Why did my brakes fail, and what should I do to avoid this happening again?

[MarcW]

I use this exact rotor on my rear wheel with both XT and XTR Brake setup and Qaxar pads. No issues to date with fading, and I've been down that same descent that you fell on Brandon. I'm not too hard on brakes though.

 

But your issue does sound like brake fade from overheating. Guess the only way to find out if it is the rotor is to switch pads and try heat them up down a safer descent.

 

Heal up quick

[JXV]

..dont scream at me, Im only a child...

 

Just kidding,..yeah, Im the worlds worst weight weenie,..ok, maybe second worst after Evan Kevins..(or whatever),..

 

I dont pay for anything done on my car, petrol, installment, insurance etc etc, so I cannot comment.

 

But I do like to experiment,..and in "this case" ..got burned...#pointtaken????

Sorry if I came over a bit harsh but your life is on the line here...... get rid of the emmentaler brake discs. Save grams elsewhere.

[emoji3]

[BrandonF_]

Sorry if I came over a bit harsh but your life is on the line here...... get rid of the emmentaler brake discs. Save grams elsewhere.

[emoji3]

No offence taken ???? we all have reason for our own opinions, and each is valid in its own respect ????

 

I hear you, and will most definitely take heart in your opinion ????

 

Thx for sharing ????

[SCD]

I was at the same downhill today and jep it was very steep. To add to the steepness the downhill was quite long throwing a lot of energy at the brake disks to dissipate.

 

I had rotors like this a while back and replaced them when I got them glowing red on the Tokai mast downhill. The energy absorption capacity of such thin metal is just too little and the small surface will not offer great cooling. The below link offers some interesting inside into the internals of brakes. The effects of "friction fade" and "vapor fade" are explained on page 9: http://www.sram.com.cn/sites/default/files/techdocs/gen.0000000004234_rev_a_hydraulic_disc_brakes_overview.pdf 

 

It would add value if brake disks were sold with their energy dissipation capacity stated and not just the weight. This would make for some better decisions I guess

 

Glad you are ok Brandon

[DJR]

They are pretty good looking rotors though.....matches the spoke pattern almost perfectly. Just kidding!   

[BrandonF_]

I was at the same downhill today and jep it was very steep. To add to the steepness the downhill was quite long throwing a lot of energy at the brake disks to dissipate.

 

I had rotors like this a while back and replaced them when I got them glowing red on the Tokai mast downhill. The energy absorption capacity of such thin metal is just too little and the small surface will not offer great cooling. The below link offers some interesting inside into the internals of brakes. The effects of "friction fade" and "vapor fade" are explained on page 9: http://www.sram.com.cn/sites/default/files/techdocs/gen.0000000004234_rev_a_hydraulic_disc_brakes_overview.pdf

 

It would add value if brake disks were sold with their energy dissipation capacity stated and not just the weight. This would make for some better decisions I guess

 

Glad you are ok Brandon

Thank you Sebastian, as usual, proper, insightful input, and information added. Well appreciated.

[MarcL]

Hi

In my view it was over heating. That was a serious downhill.

 

I'm a big guy, over 95kg and have used those KCNC rotors for a long time with SRAM brakes with little to no issue.

 

On me new bike, I had XTR Ice tech which frequently over heated, even with 180 rotor.

 

I know XTR are the best, but for me they did not cut it.

 

On researching, I learnt the SRAM use a different oil with a higher boiling point, so at great expense, I change to SRAM Guides and surprise surprise, after yesterday's downhill, I still had perfectly good brakes. I doubt I could say the same with my XTR.

 

All this is from my personal experience, so I'll leave it to you to decide.....

 

Hope that helps.

[SwissVan]

..not really sir. Maybe "Alligator metal pads failure",...but prior to that, been running "Baradine Metal pads/KCNC Razor rotors,..no probs....sir

Proof is in the pudding, look at your thread title

The rotors were your main problem, however the combination also contributed.

 

dont be that guy, no need for sarcasm

[Thermophage]

Those are ridiculous

+ metal pads

+ steep descent

= YouTube comedy material

Well to be honest I don't think it's the rotors...I run these and they're similarly lacking in metal. I also rode the 40km and there were some waaaay longer and steeper downhills later in the ride.

Although I am running the Zee brakes and not XT.

However...perhaps it is the pads afterall? Or maybe the quad pistons on the Zee's help, but I had no fade.

Just bleed em and get some Shimano metal sintered pads (with or without fins).

And don't take it to a bike shop to bleed them...Go buy the bleed funnel for R50 and some syringes for R5 as Dischem then 1l oil for R300 (instead of R150 got 150ml!) and DIY.

Super simple and then you will have a little more confidence in them too

[BrandonF_]

Hi

In my view it was over heating. That was a serious downhill.

 

I'm a big guy, over 95kg and have used those KCNC rotors for a long time with SRAM brakes with little to no issue.

 

On me new bike, I had XTR Ice tech which frequently over heated, even with 180 rotor.

 

I know XTR are the best, but for me they did not cut it.

 

On researching, I learnt the SRAM use a different oil with a higher boiling point, so at great expense, I change to SRAM Guides and surprise surprise, after yesterday's downhill, I still had perfectly good brakes. I doubt I could say the same with my XTR.

 

All this is from my personal experience, so I'll leave it to you to decide.....

 

Hope that helps.

Great info, thx Mark

[BrandonF_]

Proof is in the pudding, look at your thread title

The rotors were your main problem, however the combination also contributed.

 

dont be that guy, no need for sarcasm

Apologies, just found your comment a bit sarcastic and pointless too.

 

Thx for the correction.

[SwissVan]

Well to be honest I don't think it's the rotors...I run these and they're similarly lacking in metal. I also rode the 40km and there were some waaaay longer and steeper downhills later in the ride.

Although I am running the Zee brakes and not XT.

However...perhaps it is the pads afterall? Or maybe the quad pistons on the Zee's help, but I had no fade.

Just bleed em and get some Shimano metal sintered pads (with or without fins).

And don't take it to a bike shop to bleed them...Go buy the bleed funnel for R50 and some syringes for R5 as Dischem then 1l oil for R300 (instead of R150 got 150ml!) and DIY.

Super simple and then you will have a little more confidence in them too

Yes good pads will make a difference, but there is a limit to the ability of those rotors which will be reached sooner rather than later.

 

There is a good reason why u don't see such "minimalistic" discs on the majority of mtbks

[RockCoach]

I think by now you realise your error.

 

How to minimize fade:

Use larger rotors

Use thicker rotors

Use rotors with more braking surface

Use high quality metal pads

Use braided lines

Use callipers with twin pistons

Use hydraulic fluid with a higher boiling point

 

I use all of the above: Hope brakes

 

Hope Race X2 are some of the lightest brake sets you can get

But they don't compromise metal in their rotors which are probably the heaviest.

[PhilipV]

Brandon, I really like your attitude here. You had a crash, you asked questions, you get varied questions, and you seem willing to try out the different solutions. Lekker ou.

 

My last advice, I've used alligator pizza cutter rotors before, and they faded badly on the front wheel. I now only use meatier rotors, and 180mm on front wheel My wife on the other hand, has no such issues with it on her bike. Some times you just work the brakes harder, and can reach the compromise points earlier, and I think this happened here.

I do believe the combination of pads and rotors are not ideal, but I'll switch the pads to OEM spec first, and then try to reach the brake fade point to see if it was the pads, and if it happens again, switch the rotors. Do remember that the warm outside temp might also have added to your woes.

I've only experienced brake fade a couple of times, first with pizza cutter rotors, and the using alivio brakes chasing a downhiller down Helderberg. The alivio never stood a chance, I asked too much of it.

[Captain Fastbastard Mayhem]

What Philip said