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  1. #1
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    Scientific Brake Tests...

    After watching this interesting youtube video I had a thought. Why don't we see more factually documented proof of the various MTB brake manufacturer's model's true braking power. I mean, how many times do we see on our fav MTB forums: 'My brakes are really great - way more powerful than brand x or brand y' and in response 'Nah, you've got it wrong, my brand y brakes are way more powerful than yours' in response 'Whoah there, you're talking crap, my brakes Are more powerful than yours' blah blah blah

    I often use this forum to help me with my MTB gear purchases but this situation makes me trawl through posts finding very subjective info seemingly based on members 'Ramping' fav kit. Especially with brakes.

    I know that Magura publish stats for their models such as this for the '08 Louise:
    Deceleration in m/sec according to DIN 79100 (100N handforce): 7,2m/s (203mm), 6,8m/s (180mm), 6,2m/s (160mm)

    But, why don't we see simple but relatively accurate performance graphs using 'Braking Power' and 'Lever Pull' as axis? Then we could more acurrately gauge lever feel/ modulation and true braking power and therefore for example be accurately able to compare Louise's with K24's. I mean, wouldn't that be great?

    P.S. Apologies if this post seems like a rant
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  2. #2
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    I think it is because then one set of brakes will be 'considered' not as 'good'? And if you are a manufacturer i do not think you will want to assign to that.

    Cost? ... extra resources that could be channeled into making the next set of brakes cheaper? Other factors decide if a set of brakes is 'better' ...
    Last edited by chinaman; 01-30-2008 at 01:12 PM.

  3. #3
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    most on here wouldn't believe such test data anyway. I'd hope the manufacturers do that sort of testing anyway (I wouldn't sell a product without a pretty good idea how it performed), but IME cyclists don't tend to be particularly interested in hard data.

  4. #4
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    I think that you'll find....

    it is primarily because those figures mean absolutely nothing to most people. While it may be a "reasonable" gauge of braking power, it tells you nothing about lever feel and modulation. The reason being is in order to make the braking force figures realavent you have to use a set amount of force on the lever. And as with all "scientific data" it is set up with "fixed variables", or restrictions on the conditions of the test. Otherwise your data is flawed. In other words each test of each different brake set must be done in exactly the same way under the same conditions or the data is meaningless. To do that requires a laboratory or testing facility. And we all know that 99% of the time that laboratory results are rarely accurate when it comes to the "real world".

    I understand your pain believe me. The problem is people are subjective in their likes, dislikes, and preferences. Most don't have the funds or the desire to go out and buy 10 different brakes sets form different manufacturers and compare them. Most folks are limited to one or two different sets. And the set they like the best is the shizznit for them. And people tend to defend what they like or prefer even in the face of incontrovertable evidence that something else may be superior.

    Bottom line? Scientifically "valid" test data has limited realevance to the real world, i.e. there are to many variables out there where we ride. The test data may say one brake is supperior in stopping power to another, but it just can't tell you how the brake performs in sloppy muddy conditions or when the temp is 15 degrees, or how that lever pull will feel to you. The data only applies to the conditions under which the tests were made so it is of highly limited value. Yes it does elimnate "personal opinion" and personal preference, but does it really get you the information that you are looking for. In one respect yes, it tells you that brake a applies more force to a given size rotor for a given lever pull force than brake b. But that's a far cry from a comparison of the over all performance of the two brakes. You have to "assume" that the brake with better stopping power is going to modulate better and have a better lever feel. This may or may not be so. It's way to little information for me to base a buying decision on, it would certainly help a bit, but only in the most limited way. And I'm sure the bake manufacturers know this. So why spend the money that it would require for testing to aquire data of such limited value. The best test is still in the ride! Opinionated and subjective as that "ride" may be.

    I'm not saying that the data is useless. It just doesn't tell enough of the story. And that's my opinion so take it for what it's worth!

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  5. #5
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    A brake dynamometer test for bike brakes would need some rigorous standards set (ANSI, ISO etc) so that they were all performed exactly the same. If they had very specific standards you could glean some info from comparisons in ideal conditions, but as noted previously they couldn't reflect all the environmental variables, or even the variables around the mounting to the bike.

    The two things that standardized brake dynamometer tests could accurately document across a wide range of brands and products are absolute braking power plotted against lever pressure (for various rotor sizing), and fade for repeated stops.

    But it would be extremely difficult to standardize environmental impact of water, mud, ice, sand, etc. You could easily have brakes that perform the best in dynamometer tests be the most adversely affected by being wet or from having an out of true rotor.

  6. #6
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    50 years ago that information probably would have been given, had biking and brakes been where they are now.

    The problem is that people don't expect to have to know how something works in order to use it these days.

    Go back to the 1920s and if you had a car, you probably had a good idea of how a combustion engine worked, a gearbox, etc because you had to in order to be able to drive it and look after it. Now people just expect their car to do what it does, day in, day out.

    Look at hifi. From the 1950s through the 1970s hifi was mainly judged on measurement (frequency response, distortion). Magazine reviews were discussions of the engineering of an amplifier or pair of speakers, and how and why that made them measure why they did. Pick up a copy of "What hifi" and you won't see a single measurement made by the magazine, in reviews written by people who couldn't tell an opamp from a capacitor.

    And so it is the same with bike stuff. To average joe, 7.2ms^-2 does not mean anything. Remember that a forum like MTBR attracts only a tiny fraction of a percent of the people who buy these products, and generally those attracted to a forum like this are the more technically inclined.

    Now, I personally think, as an engineer, that you CAN quantise things like "lever feel". Each brake has an effective lever length (determined by blade length, positioning of pivot and piston) - you can come up with force v lever travel (or angle) that will characterise the lever feel on a graph. Then you can relate brake force at the caliper to that lever force, and then deceleration to that caliper force for different pads.

    The problem is that it requires people to understand Newtons, metres per second squared, and how graphs of various things read. Since 99.9% of people either don't understand those things or are not interested, there's no motivation for magazines to test and publish such information, when those people are happy with "They feel firm and stop great". That then means that people don't become interested in the technical side of things, which starts the vicious circle of dumbing down.

  7. #7
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    There were some torque tests on a few disc brakes a while back by a german magazine.. I think they found the Gustav to exert highest torque and the rest of it sort of went along with general agreement.

    The problem is that the performance of brakes depends on so much more than the calliper that comes out of the factory, it's down to calliper mounting, tab facing, rotor allignment and material, pads, ambient conditions, spoke tension blah blah blah so a true scientific test can't really be done as such .

    Besides there will always be silly people who complain their brand new brakes lack power, not realising they had spilt oil all over the pads or something stupid like that, so opinions on brakes will always vary.

  8. #8
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    You have to remember that the only reason they have braking stats for cars is because of safety standards. Not to mention that just about every human over 16 drives a car in the US and a vehicles braking ability is one of the greatest safety factors next to the driver's abilities. Bicycles are just run of the mill toys, and for the industry to create a set of "standard testing" procedures in relation to performance would be far beyond the cost effectiveness.

    Of all the bikes sold in the US, I bet the average speed of all those bikes is under 12 mph. Now compare that to a runner. Should there be a set standard for running shoes too?

  9. #9
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    I understand what Chinaman means when he says "I think it is because then one set of brakes will be 'considered' not as 'good'? And if you are a manufacturer i do not think you will want to assign to that." I kind of get the same feeling as him about it.

    Re Squash's comments - When I used the word Scientific I was perhaps overstating it a bit. I realise that the sheer number of variables makes for inconclusive results but felt that a simple graph showing power and lever feel might make comparisons easier.

    "And people tend to defend what they like or prefer even in the face of incontrovertable evidence that something else may be superior".
    Too true, I know of an MTB forum(not this one) where there's a guy with well over 30,000 posts who 50% of the time I think talks out of his a*se. He never seems to qualify why he recommends kit simply stating this is good or that is bad. It seems he's not on his own.

    Re Rockyuphill, as I'm sure we'd both agree one dynomometer is going to give differing results to another isn't it...but a comparison of brakes done on the same device might yield some useful results? with a disclaimer I suppose. Too many variables is certainly an issue that's for sure and I don't quite know how it would be overcome if at all.

    Re Isaac, I hear what you're saying about HiFi magazines, having been an audiophile for a long time myself. Quoting wattage and distortion doesn't give any inkling as to subjective sound quality does it. Regarding the brake power/feel characteristics of MTB brakes, pure numbers on a page probably wouldn't mean that much to me too if I was honest, hence me suggesting a simple graph to illustrate.

    If such graphs as these below were produced (I made them up obviously ) I'd find it very helpful to be honest. Note both brakes ultimately end up with the same max brake power:




    If some brand new Juicy 7's, Louise's and K24's were tested and plotted and overlaid on a graph as a basis, then people would certainly be able to make comparisons with other tested brakes such as Codes, Gustavs et al...

    Re nnn's post, I'd really like to see the format and results of the German bike magazine's torque test. That sounds just the sort of thing I'd be very interested in Any chance of a link?

    Treybiker, I'm not bragging, as my average speed is probably way slower than the 12mph average you mention, but my max speed to date is 48.6mph on a long steep decent near to where I live. Here's an impression of me at the bottom of the hill I was glad my brakes were set up just fine that's for sure! even if they did cook a bit and temper the fr rotor a little blue.

    I hear what everyone's saying about my perhaps slightly naive proposal for comparator test graphs, but I still don't think manufacturers should be able to get away with not supplying more info than 'Our brakes are Great'.
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  10. #10
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    Quote Originally Posted by RedBlueGreen

    Re Isaac, I hear what you're saying about HiFi magazines, having been an audiophile for a long time myself. Quoting wattage and distortion doesn't give any inkling as to subjective sound quality does it. Regarding the brake power/feel characteristics of MTB brakes, pure numbers on a page probably wouldn't mean that much to me too if I was honest, hence me suggesting a simple graph to illustrate.
    But it can. "Clarity, air, separation" = low intermodulation distortion, "smooth" = low harmonic distortion, "harsh" = high odd order distortion products, "wooly, bloated" = poor damping factor, etc. There's much more to it, and with many things in audio we don't know necessarily what to measure to correlate to what we hear. I co-wrote an AES paper that touched on this a few years ago.

    That matches up with what I was saying earlier that people buy things on the basis of too little technical knowledge to be able to relate those things to the subjective "feel" or "sound".

    For example, look at two cars, both have 150bhp. One has the power peak at 7000rpm, and 130lbft of torque at 5500rpm, the other has 250lbft of torque at 2000rpm and power peaks at 4000rpm. You can already tell a lot about how they will drive day to day, that the first one will have have the nuts revved out of it and be kept on the boil to make much progress, whereas the second will be a much lazier drive (and you can also infer that the first is most likely a petrol and the second a diesel). Of course, those numbers don't tell you whether the diesel falls off the torque curve below 2000, and might be very sluggish off the line, but looking at the overall torque and power curves will.

    You prove this with your graphs - you're putting numbers and graphs down, and inferring from that the "feel" of the brake. The graphs are just another way of showing the numbers. Because you know what brake power and lever travel are, you understand the graphs and can use them to make a more informed choice. This applies to cars, hifis, camera lenses, etc whereby if you know something about the technical side of the subject then you can relate measures to subjective experience. Of course, it gets more and more complex as you know more about something - for example on the engines theme, an experienced engine designer or mechanic would be able to infer more about the feel of the engine from things like cylinder configuration, bore and stroke, etc.

  11. #11
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    I think MBUK did a more scientific brake test not too long ago to compare the power of a bunch of dick brakes...can't remember when, but if I come across it, I'll let you know.

    Realistically, these days most riders don't care how much power their brakes make....just that the feel right and stop them as needed. Heck, a lot of folks I meet out on the trail don't have a clue about getting their brakes set up right (i.e. I can hear the pad drag or intermittent contact quite some distance away) and don't have any idea about maintenance or bleeding.

    As nice as it would be to have a scientific shootout that gives real data and plots about modulation and power, n oone will drop that amount of coin on testing for something that most riders will ignore.
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  12. #12
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    Just do it, Faster, Better, Lighter.
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  13. #13
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    If a brake dynamometer is standards based and the equipment is calibrated, there'd be no reason to have different units provide different results (beyond the deviation allowed by the standards). This sort of standardized measurement and evaluation hardware exists for every other type of ANSI/ISO standards based test gear.

    BUT, it doesn't guarantee that equipment will be mounted or tested correctly, or that a manufacturer would disclose the results that were at the lower end of the standard deviation (much like the way every cheap hifi speaker has a 20Hz-20kHz response, they just don't define the deviation from the nominal level). Seeing the extent of standard deviation would be a good indicator of product QC, pad variability, or sensitivity to setup, all of which would be handy to know.

    It's data that is subject to the same marketing department graph smoothing and manipulation that every other hardware spec is unless they were all tested by an outside lab. Unless it was a safety standard, that won't ever happen.

  14. #14
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    Quote Originally Posted by rockyuphill
    (much like the way every cheap hifi speaker has a 20Hz-20kHz response, they just don't define the deviation from the nominal level)
    Very few speakers get down to 20Hz. Amplifiers do, speakers don't... Just a few high-end subs and big full range models do.

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    While I agree that it would be a good test to have...really, in the long run, it would be a waste of money. Look at the carbon fibre handlebar test done a few years back...even though it was done in a controlled and scientific manner, people still complain that it wasn't a "real world" test, or that their "Brand X bar" which failed the test is a great bar, they dont' know where they're coming from...yadda yadda....

    The thing is, brakes are a personal thing. What I like in a brake might be different than what you like. Not only that, but atmospheric, weather and trail conditions can all play a factor in how a brake performs and "feels". So again, you and I could both ride "brand X" brakes, and have two different opinions on them.

    I use BB7s on my bike, and find they've got great modulation, power and are more than adequate for the job....while others on this board say that hydro is the only way to go. Unfortuantly, brakes, like many other things, are a personal thing. It would be no different than having a test for the most comfortable bike seat...too many personal preferences to get in the way. Sure, you could have a firmness vs. comfort graph to show which is which, but I still think riders wouldn't care :P Brand loyalty goes too far.

    I like the idea from a purely scientific point of view, but honestly I think all bike brakes perform above what is required of them, irregardless of braking/clamping force, etc.

    Tim

  16. #16
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    Quote Originally Posted by Isaac Sibson
    Very few speakers get down to 20Hz. Amplifiers do, speakers don't... Just a few high-end subs and big full range models do.
    -40dB no problem...

  17. #17
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    Re Isaac, I have to admit whenever I was choosing Hifi kit I found quoted technical specs difficult to take on board...i.e. whenever I read some amp review quoting 0.002% THD I'd think ooooo that's going to be great! after going to a shop to hear the said amp I most often was disappointed in the subjective sound quality. In the end after reading tons of mag reviews I became disillusioned, gave up on mag reviews and bought my fav amp based totally on what I heard (in the end I got a Sugden).

    Re Psycho Mike, 'As nice as it would be to have a scientific shootout that gives real data and plots about modulation and power, no one will drop that amount of coin on testing for something that most riders will ignore.

    I hear what you're saying Mike and I can't speak for other riders but I'm really interested in graphs that plot brake performance.

    I see that the UK magazine What Mountain Bike are going to do a disc brake group test in their March '08 edition. I just hope it's not one of those 'we tested the brakes and gave them 5 gold stars' type BS reviews UK bike mags suffer from.

    Re BigFish, Thanks for the urls, they are awesome, what a revelation for me with this thread.

    I think those German Bike mag brake tests are great, just what I wanted to see...in fact I've just spent nearly 2 hours looking at them. I do feel there are some inconsistencies in the results though e.g. they tested Hope Mono 6's and Marta SL's and got very similar results for both, I'd of thought the Mono6's were way more powerful than Martas? As well, the Gustav graph looks like braking force was occurring with no lever force being applied.

    But overall I think the German bike mag brake tests are brilliant. So it's a big thanks to BigFish

    Re Sullycanpara, The thing is, brakes are a personal thing. What I like in a brake might be different than what you like. Not only that, but atmospheric, weather and trail conditions can all play a factor in how a brake performs and "feels". So again, you and I could both ride "brand X" brakes, and have two different opinions on them.

    I very much agree with you, hence my curiosity about a test which surpasses subjectivity in personal recommendations on bike forums. The German bike mag tests BigFish provides links for show results for both wet and dry conditions, attempting to address the point you make about conditions. If you see the results you'll see two graph lines - red for dry and blue for wet. I had to use Google translate quite a bit to find that out

    An additional factor which I think is important is how well the brakes are set up...alignments, pad/rotor condition, contamination to name but three points that I think are very important to overall performance.

    As final thoughts, it looks like my original post question has been fully answered by the German Bike mag brake tests.

    If I'd produced guesses of each model of brake's power characteristics I don't think I'd of been far wrong after seeing the mag's test graphs. However that 'knowledge' of mine has been gained from reading thousands of forum posts over a long period of time. If I'd of seen the German bike mag tests all that time ago, I wouldn't have had to trawl through so much subjectivity

    After reading how they setup the tests I couldn't have done a better job myself and I could kick them for nicking my idea
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  18. #18
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    Quote Originally Posted by RedBlueGreen
    Re Isaac, I have to admit whenever I was choosing Hifi kit I found quoted technical specs difficult to take on board...i.e. whenever I read some amp review quoting 0.002% THD I'd think ooooo that's going to be great! after going to a shop to hear the said amp I most often was disappointed in the subjective sound quality. In the end after reading tons of mag reviews I became disillusioned, gave up on mag reviews and bought my fav amp based totally on what I heard (in the end I got a Sugden).
    Indeed, just quoting a THD number without conditions or information on the harmonics that give rise to it, etc is not very informative. Right now I'm running Monarchy SM70 class A power amps (monoblocked), so not entirely dissimilar to your sugden.

    I see that the UK magazine What Mountain Bike are going to do a disc brake group test in their March '08 edition. I just hope it's not one of those 'we tested the brakes and gave them 5 gold stars' type BS reviews UK bike mags suffer from.
    Chance would be a fine thing.

  19. #19
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    Quote Originally Posted by Isaac Sibson
    Indeed, just quoting a THD number without conditions or information on the harmonics that give rise to it, etc is not very informative. Right now I'm running Monarchy SM70 class A power amps (monoblocked), so not entirely dissimilar to your sugden.
    Wow Isaac, I think my Sugden's super modest next to your Audiophile rig! I've an 'Audition C' and when I phoned Sugden last year they said it was one of their least popular amps...still, I like it a lot and that's what matters eh.
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  20. #20
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    Quote Originally Posted by Sullycanpara

    I use BB7s on my bike, and find they've got great modulation, power and are more than adequate for the job....while others on this board say that hydro is the only way to go. Unfortuantly, brakes, like many other things, are a personal thing. It would be no different than having a test for the most comfortable bike seat...too many personal preferences to get in the way. Sure, you could have a firmness vs. comfort graph to show which is which, but I still think riders wouldn't care :P Brand loyalty goes too far.

    I like the idea from a purely scientific point of view, but honestly I think all bike brakes perform above what is required of them, irregardless of braking/clamping force, etc.

    Tim
    Besides most people not being able to decipher the numbers, the only thing that these numbers would reveal is that the "power" of the brake is strictly dependent upon the coefficient of friction between the rotor and pad and the radius of the clamp.

    Hydraulics do not produce power. They are just a convenient way of transmitting it and managing mechanical leverage. Of course, increasing mechanical leverage decreases increases lever travel and there is only so far you can pull that lever before it either hits your fingers or the bar.

    The best idea I've seen out there has been the Shimano servo-wave concept that varies the lever travel through the stroke.

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