Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > Porsche 911 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
Join Date: Sep 2015
Location: Houston, TX
Posts: 468
Zimmerman Z-Coat Rotor Damage? Follow up Question

I recently posted a thread showing some scuff marks on my newly received Zimmerman Z-Coat rotors. I was quickly informed by the members that this was normal and I was worrying about nothing. However, I noticed something last night that I hadn't when I originally posted. Of the two rotors, one has a notch or cutout on the edge. See attached photo. Is this damaged or is this done on purpose? I can't imagine this could be good for balance, unless it is actually done to correct a balance issue due to casting imperfections. In any case, it strikes me as odd that only one of two has this notch. Thanks in advance.

__________________
_______________
John
1988 Carrera Targa 3.2 G50
2017 Chevy Silverado K1500.
Old 02-09-2016, 04:48 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Cars Ruined My Life
 
impactbumper's Avatar
 
Join Date: Feb 2013
Location: Right in your face
Posts: 1,868
nothing to worry in that picture
Old 02-09-2016, 05:46 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
KTL KTL is offline
Schleprock
 
KTL's Avatar
 
Join Date: Sep 2000
Location: Frankfort IL USA
Posts: 15,646
Send a message via Yahoo to KTL
Yes that is completely normal. It's a machining mark/relief to balance the rotor.
__________________
Kevin L
Present: '86 Carrera, '79 911SC widebody conversion rolling racecar shell
Past: '87 Carrera
Old 02-09-2016, 05:47 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered User
 
SweetWaterSurprise's Avatar
 
Join Date: Nov 2011
Location: EastCoast
Posts: 286
Agree with what's been posted. Seen it before, nothing to worry about.
Old 02-09-2016, 06:01 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered User
 
Join Date: Sep 2015
Location: Houston, TX
Posts: 468
OK thanks all. I guess the reason that the other one didn't have this was that it was cast perfectly and didn't require balancing?
__________________
_______________
John
1988 Carrera Targa 3.2 G50
2017 Chevy Silverado K1500.
Old 02-09-2016, 06:52 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
seafood10's Avatar
 
Join Date: Sep 2008
Location: Rancho Palos Verdes, CA
Posts: 188
Quote:
Originally Posted by JRSIII View Post
OK thanks all. I guess the reason that the other one didn't have this was that it was cast perfectly and didn't require balancing?
Hey, I know this is an older post but glad I found it as I am installing 2 zimmerman rotors on my 84 and noticed the same marks in mine.
I figured they were for balancing but this post confirms it.
Would it be too difficult for them to slip a piece of paper into the box to let us know that this is done for balancing??
__________________
84 Carrera Cabriolet
62 356 B Gone
Old 09-12-2018, 12:43 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
914-6Werkshop
 
Join Date: Dec 2009
Location: Wilmington, DE
Posts: 1,714
Quote:
Originally Posted by seafood10 View Post
Hey, I know this is an older post but glad I found it as I am installing 2 zimmerman rotors on my 84 and noticed the same marks in mine.
I figured they were for balancing but this post confirms it.
Would it be too difficult for them to slip a piece of paper into the box to let us know that this is done for balancing??
That would be unusual. It's just a part made to spec. Most parts don't include an explanation to their manufacture. Maybe on their website but rarely in a box.
__________________
A part isn't purchased until paid
Old 09-12-2018, 01:34 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered User
 
seafood10's Avatar
 
Join Date: Sep 2008
Location: Rancho Palos Verdes, CA
Posts: 188
Quote:
Originally Posted by mepstein View Post
That would be unusual. It's just a part made to spec. Most parts don't include an explanation to their manufacture. Maybe on their website but rarely in a box.
I guess we have not purchased many of the same items then.
__________________
84 Carrera Cabriolet
62 356 B Gone
Old 09-12-2018, 01:50 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
914-6Werkshop
 
Join Date: Dec 2009
Location: Wilmington, DE
Posts: 1,714
Quote:
Originally Posted by seafood10 View Post
I guess we have not purchased many of the same items then.
I'm mostly familiar with parts that come into our shop from distributors. Probably $10-20K a month. I imagine boutique parts from small manufacturers, custom and consumer oriented retail has more info but your average replacement part (rotors) is just shipped in a box. No instructions
__________________
A part isn't purchased until paid
Old 09-12-2018, 06:06 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Chain fence eating turbo
 
Join Date: Dec 2008
Location: Austin, TX
Posts: 8,625
Quote:
Originally Posted by JRSIII View Post
OK thanks all. I guess the reason that the other one didn't have this was that it was cast perfectly and didn't require balancing?
Cast perfect is probably an oxymoron, hence the balance notches you saw.
Old 09-12-2018, 06:25 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Registered User
 
midnight911's Avatar
 
Join Date: Apr 2007
Location: PDX, OR
Posts: 962
Garage
That looks dangerous. I'll take them off your hands. Just send them to me.
__________________
1984 911 Carrera Coupe - 32C #73 - M64/05
1998 E36 M3 4dr
1989 E30 325i 4dr
2006 Sienna 5dr - the hauler
2010 Cannondale Caffeine II - Lefty
Old 09-13-2018, 10:44 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
Registered User
 
GaryR's Avatar
 
Join Date: Mar 2005
Location: Valencia, Spain
Posts: 4,539
Garage
Send a message via ICQ to GaryR
I would be more concerned with the special "these rotors are defective, do not use" codes on there!



__________________
Gary R.
Old 09-13-2018, 12:26 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
 
Registered User
 
Fleming's Avatar
 
Join Date: Oct 2002
Location: Minneapolis
Posts: 680
Has anyone measured the width of the machined divot?

Confirm or deny if it is the wear limit to minimum rotor thickness.

I've been told it is the rotor thickness "visual check". Is this true?
Old 09-13-2018, 01:28 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)
Registered User
 
Join Date: Sep 2015
Location: Houston, TX
Posts: 468
That would make a heck of a lot of sense. Much like a tell tale holes in chemical plant / refinery piping. But only one of the two rotors I ordered had this.
Old 09-13-2018, 01:34 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #14 (permalink)
Registered User
 
sugarwood's Avatar
 
Join Date: Apr 2014
Posts: 4,711
Garage
Oh funny, I always thought it was a "wear bar" like on tires.
__________________
1986 3.2 911 coupe.
Old 09-13-2018, 02:19 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #15 (permalink)
Registered User
 
old man neri's Avatar
 
Join Date: Jul 2007
Location: Halifax, Canada
Posts: 1,182



Here my two old rotors. I just measured them. A hair under 20mm.
Old 09-13-2018, 02:39 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #16 (permalink)
gtc gtc is offline
abides.
 
gtc's Avatar
 
Join Date: Nov 2006
Location: Seattle, WA
Posts: 7,383
Garage
The pads don't usually wear all the way to the edge of the rotor, so the grooves wouldn't be too useful as wear indicators.
__________________
Graham
1984 Carrera Targa
Old 09-13-2018, 04:22 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #17 (permalink)
Registered User
 
Join Date: Feb 2005
Location: Mexico
Posts: 1,662
All rotating parts need to be balanced to avoid vibration.
To correct unbalance you add weight like when balancing wheel and tire assemblies or remove weight like in this case where they milled the rotor.
Sometimes the unbalance falls between a tolerance of the balance quality grade and you do not need to do any correction, that is why JRSIII does not see this milled part in one of the rotors he received.
Other parts where you will see milled parts or drilled parts to correct unbalance are flywheels, electric motor rotors, crankshafts, con rods, fans etc.

Last edited by donporfi; 09-13-2018 at 08:45 PM..
Old 09-13-2018, 08:20 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #18 (permalink)
Registered User
 
djpateman's Avatar
 
Join Date: Jan 2003
Location: Burford, ON, Canada
Posts: 1,899
I used to see heavy pieces of wire used for balancing.
__________________
Keeper of 911, 912 & 914 databases Kardex source
Researching 356, 911, 912 & 914 Paint codes, Engine #'s and Transmission #'s
Addicted since 1975
Old 09-15-2018, 10:59 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #19 (permalink)
Chain fence eating turbo
 
Join Date: Dec 2008
Location: Austin, TX
Posts: 8,625
Thank you for using the proper term, unbalance. Imbalance is generally incorrectly used instead.
Old 09-15-2018, 09:08 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #20 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 04:57 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.