Juin's 6 Piston Semi-Hydraulic Brakes - Taipei Cycle Show 2024
One of these things is not like the others.
The Taipei Cycle Show is known for fielding some of the more unique products that are coming to market, and this year has proven to be no exception. In a field of cool and unusual offerings, some little gems still stand out, whether they're particularly clever or just outright unusual. This GTP-6 brake falls more in to that latter category, with a combination of features that is truly unlike anything else.
Juin is a Taiwanese manufacturer known for their colorful and budget-friendly brake offerings. The GTP-6 may cast a fairly typical shadow, but it's anything but. These are 6 piston brakes, and though the caliper itself is hydraulically driven, the brake is mechanically actuated. The calipers use mineral oil, and weigh 158 grams apiece.
There are a few mechanically-actuated hydraulic brakes out there, such as the Yokozuna Ultimo and TRP Hy-Rd, but neither is squarely positioned at the mountain bike market.
Honestly it's a bit hard to tell if the Juin brakes are either, as the tagline "it's about control not power" sends a bit of a mixed message - I tend to prefer to have both if given the option. Shade aside, I understand what they're going for here, and it's cool to see a novel approach.
Typically, there are some endemic drawbacks to the tightly enclosed hydraulic system used in brakes like this, namely in the form of heat buildup. As descents get heavier and longer, there's nowhere for the heated fluid to go and no thermal chain up the hose to draw heat away, which can lead to more heat buildup and fade.
Clearly we haven't tested these yet, so consider this all through a speculative lens. I'd be keen to give this system a try though, as there's something charming about the analog nature of a cable brake, though I can't say I ever complain about the newfangled ways of today's amazing hydraulic brakes. If you do decide to try something like these, remember to use compressionless housing, and to constantly tell your friends about how much better your cable brakes are and how you're never going back to fluids.
If anything, it's an excuse to dig out those old levers in your parts bin.
Though Juin doesn't have a direct sales website, you can find out more information and buy a set on a few online shops such as this one. They retail for about 390 Euro per pair, depending on color and market.
Author Info:
Must Read This Week
Sign Up for the Pinkbike Newsletter - All the Biggest, Most Interesting Stories in your Inbox
PB Newsletter Signup
Mercedes used to have a concept that was 100% drive by wire, it looked pretty cool, would be like driving my bobcat
I am kinda with you, not sure I'd be an early adopter
If youre ready for cars costing as much as airplanes, you can have drive by wire.
en.wikipedia.org/wiki/Functional_safety?wprov=sfla1
The main difference is indeed the much lower friction in the fluid vs the cable.
Another test is put big weights on the cables and measure them after days, weeks, months and see that the cables do not stretch. An old shop I worked at did this, a few engineering students I knew did this in college, etc. Same results, cables don't stretch in a meaningful way.
In other hydraulic applications there are internal braids or external woven covers that resist expansion from fluid pressure. Most bike hydraulic brake housings all expand under pressure and it's a bummer.
i.e. automatically moving in with pad wear,
which fully mechanical brakes do not.
So this Juin system gives you that advantage.
It also allows you to activate both sets of pistons.
Most mechanical disc brakes have a fixed side, while the other side is activated by the cable.
TRP Spyre brakes are a rare mechanical design that activates both pads;
Ask anyone who has installed or maintained Spyres, and they'll tell you it's a headache.
So yes, it's not going to give you the silky feeling of full hydros, but it's a nice in-between option, when you don't want to deal with hydraulic systems.
I personally buy cable activated dropper posts for this reason (which are sometimes hydraulically driven)
I just effing hate setting up hydraulic lines (in other words, I'm bad at it)
Auto adjust is a clearly listed feature on TRP HY-RD product page, whereas Yokozuna only notes "Simple one knob pad adjustment", which, to be fair, is a benefit vs mechanical disc brakes, which often require adjusting the fixed side with a tool, and the active side with a barrel.
Brake lines do expand under pressure, since the materials youngs modulus is finite.
It might not be much, but the sum of your brake line expaning, the seals compressing and the caliper spreading all add up to significantly reduce the stiffness of your brake way below the fluids bulk modulus. Otherwise you couldnt move the lever a millimeter after your pads made contact.
Just a few weeks ago, we had someone at our hydraulic lab measure the effective bulk modulus for steel braided brake line filled with HLP, and while I cant tell you the exact numbers, it was more than HLP alone.
Iam not trying to start an argument about semantics, but saying it doesnt expand is just wrong.
This line cracked up lol ....
Anyway, if this is somewhat reliable, it would potentially be a great option for the Slopestyle Dudes since they could run a cheap cable gyro and then still have ample power out back.
Few years ago I built 2 travel bikes (29" Genesis Longitude) for a couple who travelled 12000km in South America. They reported zero issue with their brakes and had all the power and reliability they needed. Just an experience I share...
So I think this six piston brake is probably intended for commuter ebikers. A lot of cheap entry level commuter ebikes come with bad mechanical disk brakes, and this product allows them to replace their brakes with something significantly more powerful without having to replace levers or bleed anything. If you go to the Amazon review for the Juin Tech M1, almost every review is written by someone with a cheap commuter ebike who replaced their underpowered mechanical disk calipers. That makes a lot more sense.
Any other explanations?
Unless I'm missing something, more pistons does not necessarily change that, or at least it's not the only way to influence it.
Meanwhile I think: more pistons, more problems will hold true, more chance for unequally moving pistons and inconsistent brake feel..
The only way I can see multi piston brakes improving "modulation" is the ability to have different size pistons, so that one side of the pad contacts first, avoiding a harsh "first contact" and reducing the grabby feeling.
Either way, I can't see how these could possibly perform better and be more simple than a fully hydraulic system. It isn't even cheaper than a decent hydraulic disc brake system.
Bonus was the rotor mounted w/ 3 bolts (so lightweight..!)
6 pistons is just an odd choice for that market, since they are typically not very interested in maximizing braking power.
No shit. The point is that it's almost always not an option to have both, for a reasonable cost, there is pretty much always a trade-off.