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  #1  
Old 01-06-2018, 02:02 PM
WSSix WSSix is offline
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Default Brake rotor centering

Should brake rotors be centered by the studs or the hub register on the axle? Just slowly working on my vibration issue before I decide to set the car on fire.

Thank you
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Old 01-06-2018, 05:15 PM
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The hub should index the rotor. Same with the wheel.
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Old 01-06-2018, 05:58 PM
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Yup both

Explain your vibration and mods
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Old 01-06-2018, 06:29 PM
WSSix WSSix is offline
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Thanks guys. That's what I was expecting you to say.

I found that my rotor bores are at 2.78 inches and the axle hub is 2.68 inches. This cased the rotors to drop down onto the hub when putting everything back together. I thought I was locking the rotors in eccentrically and this might be the cause of my vibration. So I got some shim stock, put it between the rotors and hub register to tighten up the slop, and that did squat to help the issue. I was so fed up I just parked the car. For all I know, the shim stock didn't stay put some how but I doubt it since it felt the exact same. Maybe I'll look at it tomorrow.

Randy, I talk about the issue in the last few pages of my build thread. There are also other threads I've started concerning the issue. If you do a search for threads started by me, I'm sure it'll come up. The simple answer is I start vibrating at 55mph and up. It's at its worst at 55-60. It's speed related not engine or rpm related. It's definitely the rear end area, confirmed via dyno, and the wheels are true, confirmed via Wheel Wizards a rim straightening company here in Atlanta. Literally, nothing I have done has had any affect on it positively or negatively. It's maddening.

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Old 01-06-2018, 09:16 PM
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unfortunately rear end vibrations can be a number of issues. u-joint angles, wheel tire combo, brakes, axle itself.

you said you had the rims checked, was that with tires installed (good balance)?
rotate the wheels front to back if possible?
double check all drive line angles.
if you do believe it is brake related, can you safely put rear on jack stands (weight of vehicle on axle) and accelerate to 55-60mph, see if vibration there. then slowly start removing parts and retesting. remove wheels, install lugnuts, torque to specs and check for vibration. remove rotors (ziptie block of wood in caliper not to blow out pistons), and see if vibration still there.
if still there, vibration maybe within axle, or drive shaft.

also vibration is worse between 55-60mph, does it dissipate or get worse with more mph? if the vibration intensity is matched at 110-120mph you would be looking at u-joint area for binding
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Last edited by carkrazy1987; 01-06-2018 at 09:20 PM.
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Old 01-07-2018, 05:43 AM
WSSix WSSix is offline
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Quote:
Originally Posted by carkrazy1987 View Post
unfortunately rear end vibrations can be a number of issues. u-joint angles, wheel tire combo, brakes, axle itself.

you said you had the rims checked, was that with tires installed (good balance)?
rotate the wheels front to back if possible?
double check all drive line angles.
if you do believe it is brake related, can you safely put rear on jack stands (weight of vehicle on axle) and accelerate to 55-60mph, see if vibration there. then slowly start removing parts and retesting. remove wheels, install lugnuts, torque to specs and check for vibration. remove rotors (ziptie block of wood in caliper not to blow out pistons), and see if vibration still there.
if still there, vibration maybe within axle, or drive shaft.

also vibration is worse between 55-60mph, does it dissipate or get worse with more mph? if the vibration intensity is matched at 110-120mph you would be looking at u-joint area for binding
I appreciate the response. I've checked all of those components multiple times. That's what is so frustrating, nothing changes with any of my adjustments. It's not on or off throttle dependent either only speed.

I've put the car on jack stands before but the vibrations were minimal compared to on the road. I put the car on a dyno to verify it was the rear area of the car for that reason.

Thank you
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Old 01-09-2018, 09:26 PM
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I believe I've goofed on my working angles and I'm way over the 3* limit. I had always taken my measurements with the car sitting at ride height. Well, tonight I took them with only the rear off the ground and it became obvious to me that I think I screwed that math up. I'll see what Lucas at Drive Shaft Shop says in the morning.

Thanks
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Old 01-09-2018, 09:34 PM
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Quote:
Originally Posted by WSSix View Post
I believe I've goofed on my working angles and I'm way over the 3* limit. I had always taken my measurements with the car sitting at ride height. Well, tonight I took them with only the rear off the ground and it became obvious to me that I think I screwed that math up. I'll see what Lucas at Drive Shaft Shop says in the morning.

Thanks


Easy enough to do ----

Motor should be about 2 to 3* DOWN at the tranny pan --- REAR END should be about 2* UP --- and if the slip yoke is correct (they make all kinds of lengths) -- you should be close.

The other thing I've seen --- a too small diameter drive shaft for the overdrive tranny / rear end gear combo. The shaft has a working RPM and when exceeded can go into harmonic death wobble. LOL

Glad you're on it.
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Old 01-10-2018, 11:30 AM
WSSix WSSix is offline
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Those values are actually pretty close to what I have for pinion angles now. The issue is my rear end if higher than the rear of the transmission so the drive shaft is down in front. The solution is to raise the trans more. I'm not sure I have the room due to my headers though.

I didn't want to get into it just yet as I'm waiting to see what the Drive Shaft Shop has to say, but I'm getting really concerned with some things about my build compared to what others have had to do with their similar builds. This whole car is a learning experience for me. I'm worried I may have missed or done some critical stuff wrong after all. We'll see what happens. I hope I'm just over reacting.

Thanks
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  #10  
Old 01-10-2018, 11:34 AM
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Ah -- yeah that won't work....


Tunnel issues with the new bigger transmissions --- and combine that with our low stances --- yeah --- that's usually a tranny hump mod and driveline tunnel raise....

Those are easy mods even in a done car..... it's a carpet issue --- and back seat tunnel modification...
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