Pinion Shim Question - Team Camaro Tech
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post #1 of 9 (permalink) Old Oct 6th, 17, 06:00 AM Thread Starter
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Pinion Shim Question

Since pinion shims sit in-between the perch and spring, like a lowering block, I'm assuming that they will lower the car to a degree as well correct?

67 Black RS Coupe, 383, M21 & 10 Bolt Posi. Edelbrock E-Tech 170 Heads, 2204 Roller Cam, Air Gap Intake.
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post #2 of 9 (permalink) Old Oct 6th, 17, 06:14 AM
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Re: Pinion Shim Question

A small fraction of inch; as only the narrowest tip of the wedge is actually lowering the car. The thickest part is just rotating the rear end.

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post #3 of 9 (permalink) Old Oct 6th, 17, 06:50 AM Thread Starter
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Re: Pinion Shim Question

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Originally Posted by Larger Dave View Post
A small fraction of inch; as only the narrowest tip of the wedge is actually lowering the car. The thickest part is just rotating the rear end.

Big Dave
Thanks Dave. So if a lowering block goes in the same place between the perch and spring, how does it work differently? I've got a 6 degree shim that's thicker on the fat side than my lowering block.

67 Black RS Coupe, 383, M21 & 10 Bolt Posi. Edelbrock E-Tech 170 Heads, 2204 Roller Cam, Air Gap Intake.
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post #4 of 9 (permalink) Old Oct 6th, 17, 10:06 AM
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Re: Pinion Shim Question

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Originally Posted by cv2065 View Post
Thanks Dave. So if a lowering block goes in the same place between the perch and spring, how does it work differently? I've got a 6 degree shim that's thicker on the fat side than my lowering block.
Gave it some thought and after throwing out the idea of center of gravity and 3D centroids which were clogging up my mental synapse went back to basic geometry. If you have a 6 inch by 2-1/4 inch wide wedge, the thickness at the point three inches in is how much it will lower the car. Not the thickest part of the wedge. This is because the thickest part is countered by the thinnest leaving the axle to rotate about the middle (where there should be a hole to accept the pin in the spring pack).

Think about it as lowering one edge of the spring perch while you raise the other end. Net effect at the axle tube is zero change except for the thickness of the wedge at the mid point.

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post #5 of 9 (permalink) Old Oct 6th, 17, 10:43 AM Thread Starter
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Re: Pinion Shim Question

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Originally Posted by Larger Dave View Post
Gave it some thought and after throwing out the idea of center of gravity and 3D centroids which were clogging up my mental synapse went back to basic geometry. If you have a 6 inch by 2-1/4 inch wide wedge, the thickness at the point three inches in is how much it will lower the car. Not the thickest part of the wedge. This is because the thickest part is countered by the thinnest leaving the axle to rotate about the middle (where there should be a hole to accept the pin in the spring pack).

Think about it as lowering one edge of the spring perch while you raise the other end. Net effect at the axle tube is zero change except for the thickness of the wedge at the mid point.

Big Dave
Got it. Thanks for the explanation. I'm assuming that if that mid point value of the shim is 1/4", then it would lower the car a full 1/2"? Same philosophy as a lowering block?

Reason I ask is that I have 2" lowering springs and may need to adjust the pinion angle, however, I cannot afford to drop the car anymore or I'll be riding the wheel well and bottoming out. So I guess the answer is to use different lowering springs.

67 Black RS Coupe, 383, M21 & 10 Bolt Posi. Edelbrock E-Tech 170 Heads, 2204 Roller Cam, Air Gap Intake.
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post #6 of 9 (permalink) Old Oct 6th, 17, 01:11 PM
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Re: Pinion Shim Question

No the thickness of the block or angled shim is the amount up that the axle moves. You don't double it.

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post #7 of 9 (permalink) Old Oct 6th, 17, 04:56 PM
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Re: Pinion Shim Question

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Originally Posted by cv2065 View Post
Thanks Dave. So if a lowering block goes in the same place between the perch and spring, how does it work differently? I've got a 6 degree shim that's thicker on the fat side than my lowering block.

Do you actually have a lowering block installed with your 2" drop springs? If so, have the thickness at the mid point of the 6 degree wedge milled off of the lowering block.
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post #8 of 9 (permalink) Old Oct 6th, 17, 09:10 PM Thread Starter
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Re: Pinion Shim Question

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Originally Posted by schnide View Post
Do you actually have a lowering block installed with your 2" drop springs? If so, have the thickness at the mid point of the 6 degree wedge milled off of the lowering block.

I had a lowering block and shim with standard multi leaf springs. I just changed over to the DS 2" drop springs to get rid of that 'sandwich' going on in my suspension. Hopefully I won't need a shim now that I'm using a spring and not a block.

67 Black RS Coupe, 383, M21 & 10 Bolt Posi. Edelbrock E-Tech 170 Heads, 2204 Roller Cam, Air Gap Intake.
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post #9 of 9 (permalink) Old Oct 6th, 17, 09:13 PM Thread Starter
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Re: Pinion Shim Question

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Originally Posted by Larger Dave View Post
No the thickness of the block or angled shim is the amount up that the axle moves. You don't double it.

Big Dave
Ah...I was thinking of coil spring spacers. Thanks.

67 Black RS Coupe, 383, M21 & 10 Bolt Posi. Edelbrock E-Tech 170 Heads, 2204 Roller Cam, Air Gap Intake.
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