A proper disc brake test protocol !!

User avatar
MichaelB
Posts: 9316
Joined: Tue Feb 20, 2007 9:29 am
Location: Adelaide, South Australia

A proper disc brake test protocol !!

Postby MichaelB » Tue May 08, 2018 10:13 am

Yeah, I know it's MTB based, but the whole testing regime and results is what I call a proper test protocol.

Now, if those naysayers who say rim brakes are just as good, or argue against discs ***, this is how I think Alto should have done their test. (see their youtube test below)

Enduro MTB Disc test

Image

Now that's what I call braking !!!! I'd love to see a similar test protocol for rim brakes to be able to show the differences and settle arguments once and for all.

A snip of their testing protocol :
Deceleration testing – Once bedding in the real testing began. The dynamometer accelerated the rotor to 35 kph, and the brakes were pulled hard, the computer measured the braking torque applied, the temperature build up and the time taken to decelerate the 100 kg simulated rider from 35 – 15 kph. This was repeated 10 times in succession to take an average deceleration time. Testing was repeated at 35 – 0 kph and finally the toughest test of all, 10 repeated hard cycles pulling down from 45-0 kph, a very demanding test that scorched the brake pads and saw disc temperatures climb over 400 degrees.

Yeah, yeah, you need to download their app to get the full results (which I'll probably do as I'm a geek for this stuff and it piques my engineering curiosity to see the differences between calipers (2 & 4 pot) & brands.

EDIT : Actually, it's free and the writeup is VERY detailed !!





What unsettles me in the alto test is the uneven braking and the wheel skipping when it gets hot - whether that happens in real life, dunno. Never had carbon wheel rim brakes on any of my bikes.




***albeit it's your opinion and your riding conditions, routes, weight, style etc may not have a need for discs, or that disc brakes are deemed to be ugly, heavy, non-aero, then no problem. All good.

human909
Posts: 9123
Joined: Tue Dec 01, 2009 11:48 am

Re: A proper disc brake test protocol !!

Postby human909 » Tue May 08, 2018 11:56 am

MichaelB wrote:Now, if those naysayers who say rim brakes are just as good, or argue against discs ***, this is how I think Alto should have done their test.

Could you please elaborate on how this addresses the discussion about rim brakes?

MichaelB wrote:Now that's what I call braking !!!!

Which part? The torque? Yep rim brakes can readily do that. Even without test a quick calculation will give you that answer.

MichaelB wrote:I'd love to see a similar test protocol for rim brakes to be able to show the differences and settle arguments once and for all.

What are the test goals and requirements? How would a bunch of graphs settle the differences in different needs and roles?

MichaelB wrote:***albeit it's your opinion and your riding conditions, routes, weight, style etc may not have a need for discs, or that disc brakes are deemed to be ugly, heavy, non-aero, then no problem. All good.

Exactly.

User avatar
MichaelB
Posts: 9316
Joined: Tue Feb 20, 2007 9:29 am
Location: Adelaide, South Australia

Re: A proper disc brake test protocol !!

Postby MichaelB » Tue May 08, 2018 1:14 pm

human909 wrote:
MichaelB wrote:Now, if those naysayers who say rim brakes are just as good, or argue against discs ***, this is how I think Alto should have done their test.

Could you please elaborate on how this addresses the discussion about rim brakes?

It shows how a proper test should be done. If rim brakes would be tested with the same methodology, we'd actually have results rather than conjecture about how good/bad either system is.


MichaelB wrote:Now that's what I call braking !!!!

Which part? The torque? Yep rim brakes can readily do that. Even without test a quick calculation will give you that answer.

Can they do it repeatedly with the similar results ? Dunno. That's what I'd like to see.

MichaelB wrote:I'd love to see a similar test protocol for rim brakes to be able to show the differences and settle arguments once and for all.

What are the test goals and requirements? How would a bunch of graphs settle the differences in different needs and roles?

It shows WHAT the system is capable of. Hardly anyone would use the system to it's limits, bit show capability and repeatability of maximal capability.

MichaelB wrote:***albeit it's your opinion and your riding conditions, routes, weight, style etc may not have a need for discs, or that disc brakes are deemed to be ugly, heavy, non-aero, then no problem. All good.

Exactly.


:?:

human909
Posts: 9123
Joined: Tue Dec 01, 2009 11:48 am

Re: A proper disc brake test protocol !!

Postby human909 » Tue May 08, 2018 5:55 pm

The thing is that in terms of shear braking performance it is well known that large rotor hydraulic disc brakes are better performers in most braking metrics especially under adverse or extreme conditions. I don't think there has been a whole lot of dispute there.

Showing a bunch of graphs on the torque of various brakes and suggesting one is better than another is sort of like comparing the power output of a 4L V8 engine to a small 1.2L engine and saying one is clearly 'better' than another. But that V8 is more expensive to fuel, to maintain and has totally unnecessary power for a small city car for a single person.

So yes we have a bunch of test data on brakes but what is it actually telling us? For example the graph you posted show a brakes torque based on constant brake lever force. Is that necessarily desirable metric of comparison? None of that is clear.

human909
Posts: 9123
Joined: Tue Dec 01, 2009 11:48 am

Re: A proper disc brake test protocol !!

Postby human909 » Tue May 08, 2018 6:06 pm

MichaelB wrote:What unsettles me in the alto test is the uneven braking and the wheel skipping when it gets hot - whether that happens in real life, dunno. Never had carbon wheel rim brakes on any of my bikes.

If that unsettles you then remember that the energy put into the braking surface in these test is between twice and twenty times more than the most demanding test that is done on the disc brakes.

10 repeated hard cycles pulling down from 45-0 kph, a very demanding test that scorched the brake pads and saw disc temperatures climb over 400 degrees.

(AKA equivalent of around 70seconds of the Alto test)

Jmuzz
Posts: 567
Joined: Mon Jan 29, 2018 1:42 pm

Re: A proper disc brake test protocol !!

Postby Jmuzz » Tue May 08, 2018 6:12 pm

It's sort of all done for motorcycles and cycling is just lagging a few decades behind claiming "tech advancement" on ancient stuff.
Hopefully Brembo just step in and fast forward the industry 20 years.

Double sided pistons are far better than single sided.
Multiple pistons are better, 2 per side is a big jump from 1, 3 is slightly better. More is no real use for tiny bike pads but does make a difference the bigger/longer the pad gets.
Two smaller discs, one on each side, is better than a single sided larger disc.
Disc must be floating.
Rear can be far smaller than front since it does almost nothing when braking hard. Though on cycle it is still usefull to spread heat during a prolonged light braking descent.

Of course lower tech still works adequately, most cars still have basic single sided calipers and non floating discs.
But they aren't built for sport. Expect top end bikes to get the full features of modern sportsbike motorcycles.

human909
Posts: 9123
Joined: Tue Dec 01, 2009 11:48 am

Re: A proper disc brake test protocol !!

Postby human909 » Tue May 08, 2018 6:32 pm

Tech advancement? Most of this is just century old tech being sold to consumers as the latest and greatest when for decades we the consumers didn't want or need such 'technology'. Don't confuse consumerism with engineering and technology.

Disc brakes were introduced for mountain biking responding to a real need. The real need for discs for road cycling is doubtful. But the benefit of convincing road cyclists that they need disc brakes is very real for the profits of bicycle manufacturers. :wink:

User avatar
MichaelB
Posts: 9316
Joined: Tue Feb 20, 2007 9:29 am
Location: Adelaide, South Australia

Re: A proper disc brake test protocol !!

Postby MichaelB » Tue May 08, 2018 10:07 pm

Hi jmuzz,

Agree there with most points but cycling requirements don’t really need some of those items.
But, the ‘longer’ pad and 4 piston (gives great power and more importantly modulation , and hence why I went to the Zee calipers on my setup.
The other benefit is greater thermal capacity in the larger pad as well as longer life compared to some of the smaller pads as used in the SRAM calipers.

What I liked about the test is the recording of the data that proves certain facts, but some of the editing in the writeups on each calipers need better checking !!

User avatar
MichaelB
Posts: 9316
Joined: Tue Feb 20, 2007 9:29 am
Location: Adelaide, South Australia

Re: A proper disc brake test protocol !!

Postby MichaelB » Thu May 10, 2018 2:44 pm

human909 wrote:
MichaelB wrote:What unsettles me in the alto test is the uneven braking and the wheel skipping when it gets hot - whether that happens in real life, dunno. Never had carbon wheel rim brakes on any of my bikes.

If that unsettles you then remember that the energy put into the braking surface in these test is between twice and twenty times more than the most demanding test that is done on the disc brakes.

10 repeated hard cycles pulling down from 45-0 kph, a very demanding test that scorched the brake pads and saw disc temperatures climb over 400 degrees.

(AKA equivalent of around 70seconds of the Alto test)


If you are going to make statements like the red highlighted passage above, please provide evidence of your calculation.

The Alto 'test' ** was a very different type altogether, and amateurish at best compared to that done by Enduro.


**I used that term loosely, as it was more a demonstration of a particular trait/capability of the Alto rim vs others

human909
Posts: 9123
Joined: Tue Dec 01, 2009 11:48 am

Re: A proper disc brake test protocol !!

Postby human909 » Thu May 10, 2018 10:26 pm

MichaelB wrote:If you are going to make statements like the red highlighted passage above, please provide evidence of your calculation.

In my experience those there isn't much use detailing calculations in posts because those who understand them can readily do it and those who can't will ignore it and stick to their beliefs.

I won't post the calculation. But you can do it as an exercise yourself and feel free to dispute my assertion. The Alto test is a simple power X time calculation. The Enduro MTB Disc test is a simple kinetic energy X (estimated rider mass) X repetitions scenario.

Nothing complex. A quick back calculation also gave me similar power levels rates in the Enduro MTB to the Alto test. (Though power levels were not constant in the Enduro tests, both between tests and during tests.)

User avatar
MichaelB
Posts: 9316
Joined: Tue Feb 20, 2007 9:29 am
Location: Adelaide, South Australia

Re: A proper disc brake test protocol !!

Postby MichaelB » Fri May 11, 2018 8:21 am

human909 wrote: In my experience those there isn't much use detailing calculations in posts because those who understand them can readily do it and those who can't will ignore it and stick to their beliefs.

I won't post the calculation.


What tosh.

If you are not willing to substantiate claims when asked, then don't bother making them.

Refusal to do so usually means one thing.

:roll:

User avatar
outnabike
Posts: 2171
Joined: Tue Jan 08, 2013 2:53 pm
Location: Melbourne Vic

Re: A proper disc brake test protocol !!

Postby outnabike » Fri May 11, 2018 8:40 am

human909 wrote:
MichaelB wrote:If you are going to make statements like the red highlighted passage above, please provide evidence of your calculation.

In my experience those there isn't much use detailing calculations in posts because those who understand them can readily do it and those who can't will ignore it and stick to their beliefs.

[/i]

That's my problem human99 I just don't know the basics on how to work that stuff out and ensuing conjecture is just that to me. I know that is my problem.

To me it's about personal experience and what happens to me when braking. literal seat of the pants stuff.

My bike has a disk brake front and a rim brake rear. The other day a car kept going straight on at a tee intersection that I was entering. They had their indicator on to turn left but went straight on.
My brakes are well adjusted and I just had time to stop, applying both brakes hard.
Going down a slight incline the front brake (disc) worked well and the rear brake skidded out the rear wheel. No problem either way as I had to turn slightly left during the event. I have no arguement with either set up, but I have found the disc to be more requiring of servicing than the simple pad rear brakes.
I like the disc brakes in hilly terrain. But my hills are not what the real hills riders call hills. :)
Vivente World Randonneur complete with panniers

human909
Posts: 9123
Joined: Tue Dec 01, 2009 11:48 am

Re: A proper disc brake test protocol !!

Postby human909 » Fri May 11, 2018 9:43 am

MichaelB wrote:What tosh.

If you are not willing to substantiate claims when asked, then don't bother making them.

Refusal to do so usually means one thing.

:roll:

I'm not here to teach you high school physics. You were the one posting the results yet if you don't know the basics on how to interpret them then why are you engaging in this discussion so enthusiastically? I'd be more than willing to explain my statements to somebody who engaged in a constructive way. You don't seem to be doing this.

human909
Posts: 9123
Joined: Tue Dec 01, 2009 11:48 am

Re: A proper disc brake test protocol !!

Postby human909 » Fri May 11, 2018 9:58 am

outnabike wrote:That's my problem human99 I just don't know the basics on how to work that stuff out and ensuing conjecture is just that to me. I know that is my problem.

Fair enough. I'll give a quick summary regarding my previous comments.

The Alto test and Enduro "toughest test" both were tests that stressed the braking system's ability to absorb alot of energy. Braking systems that can't absorb alot of energy end up with fade, burnt pads, boiling hydraulic fluid and/or destroyed rims... But in reality these are really extreme tests that you are unlikely to ever subject your brakes to.

With the information given you can readily work out the sort of conditions required. I think I did the same in the last discussion of the Enduro test... 20minutes? You'd have to descend half of Mt Everest at 70kph braking the whole time. (I haven't calculated this today, but I did to it in the last discussion.)

outnabike wrote:To me it's about personal experience and what happens to me when braking. literal seat of the pants stuff.

Same here. I like discs for their good braking and predictability in wet and gritty conditions.

outnabike wrote:I have no arguement with either set up, but I have found the disc to be more requiring of servicing than the simple pad rear brakes.

Same here. :D

User avatar
MichaelB
Posts: 9316
Joined: Tue Feb 20, 2007 9:29 am
Location: Adelaide, South Australia

Re: A proper disc brake test protocol !!

Postby MichaelB » Fri May 11, 2018 10:24 am

human909 wrote:
MichaelB wrote:What tosh.

If you are not willing to substantiate claims when asked, then don't bother making them.

Refusal to do so usually means one thing.

:roll:

I'm not here to teach you high school physics. You were the one posting the results yet if you don't know the basics on how to interpret them then why are you engaging in this discussion so enthusiastically? I'd be more than willing to explain my statements to somebody who engaged in a constructive way. You don't seem to be doing this.


I'm not asking you to teach me. I have never made a claim that rim brakes don't work well.

The whole idea of this post was to highlight a well documented and conducted test protocol and the results obtained, and wish that we could see something similar for rim brakes that would provide facts and not just conjecture or opinion on performance. The Alto test that I mentioned did not have a real methodology, detailed recording of results, accurate equipment, as well as doing a different test altogether.

The test above done by Enduro is about braking performance via repeated stops following a strict methodology in a controlled environment. Not real world, and they acknowledge this. But what it does provide is a very good set of data on relative performance between different brands at the same level of lever application.

I'd LOVE to see a similar test for rim brakes, as it would then provide a direct comparison between the two systems, and if I'm wrong, and the data for rim brakes show that they are better, I'll go "he". But there isn't any COMPARABLE data.

The Alto test shows something completely different (different lever force, method of force application is flawed (not stable ), the wheels jump around during test and therefore energy imparted to the wheel is not constant, and the test is done to rim failure (or a set time)) - it does not look at what is the braking capability of the system for repeated stops. It is a constant drag of a set force application at a constant speed.

THAT is what I was illustrating by putting the post above.

If you think that you don't want to educate others to help learn, then that is your problem, not mine.

How am I not constructive ? I've provided good reasoning WHY this test is sound and a good method to measure and provide repeatable results. I've also done the same for the Alto test, to show that it isn't the same, but also that it tests for a different aspect altogether.

I'm engaging enthusiastically, as I love and appreciate good engineering, especially when it comes to how to test 'stuff' properly.

I'm also enthusiastic, as I'd like to see how the rim brakes measure up, as it may also debunk the myth that current carbon clincher rims are great for descents and braking power, it's just that they are different to rims, whether that be outright power, braking repeatability (i.e. is the 10th stop the same as the 1st), impact of heat and performance comparison when braking at different speeds (30-0 vs 45-0) and the level of deceleration reduction during those tests.

That is why I'd love to see something backing up your claim, as I would probably agree with most of it.

Meh, whatever.

User avatar
MichaelB
Posts: 9316
Joined: Tue Feb 20, 2007 9:29 am
Location: Adelaide, South Australia

Re: A proper disc brake test protocol !!

Postby MichaelB » Fri May 11, 2018 10:25 am

outnabike wrote: ..
To me it's about personal experience and what happens to me when braking. literal seat of the pants stuff.

...


Especially when emergency braking !! Well put :)

human909
Posts: 9123
Joined: Tue Dec 01, 2009 11:48 am

Re: A proper disc brake test protocol !!

Postby human909 » Fri May 11, 2018 10:48 am

MichaelB wrote:That is why I'd love to see something backing up your claim, as I would probably agree with most of it.

I've already posted the methodology.

MichaelB wrote:The test above done by Enduro is about braking performance via repeated stops following a strict methodology in a controlled environment. Not real world, and they acknowledge this. But what it does provide is a very good set of data on relative performance between different brands at the same level of lever application.

No it doesn't give data on relative "performance" between different brands at the same level of level application. It simply shows the resultant braking torque from a controlled force level application. This is not what I would describe as an particularly important performance characteristic unless you have especially weak hands.

I could mix and match standard pull brake levers with V-brakes and get results that probably shoot off the charts shown as I would drastically increase my mechanical advantage. There is alot more to braking that mechanical advantage...

User avatar
MichaelB
Posts: 9316
Joined: Tue Feb 20, 2007 9:29 am
Location: Adelaide, South Australia

Re: A proper disc brake test protocol !!

Postby MichaelB » Fri May 11, 2018 3:27 pm

I should heed my own advice re bovines and singing lessons .....

When will I learn :?

User avatar
baabaa
Posts: 849
Joined: Sun Apr 19, 2009 8:47 am

Re: A proper disc brake test protocol !!

Postby baabaa » Sat May 12, 2018 1:19 am

MichaelB wrote:I should heed my own advice re bovines and singing lessons .....

When will I learn :?

Well, as someone who has only read the very first point ( and then, the very last...) I think it is a good discussion so thanks fella.

User avatar
MichaelB
Posts: 9316
Joined: Tue Feb 20, 2007 9:29 am
Location: Adelaide, South Australia

Re: A proper disc brake test protocol !!

Postby MichaelB » Sat May 12, 2018 1:51 pm

:D

Who is online

Users browsing this forum: tubby74