These mechanical disc brakes are ridiculous! - JuinTech GTF-6

These 6 piston mechanical disc brakes from JuinTech might be the most powerful ones I've ever used, but can they justify the incredibly high price?

I have always had a soft spot for mechanical disc brakes on road bikes. They’re simple to use, easy to setup and maintain, and you can make use of older mechanical groupsets, so are great on more budget oriented bike builds.

I have tested A LOT of different ones in my time, but I've never seen anything like the JuinTech GTF-6. It’s an expensive, oversized mechanical caliper, with 6 brake pistons, that also makes use of large brake pads from an obscure MTB groupset.

So in order to properly assess the performance, I'm going to pit the GTF-6 caliper against the two other mechanical callipers JuinTech offer, the 2 piston F1, and the 4 piston GT-F.

In short, the braking performance was pretty phenomenal, but in light of other options on the market right now, for the average road cyclist, they are just too expensive. Plus, if you watch the bonus clip, the TRP HY/RD calipers are still my favourite!

Semi-metallic brake pads:

Timestamps:
00:00 – Start
00:23 – JuinTech overview
02:01 – F1 brake caliper bleed
04:00 – Hill testing
05:10 – Sponsor spot
06:06 – Hill testing cont.
09:57 – Hill testing results
10:31 – Multi-piston caliper discussion
12:16 – Brake distance test
13:36 – Conclusion
15:26 – Bonus clip (TRP HY/RD)

Intro roll:

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Please note:
I am not a professionally trained bike mechanic. There can be risks associated with using products that are unbranded, untested, or come from sources where the provenance is unknown. Please talk to a qualified bike mechanic if you are in any doubt.

In essence, be careful, do your research, and cycle safe!!!

[hisdadjames]

Luke, you are absolutely not ‘a loser talking to himself in his garage’. You are talking to thousands of interested and admiring viewers, creating compelling content of which this vid is another example.

[rascal]

The pistons are all a different color. Worth it.

[helicart]

It would have been helpful to compare the performance of the GTF-6 with full hydraulic brakes.

[chiliishot]

Cargo bike upgrades fit in there too.

Low maintenance, high stopping power seems perfect for a business oriented cargo bike operator.

[nikosbalakos]

Dude you've helped me make decisions about what sort of brakes to get from AliExpress and I really want to thank you for all your hard work and the detailed tests. Greetings from Sydney

[DuckRideDuck]

🥖 🥖 🥖 🥖 🥖 🥖, 6 one for each piston!!

[leadgtr]

Friction is force is F=u * Fn where u is the coefficent of friction and Fn is the normal force applied perpendicular to the frictional surface. Pressure is Force / Area however in a hydraulic system like this the number of pistons would all share the same pressure and hence you'd have n times (6 or 4 or 2) worth of force for the same given pressure. and because friction is proportional to the force and not really the pressure (although it would be the same if you only had one area where force is applied) you should have an increase in force due to multiple pistons. either way great video as always!

[englishwithtimusa]

If I'm not mistaken, the additional braking force afforded by quad (or in this case, hex) piston brakes come from the fact that the pistons are different sizes. Smaller pistons move the pads a greater distance for every millimeter of input at the lever, but squeeze with less force. Bigger pistons do the opposite- they move a shorter distance but squeeze harder.
Heat management is an additional bonus of quad or hex piston brakes.

[malcontent_]

Thanks for this, Luke. I'd be very curious to see a comparison between the GT-F6 vs. _Growtac Equal_ calipers.

[ryanyandell]

This pressure is transmitted through the hydraulic fluid to a piston, which can be used to exert a larger force. The mechanical advantage of a hydraulic system is determined by the ratio of the area of the piston on the output side to the area of the piston on the input side.

This is the google result when you search hydraulic mechanical advantage. The surface area of the plunge of the master cylinder and the surface area of all the surfaces that it will push onto, (which in this case is the back of each of the six pistons )are critical for understanding the pressure applied. A six piston brake caliper should have three times the clamping pressure of a two piston brake caliper.

Your understanding of surface area and friction was really good, though. Thank you for making these videos. I've been thinking about upgrading my brakes and wasn't sure how much of a difference it would actually make?

[tinman]

6 piston calipers 😮 they sound really impressive.

[KaminKevCrew]

As someone else has already highlighted, hydraulics kind of change the way this work. That’s because in the hydraulic system, you have a certain amount of pressure. The thing is that while you would have the same amount of pressure in the system (PSI), you have more area across more pistons. Because it’s a hydraulic system, the more surface area you have (by adding more pistons), the more pressure you have acting on the brake pad.

If you have 100 PSI of pressure in the hydraulic system, and you have 1 square inch of piston surface area and two pistons, you would have 200 pounds of force acting on the brake pads/brake rotor. If you have the same amount of pressure, but 6 pistons each of the same side, you will have 600 pounds of force instead, because you have a larger surface area that the pressure can act on. The thing that you end up losing is travel. The 6 piston caliper will only be able to move the piston 1/3 the distance of the 2 piston caliper.

That’s why they felt so much stronger - they are literally applying more force because they have more area that the hydraulic pressure can act on. They’re not going to be 3 times as strong as the two piston calipers, since the other pistons are smaller, but that’s why they were stronger.

[alexanderauer]

Love your channel ! Greetings from Germany !!
Gold standard in DH Mountain Biking are still 4 pistons like the Shimano Saint or the new Sram Maven, 6 is extremely exotic even there. Trend currently is going fom 203mm to 220 or 223 rotors …

[richardharker]

My first bike as a kid had brakes so good I had to plan my stops a street away. These days we are spoilt for choice. Luckily we can choose depending on budget and the type of riding we're going to do. I had the early version of Hy/Rd brakes but the inside piston on both brakes would never retract properly driving me nuts.
A thank you for making this video and offering your personal opinions.

[BikesKomsCRO]

This mans crazy doing a Vs, Vs, Vs and paying for it himself... god damn.

[ForeJaapie]

Ive had the Juin Tech R1 breaks for a while, post mounted version of the F1. I had no idea these could be bled, thanks so much for that! I'll keep that in mind if the performance drops off at any point. Im using them with compressionless housings. It doesnt feel as good as hydraulic but they break well and reliable, much better than the stock breaks from Cannondale

[proffesorDub]

Great video Luke! Just as a potential ‘other scenario’ that people would buy these for. I myself am a juin tech owner, mainly because in 2022 I went from rim brakes to disc, but only wanted to upgrade the frame and didn’t want to buy a whole new groupset (I have a sram red 12 speed axs grupo). So initially I went with the 1 piston caliper, which whilst it worked it felt a little lacklustre. I ended up buying two of the 6 piston in the fetching purple (weighing it up against he Paul klampers which are slightly cheaper)

In my opinion the brake performance offered by the GT 6 is exceptional, and more than what I need for my road bike. What it did mean is that for 400 pounds, I avoided spending over 5x that on a new sram red grupo. And are still cheaper than just buying a sram red pair of Brifters and callipers

A very niche use case I know, but they’ve given me the ability to use a disc brake frame without too many additional costs.

Keep up the great work!

[williamcrampton]

Fantastic video and research. Well done. I love your work.

[BigGdh]

Luke, I'm mainly a mountain biker, used to race DH and even on DH bikes they only run 4 piston brakes. Hope brought out some 6 caliper brakes like 20 years ago but they stopped selling them years and years ago. As you've said, pad material and the power and modulation in the system is more important.
Love the channel though, keep up the good work 🥖🥖🥖🥖

[LawrenceSeetoh]

that is a great review, thank you Luke It seems like JuinTech makes rather decent brakes. I'll keep that in mind for my next brake upgrade.