BMW M3 Forum (E90 E92)

BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read


Go Back   M3Post - BMW M3 Forum > E90/E92 M3 Technical Topics > Track / Autocross / Dragstrip / Driving Techniques
 
Evolve Automotive
Post Reply
 
Thread Tools Search this Thread
      01-07-2014, 04:32 PM   #1
yandy
Lieutenant Colonel
 
yandy's Avatar
 
Drives: 2009 e92 MR "Civic" ///M3
Join Date: Feb 2009
Location: Miami, FL

Posts: 1,965
iTrader: (3)

Garage List
2009 BMW M3  [0.00]
Send a message via AIM to yandy Send a message via MSN to yandy Send a message via Skype™ to yandy
Question Wonder if these have another day in them? (rotors)

I'm fairly close to convincing the boss that I "need" a BBK, so don't want to make the investment fo $800+ for front rotors right now. Now the BBK may happen before my next track day anyway (March 29-30), but in case it doesn't. I'm wondering if these would be ok to run. They're micro-cracks, but noticing that they're starting to span from hole to hole.

P.S - I know there's threads on here about this, but don't want to hijack others.

Any input is appreciated.

Click for Full Res


Click for Full Res


Click for Full Res


Click for Full Res


Thanks for looking
__________________
|| DCT | ESS Tune | ACM Test-pipes | AA Green Filter | Swift Spec-R Springs | Stoptech ST-40 F || || My Youtube Channel|| My Vimeo Channel ||
yandy is offline   United_States
0
Reply With Quote
      01-07-2014, 04:53 PM   #2
Jon H
New Member
 
Drives: 2013 GT-R
Join Date: Aug 2013
Location: Arroyo Grande, CA

Posts: 15
iTrader: (0)

General rule of thumb is if you can catch one of the cracks with a fingernail, it's probably not safe to run.
__________________
2013 GT-R
Previous cars: '09 GT-R, '06 Z06, '06 Evo MR, '05 M3, '03 Evo, '00 Miata.
Jon H is offline  
0
Reply With Quote
      01-07-2014, 06:08 PM   #3
USCTrojanMan29
Captain
 
Drives: Purple People Eater
Join Date: Nov 2007
Location: Around

Posts: 753
iTrader: (2)

Quote:
Originally Posted by Jon H View Post
General rule of thumb is if you can catch one of the cracks with a fingernail, it's probably not safe to run.
I thought the rule of thumb is to replace the rotors if the cracks extend from one hole to another and/or from a hole to the edge of the rotor.
USCTrojanMan29 is offline  
0
Reply With Quote
      01-07-2014, 08:10 PM   #4
klammer
Brigadier General
 
Drives: 11 spc gry m3 e90, 07 X5
Join Date: Jan 2010
Location: chicago

Posts: 3,224
iTrader: (0)

They look fine to me and that's why you don't run drilled rotors on the track, they always crack around the holes in a relatively short time and both responses above are correct from what I've heard.
__________________
mods: akra evo, dinan 3.45 diff, ess akra tune, dinan stg.3, Alcon bbk, HRE P40
klammer is offline  
0
Reply With Quote
      01-07-2014, 08:27 PM   #5
Estoril Blue
Second Lieutenant
 
Drives: 2006 M3
Join Date: Dec 2006
Location: Maryland

Posts: 216
iTrader: (0)

In those pics they appear okay to run. The two rules above both apply. Also no chunks or missing material - or other obvious issues and of course, they need to be within spec (are they?).

*Always* inspect after every session.
__________________
Estoril Blue is offline  
0
Reply With Quote
      01-07-2014, 08:59 PM   #6
bigjae1976
Takes threads off topic...daily
 
bigjae1976's Avatar
 
Drives: 11 E90 M3 Individual
Join Date: Mar 2006
Location: Milwaukee, WI

Posts: 5,244
iTrader: (12)

Garage List
2004 BMW M3  [4.50]
2011 BMW E90 M3  [5.00]
2013 BMW 328i  [5.00]
I would say no. There's a crack in the 3rd pic that runs to the edge...that would be no good.
__________________


Sponsored by Momentum BMW #593...We Bleed BMW BLUE!
bigjae1976 is offline  
0
Reply With Quote
      01-07-2014, 09:10 PM   #7
CanAutM3
Brigadier General
 
CanAutM3's Avatar
 
Drives: 2008 E92 M3 (2015 M4 on order)
Join Date: Jan 2012
Location: Montreal

Posts: 3,491
iTrader: (0)

Garage List
2008 BMW M3  [0.00]
2006 Audi S4  [0.00]
Quote:
Originally Posted by USCTrojanMan29 View Post
I thought the rule of thumb is to replace the rotors if the cracks extend from one hole to another and/or from a hole to the edge of the rotor.
Exactly my rule.

In the pics, I see quite a few cracks extending from one hole to another and a few extending to the inner edge. The worst cracks are the ones that extend to the outer edge, which I don't see in the pictures.

Using them one more time would be on borrowed time and taking chances. Examine them closely and if you do find cracks that extend to the outer edge of the disc, I would definitely recommend not using the rotors any further.

On a side note, the disc wear does not look very nice (circumferential ridges and grooves). What pads are you using?
CanAutM3 is offline   Canada
0
Reply With Quote
      01-08-2014, 12:55 AM   #8
admranger
First Lieutenant
 
admranger's Avatar
 
Drives: 2002 M3, 2005 X5, 2011 M3
Join Date: May 2011
Location: Las Vegas

Posts: 349
iTrader: (0)

Quote:
Originally Posted by Jon H View Post
General rule of thumb is if you can catch one of the cracks with a fingernail, it's probably not safe to run.

Quote:
Originally Posted by USCTrojanMan29 View Post
I thought the rule of thumb is to replace the rotors if the cracks extend from one hole to another and/or from a hole to the edge of the rotor.
You're both right.

Either/Or. Of course, if you don't have drilled rotors you need a rule of thumb and that's the first one. If you have drilled rotors, both apply.

There is a third test, the "float test". Toss these rotors into a body of water. If they float, you can use them.

My two decades of experience on track in HPDE's, instructing, and racing say these rotors are toast. Toss them in the recycle bin.

Oh, you don't need a BBK. Sorry.

Get some PFC direct drive rotors and pair them with PFC pads (Z-rated for street, '08s for HPDE). Extra cooling won't hurt you...

FWIW, I ran my E46M3 at Spring Mountain in a somewhat spirited manner (USC and others can confirm) with DD rotors and PFC '06 pads. 0.001" of wear on each rotor. The track isn't the easiest on rotors (easier than Laguna, but much harder than BW, WS, or Chuckwalla imho). Cool weather helped. No braking drama at all. I have less than 0.050" of wear left on the rotors. No cracks.
__________________
'11 E90 M3, Mebourne/Black/Fox Red/Black, 6MT, PP2, heated seats, moonroof, split folding rear seats, iPod/USB adapter, Technic harness, JL XD 6/600.
'02 E46M3, Imola/Black, 6MT, CWP, no sunroof, Ohlins, Eibachs, PFC DD rotors, PFC pads! HAT Clarus/Legatia speakers, 2 big amps in the back.
'05 X5 4.4i, Imola/Black, Premium, Cold, HAT Imagine 6.5's, Intravee iPod adapter
admranger is offline  
0
Reply With Quote
      01-08-2014, 01:03 AM   #9
dapopa9
Captain
 
dapopa9's Avatar
 
Drives: 2008 E90 M3
Join Date: Apr 2008
Location: San Diego

Posts: 609
iTrader: (0)

usually say run them tell the crack...as in basically break
dapopa9 is offline  
0
Reply With Quote
      01-08-2014, 08:13 AM   #10
yandy
Lieutenant Colonel
 
yandy's Avatar
 
Drives: 2009 e92 MR "Civic" ///M3
Join Date: Feb 2009
Location: Miami, FL

Posts: 1,965
iTrader: (3)

Garage List
2009 BMW M3  [0.00]
Send a message via AIM to yandy Send a message via MSN to yandy Send a message via Skype™ to yandy
Quote:
Originally Posted by Jon H View Post
General rule of thumb is if you can catch one of the cracks with a fingernail, it's probably not safe to run.
Quote:
Originally Posted by USCTrojanMan29 View Post
I thought the rule of thumb is to replace the rotors if the cracks extend from one hole to another and/or from a hole to the edge of the rotor.
There's a bit of both here, I don't exactly catch the cracks with my nail, but enough to feel the bump.

Quote:
Originally Posted by klammer View Post
They look fine to me and that's why you don't run drilled rotors on the track, they always crack around the holes in a relatively short time and both responses above are correct from what I've heard.
Quote:
Originally Posted by Estoril Blue View Post
In those pics they appear okay to run. The two rules above both apply. Also no chunks or missing material - or other obvious issues and of course, they need to be within spec (are they?).

*Always* inspect after every session.
Thickness is within specs, cracks are the worrisome bits.

Quote:
Originally Posted by bigjae1976 View Post
I would say no. There's a crack in the 3rd pic that runs to the edge...that would be no good.
Thanks for the input, seems like new rotors coming in, regardless of BBK decision if not on time.

Quote:
Originally Posted by CanAutM3 View Post
Exactly my rule.

In the pics, I see quite a few cracks extending from one hole to another and a few extending to the inner edge. The worst cracks are the ones that extend to the outer edge, which I don't see in the pictures.

Using them one more time would be on borrowed time and taking chances. Examine them closely and if you do find cracks that extend to the outer edge of the disc, I would definitely recommend not using the rotors any further.

On a side note, the disc wear does not look very nice (circumferential ridges and grooves). What pads are you using?
I've been using Carbotechs for a while now, they're supposed to be "easy" on rotors. But heat down here is not exactly easy on anyone, specially during the summer months.

Quote:
Originally Posted by admranger View Post
You're both right.

Either/Or. Of course, if you don't have drilled rotors you need a rule of thumb and that's the first one. If you have drilled rotors, both apply.

There is a third test, the "float test". Toss these rotors into a body of water. If they float, you can use them.

My two decades of experience on track in HPDE's, instructing, and racing say these rotors are toast. Toss them in the recycle bin.

Oh, you don't need a BBK. Sorry.

Get some PFC direct drive rotors and pair them with PFC pads (Z-rated for street, '08s for HPDE). Extra cooling won't hurt you...

FWIW, I ran my E46M3 at Spring Mountain in a somewhat spirited manner (USC and others can confirm) with DD rotors and PFC '06 pads. 0.001" of wear on each rotor. The track isn't the easiest on rotors (easier than Laguna, but much harder than BW, WS, or Chuckwalla imho). Cool weather helped. No braking drama at all. I have less than 0.050" of wear left on the rotors. No cracks.
Thanks, only thing with the PFC and RB rotors are the price? for a grand more or so, I can get a front BBK, and probably save myself in the long run on PADS. That of course is just a theory, no direct experience.

Thanks for the input.

---------------------

Thanks to all for the feedback, looks like I'll be replacing them one way or another.
__________________
|| DCT | ESS Tune | ACM Test-pipes | AA Green Filter | Swift Spec-R Springs | Stoptech ST-40 F || || My Youtube Channel|| My Vimeo Channel ||
yandy is offline   United_States
0
Reply With Quote
      01-08-2014, 10:30 AM   #11
LiM3y
Major
 
LiM3y's Avatar
 
Drives: 2008 E90 M3
Join Date: Jun 2009
Location: CT

Posts: 1,216
iTrader: (2)

I replaced mine long before they looked like that...for me, if it is enough to worry about, it is enough to change. I don't want to spoil my fun by worrying about my rotors as I hit my braking point at 125mph on the front straight...
__________________
LiM3y is offline   United Kingdom
0
Reply With Quote
      01-08-2014, 10:53 AM   #12
yandy
Lieutenant Colonel
 
yandy's Avatar
 
Drives: 2009 e92 MR "Civic" ///M3
Join Date: Feb 2009
Location: Miami, FL

Posts: 1,965
iTrader: (3)

Garage List
2009 BMW M3  [0.00]
Send a message via AIM to yandy Send a message via MSN to yandy Send a message via Skype™ to yandy
Quote:
Originally Posted by LiM3y View Post
I replaced mine long before they looked like that...for me, if it is enough to worry about, it is enough to change. I don't want to spoil my fun by worrying about my rotors as I hit my braking point at 125mph on the front straight...
Absolutely, the only reason I brought it up it's difficult to dish out $1k for rotors, if BBK may come after. Hoping I have a decision soon, on either direction, but you're absolutely right. If I even have to ask, then they should be coming out regardless.
__________________
|| DCT | ESS Tune | ACM Test-pipes | AA Green Filter | Swift Spec-R Springs | Stoptech ST-40 F || || My Youtube Channel|| My Vimeo Channel ||
yandy is offline   United_States
0
Reply With Quote
      01-08-2014, 11:12 AM   #13
Sebringjetta
Colonel
 
Sebringjetta's Avatar
 
Drives: E46m3
Join Date: Mar 2011
Location: Sacramento

Posts: 2,474
iTrader: (26)

Quote:
Originally Posted by bigjae1976 View Post
I would say no. There's a crack in the 3rd pic that runs to the edge...that would be no good.
thats what the rotors you sold me look like.....just kidding i dont think they look bad but mentally you have kind of screwed your self as next time you track you will in the back of your head be wondering if your brakes are ok so it might be a good idead to change them....you never want to second guess things when your on the track...just my 2 cents
__________________
Sebringjetta is offline   United_States
0
Reply With Quote
      01-08-2014, 04:55 PM   #14
yandy
Lieutenant Colonel
 
yandy's Avatar
 
Drives: 2009 e92 MR "Civic" ///M3
Join Date: Feb 2009
Location: Miami, FL

Posts: 1,965
iTrader: (3)

Garage List
2009 BMW M3  [0.00]
Send a message via AIM to yandy Send a message via MSN to yandy Send a message via Skype™ to yandy
Quote:
Originally Posted by Sebringjetta View Post
thats what the rotors you sold me look like.....just kidding i dont think they look bad but mentally you have kind of screwed your self as next time you track you will in the back of your head be wondering if your brakes are ok so it might be a good idead to change them....you never want to second guess things when your on the track...just my 2 cents
agreed, if I'm going to be questioning it, then it probably isn't safe for more than physical reasons. I will order a front set to be safe, then worry about the BBK.
__________________
|| DCT | ESS Tune | ACM Test-pipes | AA Green Filter | Swift Spec-R Springs | Stoptech ST-40 F || || My Youtube Channel|| My Vimeo Channel ||
yandy is offline   United_States
0
Reply With Quote
      01-08-2014, 05:19 PM   #15
SlowSaloonM3
Major General
 
SlowSaloonM3's Avatar
 
Drives: m3 saloon in granny mode.
Join Date: Dec 2009
Location: lost angeles

Posts: 6,707
iTrader: (0)

was wondering where yandy went!
__________________

When is this episode coming?!
me no care about lap times. its all about skids, way more fun = next car ///M6.
SlowSaloonM3 is offline  
0
Reply With Quote
      01-08-2014, 06:17 PM   #16
yandy
Lieutenant Colonel
 
yandy's Avatar
 
Drives: 2009 e92 MR "Civic" ///M3
Join Date: Feb 2009
Location: Miami, FL

Posts: 1,965
iTrader: (3)

Garage List
2009 BMW M3  [0.00]
Send a message via AIM to yandy Send a message via MSN to yandy Send a message via Skype™ to yandy
Quote:
Originally Posted by pkim1079 View Post
was wondering where yandy went!
Yandy was taking care of some personal stuff, home refi things like that. But done with that for now, ready to play
__________________
|| DCT | ESS Tune | ACM Test-pipes | AA Green Filter | Swift Spec-R Springs | Stoptech ST-40 F || || My Youtube Channel|| My Vimeo Channel ||
yandy is offline   United_States
0
Reply With Quote
      01-08-2014, 10:39 PM   #17
Sleeper519
Captain
 
Sleeper519's Avatar
 
Drives: 08 E92 M3 DCT
Join Date: Nov 2009
Location: Atlanta, GA

Posts: 723
iTrader: (0)

People love to tell other people that they don't need a BBK. So,hey, we really don't NEED an M3 either...

Just get an ST-60 for the front and be done with it. You want it and you're tracking a fair amount on the hot S.Fla. tracks. I wouldn't spend the money on the PFC DDs and then turn around and finally get the BBK.

Just do it, you'll be glad you did.
__________________

2008 M3 Coupe / DCT // StopTech BBK 380/355 / Pagid RS29 / Motul / Apex Arc-8 / BFG R1S / Ground Control / MS filter / Performance spoiler / BPM tune // Road Atlanta 1:39.80 / VIR Full 2:10.87 / Barber 1:42.20
Sleeper519 is offline   United_States
0
Reply With Quote
      01-08-2014, 10:45 PM   #18
yandy
Lieutenant Colonel
 
yandy's Avatar
 
Drives: 2009 e92 MR "Civic" ///M3
Join Date: Feb 2009
Location: Miami, FL

Posts: 1,965
iTrader: (3)

Garage List
2009 BMW M3  [0.00]
Send a message via AIM to yandy Send a message via MSN to yandy Send a message via Skype™ to yandy
Quote:
Originally Posted by Sleeper519 View Post
People love to tell other people that they don't need a BBK. So,hey, we really don't NEED an M3 either...

Just get an ST-60 for the front and be done with it. You want it and you're tracking a fair amount on the hot S.Fla. tracks. I wouldn't spend the money on the PFC DDs and then turn around and finally get the BBK.

Just do it, you'll be glad you did.
The BBK is going in sooner or later, just doing the convincing "the boss" thing for now. I won't spend the money on the PFC DD's, just not worth it to me. BBK is higher up-front but will pay off later on.

I just need something between now and when the BBK finally comes in.

Thanks for your feedback.
__________________
|| DCT | ESS Tune | ACM Test-pipes | AA Green Filter | Swift Spec-R Springs | Stoptech ST-40 F || || My Youtube Channel|| My Vimeo Channel ||
yandy is offline   United_States
0
Reply With Quote
      01-09-2014, 01:24 PM   #19
dmw16
Captain
 
Drives: 2005 ///M3
Join Date: Aug 2010
Location: Maryland

Posts: 930
iTrader: (1)

I see connecting cracks. That's the point where they are clearly toast. Get new rotors, or rather than spend that money, just get a BBK and call it a day. When you get your BBK get solid (or slotted) rotors. Drilled rotors are (as you see here) not ideal.
dmw16 is offline  
0
Reply With Quote
      01-09-2014, 01:58 PM   #20
Groundpilot
Major
 
Groundpilot's Avatar
 
Drives: 135I DCT , e92 M3 DCT, Audi A6
Join Date: Mar 2010
Location: long island,ny

Posts: 1,106
iTrader: (0)

Send a message via ICQ to Groundpilot
Quote:
Originally Posted by Sleeper519 View Post
People love to tell other people that they don't need a BBK. So,hey, we really don't NEED an M3 either...

Just get an ST-60 for the front and be done with it. You want it and you're tracking a fair amount on the hot S.Fla. tracks. I wouldn't spend the money on the PFC DDs and then turn around and finally get the BBK.

Just do it, you'll be glad you did.
Sorry for the off topic question, but doesnt ST-60 front only puts too much front bias with stock rear brakes? I hear that if you install front bbk only, ST-40 is the way to go. I need to reaserch more on this, because i will be installing front bbk, not rear as i think it will be more than enough for HPDE type of driving.
__________________

David
Groundpilot is offline   United_States
0
Reply With Quote
      01-09-2014, 04:44 PM   #21
yandy
Lieutenant Colonel
 
yandy's Avatar
 
Drives: 2009 e92 MR "Civic" ///M3
Join Date: Feb 2009
Location: Miami, FL

Posts: 1,965
iTrader: (3)

Garage List
2009 BMW M3  [0.00]
Send a message via AIM to yandy Send a message via MSN to yandy Send a message via Skype™ to yandy
Quote:
Originally Posted by Groundpilot View Post
Sorry for the off topic question, but doesnt ST-60 front only puts too much front bias with stock rear brakes? I hear that if you install front bbk only, ST-40 is the way to go. I need to reaserch more on this, because i will be installing front bbk, not rear as i think it will be more than enough for HPDE type of driving.
This is something I've been wondering as well, good question.
__________________
|| DCT | ESS Tune | ACM Test-pipes | AA Green Filter | Swift Spec-R Springs | Stoptech ST-40 F || || My Youtube Channel|| My Vimeo Channel ||
yandy is offline   United_States
0
Reply With Quote
      01-09-2014, 07:47 PM   #22
bigjae1976
Takes threads off topic...daily
 
bigjae1976's Avatar
 
Drives: 11 E90 M3 Individual
Join Date: Mar 2006
Location: Milwaukee, WI

Posts: 5,244
iTrader: (12)

Garage List
2004 BMW M3  [4.50]
2011 BMW E90 M3  [5.00]
2013 BMW 328i  [5.00]
Quote:
Originally Posted by Groundpilot
Quote:
Originally Posted by Sleeper519 View Post
People love to tell other people that they don't need a BBK. So,hey, we really don't NEED an M3 either...

Just get an ST-60 for the front and be done with it. You want it and you're tracking a fair amount on the hot S.Fla. tracks. I wouldn't spend the money on the PFC DDs and then turn around and finally get the BBK.

Just do it, you'll be glad you did.
Sorry for the off topic question, but doesnt ST-60 front only puts too much front bias with stock rear brakes? I hear that if you install front bbk only, ST-40 is the way to go. I need to reaserch more on this, because i will be installing front bbk, not rear as i think it will be more than enough for HPDE type of driving.
No, the bias is fine with an ST60. I still wished I got an ST40. More wheel choices (you can run 17s), more pad choices, cheaper pads and thicker pads.

ST60 is just a PIA when it comes to street wheels unless you want to run 19s. I like 18s.
__________________


Sponsored by Momentum BMW #593...We Bleed BMW BLUE!
bigjae1976 is offline  
0
Reply With Quote
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 01:29 PM.




m3post
Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST