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PostPosted: Thu May 22, 2014 12:51 pm 
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Joined: Tue Dec 27, 2011 2:19 pm
Posts: 651
tallicaboy wrote:
imho if Shimano failed to produce a proper road disc brake set, you just won't get it from elsewhere.


I figured they would pioneer carbon fiber discs/ pads first. They have a lot of carbon drag systems in their fishing reels that they could borrow the heat shedding/resins/designs from.


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PostPosted: Fri May 23, 2014 6:39 pm 
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I don't want to sound conspiracy minded here, but some of you may have seen that this exact scenario played out with the Shimano ICE tech rotors on the XTR test in one of the German MTB magazines (from the same publisher as Tour) a few years ago.

It caused a similar hubbub, as generally the German magazines seem to bring a nice degree of objectivity to testing of parts, actually measuring stiffness of frames and wheels, stripping frames to confirm weights, measuring crr of tires, etc...

If memory serves, they got the XTR rotor to fail in both lab and outdoor riding settings, which provides more exacting data on what the conditions were. Here is actually a little translated summary of those findings I found: "The "XTR Melt-down" happened firstly at Fade-Test when constant hand force of 115N was applied on brake lever as many times as needed either to reach maximum of 40 cycles or critical temperature of 400*C was gained and test must have been cancelled. Both XTR XC with organic pads and XTR Trail with metalic pads melted the aluminium "core" of their Ice-Tec-Rotors (alu-core seems to be the alu part of rotor?) and disc rotors deformed!
Practical-test only confirmed the result of Fade-test from lab. During the test ride, all Ice-Tec-Rotors melted. The alu-core of rotor got very soft and "was stuck in combination of greater heat and force required" (my interpretation). Test rider weight was only 75kg / 165lbs.
After they used and destroyed all Ice-tec-Rotors they replaced them with some standard/classic rotors that behaved much better. But even with these brake the mineral oil "rised up all over the set up" (I can't translate this).
"

Either way, that was 3 years ago, and so far I have seen no real world reports of this occurring in the field, even when used on a Tandem. In addition, Shimano claims they were unable to replicate this type of failure in the lab.

So in short, I have to wonder about the following:
A. If this was a real issue why wouldn't it have surfaced from more sources in the past 3 years.
B. If there was a real risk, why wouldn't Shimano have discontinued manufacture of the rotors. With all of the lawsuits and recalls in the bike biz, how could they stand the risk exposure of a fundamentally flawed brake?
C: Ergott mentioned above that Alu melts at 660C whereas the MTB test protocol seems to stipulate that they cut the test off at 400C. If those figures are correct, the discrepancy should be obvious.

If their lab testing exceeded any conditions reached in the real world, I could understand the possibility of a failure in the lab, but none in the real world. But in both the MTB and Road cases here, they seem to have achieved failure in the real world too.


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Posted: Fri May 23, 2014 6:39 pm 


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PostPosted: Sat May 24, 2014 1:35 am 
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I was doing some googling (a little knowledge can be dangerous). I appears that at elevated temperatures (like 400*C, but even at lower temps), aluminium is more likely to deform for a given strain rate. I think the brakes and outer steel layers of the rotor are acting like forms and squeezing the aluminium without actually melting it. That would account for the lack of discoloration seen while the braking episodes were at their most extreme. It could be that the alloy core will deform and squeeze out at temperatures much lower than 660C.

The good news for me is I ride in situations far less demanding than those tested. If this does indeed prove to be a legitimate issue, I can always switch out the rotors. I've actually thought of moving to a 160mm front if need be. It's just an adapter away from happening.

I will say that for absolute braking force, the 140mm rotors have been more than adequate for my needs right now. I was surprised how well they worked.


source - http://essay.utwente.nl/58200/1/defal_g ... haaren.pdf

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PostPosted: Sat May 24, 2014 1:55 am 
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TheKaiser wrote:
I don't want to sound conspiracy minded here, but some of you may have seen that this exact scenario played out with the Shimano ICE tech rotors on the XTR test in one of the German MTB magazines (from the same publisher as Tour) a few years ago.

It caused a similar hubbub, as generally the German magazines seem to bring a nice degree of objectivity to testing of parts, actually measuring stiffness of frames and wheels, stripping frames to confirm weights, measuring crr of tires, etc...[\quote]

Well It's no news that some German publications or orgnizations have forge results in past.
Most recent one was the ADAC scandal.

TheKaiser wrote:
C: Ergott mentioned above that Alu melts at 660C whereas the MTB test protocol seems to stipulate that they cut the test off at 400C. If those figures are correct, the discrepancy should be obvious.

If their lab testing exceeded any conditions reached in the real world, I could understand the possibility of a failure in the lab, but none in the real world. But in both the MTB and Road cases here, they seem to have achieved failure in the real world too.


Metal getting soft as temp rises. So maybe it did't melt down at all.It just creep under test load at 400C degree. However, as a large weight rider(90kg), XTR brakes never have a single failure during my ride in years.In competition scenario or very deep descend they all works fine. I don't even have to bother to think if I should control the temp of the rotor.I Actually scalded my finger tip when check rotor temp after 1 minute stop riding once.


One more thing for the conspiracy theory...
As a mechanical design engineer works in automation industry. I work both with many German and Japanese car parts suppliers. When I make suggestions to German production engineers and industrial engineers that they may use more simple method to build the machines just as their Japanese tiers.Most of them smiles in stance of deliberate contempt. I guess there's a strong pride behind.
But the truth is,Japanese produce beter quality goods at lower cost. In addition, For the very same product design.
A little off topic though.
And absoluty no offense to any German folks on the forum. That's just what I have observed and expierenced in years.


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PostPosted: Sat May 24, 2014 4:42 am 
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Considering that this issue has never surfaced on any mountain bike forum I suspect either their test is faulty, they are testing under conditions way outside the norm, or are using faulty rotors....

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PostPosted: Sat May 24, 2014 10:52 am 
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Location: Glermsford, Suffolk U.K
I run XTR rotors on my MTB and have never had this but I do not brake in the way the test describes. I am not sure that test reflects real world braking.

Oswald your comments strike me a someone who has not used disc brakes on road bikes. Those that have are not comaplining about failures. On my wifes bike I am building at present using this very R785 setup I am using 160mm XTR rotors front and rear. Given there are no mountian in England and we live in Suffolk I see no problems. I will be running mechanical discs as I want to run Campagnolo again 160mm centre lock XTR rotors is what I will use.

MTB racers can get up to a fair lick and on hilly courses and the fast guys do not get brake failure we use proper bebbed in pads and 180mm rotors on the front though. Some are using 160mm rotors as well with no reported issues. There is alot of scaremongering about disc brakes and this "test" is another. What Tour have done is test the brake to failure without putting the test into context - i.e are these conditions a rider would find themselves in. That is a pointless test which will be mis interpreted.

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PostPosted: Sat May 24, 2014 1:14 pm 
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This is just silly. The tester happily says he's using both brakes... nice, but that's actually just saying he's only using the front brake. If you use your front brake you might as well not use your rear as all braking will be happening at the front (physics). :roll:

Also, I would not like to descend like he did with rim brakes either, as I would be scared of a blowout.

Not saying there's no issue, but this test seems flawed


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PostPosted: Sat May 24, 2014 1:27 pm 
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bm0p700f wrote:
Oswald your comments strike me a someone who has not used disc brakes on road bikes. Those that have are not comaplining about failures. On my wifes bike I am building at present using this very R785 setup I am using 160mm XTR rotors front and rear. Given there are no mountian in England and we live in Suffolk I see no problems. I will be running mechanical discs as I want to run Campagnolo again 160mm centre lock XTR rotors is what I will use.


I have never ridden a roadbike with disc brakes. In all honesty, I just don't see the need... I used to race mtb (both xc and marathon) and always used xtr v brakes. I did race xc for a short while on a Cannondale mtb and still have a freeride bike with discs. For mtb or cross use, I think they are a good thing when the track is muddy. But on a road bike?? I just don't see the need...


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PostPosted: Sat May 24, 2014 11:22 pm 
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You don't live somewhere damp then do you Oswald. The argument you are using is like saying improved braking on your car is not needed it maybe under some circumtances. I been out serveral time on wet and muddy roads where my caliper brakes have shall we say not been performing well. Also given I wore out my rims on my wet weather bike (it only gets ridden in the wet) in 3000 miles I am selling it now and building up a disc brake road bike instead.

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PostPosted: Mon May 26, 2014 11:55 am 
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Oswald wrote:
I have never ridden a roadbike with disc brakes. In all honesty, I just don't see the need... I used to race mtb (both xc and marathon) and always used xtr v brakes.


I don't think anyone is saying disc brakes are absolutely *needed* just that they are better and so many people would *choose* them. Indeed the reasons not to choose them are relatively few (maybe price, 300g, or unquantified aero disadvantage). Kinda like front suspension on your mountain bike. Also not needed (indeed I do marathon and xc racing on a rigid fork, perhaps you do too), but I am sure we would both agree that suspension forks do offer plenty of advantages and hence most people would choose to have them on their mountain bikes. But I would give up suspension on my MTB long before going back to V brakes :)


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PostPosted: Mon May 26, 2014 6:52 pm 
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bm0p700f wrote:
You don't live somewhere damp then do you Oswald. The argument you are using is like saying improved braking on your car is not needed it maybe under some circumtances. I been out serveral time on wet and muddy roads where my caliper brakes have shall we say not been performing well. Also given I wore out my rims on my wet weather bike (it only gets ridden in the wet) in 3000 miles I am selling it now and building up a disc brake road bike instead.


Sadly, it does rain from time to time in Belgium... We have +/- 200 rainy days a year on average :(


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PostPosted: Fri May 30, 2014 5:31 am 
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Sunny and 100 degrees here in Arizona and I am absolutely loving hydro discs. Theyre better wet or dry. The modulation is incredible and especially so whe you match them versus any carbon rim brake surface...

Hell, even SRAM's hydro rim brakes work better, with better modulation, smoother actuation and at least equal full stopping power than any other rim brake.

You can make any disc fail on a long descent by adding enough weight and riding the brakes long enough.

The complaints about XTR were just as valid, which is to say there was virtually no concern in real world use, when used properly...

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PostPosted: Fri May 30, 2014 9:59 pm 
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Belgium might be even wetter than east anglia so you win there. But now I have set up my wifes R785 equipped bike the modulation on the brakes is far better than anything I have ever tried with rim brakes. Pull the lever and you get progessivley sharper braking until the wheels lock it not on of off. I love them.

In fact now I have tried these I am going to have to ditch my old and faithful Hope Mono mini's for some new XT or XTR disc brakes on my MTB. I still use canit's some

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