Why are these pads glazing so bad?
#1
Senior Member
Thread Starter
Join Date: Jan 2020
Posts: 2,365
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 685 Post(s)
Liked 951 Times
in
558 Posts
Why are these pads glazing so bad?
they are on our tandem with 203mm rotors 4 piston Shimano deore calipers. right now I am trying a basic sram rotor. they are glazing just from going down a 18% grade thats about 1.5 blocks and keeping the speed at 25mph. the tandem is heavy around 400 pounds but this is only 20 or 30 seconds of braking. maybe 3 or 4 times. week. only on the back too. these are MTX ceramic pads. I had al little of this on an ice-tech rotor but that was from longer decents a lot longer. the scratch was from the ice-tech rotor when it was worn. the thing is we have a 5 degree slope we go down every time we ride and if I use the back brake the whole way down it works normally till the next day and I have to repeat it.
#2
ignominious poltroon
Join Date: Jan 2022
Posts: 4,183
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 2301 Post(s)
Liked 3,536 Times
in
1,861 Posts
Lack of heat dissipation fins on the pads and (I am guessing) on the rotors. What is with the huge groove on one of the pads?
Likes For Polaris OBark:
#3
Senior Member
Thread Starter
Join Date: Jan 2020
Posts: 2,365
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 685 Post(s)
Liked 951 Times
in
558 Posts
well yes but its only 30 or so seconds of hard use. the groove was from a worn rotor that I replaced with the sram. I am debating going back to an ice tech rotor. the front ever does it no matter how hard I brake.
#4
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 39,055
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 141 Post(s)
Tagged: 1 Thread(s)
Quoted: 5971 Post(s)
Liked 2,878 Times
in
1,602 Posts
Simply put, it's too much bike for the braked. Your descent would represent a heavy load with a solo bike. With a random, it's twice as bad.
There are a variety of techniques that can help.
1 try using the "air brakes" more by allowing a slightly higher speed. Since air drag is proportional to the square of speed, going even 5mph faster will increase air drag by over 45%, greatly reducing demand on the brakes.
Also do whatever you can to worsen your aero profile.
2- use effective braking technique by cycling the brakes. Rather than holding 25mph, allow the bike to exceed that, then brake down to 20 or so, then repeat. This improves cooling, and should reduce the glazing.
If technique alone isn't enough, improvise a mister to cool the rotor. Or if all else fails, and descents like this are only occasional, consider making a drogue chute which the stoker can deploy when needed.
There are a variety of techniques that can help.
1 try using the "air brakes" more by allowing a slightly higher speed. Since air drag is proportional to the square of speed, going even 5mph faster will increase air drag by over 45%, greatly reducing demand on the brakes.
Also do whatever you can to worsen your aero profile.
2- use effective braking technique by cycling the brakes. Rather than holding 25mph, allow the bike to exceed that, then brake down to 20 or so, then repeat. This improves cooling, and should reduce the glazing.
If technique alone isn't enough, improvise a mister to cool the rotor. Or if all else fails, and descents like this are only occasional, consider making a drogue chute which the stoker can deploy when needed.
#5
Senior Member
Thread Starter
Join Date: Jan 2020
Posts: 2,365
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 685 Post(s)
Liked 951 Times
in
558 Posts
this is such a short section but its also has several houses on it and people back out o their driveways right onto the road. like I sad a block or so. going faster is not safe and I would not be able to do an emergency stop if someone pulls out and they have. every 25 may be pushing it with the rough road.
but its so short you would not think the system has enough time to heat up. it is last most 20 or 30 seconds.
here is a pic. not a road you want to fly down. so debating on buying another ice tech rotor. my wife can use the back rim brake.
but its so short you would not think the system has enough time to heat up. it is last most 20 or 30 seconds.
here is a pic. not a road you want to fly down. so debating on buying another ice tech rotor. my wife can use the back rim brake.
#6
aged to perfection
Join Date: Jun 2009
Location: PacNW
Posts: 1,877
Bikes: Dinucci Allez 2.0, Richard Sachs, Alex Singer, Serotta, Masi GC, Raleigh Pro Mk.1, Hetchins, etc
Mentioned: 24 Post(s)
Tagged: 0 Thread(s)
Quoted: 865 Post(s)
Liked 1,305 Times
in
690 Posts
This does not look like a descent that could heat rotors or pads badly enough to render them unusable
suggest try softer pads ? and maybe drag the rear brake only ?
I liked the mister idea. or the drag chute
/markp
suggest try softer pads ? and maybe drag the rear brake only ?
I liked the mister idea. or the drag chute
/markp
#7
Senior Member
Thread Starter
Join Date: Jan 2020
Posts: 2,365
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 685 Post(s)
Liked 951 Times
in
558 Posts
I know thats the thing we have done worse then this the nI had the ice-tech rotors and finned pads. I dont think I had an issue with the ceramic pads on the ice-tech rotor but cant remember for sure as the ice-tech was on its last legs when I changed over. I guess if I buy the ice tech and still have issues I I will have to go back to the overpriced finned pads. I used to only have issues when I keep the speed at 25 on mile long decents. then I would get black buildup on the rotor and that was a real pain to remove had to sand off. we have not been riding hills but this guy in the last several months and it only takes a few times to cause issues. I will email mtx and ask them too.
#8
Senior Member
Join Date: Oct 2022
Posts: 1,378
Bikes: a couple
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 563 Post(s)
Liked 870 Times
in
457 Posts
they are on our tandem with 203mm rotors 4 piston Shimano deore calipers. right now I am trying a basic sram rotor. they are glazing just from going down a 18% grade thats about 1.5 blocks and keeping the speed at 25mph. the tandem is heavy around 400 pounds but this is only 20 or 30 seconds of braking. maybe 3 or 4 times. week. only on the back too. these are MTX ceramic pads. I had al little of this on an ice-tech rotor but that was from longer decents a lot longer. the scratch was from the ice-tech rotor when it was worn. the thing is we have a 5 degree slope we go down every time we ride and if I use the back brake the whole way down it works normally till the next day and I have to repeat it.
Glazing is caused by heat. heat is caused by as you know, friction. Certain pad materials can generate more heat.
Ceramic is generally mixed with an organic material, but the higher the ceramic content the longer the bed in, lower is a faster bed in. (higher noise with high ceramic too)
The MTX pads are sold as a fast bed in. so they are softer pads. lower ceramic content.
Your short run is just enough to overheat those pads.
I'd get something semi metallic or metallic and use the crap out of disk brake quiet.
.
Last edited by Schweinhund; 07-14-23 at 05:07 AM.
#9
Senior Member
Join Date: Oct 2022
Posts: 1,378
Bikes: a couple
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 563 Post(s)
Liked 870 Times
in
457 Posts
Just to put it out there, ceramic is low dust and low noise and doesn't chew up rotors. That's the why of it.
It ain't the best braking material. IMHO.
It ain't the best braking material. IMHO.
#10
Hello
As was suggested above "cycling" the brakes to mitigate heat build up.
The technique from the days of rim brakes was to alternate front and back.
Pulse the back brake hard for a moment and then the front or vice versa.
The technique from the days of rim brakes was to alternate front and back.
Pulse the back brake hard for a moment and then the front or vice versa.
#11
I'm good to go!
Join Date: Jul 2017
Location: Mississippi
Posts: 15,288
Bikes: Tarmac Disc Comp Di2 - 2020
Mentioned: 52 Post(s)
Tagged: 0 Thread(s)
Quoted: 6353 Post(s)
Liked 4,956 Times
in
3,413 Posts
I always thought the better braking technique for going down steep hills was to slow the bike to a low speed fairly rapidly, then let it accelerate on it's own with out brakes. When the speed gets high, then again slow the bike back down rapidly to a low speed with the brakes.
If you need to get to the bottom faster so you can beat everyone else, then you still have to modulate the braking. On then off to maintain a speed range that you can safely descend at.
Dragging one or both brakes for extended times is never a good thing.
If you need to get to the bottom faster so you can beat everyone else, then you still have to modulate the braking. On then off to maintain a speed range that you can safely descend at.
Dragging one or both brakes for extended times is never a good thing.
Likes For Iride01:
#12
Senior Member
Thread Starter
Join Date: Jan 2020
Posts: 2,365
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 685 Post(s)
Liked 951 Times
in
558 Posts
that's what I am thinking its cheaper getting new pads for sure. they would be ok if I went back to the ice tech rotors but its far less to go back to normal metallic pads. t=I will use them in the front as they do fine there and I have pas to go through.
Likes For fooferdoggie:
#13
Senior Member
Thread Starter
Join Date: Jan 2020
Posts: 2,365
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 685 Post(s)
Liked 951 Times
in
558 Posts
I always thought the better braking technique for going down steep hills was to slow the bike to a low speed fairly rapidly, then let it accelerate on it's own with out brakes. When the speed gets high, then again slow the bike back down rapidly to a low speed with the brakes.
If you need to get to the bottom faster so you can beat everyone else, then you still have to modulate the braking. On then off to maintain a speed range that you can safely descend at.
Dragging one or both brakes for extended times is never a good thing.
If you need to get to the bottom faster so you can beat everyone else, then you still have to modulate the braking. On then off to maintain a speed range that you can safely descend at.
Dragging one or both brakes for extended times is never a good thing.
#14
Senior Member
Join Date: Apr 2010
Location: Elevation 666m Edmonton Canada
Posts: 2,512
Bikes: 2013 Custom SA5w / Rohloff Tourster
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 1253 Post(s)
Liked 338 Times
in
254 Posts
My tour bike loaded is 290 lbs. With my front SA XL dyno DRUM brake it's child's play. For the 1st tour and across B.C. the 2nd tour I had an absolute POS rim caliper on the Rohloff.
I was stopping from over 30 mph in the middle of a hill to take pics in the mountains. Overheating is a laughable concept. ZERO drama in any weather.
Now with a cable TRP Spyre and resin pads on the Rohloff it stops instantly.
Before >>
Kicking Horse Pass >>
After I got the disc mount welded in Seattle. The front fork is a tandem from R+E. I put a 3" CF wrap by the clamp for the brace arm.
I was stopping from over 30 mph in the middle of a hill to take pics in the mountains. Overheating is a laughable concept. ZERO drama in any weather.
Now with a cable TRP Spyre and resin pads on the Rohloff it stops instantly.
Before >>
Kicking Horse Pass >>
After I got the disc mount welded in Seattle. The front fork is a tandem from R+E. I put a 3" CF wrap by the clamp for the brace arm.
Last edited by GamblerGORD53; 07-14-23 at 09:50 AM.
#16
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 39,055
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 141 Post(s)
Tagged: 1 Thread(s)
Quoted: 5971 Post(s)
Liked 2,878 Times
in
1,602 Posts
You might try a 10 second stop midway down, or descend slower so rotors have more time to dissipate heat.
#17
Senior Member
Join Date: Apr 2021
Posts: 4,083
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 2333 Post(s)
Liked 2,097 Times
in
1,314 Posts
This is why disc brakes suck
I have the same problem. A week don't go by that I am not fixing them.
I know how to brake and have more than a basic understanding of physics. Of course, I could dynamite those 20% gradients, block off the driveways and side streets.
I have the same problem. A week don't go by that I am not fixing them.
I know how to brake and have more than a basic understanding of physics. Of course, I could dynamite those 20% gradients, block off the driveways and side streets.
#18
Senior Member
Thread Starter
Join Date: Jan 2020
Posts: 2,365
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 685 Post(s)
Liked 951 Times
in
558 Posts
we have been going down this hill for over 3 years. but only now that we have not been doing any other hills and a new rotor have I had issues. I will replace the pads with shimano pads and see.
#19
Senior Member
Join Date: Jul 2015
Location: NW Oregon
Posts: 2,999
Bikes: !982 Trek 930R Custom, Diamondback ascent with SERIOUS updates, Fuji Team Pro CF and a '09 Comencal Meta 5.5
Mentioned: 15 Post(s)
Tagged: 1 Thread(s)
Quoted: 1308 Post(s)
Liked 751 Times
in
544 Posts
Are they squealing? Not braking as well as when freshly resurfaced?
Seriously.. WHY are you complaining of "glazing" when none is evident?
Are you just misusing the term?
And it sounds, from your description of your riding technique, that you constantly drag the rear brake on downhills... Take the advice already given as to brake/release/brake/release, instead of dragging the brake in one long pad overheating session.. and learn to use the front brake more often.
Last edited by maddog34; 07-14-23 at 02:49 PM.
#20
Senior Member
Thread Starter
Join Date: Jan 2020
Posts: 2,365
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 685 Post(s)
Liked 951 Times
in
558 Posts
WHY do you think "The pads are glazing"? cuz' i ain't seeing any "glazing".. all i'm seeing is normal use , and edge chips from screwdriver abuse or impatience when re-installing the wheel.....
Are they squealing? Not braking as well as when freshly resurfaced?
Seriously.. WHY are you complaining of "glazing" when none is evident?
Are you just misusing the term?
And it sounds, from your description of your riding technique, that you constantly drag the rear brake on downhills... Take the advice already given as to brake/release/brake/release, instead of dragging the brake in one long pad overheating session.. and learn to use the front brake more often.
Are they squealing? Not braking as well as when freshly resurfaced?
Seriously.. WHY are you complaining of "glazing" when none is evident?
Are you just misusing the term?
And it sounds, from your description of your riding technique, that you constantly drag the rear brake on downhills... Take the advice already given as to brake/release/brake/release, instead of dragging the brake in one long pad overheating session.. and learn to use the front brake more often.
#21
Senior Member
Join Date: Jul 2015
Location: NW Oregon
Posts: 2,999
Bikes: !982 Trek 930R Custom, Diamondback ascent with SERIOUS updates, Fuji Team Pro CF and a '09 Comencal Meta 5.5
Mentioned: 15 Post(s)
Tagged: 1 Thread(s)
Quoted: 1308 Post(s)
Liked 751 Times
in
544 Posts
they are glazed and it only takes a bit of sanding to make them look normal. if I dont they dont grab. My mechanic at the shop thinks when I use a smaller hill to bed the pads in it may be causing them to glaze as its too much heat to start with and I may have overheaded the rotor and thats causing issues since they have glazed so many times. I showed the hill its way too steep and short to let the speed go we would hit 35mph or more its on 9 seconds of braking. I have been doing it for years with no problem till now.
learn to use more front brake... Seriously.
and 35mph is fun to most riders.... about double that speed gets scary.. i love downhills.
brake with BOTH brakes for 3-5 seconds, release for 2-3 seconds, repeat as needed. What you want to achieve is a cooling of the INTERFACE between the pad surface and the Disc surface...this only takes a second or two... you are allowing the PLASMA created when Brakes Operate to dissipate... brakes turn motion into HEAT energy, Period. That SURFACE heat needs a way to dissipate.
Try this old M/C trick.. file tiny Grooves in the Pad surfaces... 1/4", tiny groove, 1/4", next tiny groove, etc...the Grooves will be filed as to route the PLASMA towards the outside of the caliper, at about a 45 deg. angle... ok? and quit just applying the brake all the way down your nemesis hill... report back with the results.
one other thing... pads that were seated to a different disc have LESS Contact with the new disc, period.. what happens to the areas that Do touch? They Get Used Harder... and get.. HOTTER.
a request.. could you post a pic of the DISCS involved? not seeing them here.... and if you simply post the brand/model number, then i look them up, i'll see hundreds of ads for bicycle brakes for the next several months, possibly years...... sigh.
Last edited by maddog34; 07-14-23 at 03:25 PM.
#22
Senior Member
I am new in using disk brakes, so my opinion might not be the best. But I don't think they are glazed because they don't look glossy. They rather look like hardly used and porous, with some materials filling the pores - as expected. Plus a scratch that might come from some dirt on the disk, which should not generate important issues.
I also have issues with front disk brake. While sanding pads (not sure it was needed), I noticed some metallic small parts inside the resin which remained after sanding, but I consider it is by design and not a sign of glazing.
I also have issues with front disk brake. While sanding pads (not sure it was needed), I noticed some metallic small parts inside the resin which remained after sanding, but I consider it is by design and not a sign of glazing.
#23
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 39,055
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 141 Post(s)
Tagged: 1 Thread(s)
Quoted: 5971 Post(s)
Liked 2,878 Times
in
1,602 Posts
Consider the problem. Glazing will happen when the rotor heats to above a critical temp. In other words, during the last few of those 7-9 seconds.
If you were to pulse the brakes, you could prevent heating to that level, or better balance the glazing/deglazing cycle. Likewise more use of brakes between revisits to this hill will help.
BTW other things that may help include a thicker or heavier rotor, which will be a better heat sink, and stay cooler. Also, check for pads with better hot performance, less likely to "melt" into glaze.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
#24
Senior Member
If 7-9 seconds (or less) of hard braking create an issue, then I would say that disk brakes have a critical issue of functionality. I used rim brakes (Al. rims) for a much longer period than 7-9 seconds of hard braking (front) and I never had an issue. But I would rather say that in this post, the pads from the picture show no sign of glazing; just signs of heavy usage.
#25
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 39,055
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 141 Post(s)
Tagged: 1 Thread(s)
Quoted: 5971 Post(s)
Liked 2,878 Times
in
1,602 Posts
If 7-9 seconds (or less) of hard braking create an issue, then I would say that disk brakes have a critical issue of functionality. I used rim brakes (Al. rims) for a much longer period than 7-9 seconds of hard braking (front) and I never had an issue. But I would rather say that in this post, the pads from the picture show no sign of glazing; just signs of heavy usage.
However, preferences aside, the OP is looking for help with what he has, not advice to change.
Also keep in mind that the OP's tandem weights 400#s so it's a very different animal than a solo bike. Just as heavier and/or faster motor vehicles use larger brakes, so should bikes.
My initial post here was that the OP had too much bike for the brakes. I believe that's the key issue, but I also believe that it can be managed, if the OP changes things (both hardware and/or technique) to create more breathing room.