Rotors changing color
#1
Senior Member
Thread Starter
Rotors changing color
Some parts of my rotor are starting to turn into a copper color whereas the rotor is mostly silver color. I'm pretty sure these are not rust spots because they're not distinct dots, but rather large patches and they are in the area that gets scrubbed by the pads. It's more of a copper color like a new shiny penny rather than the darker rust color.
Are my rotors worn out? I've used up three sets of pads on the rotor but that's only about 5000 miles of commuting.
Are my rotors worn out? I've used up three sets of pads on the rotor but that's only about 5000 miles of commuting.
#3
Senior Member
Join Date: Aug 2012
Location: Colorado Springs
Posts: 1,134
Bikes: Borealis Echo, Ground Up Designs Ti Cross bike, Xtracycle, GT mod trials bike, pixie race machine
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Likes: 0
Liked 2 Times
in
2 Posts
Probably from heat build up.
If you want to measure your rotors to see if they are worn (very unlikely with only commuting) you can take a set of calipers and measure rotor thickness, if it is 1.5mm they should be replaced, new they should be right at 2mm.
If you want to measure your rotors to see if they are worn (very unlikely with only commuting) you can take a set of calipers and measure rotor thickness, if it is 1.5mm they should be replaced, new they should be right at 2mm.
#4
Senior Member
Thread Starter
Is it safe to continue using a scorched rotor? I have to descend about 500ft every day on the way home, average 7% grade but the steepest section is around 17%, and there are stop signs every 500ft or so.
#5
Mad bike riding scientist
Join Date: Nov 2004
Location: Denver, CO
Posts: 27,355
Bikes: Some silver ones, a red one, a black and orange one, and a few titanium ones
Mentioned: 152 Post(s)
Tagged: 1 Thread(s)
Quoted: 6215 Post(s)
Liked 4,213 Times
in
2,362 Posts
It shouldn't be a problem. It may even temper the metal and make it harder which will make the rotors last longer but squeal more.
__________________
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
#6
Cyclist
Join Date: Jun 2010
Posts: 639
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 39 Post(s)
Likes: 0
Liked 16 Times
in
15 Posts
I doubt it. Tempering actually reduces the hardness of hardened steel so that it is less brittle. If the rotors got too hot, they might be softened. To harden the rotors, you'd have to cool them suddenly, typically by plunging into water.
But I doubt the heating is enough to affect the temper.
But I doubt the heating is enough to affect the temper.
#7
Senior Member
Join Date: Feb 2013
Location: Mesa, AZ
Posts: 561
Bikes: 1992 Trek 800 Antelope, 1971 Triumph
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
When I first saw this topic, I thought the answer was easy: over heating and/or rapid cooling by pouring water on the rotor while it's hot. But now that you say the rotor is turning a copper color... my only guess is that it's something from the pads maybe rubbing off onto the rotor. Try taking apart the caliper, take out the pads, and give them a good wipe down with an alcohol pad and see what color the towel is afterwards. Also clean the rotors with an alcohol pad as well. Maybe the color will go away after you wipe it but also check to see what the color of the towel is after that. Do this and let us know the results.
Josh
Josh
#8
Banned.
Join Date: Feb 2013
Location: Brighton UK
Posts: 1,662
Bikes: 20" Folder, Road Bike
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
Hi,
It could be heating to the bottom of the steel tempering range.
Bottom of the range (light straw) is just over 200 degrees C.
rgds, sreten.
Last edited by sreten; 03-09-13 at 11:52 AM.
#9
Senior Member
Join Date: Feb 2013
Location: Mesa, AZ
Posts: 561
Bikes: 1992 Trek 800 Antelope, 1971 Triumph
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
This is assuming that the rotors are made of stainless steel. They are commonly made of SS because of the anti-rusting properties, but can also be made of aluminum or titanium. The OP never said what disc brakes he has so it's not completely safe to say it's the heating of steel.
The picture posted by sreten above is very helpful. The copper color the OP is reporting is exactly what you see in the left side of the picture.
Josh
The picture posted by sreten above is very helpful. The copper color the OP is reporting is exactly what you see in the left side of the picture.
Josh
Last edited by jowilson; 03-09-13 at 11:44 AM.
#10
Senior Member
Join Date: Oct 2009
Location: England, currently dividing my time between university in Guildford and home just outside Reading
Posts: 1,921
Bikes: Too many to list here!
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 4 Times
in
2 Posts
This is assuming that the rotors are made of stainless steel. They are commonly made of SS because of the anti-rusting properties, but can also be made of aluminum or titanium. The OP never said what disc brakes he has so it's not completely safe to say it's the heating of steel.
The picture posted by sreten above is very helpful. The copper color the OP is reporting is exactly what you see in the left side of the picture.
Josh
The picture posted by sreten above is very helpful. The copper color the OP is reporting is exactly what you see in the left side of the picture.
Josh
#11
Senior Member
Join Date: Feb 2013
Location: Mesa, AZ
Posts: 561
Bikes: 1992 Trek 800 Antelope, 1971 Triumph
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Titanium brake rotors are available for sale and are very light weight when compared to SS rotors, weighing in at just 88 grams. The Avid G2 Clean Sweep rotors, made of Stainless Steel, weigh 111 grams. A popular disc brake among bikers is the Avid X0's which are aluminum and those weigh in at 108 grams. There are many other alloys out there being used in rotors but those 3 are the most popular.
Josh
Josh
#12
Senior Member
Join Date: Jan 2013
Location: Llano Estacado
Posts: 3,702
Bikes: old clunker
Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 684 Post(s)
Likes: 0
Liked 105 Times
in
83 Posts
Yes, and that very large 20% mass reduction acts on a very long moment!
Last edited by AnkleWork; 03-09-13 at 01:30 PM. Reason: typo
#13
Senior Member
Join Date: Oct 2009
Location: England, currently dividing my time between university in Guildford and home just outside Reading
Posts: 1,921
Bikes: Too many to list here!
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 4 Times
in
2 Posts
Titanium brake rotors are available for sale and are very light weight when compared to SS rotors, weighing in at just 88 grams. The Avid G2 Clean Sweep rotors, made of Stainless Steel, weigh 111 grams. A popular disc brake among bikers is the Avid X0's which are aluminum and those weigh in at 108 grams. There are many other alloys out there being used in rotors but those 3 are the most popular.
Josh
Josh
#14
Mad bike riding scientist
Join Date: Nov 2004
Location: Denver, CO
Posts: 27,355
Bikes: Some silver ones, a red one, a black and orange one, and a few titanium ones
Mentioned: 152 Post(s)
Tagged: 1 Thread(s)
Quoted: 6215 Post(s)
Liked 4,213 Times
in
2,362 Posts
This is assuming that the rotors are made of stainless steel. They are commonly made of SS because of the anti-rusting properties, but can also be made of aluminum or titanium. The OP never said what disc brakes he has so it's not completely safe to say it's the heating of steel.
The picture posted by sreten above is very helpful. The copper color the OP is reporting is exactly what you see in the left side of the picture.
Josh
The picture posted by sreten above is very helpful. The copper color the OP is reporting is exactly what you see in the left side of the picture.
Josh
__________________
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
#15
Senior Member
Thread Starter
The rotors are some sort of steel because there are some small rust spots where the pads don't scrub the rotors. The rotors are original Hayes rotors installed by Marin.
#18
Mad bike riding scientist
Join Date: Nov 2004
Location: Denver, CO
Posts: 27,355
Bikes: Some silver ones, a red one, a black and orange one, and a few titanium ones
Mentioned: 152 Post(s)
Tagged: 1 Thread(s)
Quoted: 6215 Post(s)
Liked 4,213 Times
in
2,362 Posts
OEM rotors are very likely to be steel. Probably 302 stainless. Given that you use this for commuting, your rust spots are likely due to salt. 'Stainless' will rust if exposed to road salt, specifically the chloride ion in the salt. It probably won't cause too many problems but you may want to remove the salt from time to time before it gets too out of hand.
__________________
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
#19
Senior Member
Join Date: Dec 2010
Location: Above ground, Walnut Creek, Ca
Posts: 6,681
Bikes: 8 ss bikes, 1 5-speed touring bike
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 86 Post(s)
Likes: 0
Liked 4 Times
in
4 Posts
IME, stainless steel turns various colors as it heats and will stay that way under various conditions.
i would ignore it.
i would ignore it.
#20
Curmudgeon
Join Date: Aug 2005
Location: Nausea, New Hamster
Posts: 1,572
Bikes: (see https://wildavis.smugmug.com/Bikes) Bianchi Veloce (2005), Nishiki Cascade (1992), Schwinn Super Sport (1983)
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 4 Times
in
4 Posts
I doubt it. Tempering actually reduces the hardness of hardened steel so that it is less brittle. If the rotors got too hot, they might be softened. To harden the rotors, you'd have to cool them suddenly, typically by plunging into water.
But I doubt the heating is enough to affect the temper.
But I doubt the heating is enough to affect the temper.
- Wil
#21
Senior Member
Thread Starter
OEM rotors are very likely to be steel. Probably 302 stainless. Given that you use this for commuting, your rust spots are likely due to salt. 'Stainless' will rust if exposed to road salt, specifically the chloride ion in the salt. It probably won't cause too many problems but you may want to remove the salt from time to time before it gets too out of hand.
I'm well aware that stainless is just more resistant to rust rather than rust proof.
When I posted this I thought that the rotors might have multiple layers of different metals and I wore through whatever the top layer is. If it's just due to heating of the metal, then I'm not too concerned about it. I did not realize that I am heating the rotors to 200C/400F though
#22
Mad bike riding scientist
Join Date: Nov 2004
Location: Denver, CO
Posts: 27,355
Bikes: Some silver ones, a red one, a black and orange one, and a few titanium ones
Mentioned: 152 Post(s)
Tagged: 1 Thread(s)
Quoted: 6215 Post(s)
Liked 4,213 Times
in
2,362 Posts
I'm in San Francisco, so no road salt here. If anything it's due to higher humidity. I don't know if salt air is a real thing or not but I'm about 1 mi from the Pacific Ocean so we get lots of fog too.
I'm well aware that stainless is just more resistant to rust rather than rust proof.
When I posted this I thought that the rotors might have multiple layers of different metals and I wore through whatever the top layer is. If it's just due to heating of the metal, then I'm not too concerned about it. I did not realize that I am heating the rotors to 200C/400F though
I'm well aware that stainless is just more resistant to rust rather than rust proof.
When I posted this I thought that the rotors might have multiple layers of different metals and I wore through whatever the top layer is. If it's just due to heating of the metal, then I'm not too concerned about it. I did not realize that I am heating the rotors to 200C/400F though
Heavy braking can generated a lot of heat on a rotor. The rotor is smaller than a rim brake and isn't as large a heat sink as a rim is so it can heat to higher temperatures. You are correct to not be concerned about wear for now. Watch the thickness over time however.
__________________
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Last edited by cyccommute; 03-11-13 at 06:45 AM.
#23
Banned.
Join Date: Feb 2013
Location: Brighton UK
Posts: 1,662
Bikes: 20" Folder, Road Bike
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
Hi,
Apparently the colours are for a one off heating cycle. If you bake or
keep repeating the heating cycle, the colour will go up the heating
scale and no longer indicate the actual maximum temperature.
Hard to say what temperature your brakes are really reaching.
rgds, sreten.
Apparently the colours are for a one off heating cycle. If you bake or
keep repeating the heating cycle, the colour will go up the heating
scale and no longer indicate the actual maximum temperature.
Hard to say what temperature your brakes are really reaching.
rgds, sreten.
#24
Certified Bike Brat
Join Date: Jan 2011
Location: Montreal, Quebec
Posts: 4,251
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Likes: 0
Liked 6 Times
in
6 Posts
Your brake rotors can handle temperatures of up to 425 C and still work fine. Since you haven't reported rainbow coloring or brake fading, which would indicate possible rotor glazing - just ride.
A larger rotor will disipate heat more effectively, as will an aluminum core rotor or a rotor with an aluminum spider. Doesn't sound like you need any of those.
A larger rotor will disipate heat more effectively, as will an aluminum core rotor or a rotor with an aluminum spider. Doesn't sound like you need any of those.
#25
Senior Member
Join Date: Feb 2013
Location: Mesa, AZ
Posts: 561
Bikes: 1992 Trek 800 Antelope, 1971 Triumph
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Say you're (your weight is 68kgs) riding along a road at a constant speed of 16 kph and you're trying to stay at that speed for training or whatever reason have you. Using your speed and weight, you can calculate your energy to about 69 joules. You start going down a hill and your speed starts to increase, but for training purposes, you must stay at a speed of 16 kph and so you start to use your brake. In this case, you have rim brakes on a 700c wheel. Convert all that energy into a 700c wheel and you don't raise the temperature a whole lot unless you are braking to not lock up the wheel and on a hill like the example above.
Imagine the same scenario but you have disc brakes. You are converting the same amount of energy to heat but on a smaller "wheel". The rotor is bound to heat up more than the rim because if you focus heat on a larger area, it will heat up slower than if you focus heat on a point. It's like cooking a fat steak with a grill versus cooking it with a soldering iron.
Josh