We've still not posted a follow up to the brake testing, nor have we posted our mtb handlebar testing yet. We're in the process of making some large changes to our website and are still trying to find the best way to put up our reviews. We do plan on more testing in the future and will continue to publish them, but the timeline is still a little grey.
For now here are links to some of our more popular reviews:
Cranks: http://fairwheelbikes.com/c/forums/topi ... eview-5-2/
Road bars: http://fairwheelbikes.com/c/2014-road-h ... -review-2/
Stems: http://fairwheelbikes.com/c/forums/topi ... -review-3/
Hubs: http://fairwheelbikes.com/c/forums/topi ... ub-review/
Skewers: http://fairwheelbikes.com/c/forums/topi ... -reviewed/
Rims: http://fairwheelbikes.com/c/forums/topi ... m-roundup/
FairWheel Bikes Brake Review 2014
Moderator: robbosmans
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wrcompositi
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madcow wrote:For now here are links to some of our more popular reviews:
Cranks: http://fairwheelbikes.com/c/forums/topi ... eview-5-2/
Road bars: http://fairwheelbikes.com/c/2014-road-h ... -review-2/
Stems: http://fairwheelbikes.com/c/forums/topi ... -review-3/
Hubs: http://fairwheelbikes.com/c/forums/topi ... ub-review/
Skewers: http://fairwheelbikes.com/c/forums/topi ... -reviewed/
Rims: http://fairwheelbikes.com/c/forums/topi ... m-roundup/
Great! Do you have archive of the older reviews for cranks and hubs, Jason?
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Plot of deflection ratio vs cable pull for selected brakes:
This is basically the derivative, so is the inverse of the mechanical advantage.
It seems what you want, for brakes set up properly on a given rim width, is for the brakes to move quickly for clearance and then slow down to provide mechanical advantage right before contacting the rim. With this design, if you swap in a wider rim, you lose braking power, but the brakes still work, unless you loosen the cable. If you swap in a narrower rim, you may need to tighten the cable.
The Shimano 9000 comes closest to this, slowing down end of range to provide maximal mechanical advantage. I had expected EE was a similar design, with the complex pivots, but it's apparently not. I'm fairly sure my Zero-G's are similar: if you swap for a different rim width without adjusting cable length, they become virtually nonfunctional due to catastrophic loss of mechanical advantage.
Other brakes follow a flatter trajectory. This doesn't require any real tuning. The Fibula, for example, stays at high mechanical advantage through its full range. But this means that there's not much margin in the case a rim is out-of-true, for example, or for getting wheels in and out with muffin-top tire profiles. Same deal with EE, it seems.
The Campag 1 (single pivot) is sort of the opposite: low mechanical advantage, high deflection ratio. Campag 2 (dual pivot) provides maximum mechanical advantage at the smallest deflections. That doesn't make much sense to me.
This is basically the derivative, so is the inverse of the mechanical advantage.
It seems what you want, for brakes set up properly on a given rim width, is for the brakes to move quickly for clearance and then slow down to provide mechanical advantage right before contacting the rim. With this design, if you swap in a wider rim, you lose braking power, but the brakes still work, unless you loosen the cable. If you swap in a narrower rim, you may need to tighten the cable.
The Shimano 9000 comes closest to this, slowing down end of range to provide maximal mechanical advantage. I had expected EE was a similar design, with the complex pivots, but it's apparently not. I'm fairly sure my Zero-G's are similar: if you swap for a different rim width without adjusting cable length, they become virtually nonfunctional due to catastrophic loss of mechanical advantage.
Other brakes follow a flatter trajectory. This doesn't require any real tuning. The Fibula, for example, stays at high mechanical advantage through its full range. But this means that there's not much margin in the case a rim is out-of-true, for example, or for getting wheels in and out with muffin-top tire profiles. Same deal with EE, it seems.
The Campag 1 (single pivot) is sort of the opposite: low mechanical advantage, high deflection ratio. Campag 2 (dual pivot) provides maximum mechanical advantage at the smallest deflections. That doesn't make much sense to me.
I updated the above plot, and added a second for the KCNC brakes. The contrast between the Shimanos is striking. The 7900 clearly has less throw, more mechanical advantage, with the maximum mechanical advantage toward the end of the range where it's needed.
I put the KCNC on a separate plot with equivalent axes:
I put the KCNC on a separate plot with equivalent axes:
One of the things regarding Shimano is that the cable pull of their levers is non-linear. And their brakes always seem to be designed to compensate / maximise their function based around that too.
Noted that the brakes were all tested based on amount of cable pull versus amount of caliper arm deflected. But the non-linear nature of Shimano brake levers may explain why the DA9000 brake calipers look different when compared to the DA7900 ??
In real use, they feel very similar in power. I cannot honestly tell them apart using identical wheels and pads.
Noted that the brakes were all tested based on amount of cable pull versus amount of caliper arm deflected. But the non-linear nature of Shimano brake levers may explain why the DA9000 brake calipers look different when compared to the DA7900 ??
In real use, they feel very similar in power. I cannot honestly tell them apart using identical wheels and pads.
It does make sense to put the nonlinearity in the lever rather than the brake because then as the brake pads wear, the cable can be adjusted, restoring the same brake lever range of motion, while the caliper range of motion shifts. Same deal for switching to rims with different braking surface width. Otherwise you'd need a mechanical means to shift the caliper sweet spot (high mechanical advantage range).
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Interesting graphs. I'd like to know what the cable pull rates look like for the levers.
One possible benefit of decreasing mechanical advantage is increased modulation when getting near the point of lock up. Anything wildly non-linear would seem to complicate this, but losing mechanical advantage might allow the pads to be more reactive to hand pressure.
I could be all wrong on this though.
One possible benefit of decreasing mechanical advantage is increased modulation when getting near the point of lock up. Anything wildly non-linear would seem to complicate this, but losing mechanical advantage might allow the pads to be more reactive to hand pressure.
I could be all wrong on this though.
A comment here: if the brake is perfectly stiff than the ratio of force on the cable to force on the brake pad = the incremental ratio of motion at the brake pad to pull on the cable. This is conservation of energy. The Shimano 9000 has more pad motion per cable motion than the 7900. This means force is less for most caliper deflections. However the force tests show the two are quite close. Is this because of the specific pad thickness and effective rim width, and the difference would be larger with worn pads or different rim width?
The force results confuse me a bit. For example the difference in braking force between 60 and 90 lbs of cable force is the same, 45 lb (150%) between the Campag single pivot and the EE. But the EE has a much greater mechanical advantage through the range. The Campag is close to 1:1, not the 3:2 needed for 150% even with perfect stiffness. Yet I'd expect the EE to be stiffer. What am I missing?
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The force results confuse me a bit. For example the difference in braking force between 60 and 90 lbs of cable force is the same, 45 lb (150%) between the Campag single pivot and the EE. But the EE has a much greater mechanical advantage through the range. The Campag is close to 1:1, not the 3:2 needed for 150% even with perfect stiffness. Yet I'd expect the EE to be stiffer. What am I missing?
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DJ,
I didn't look at all the data, and I'm not sure if I'm addressing your point, but the above demonstrates the motion ratios. Yes, the force curves overlay assuming 100% rigidity, but if the parts are not 100% rigid, then the force delivered will slip back along the curve towards origin. This can easily account for a significant % change in force delivered.
I didn't look at all the data, and I'm not sure if I'm addressing your point, but the above demonstrates the motion ratios. Yes, the force curves overlay assuming 100% rigidity, but if the parts are not 100% rigid, then the force delivered will slip back along the curve towards origin. This can easily account for a significant % change in force delivered.
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andreszucs
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JensW wrote:would be interesting to se a comparison with sram hydraulic rims brakes
I wonder the same, would be interesting to see those numbers on the new ROAD Hydraulic brake systems out there. Any studies on that so far? Would need to be a 'piston' pull system if the goal is to eliminate the lever (length differences from each model would vary).
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Here's plots of the force transfer curves. These would presumably be different if the rim or pad width were different. But I don't understand how they relate to the deflection curves.
I'd think here a bit of a progressive response would be good, but not too slow to engage... sort of like the EE. Or perhaps a flat response is good (linear). Almost certainly you don't want a decreasing response. Remember this is slope of force-vs-force, not force-vs-force itself.
But the Campag brakes come out looking really good here, at least to my eye. It looked less good in the deflection plot.
I'd think here a bit of a progressive response would be good, but not too slow to engage... sort of like the EE. Or perhaps a flat response is good (linear). Almost certainly you don't want a decreasing response. Remember this is slope of force-vs-force, not force-vs-force itself.
But the Campag brakes come out looking really good here, at least to my eye. It looked less good in the deflection plot.
Last edited by djconnel on Fri Sep 12, 2014 5:35 am, edited 1 time in total.
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andreszucs
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I'd say from all these different tests, the first and second tests are the most important ones. To my eyes...Shima 7900 is the winner!
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What this test doesn't tell you is how the brake works if the pads wear or if the rim width is changed. The deflection test provides insight to that.
But considering also mass, I think the Fibula wins, while considering also price with a reasonable $/gram equivalence, the EE brake wins. Perhaps a bit better modulation at lower forces is a good thing for tuning speed (I'm not sure). Ignoring weight I agree the Shimano 7900 does well if it provides adequate rim clearance.
A concern is a variable force transmission indicates the brake is bending, or it could simply be due to pad compression, the latter the same for all the brakes. If a brake flexes too much, it means you need to pull the levers too far to adjust the force. Ideally you pull the levers until the brakes engage, then just adjust the force, not moving the levers much, to modulate. That's the characteristic of a stiff system (lever + cable + brake + pad). Of course you need some compliance in the pad to track imperfect braking surfaces.
I wish I understood the comparison between the two tests.
But considering also mass, I think the Fibula wins, while considering also price with a reasonable $/gram equivalence, the EE brake wins. Perhaps a bit better modulation at lower forces is a good thing for tuning speed (I'm not sure). Ignoring weight I agree the Shimano 7900 does well if it provides adequate rim clearance.
A concern is a variable force transmission indicates the brake is bending, or it could simply be due to pad compression, the latter the same for all the brakes. If a brake flexes too much, it means you need to pull the levers too far to adjust the force. Ideally you pull the levers until the brakes engage, then just adjust the force, not moving the levers much, to modulate. That's the characteristic of a stiff system (lever + cable + brake + pad). Of course you need some compliance in the pad to track imperfect braking surfaces.
I wish I understood the comparison between the two tests.
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andreszucs
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By the way, very nice Test! Thank you for putting this study out there! A big question that I have now is how Hydraulic brakes would behave under the same Tests, either MTB or Road...would be very interesting to see it.
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