i still have the same pinion angle but now the front of the torque arm is much lower? am i starting to get this?

That's what i'm thinkin, I have basically the same setup as you, except I have the crossmember for the th-400 from yank instead of bmr, but they're basically the same piece, i'm gonna try and move it so the bottom bolts to the lowest hole.

Hey, this is the number I got off ur website (281.290.8899), is that still the right number, cuz on the front page it says it's changed, just wanna make sure I call the right one.

Okay. So pinion angle is set in relation to what? There are only a few choices…the ground or the driveshaft.

I understand why it would be in relation of the drive shaft but I do not know why it would be in relation to the ground unless you are assuming that the engine/transmission and drive shaft are at 0 degrees in relation to the ground.

John

You are right 4link tuning versus ladder bar versus t/a suspensions all tune differently. The point is that pinion angle is exactly what it says "PINION ANGLE". It has no bearing on the crackshaft centerline or the tailshaft or the driveshaft. Correct. PINION ANGLE is just what it says - a meaningless phrase. It has no meaning without a frame of reference. ie, pinion is at 2* down from the moon, or pinion is at 2* down from horizontal, or pinion is at 2* down from imaginary line from rear contact patch through instant center, or whatever. So saying pinion angle is 2* down has no meaning what so ever.


On this same car the crank shaft is lower than the pinion in the car. The driveshaft runs uphill to the pinion. If we put 2 degrees in with your method or the driveshaft method the pinion would be way down.
Um, no, if your crank is at 0* WRT horizontal, and the pinion is down 2* from horizontal, you have done it right. Like I said, the drive shaft angle from horizontal doesn't mean squat. What you have done is set the pinion angle 2* down WRT the crank.

So the lower the LCA's are the more the car would want to wheelie?


I need some relocation brkts :) (tryin to rip the bumper off) :devil:
Lower in the pack, ie pointing up a bit. That should move the instant center up.

Carl, thats what I had planned next time I get to a decent track, racing at 5000DA on our local tracks suck. Its not a big issue currently being cam-only, but when I put the S/R engine back in is when I need it to work its best and/or if we put the bottle on it someday. Like I said, havn't had much time to make adjustments other than QA1 settings.

What about the location of the front torque arm mount? With a standard torque arm or aftermarket arm with a link in the front, the vertical location of the front mount has no effect on the dynamics of the chassis or load distribution under acceleration. Because of the design of the F-Body rear suspension, the torque arm plays only a minor role in instant center location. Now, a Madman TA that bolts solid in front without a link will act differently. If you remove the LCAs, you would have an instant center at the front TA mount. If you don't remove the LCAs, the rear end will bind because of the different attempted instant centers. Which would dominate? Not a clue.
Does torque arm length come into play as much as we would think it does? Lifting in the stock type location -vs- lifting more towards the rear such as the BMR/Spohn designs. :judge: Torque arm length will make a difference in chassis dynamics in two ways. First, the TA puts a vertical load into the chassis. This is distributed front to back according to the ratio of the TA length to wheel base. That is, if WB is 110" and TA is 55", the lift would split 50/50. Shorter lengths will tend to lift the rear more than the front with more of the vertical force going to the rear. Thus a shorter TA will reduce squat at lanch and can even cause rear end lift at launch if short enough. Again the TA acts sort of like lift bars (or ladder bars) except the link at the front prevents the IC from being located there. Second, a shorter TA will move the instant center to the rear, which will improve weight transfer.

Height plays a big part of the chassis setup. Height is what changes instant center. The length is not as important if you can move the height of the front mount. Only with your TA, not with a BMR or the stock one.

So what's better, higher or lower? Cuz I have a little area to play with where I mount my torque arm on my th-400 crossmember, right now I kind of have it in the middle of it, so I could go either up or down. It won't matter unless you have a Madman TA.

Wow, I leave for a few days and...Look what happened to this thread!
Just goes to show that people are learning the importance of a well tuned suspension!


OK Maggie this is getting fun.What Would moving the front of the t/a up do???
LOL...MADMAN looks I got back a little to late, seems that you covered the subject pretty well in this thread!..."move er up 'n' pitch er back"... Umm, played with some wish-bone "T"s and some old school "shortys" have we?..lol :jest: Our vernacular may differ but we think alot alike. :)


later,
maggie

[QUOTE=critter]This isn't rocket science, guys.

UH...Well, actually it is. The exact same laws of motion apply...Velosity, acceleration, weight, mass, distance and time. Without Newton's Laws we could not begin to understand the dynamics of the forces influencing the actions of the vehicle of our sport.

Happy tunning,
Maggie

[QUOTE=critter]This isn't rocket science, guys.

UH...Well, actually it is. The exact same laws of motion apply...Velosity, acceleration, weight, mass, distance and time. Without Newton's Laws we could not begin to understand the dynamics of the forces influencing the actions of the vehicle of our sport.

Happy tunning,
Maggie
I'll give you that. What I should have said was it isn't black magic - it is simple physics (or rocket science if you prefer) ;)

I think I menioned a lot of misinformation on this subject. On a lark, I googled for "pinion angle". Here are the first 10 hits. I didn't look for quality sources or filter this in anyway - just the first 10 hits.

http://www.carcraft.com/howto/91758/
http://www.2quicknovas.com/happypinions.html
http://buickperformance.com/Pinion.htm
http://www.4x4wire.com/tech/pinionangle/
http://www.iedls.com/ptsetup.html
http://www.drivetrain.com/driveline_angle_problem.html
http://www.wolferacecraft.com/pinionangle.aspx
http://www.quickperformance.com/PinionAngle.html
http://www.maliburacing.com/ssm_instructions.html
http://www.baselinesuspensions.com/info/pinionangle.htm

More than half of them get it wrong. People who should know, like Jerry Bickel, Inland, and Driveline Performance mostly get it right, but, surprisingly, Wolfe doesn't.

So since I have a Yank TA mount off the tranny and the TA is in the center holes..am I leaving some 60' on the table? I also have my LCA's set on the lowest hole and the adj. TA set at -2. It seems to hit really hard and sometimes spins just after it hooks. Is it unloading the rear because the way I have it setup? Here is a pic of it launching. It seems to do just the opposite of most people I see launching. Ya'll have any suggestions?

Magnus, did you get the car to start hooking like was before you broke your TQ?
If so, want did it take?
Thanks Man

I actually just got done working on the car....

Last time at the track I had teh new torque arm.. I adjusted pinion angle by using the flat spot of the bottom of the torque arm (under the pumpkin).. I figured this was straight out with the yoke.. when in fact it seems to be -2 below the yokes axis..

So I was realy at a -4 angle or so.. *i think*

On the passanger side of the pumpkin there is a "fin" that seems to be inline with the yoke.. I used this to set the pinion to -.5 .. at least I think the fin is parallel with the pinion..

I really couln't get a reading off of the pinion itself so I cannot verify my theory.. Just from visual though the pinion does seem to be parallell with the "fin".

I am using a strange 12 bolt..

I will probably go racing again this weekend.. i really hope I hook. It's really depressing to cut 1.3's all day long and then be stuck in the mid 1.4's with traction issues..

I'll post my results when I return..

Thanks!

Some great info Carl, being an old 4-link/ladder bar guy I just assumed the IC would change when moving the front of a non-fixed front torque arm up or down. I'm one of those guys that just got lucky on the last 3 LS1 cars and whatever parts I put on worked, always had a little anti squat and never a problem hooking at all so I never gave it much thought until I read through this - thanks.

Just out of curiousity Magnus did the MAC torque arm that broke have a sliding front like the Jegs or was it solid mounted? That would explain a lot if the MAC was solid mounted, I had one of these here a couple years ago and I didnt use it because it was solid mounted if I remember - could be wrong though.

Sliding front mount.

Putting the pinion angle as close to 0 as I could get it has fixed my traction issues and brought back my MPH to normal levels.. check drag racing results

After reading every post and the links posted I think I understand this correctly. Please correct me if I have misunderstood. There are 3 angles:

1) Driveshaft Angle (DSA)
2) Pinion Angle (PA)
3) Driveline Angle (DLA)
*it seems like the DLA is sometimes referred to as being the PA which confuses people*

The sum of the DSA and the PA gives you the DLA. Ideally the DLA should be 0. This happens when the DSA and PA have opposite values which offset eachother. A DLA angle of 0 will cause the least amount of stress on the parts. We need to avoid extreme PAs to avoid breaking parts.

It seems like PA values of 0 and less give people the best results hooking at the track. Only trial and error will let you know what angle works best for you as every car is different.

***yeah i know this is an ancient thread but thats what happens when you read the stickies***