My freakin' brembos are warping now!
04-23-2004, 01:19 PM
#41
Senior Member
Join Date: Dec 2002
Posts: 458
Originally Posted by spirilis
But are you implying that the "wavy-grooves" are suggestive of WHY the rotors "warp"? i.e. maybe the pad material sheds off onto the rotor during the process by which the metal strands in the pad cut those grooves? That'd be an interesting theory to test... (in which case, Axxis MM should be the worst for such purposes)
Not wavy in the sense of grooves like you would find on an old phonograph record. I mean wavy in the sense of disc flatness. It's called "disc thickness variation". As metal deposits in one area (or wears off the rotor), the thickness of the disc will start to vary.
Here's a good site that explains the different types of "warpage".
http://www.rtitech.com/Pedal%20Pulse.htm
Pad deposits or rotor wear would cause "DTV", it's down at the bottom of that web site.
Most people think that the very top 2 are what happens to a rotor when it feels warped. Those are run-out or flatness issues. Not torqueing a wheel properly or excessivley over heating / cooling (like hitting a puddle with a very hot rotor) can cause run-out or flatness issues.
Wavy, or a rotor with excessive DTV is *usually* caused by wear or deposits. From what I've been reading, the great majority of "warped" rotors actually have excessive DTV issues. What I'm saying is that semi-metalic pads cause wear and deposits so you end up with a lot of DTV.
In the old days with organic (asbestos non-metalic) pads, rotors didn't get worn nor did pads deposit on them, so excessive DTV wasn't an issue. But then those pads didn't last long and people complained. The manufacturers then started to compete for the longest lasting pads (they were offering "lifetime" guarantees back in the 90s). No we have pads that can lost a lot longer but they take out the rotors.
04-23-2004, 03:27 PM
#42
Originally Posted by itdood
Not wavy in the sense of grooves like you would find on an old phonograph record. I mean wavy in the sense of disc flatness. It's called "disc thickness variation". As metal deposits in one area (or wears off the rotor), the thickness of the disc will start to vary.
Here's a good site that explains the different types of "warpage".
http://www.rtitech.com/Pedal%20Pulse.htm
Pad deposits or rotor wear would cause "DTV", it's down at the bottom of that web site.
Most people think that the very top 2 are what happens to a rotor when it feels warped. Those are run-out or flatness issues. Not torqueing a wheel properly or excessivley over heating / cooling (like hitting a puddle with a very hot rotor) can cause run-out or flatness issues.
Wavy, or a rotor with excessive DTV is *usually* caused by wear or deposits. From what I've been reading, the great majority of "warped" rotors actually have excessive DTV issues. What I'm saying is that semi-metalic pads cause wear and deposits so you end up with a lot of DTV.
In the old days with organic (asbestos non-metalic) pads, rotors didn't get worn nor did pads deposit on them, so excessive DTV wasn't an issue. But then those pads didn't last long and people complained. The manufacturers then started to compete for the longest lasting pads (they were offering "lifetime" guarantees back in the 90s). No we have pads that can lost a lot longer but they take out the rotors.
Here's a good site that explains the different types of "warpage".
http://www.rtitech.com/Pedal%20Pulse.htm
Pad deposits or rotor wear would cause "DTV", it's down at the bottom of that web site.
Most people think that the very top 2 are what happens to a rotor when it feels warped. Those are run-out or flatness issues. Not torqueing a wheel properly or excessivley over heating / cooling (like hitting a puddle with a very hot rotor) can cause run-out or flatness issues.
Wavy, or a rotor with excessive DTV is *usually* caused by wear or deposits. From what I've been reading, the great majority of "warped" rotors actually have excessive DTV issues. What I'm saying is that semi-metalic pads cause wear and deposits so you end up with a lot of DTV.
In the old days with organic (asbestos non-metalic) pads, rotors didn't get worn nor did pads deposit on them, so excessive DTV wasn't an issue. But then those pads didn't last long and people complained. The manufacturers then started to compete for the longest lasting pads (they were offering "lifetime" guarantees back in the 90s). No we have pads that can lost a lot longer but they take out the rotors.
Here's an interesting tidbit I saw from the shop manual:
ROTOR
Rubbing Surface
Check rotor for roughness, cracks or chips.
Runout
1. Secure rotor to wheel hub with at least two nuts (M12 x 1.25).
2. Check runout using a dial indicator. Make sure that wheel bearing axial end play is within the specifications before measuring. Maximum runout: 0.07 mm (0.0028 inch)
3. If the runout is out of specification, find minimum runout position as follows:
1. Remove nuts and rotor from wheel hub.
2. Shift the rotor one hole and secure rotor to wheel hub with nuts.
3. Measure runout.
4. Repeat steps a to c so that minimum runout position can be found.
4. If the runout is still out of specification, turn rotor with on-car brake lathe ("MAD, DL-8700", "AMMCO 700 and 705" or equivalent). Thickness Thickness variation (At least 8 positions): Maximum 0.01 mm (0.0004 inch) If thickness variation exceeds the specification, turn rotor with on-car brake lathe. Rotor repair limit: 24.0 mm (0.945 inch)
04-23-2004, 03:55 PM
#43
Senior Member
Join Date: Dec 2002
Posts: 458
Originally Posted by spirilis
That site echos most of the other sites I saw.
Here's an interesting tidbit I saw from the shop manual:
ROTOR
Rubbing Surface
Check rotor for roughness, cracks or chips.
Runout
1. Secure rotor to wheel hub with at least two nuts (M12 x 1.25).
2. Check runout using a dial indicator. Make sure that wheel bearing axial end play is within the specifications before measuring. Maximum runout: 0.07 mm (0.0028 inch)
3. If the runout is out of specification, find minimum runout position as follows:
1. Remove nuts and rotor from wheel hub.
2. Shift the rotor one hole and secure rotor to wheel hub with nuts.
3. Measure runout.
4. Repeat steps a to c so that minimum runout position can be found.
4. If the runout is still out of specification, turn rotor with on-car brake lathe ("MAD, DL-8700", "AMMCO 700 and 705" or equivalent). Thickness Thickness variation (At least 8 positions): Maximum 0.01 mm (0.0004 inch) If thickness variation exceeds the specification, turn rotor with on-car brake lathe. Rotor repair limit: 24.0 mm (0.945 inch)
I don't have a dial caliper, not sure how much they are or where I should buy one... is it worth buying? Either way, this sounds like a good procedure to use for installing the rotor in the optimum way.
Here's an interesting tidbit I saw from the shop manual:
ROTOR
Rubbing Surface
Check rotor for roughness, cracks or chips.
Runout
1. Secure rotor to wheel hub with at least two nuts (M12 x 1.25).
2. Check runout using a dial indicator. Make sure that wheel bearing axial end play is within the specifications before measuring. Maximum runout: 0.07 mm (0.0028 inch)
3. If the runout is out of specification, find minimum runout position as follows:
1. Remove nuts and rotor from wheel hub.
2. Shift the rotor one hole and secure rotor to wheel hub with nuts.
3. Measure runout.
4. Repeat steps a to c so that minimum runout position can be found.
4. If the runout is still out of specification, turn rotor with on-car brake lathe ("MAD, DL-8700", "AMMCO 700 and 705" or equivalent). Thickness Thickness variation (At least 8 positions): Maximum 0.01 mm (0.0004 inch) If thickness variation exceeds the specification, turn rotor with on-car brake lathe. Rotor repair limit: 24.0 mm (0.945 inch)
I use a Mitutoyo dial guage. You also need a decent magnetic base. Check ebay for them, there are tons. Here's one without the base.
http://cgi.ebay.com/ws/eBayISAPI.dll...810483279&rd=1
Just do a search on Mitutoyo. They make some of the best measuring tools, IMHO.
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