Measuring Pinion Angle
08-21-2008, 09:57 PM
#1
Measuring Pinion Angle Ok, after arguing about it in one thread and reading plenty of others about finding pinion angle with varying explanations, this needs to be cleared up and made a little bit easier to understand.
Some of the confusion comes from one person measuring the pinion angle from the drivers side of the car and others measuring from the passenger side and the rest of the confusion is from the adding and subtracting of the rearend and driveshaft angles.
For this thread I want to try to keep the discussion as if you were looking at the measurements from the passenger side, like the illustrations below and the guy in the BMR video (which I'm gonna bring up in a minute). If you measure pinion angle from the drivers side then the measurements and the formulas will be inverted. So assuming we're looking at it from the passenger side, then throughout this post I'm going to keep the rearend angles on the left and the driveshaft angles on the right.
Example: A rearend angle of (-3) and a driveshaft angle of (+1) will be shown as (-3)/(+1).
1. Getting the car ready to measure pinion angle.
In order to correctly measure pinion angle your car needs to be fairly level from front to back with the weight of the car supported by all four tires and nothing else. Just as if it parked in your driveway or sitting in the staging lanes. The reason for this is that if the car is supported by jack stands, the rearend would hang lower than normal and change the angle of the driveshaft and torque arm, since they are mounted to either the body of the car or the transmission (which is also mounted to the body), which would cause your measurements to be horribly wrong at best.
Using a magnetic angle finder you can stick it to the bottom of the torque arm mounting bracket. This will allow you to measure the angle of the rearend. To find the driveshaft angle you need to put it on the driveshaft, which for us aluminum driveshaft guys means that you'll have to hold it there. So just find a clean spot on the driveshaft and either stick or hold it there until it stops moving and record that number. If you do have an aluminum driveshaft and are having to hold it in place, I recommend repeating the process a few times, just to double check that you are getting the same number. Having the angle finder tilted just slightly from side to side could affect your measurement.
2. Zero Degrees.
First off, lets start with what zero degrees of pinion angle is. This is when the angle of the rearend and the angle of the driveshaft are the same. Example: (-3)/(-3) or (+4)/(+4) or (0)/(0) or any measurement that has the mounting bracket of the torque arm and the driveshaft parallel. Easy enough, right? Now understanding what zero degrees is, lets move on to the negative angles.
3. Negative Pinion Angles.
For a negative pinion angle, the rearend has to be angle downward (from back to front) from the measurement of zero degrees. For this post we will use negative two degrees, as it is the most common and most recommend starting point. The formula to use is for finding pinion angle is: (rearend angle)-(driveshaft angle)=(pinion angle). And remember that subtracting a negative is the same as adding a positive. Examples: (+2)-(-3)=(+5) , (-2)-(-3)=(+1) , (-2)-(+3)=(-5) , (+2)-(+3)=(-1).
While setting a negative two degree pinion angle, you only want a two degree spread from rearend angle to driveshaft angle. Some examples are: (-2)/(0) or (-4)/(-2) or (-1)/(+1) or (0)/(+2). As long as the measurements are two degrees apart with the rear tilted downward from back to front, in relation to the driveshaft.
4. Positive Pinion Angles.
This is the opposite of the above, where the rearend tilts upward form back to front in relation to the driveshaft. For this I'm just going to list some examples and give their overall pinion angle. (0)/(-2)=positive two degrees, (+5)/(+1)= positive four degrees, (-2)/(-4)= positive two degrees, (+3)/(-2)=positive five degrees.
5. The BMR video.
BMR uses a different method of measuring the angles. As explained below in post #13, by Allen Miller https://ls1tech.com/forums/11216876-post13.html
Some of the confusion comes from one person measuring the pinion angle from the drivers side of the car and others measuring from the passenger side and the rest of the confusion is from the adding and subtracting of the rearend and driveshaft angles.
For this thread I want to try to keep the discussion as if you were looking at the measurements from the passenger side, like the illustrations below and the guy in the BMR video (which I'm gonna bring up in a minute). If you measure pinion angle from the drivers side then the measurements and the formulas will be inverted. So assuming we're looking at it from the passenger side, then throughout this post I'm going to keep the rearend angles on the left and the driveshaft angles on the right.
Example: A rearend angle of (-3) and a driveshaft angle of (+1) will be shown as (-3)/(+1).
1. Getting the car ready to measure pinion angle.
In order to correctly measure pinion angle your car needs to be fairly level from front to back with the weight of the car supported by all four tires and nothing else. Just as if it parked in your driveway or sitting in the staging lanes. The reason for this is that if the car is supported by jack stands, the rearend would hang lower than normal and change the angle of the driveshaft and torque arm, since they are mounted to either the body of the car or the transmission (which is also mounted to the body), which would cause your measurements to be horribly wrong at best.
Using a magnetic angle finder you can stick it to the bottom of the torque arm mounting bracket. This will allow you to measure the angle of the rearend. To find the driveshaft angle you need to put it on the driveshaft, which for us aluminum driveshaft guys means that you'll have to hold it there. So just find a clean spot on the driveshaft and either stick or hold it there until it stops moving and record that number. If you do have an aluminum driveshaft and are having to hold it in place, I recommend repeating the process a few times, just to double check that you are getting the same number. Having the angle finder tilted just slightly from side to side could affect your measurement.
2. Zero Degrees.
First off, lets start with what zero degrees of pinion angle is. This is when the angle of the rearend and the angle of the driveshaft are the same. Example: (-3)/(-3) or (+4)/(+4) or (0)/(0) or any measurement that has the mounting bracket of the torque arm and the driveshaft parallel. Easy enough, right? Now understanding what zero degrees is, lets move on to the negative angles.
3. Negative Pinion Angles.
For a negative pinion angle, the rearend has to be angle downward (from back to front) from the measurement of zero degrees. For this post we will use negative two degrees, as it is the most common and most recommend starting point. The formula to use is for finding pinion angle is: (rearend angle)-(driveshaft angle)=(pinion angle). And remember that subtracting a negative is the same as adding a positive. Examples: (+2)-(-3)=(+5) , (-2)-(-3)=(+1) , (-2)-(+3)=(-5) , (+2)-(+3)=(-1).
While setting a negative two degree pinion angle, you only want a two degree spread from rearend angle to driveshaft angle. Some examples are: (-2)/(0) or (-4)/(-2) or (-1)/(+1) or (0)/(+2). As long as the measurements are two degrees apart with the rear tilted downward from back to front, in relation to the driveshaft.
4. Positive Pinion Angles.
This is the opposite of the above, where the rearend tilts upward form back to front in relation to the driveshaft. For this I'm just going to list some examples and give their overall pinion angle. (0)/(-2)=positive two degrees, (+5)/(+1)= positive four degrees, (-2)/(-4)= positive two degrees, (+3)/(-2)=positive five degrees.
5. The BMR video.
BMR uses a different method of measuring the angles. As explained below in post #13, by Allen Miller https://ls1tech.com/forums/11216876-post13.html
08-21-2008, 10:12 PM
#2
Good post but That BMR vids PA -5 & +2 was way off compared to mine? My DS always seems to read 0 or damn close its the TA rear mounting bracket that really changes. Anyone else find this true? I have adjusted mine 25 times or so. finally found it best at -2.5 for my car. but its an M6
08-21-2008, 10:17 PM
#3
The actual numbers mean nothing, its just the relation to one another that's important. The actual numbers can be way different from car to car, depending on lowering or engine/tranny mounts or maybe your not on level ground, etc...
And just to add, I'm not suggesting any pinion angle. It's always better to play around and find what works best for your own car. I'm just trying to clear up how to measure it.
Jon
And just to add, I'm not suggesting any pinion angle. It's always better to play around and find what works best for your own car. I'm just trying to clear up how to measure it.
Jon
09-08-2008, 03:52 PM
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yeah, it does sound a little confusing, definitely don't want to confuse people! They should just make your post the only post in the thread since none of the other posts are really adding to the overall goal, then people don't have to worry about people telling them different ways to measure.
09-11-2008, 01:13 PM
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just some facts to add;
the angle youre measuring is referred to as the "working angle". it is the angular relationship btwn the two different parts. just as the rear WA is important, so is the front. your method of measuing should be applied there as well.
also, the WA should be as close to 1* as possible, without going under. in addition, the relationship btwn the front and rear should be within .5*. so if your front is 2*, your rear should be btwn 1.5* and 2.5*. too large of a working angle and too large of a difference will cause driveline vibrations.
Tim
the angle youre measuring is referred to as the "working angle". it is the angular relationship btwn the two different parts. just as the rear WA is important, so is the front. your method of measuing should be applied there as well.
also, the WA should be as close to 1* as possible, without going under. in addition, the relationship btwn the front and rear should be within .5*. so if your front is 2*, your rear should be btwn 1.5* and 2.5*. too large of a working angle and too large of a difference will cause driveline vibrations.
Tim
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09-13-2008, 05:32 PM
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Found this post in another thread which I feel is VERY accurate and informative just like the info in this thread...
you have to figure out whats going on.
THE ONLY REASON for a very negative pinion angle is when you launch hard, the torque wants to rotate the axle in the opposite direction that the wheels rotate in (think of a wheelie). So when you launch real, real hard, and if your torque arms is real weak, you can flex positive several degrees. If you have a weak torque arm set at 0 degrees and flex up 3 degrees under hard launch, you run the risk of failure.. positive 3 and strong forces. By setting the pinion angle to -3 you arrive at 0 in this scenario when forces are at their greatest (during launch) BUT this means you have to drive around with -3 the rest of the time which increases wear and often increases noise and vibration.
SO like I said..
If you have a car that never sees hard launches.. there is NO REASON WHATSOEVER to have a significantly negative pinion angle because you'll never see great enough torque to push the pinion angle positive and risk failure.
If you have a car that sees moderately hard launches but spends more time daily driving, a slight negative pinion angle is acceptable.. a little insurance during the launch (so you run a degree positive, not going to kill you on streetable power levels) and your pinion angle wont cause excessive wear
If you have a car that sees very hard launches and is actually likely that it will flex an aftermarket torque arm.. then maybe you'll want 3 or 4 degrees negative. We're talking 500 hp or more and slicks.
you've got to understand that your power, your tires, your launch and your driving habits and what kind of torque arm you have all determine what your pinion angle should be.. anybody that says something like "all auto's should have X" doesn't get it
THE ONLY REASON for a very negative pinion angle is when you launch hard, the torque wants to rotate the axle in the opposite direction that the wheels rotate in (think of a wheelie). So when you launch real, real hard, and if your torque arms is real weak, you can flex positive several degrees. If you have a weak torque arm set at 0 degrees and flex up 3 degrees under hard launch, you run the risk of failure.. positive 3 and strong forces. By setting the pinion angle to -3 you arrive at 0 in this scenario when forces are at their greatest (during launch) BUT this means you have to drive around with -3 the rest of the time which increases wear and often increases noise and vibration.
SO like I said..
If you have a car that never sees hard launches.. there is NO REASON WHATSOEVER to have a significantly negative pinion angle because you'll never see great enough torque to push the pinion angle positive and risk failure.
If you have a car that sees moderately hard launches but spends more time daily driving, a slight negative pinion angle is acceptable.. a little insurance during the launch (so you run a degree positive, not going to kill you on streetable power levels) and your pinion angle wont cause excessive wear
If you have a car that sees very hard launches and is actually likely that it will flex an aftermarket torque arm.. then maybe you'll want 3 or 4 degrees negative. We're talking 500 hp or more and slicks.
you've got to understand that your power, your tires, your launch and your driving habits and what kind of torque arm you have all determine what your pinion angle should be.. anybody that says something like "all auto's should have X" doesn't get it
12-13-2008, 08:09 AM
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03-10-2009, 07:22 PM
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Thanks to JonCR96Z for pointing out the flaw in the video. The video has been modified and the new one is available on the home page of the BMR website. Please check it out when you get a chance:
www.bmrfabrication.com
You can also watch the modified video at www.bmrtvonline.com
At BMR, we define the driveshaft angle to be negative if the driveshaft slopes downward towards the rear of the car. The driveshaft angle is positive if it slopes upward towards the rear of the car.
We define the rear end angle to be negative if it slopes downward towards the front of the car. The rear end angle is positive if it slopes upward towards the front of the car.
After you take the measurements, add them together. This is your pinion angle. Example: (-1) rear end angle + (-1) driveshaft angle = (-2) degrees.
www.bmrfabrication.com
You can also watch the modified video at www.bmrtvonline.com
At BMR, we define the driveshaft angle to be negative if the driveshaft slopes downward towards the rear of the car. The driveshaft angle is positive if it slopes upward towards the rear of the car.
We define the rear end angle to be negative if it slopes downward towards the front of the car. The rear end angle is positive if it slopes upward towards the front of the car.
After you take the measurements, add them together. This is your pinion angle. Example: (-1) rear end angle + (-1) driveshaft angle = (-2) degrees.
03-10-2009, 07:49 PM
#12
Thanks to JonCR96Z for pointing out the flaw in the video. The video has been modified and the new one is available on the home page of the BMR website. Please check it out when you get a chance:
www.bmrfabrication.com
You can also watch the modified video at www.bmrtvonline.com
At BMR, we define the driveshaft angle to be negative if the driveshaft slopes downward towards the rear of the car. The driveshaft angle is positive if it slopes upward towards the rear of the car.
We define the rear end angle to be negative if it slopes downward towards the front of the car. The rear end angle is positive if it slopes upward towards the front of the car.
After you take the measurements, add them together. This is your pinion angle. Example: (-1) rear end angle + (-1) driveshaft angle = (-2) degrees.
www.bmrfabrication.com
You can also watch the modified video at www.bmrtvonline.com
At BMR, we define the driveshaft angle to be negative if the driveshaft slopes downward towards the rear of the car. The driveshaft angle is positive if it slopes upward towards the rear of the car.
We define the rear end angle to be negative if it slopes downward towards the front of the car. The rear end angle is positive if it slopes upward towards the front of the car.
After you take the measurements, add them together. This is your pinion angle. Example: (-1) rear end angle + (-1) driveshaft angle = (-2) degrees.
Got ya.
01-26-2014, 04:47 PM
#18
old thread but so what,
i dont understand why the car has to be level ?
even if the car is standing on its nose, you still measuring the relationship between the two angles right ?
i dont understand why the car has to be level ?
even if the car is standing on its nose, you still measuring the relationship between the two angles right ?
