E46 BMW Social Directory E46 FAQ 3-Series Discussion Forums BMW Photo Gallery BMW 3-Series Technical Information E46 Fanatics - The Ultimate BMW Resource BMW Vendors General E46 Forum The Tire Rack's Tire Wheel Forum Forced Induction Forum The Off-Topic The E46 BMW Showroom For Sale, For Trade or Wanting to Buy

Welcome to the E46Fanatics forums. E46Fanatics is the premiere website for BMW 3 series owners around the world with interactive forums, a geographical enthusiast directory, photo galleries, and technical information for BMW enthusiasts.

You are currently viewing our boards as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!

If you have any problems with the registration process or your account login, please contact contact us.

Go Back   E46Fanatics > E46 BMW > General E46 Forum

General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

Reply
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 07-20-2010, 11:54 PM   #1
envoid
Registered User
 
Join Date: Apr 2008
Location: atlanta
Posts: 32
My Ride: 2008 335i
Rear Brake Oddity

Ok. My rears are gone on my 330i so I checked out the rotor to see if I need to replace them as well and I find stamped on the right-rear rotor that the minimum thickness is 20.4mm (didn't check left-rear as was checking rotor wear while making sure there was the wire as the dash light isn't lit). Is it me or is this wrong? There is no lip on the rotor and the current thickness is around 22mm (close estimate as I don't have a micrometer). Is it even safe to have the front rotor on the rear? They work fine but might explain why the rears 'thump' when the car is held at certain speeds (held around 40 it sounds like the ABS is activated but with barely any braking). And since it specifies 20.4mm should I just replace the rotors anyway with the proper rear rotors or use the front ones again?

Got the car used and never had to do the brakes for ~22k miles that I've owned her.

Thanks everyone!
envoid is offline   Reply With Quote
Ads by Google

Guests, get your FREE E46Fanatics.com membership to remove this ad.
Old 07-21-2010, 12:46 AM   #2
fotsir
Registered User
 
Join Date: Mar 2010
Location: Bham
Posts: 271
My Ride: 2004 Lexus IS300
Quote:
Originally Posted by envoid View Post
Ok. My rears are gone on my 330i so I checked out the rotor to see if I need to replace them as well and I find stamped on the right-rear rotor that the minimum thickness is 20.4mm (didn't check left-rear as was checking rotor wear while making sure there was the wire as the dash light isn't lit). Is it me or is this wrong? There is no lip on the rotor and the current thickness is around 22mm (close estimate as I don't have a micrometer). Is it even safe to have the front rotor on the rear? They work fine but might explain why the rears 'thump' when the car is held at certain speeds (held around 40 it sounds like the ABS is activated but with barely any braking). And since it specifies 20.4mm should I just replace the rotors anyway with the proper rear rotors or use the front ones again?

Got the car used and never had to do the brakes for ~22k miles that I've owned her.

Thanks everyone!
Q:Is it me or is it wrong?
A:Supposing you are able to read, it's you.

Q:Is it even safe to have the front rotor on the rear?
A:WTF are you talking about? How did the front rotor get on the rear? No, it's not safe; I don't think it's even possible! What, with the handbrake and all. I'll believe it when I see it.

Q:And since it specifies 20.4mm should I just replace the rotors anyway with the proper rear rotors or use the front ones again?
A:If you have the front rotors on the rear, you should definitely put the correct rear rotors on, unless your car has been modified to accept the front rotors. Concerning the minimum spec, that is the minimum thickness that the rotor can be at WHEN REPLACING PADS without having to replace the rotor as well.
__________________
fotsir is offline   Reply With Quote
Old 07-21-2010, 06:29 AM   #3
dmax
Registered User
 
dmax's Avatar
 
Join Date: Aug 2006
Location: NJ
Posts: 22,826
My Ride: '99 328i 1.04646 mu
20.4 is the minimum thickness stamped on the front rotors.

So, you evidently do have a front rotor on the rear...maybe you also have a front brake pad on it too...thus no lip?

It's not terribly surprising to me that our rotors would accept the e-brake, whether front or rear, as I suspect many rotors are made to accept e-brake.

But, I'm thinking, frankly, that coz the front rotor is on rear, what else is there? The caliper would need to be different...ah...that's why no lip. Front rotor, rear caliper and so the pad is sitting proud of the rotor's edge.

Anyway, that's my theory.

OP...you have to have a look at all four rotors...look for stamps. I suspect you'll have the other stamp on the fronts...a little thinner...just put away Bentley.

Get this straightened out...but you do need to see that stamp so you'll know how to proceed.

Doug
__________________


Performing at the Comedy Cove--595 Morris Ave. Springfield NJ reservations 973 376-3840

A recent set

dmax on the radio every Wednesday 7-9 p.m. NYC time. Call in! (661) 449-9340 watsonnwatson.com
dmax is offline   Reply With Quote
Old 07-21-2010, 02:42 PM   #4
envoid
Registered User
 
Join Date: Apr 2008
Location: atlanta
Posts: 32
My Ride: 2008 335i
I looked at the front rotors and they specify 23.4mm min thickness. So the mins are front 23.4mm, rear 20.4mm. Wtf?? What car did they think they have? I need to go over it a little more to see if the calipers have been changed. Another damn surprise probably.
envoid is offline   Reply With Quote
Old 07-21-2010, 02:49 PM   #5
dmax
Registered User
 
dmax's Avatar
 
Join Date: Aug 2006
Location: NJ
Posts: 22,826
My Ride: '99 328i 1.04646 mu
Hmmm...find specs on rotors from your car...it might have a superceded pn...I got this info from Bentley.

...and what's wear like in the front...you have lip there?

Out to be a pn stamped somewhere on the caliper...enough of one to help you identify it.

But, now, you at least know that bigger is in front...that's good. Car is stopping, and if something is different than it should be, it sounds like it might be by design and not accident...so could be a good thing!

Doug
__________________


Performing at the Comedy Cove--595 Morris Ave. Springfield NJ reservations 973 376-3840

A recent set

dmax on the radio every Wednesday 7-9 p.m. NYC time. Call in! (661) 449-9340 watsonnwatson.com
dmax is offline   Reply With Quote
Old 07-21-2010, 03:45 PM   #6
envoid
Registered User
 
Join Date: Apr 2008
Location: atlanta
Posts: 32
My Ride: 2008 335i
Doug, thanks for the help. I checked the PN on the front rotor and it is 34 10 1 166 071 (bold is stamped on the rotor) so it is correct. Even has the BMW logo crudely stamped on it. The caliper I'm not really finding anything that relates to the PN but they do look like they should. What I'm finding on it is "844" then smaller below that is "083/4". The fronts do have a lip on them.

So all in all I shouldn't pay attention to the books and just pay attention to what the rotors say and just get the PNs for the car. lol When you expect to have smaller rotors it kinda throws you off.

@fotsir: I'll take a pic after I put the front back on and pull the rear again. The rear rotors say "MIN TH 20.4mm".
envoid is offline   Reply With Quote
Old 07-21-2010, 04:26 PM   #7
envoid
Registered User
 
Join Date: Apr 2008
Location: atlanta
Posts: 32
My Ride: 2008 335i
Here's my front rotor:


Here's my rear rotor:


Colors look different cuz i had to use the flash on the rear, but I just shot these while on my 04' 330i.
envoid is offline   Reply With Quote
Old 03-13-2012, 09:27 PM   #8
rkneeshaw
Registered User
 
Join Date: Oct 2008
Location: Northern Michigan
Posts: 675
My Ride: 330i ZHP
This is normal. The 330i has larger rear rotors than the 328i, 325i, or 323i. In fact the 330i rear rotors are thicker than M3 rear rotors according to the Bentley manual (but not as large in diameter of course).

So the 20.4mm is the minimum thickness of your rear rotor and this is normal. You do not have front rotors on the rear.
__________________
2003 BMW 330i ZHP
BMW Performance Intake and SSK - Headers - Magnaflow - ESS Tuning
Turner Motorsports Pullies and Reinforcements - H&R Spacers - StopTech - And more...

rkneeshaw is offline   Reply With Quote
Old 03-14-2012, 04:46 AM   #9
dmax
Registered User
 
dmax's Avatar
 
Join Date: Aug 2006
Location: NJ
Posts: 22,826
My Ride: '99 328i 1.04646 mu
Quote:
Originally Posted by rkneeshaw View Post
This is normal. The 330i has larger rear rotors than the 328i, 325i, or 323i. In fact the 330i rear rotors are thicker than M3 rear rotors according to the Bentley manual (but not as large in diameter of course).

So the 20.4mm is the minimum thickness of your rear rotor and this is normal. You do not have front rotors on the rear.
It took you long enough to respond, rknee! LOL

Interesting reading me from way back!
__________________


Performing at the Comedy Cove--595 Morris Ave. Springfield NJ reservations 973 376-3840

A recent set

dmax on the radio every Wednesday 7-9 p.m. NYC time. Call in! (661) 449-9340 watsonnwatson.com
dmax is offline   Reply With Quote
Old 03-14-2012, 09:42 AM   #10
ddombrowski
Registered User
 
Join Date: Jun 2006
Location: South Florida
Posts: 909
My Ride: 01 330ci 5spd
Send a message via AIM to ddombrowski
Regardless, I rarely ever replace rotors on the rear of any car so long as they don't have a nasty lip on them and the new pad beds in well. I've never been able to feel a vibration from the rear rotors. Maybe I'm lucky, who knows. I always just pad slap the rear and see how it drives, and every car has always done well after that.

So, even if you are below min thickness on the rear, I wouldn't worry about it.
__________________
ddombrowski is offline   Reply With Quote
Old 03-14-2012, 09:44 AM   #11
Mango
A full five stars, son
 
Mango's Avatar
 
Join Date: Mar 2006
Location: Southern California
Posts: 22,626
My Ride: M54B30
Quote:
Originally Posted by rkneeshaw View Post
This is normal. The 330i has larger rear rotors than the 328i, 325i, or 323i. In fact the 330i rear rotors are thicker than M3 rear rotors according to the Bentley manual (but not as large in diameter of course).

So the 20.4mm is the minimum thickness of your rear rotor and this is normal. You do not have front rotors on the rear.
The 330 and E46 M3 both use 325mm diamater rotors up front. The M3 rotors are 3mm thicker IIRC.

if you're talking about the rear rotors then yes I believe the E46 M3 is slightly bigger in dia
__________________
A lifetime free of problems if you follow my guides
Cooling | Maintenance | Suspension | Vacuum | Supreme Reliability | Details

OVER A MILLION VIEWS
Mango is online now   Reply With Quote
Reply

Tags
330i, brakes, e46, rear, rotor

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

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 On
Censor is ON





All times are GMT -5. The time now is 10:21 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
(c) 1999 - 2011 performanceIX Inc - privacy policy - terms of use