have a 2* pinion angle, vibration at high speeds.. going to drag strip for first time
02-20-2012, 05:41 PM
#1
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have a 2* pinion angle, vibration at high speeds.. going to drag strip for first time As the title says im giong to run my 96 z28 for the first time this coming up spring.. when I installed a jegster torque arm I followed the instructions for setting up the angle using the block/oil pan as a reference and then the bottom of the differential. I set it to 2* since I planned to run the car. In the mean time I used the car as a daily driver barley ever seeing the highway, when I did, above 60 it has a bad vibration.
I plan to get the thing on a alignment rack and double check the angle. since the initial set was done on jack stands so I feel this has a lot to do with it.. Or is this normal? I know you want the car to squat from the dig
I cant see doing it on jack stands (had front supported by lower control arm so suspension was loaded and under rear axle) being inaccurate at the same time. since your taking the angle of the oil pan and subtracting or adding 2, cant remember which it was
I plan to get the thing on a alignment rack and double check the angle. since the initial set was done on jack stands so I feel this has a lot to do with it.. Or is this normal? I know you want the car to squat from the dig
I cant see doing it on jack stands (had front supported by lower control arm so suspension was loaded and under rear axle) being inaccurate at the same time. since your taking the angle of the oil pan and subtracting or adding 2, cant remember which it was
02-21-2012, 11:11 AM
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02-21-2012, 03:30 PM
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People talk about pinion angle but this is only a proxy
for the two angles you really -do- care about.
Pinion angle indicates torque arm angle which, with the
LCA angle, points to your instant center (launch bite
and brake hop). Some people adjust the LCAs with relo
brackets, some adjust the TA with a relocating cross
member. Adjusting pinion angle by twisting the nut on
an adjustable, does not change torque arm angle as
defined by the "ray" from axle centerline to torque arm
mount - it just "bends" the arm and the pinion angle.
Pinion angle is half of the driveline angle difference.
Mismatched angles increase vibration and scrub in the
yokes.
Your soft suspension components will compress, and
the torque arm may flex, changing the driveline angle
under load. So you will compromise somewhere - you
may favor cruise-load quietness, or you may go for the
"right answer" at WOT figuring this is where the load is
highest. The slight negative driveline angle is meant to
"pull itself right" under load. But with very rigid
components you might not even need that much, while
with stock rubber bits you could use more.
If you're trying to adjust launch bite using the adjuster,
you're not going to get anywhere. There will however
be a sweet spot for vibe. You might just want to do an
orderly series of settings and make notes, returning to
the best one in the end. Being as there are plenty of
unknowns.
for the two angles you really -do- care about.
Pinion angle indicates torque arm angle which, with the
LCA angle, points to your instant center (launch bite
and brake hop). Some people adjust the LCAs with relo
brackets, some adjust the TA with a relocating cross
member. Adjusting pinion angle by twisting the nut on
an adjustable, does not change torque arm angle as
defined by the "ray" from axle centerline to torque arm
mount - it just "bends" the arm and the pinion angle.
Pinion angle is half of the driveline angle difference.
Mismatched angles increase vibration and scrub in the
yokes.
Your soft suspension components will compress, and
the torque arm may flex, changing the driveline angle
under load. So you will compromise somewhere - you
may favor cruise-load quietness, or you may go for the
"right answer" at WOT figuring this is where the load is
highest. The slight negative driveline angle is meant to
"pull itself right" under load. But with very rigid
components you might not even need that much, while
with stock rubber bits you could use more.
If you're trying to adjust launch bite using the adjuster,
you're not going to get anywhere. There will however
be a sweet spot for vibe. You might just want to do an
orderly series of settings and make notes, returning to
the best one in the end. Being as there are plenty of
unknowns.
02-21-2012, 04:06 PM
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Very good info here. Not to hijack but what would be the correct pinion angle for a car lowered 1 1/2"? Im getting a bad vibration at speeds around 65 since installing new setup (in sig) and was told it was probably an out of round wheel but i would like to double check the pinion angle to be sure. whats your thoughts. Thanks
02-22-2012, 11:40 AM
#7
Very good info here. Not to hijack but what would be the correct pinion angle for a car lowered 1 1/2"? Im getting a bad vibration at speeds around 65 since installing new setup (in sig) and was told it was probably an out of round wheel but i would like to double check the pinion angle to be sure. whats your thoughts. Thanks
- Kevin
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02-22-2012, 01:45 PM
#8
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Thank you for the reply, my current setup is in sig. I'm trying to figure out the best spot to get the pinion angle on the housing with the strange third member. Torque arm mounts directly to the top and bottom of the rearend housing. Thanks again
03-18-2012, 08:08 PM
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alright, yeah I did not do the angle adjustment correctly. I will do it how the video shows and retest. April 7th is the first test and tune at byron, IL. Anyone know if you need a driveshaft hoop if your running drag radials or any other things I will need..?
04-03-2012, 04:56 PM
#11
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Finally got around to adjusting the angle the right way.. It was at positive 1* for all this time. After putting it at -2 and then test drivng what a difference. Time for the strip on saturday!
anyone recommend a tire pressure for my mickey thompson drag radials?
anyone recommend a tire pressure for my mickey thompson drag radials?
04-04-2012, 08:12 AM
#12
Mickey Thompson drag radials tend to really like higher pressure, I would start somewhere around 20-21lbs of pressure and adjust from there. Each car and track is a little different so the pressures will vary depending on power of the car and track conditions.
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Glenn ***
Sales Tech
www.bmrsuspension.com
813.986.9302
Find a Quality alignment shop near you!
Glenn ***
Sales Tech
www.bmrsuspension.com
813.986.9302
Find a Quality alignment shop near you!
