What's Going On With Loic Bruni's Brakes? - Crankworx Rotorua

Mar 29, 2017
by Mike Kazimer  
Loic Bruni brakes Formula prototype
Pressure gauge? Thermometer? Flux capacitator? What ever it is, Loic Bruni's mechanic wasn't saying.

Crankworx Rotorua is the perfect place for proper race condition testing prior to the kickoff of the World Cup season. Racers are notoriously secretive about their off-season preparation, but this week's competitions should serve as a little hint as to who's been making the most of their hours at the gym. It's also a chance to get a glimpse of new and prototype parts as they make their first public appearance, including the Formula brakes on Loic Bruni's Specialized Demo.

In the days leading up to a race it's not uncommon to see Bruni taking laps aboard a bike that's bristling with wires and sensors, all part of the data acquisition program spearheaded by his mechanic, Jack Roure. The data is used to used to monitor everything from the rate of suspension compression to the temperature of a shock, and now it looks like Bruni's brakes have been added to the mix.

Loic Bruni brakes Formula prototype

The brake's hydraulic line runs through a metal cylinder that's affixed to the seatstay, with a wire running away from the line and towards the front of the bike, which is where the main data acquisition unit typically sits. What exactly is being measured? When asked, Roure would only smile and shrug his shoulders.

More than likely, it's a brake fluid pressure sensor that's being used to gather data that could could provide valuable insights about what's happening during a downhill run. Combining the knowledge of when a bike's brakes are being applied with the information extracted from sensors on the fork and shock would make it possible to see exactly how the bike is performing during heavy braking. According to a source that's familiar with this system, it's also possible to overlay the braking data over a map of the race course, allowing the rider to see exactly where and how much they're on the brakes.

Loic Bruni brakes Formula prototype
The lever blade has less of a bend than the stock version...
Loic Bruni brakes Formula prototype
And while the caliper's shape doesn't look different, that doesn't mean that the internals are the same. That brake mount isn't the typical shape either.

As far as the brakes themselves go, the shape of the polished lever is slightly different than the stock lever – it's a little straighter, without as much of a curve back towards the handlebars. Visually, the caliper doesn't appear any different than the current version, but that doesn't meant that different piston materials or pad compounds aren't being tested. The brake mount isn't what you'd expect to see either - it's much larger than the typical post mount adaptor. We'll have to wait until race day to see how all this data gathering and experimentation plays out, but no matter what the results sheet says, it's still fascinating to witness the Specialized Gravity team's testing methods.


  • 556 3
 wireless override! when the split times are red, brakes are reduced to 50%
  • 18 54
flag polarproton (Mar 29, 2017 at 2:20) (Below Threshold)
 and when they are green, cassette de-clutches !
  • 8 12
flag jfour (Mar 29, 2017 at 19:06) (Below Threshold)
 @polarproton: no idea what either of you is talking about
  • 166 0
 I'm gonna say it's a pressure transducer based on the shape and location. No point having a temp sensor that far from the caliper. At a guess I'd say it's used simply to be able to tell when he is or is not on the brakes, and potentially correlate that with suspension position and motion characteristics.
  • 27 1
 I guess the hole in the mounting adapter could be used to mount a temperature sensor closer to piston.
  • 5 3
 Yep, measuring brake squat?
  • 9 5
 "JonGales, I'm gonna say it's a pressure transducer based on the shape and location... and potentially correlate that with suspension position and motion characteristics."
Yeah I'm with what this person might think he is not saying in relation to an alternative fact!
  • 42 2
  • 1 0
 @skiwenric: i think no because they like to block their rear wheel sometimes
  • 8 14
flag Pichy (Mar 29, 2017 at 6:26) (Below Threshold)
 It's all bullsh*t like those stickers that supposedly reduce vibrations from last season.
  • 2 1
 Given the conditions its in, looks like a challengibg measurement to take.
  • 6 0
 yes, it does look like a pressure sensor. I guess you could also get a feeling of how much brake power fades during run in correlation to pressure evolution. Or just to see where he brakes and is it too much (like they do in F1).
  • 3 0
 @skiwenric: On some street motorcycles you can spot ABS sensors on the wheels. They use a slotted disc (that looks not unlike a tiny brake rotor) with a little sensor (that looks not unlike a tiny brake caliper). Such systems also require electrical power for the sensor to work. Without those other bits, it is unlikely to be a form of mountain bike ABS.
  • 11 0
 @skiwenric: Definitely not ABS - ABS is not really feasible on mountain bikes (I worked on development of ABS systems about 10 years ago) - it's heavy (need a hydraulic valve block, an ECU, an accumulator, several solenoid valves and a powerful pump), expensive and requires a substantial power source. It also reacts very slowly for MTB applications (it took nearly 20 years after it appeared on cars to appear on motorbikes despite the obvious safety benefits, because it needs to kick in extremely quickly on a motorbike), and the ability to lock the wheel is often desirable on a mountain bike.
  • 5 1
 Definitely pressure - I have seen similar line pressure gauges in motorsports applications. Agree with JonGales too about the hole in the adapter. Could house a temp sensor and an accelerometer.
  • 1 0
 @Socket: That, and it's still bollox off road. On BMW's GS you need to turn it off once you get off road or you're screwed.
  • 101 3
 Flux capacitator? Brakes? Where he's going, he doesn't need brakes!!
  • 23 1
 Straight through the corner?
  • 8 1
 @dugglesthemuddled: straight through everything - including time...
  • 43 3
 Wait a minute, Doc, are you trying to tell me that my mother has got the hots for me? ...Precisely. ... Whoa, this is heavy. ...There's that word again; "heavy." Why are things so heavy in the future? Is there a problem with the earth's gravitational pull?
  • 16 0
 If he hits 88 mph on the bike then I'm clearly doing something wrong when I ride...
  • 9 1
 1.21 Gigawatts!!!!
  • 10 0
 French lines don't need brakes.
  • 4 0
 These brakes are my density, I mean destiny.
  • 53 9
 Thanks for braking it down for us!
  • 13 14
 Breaking news!
  • 21 5
 Just put a STOP to these puns please.
  • 8 11
 @jamesdippy: argh, give me a brake from all these bad puns.
  • 50 2
 This is all speculation and we need to have a closer Loic
  • 25 2
 The caliper of puns on this site has been in decline for a while now....
  • 4 4
 @ugez: joke caliper has been higher indeed
  • 2 5
 @MrJimLahey: I believe he has the Cura
  • 1 3
 @smallsilences: its because people feel the organic need to pad their +'s
  • 26 1
 Word on the street (actually, from someone up at Skyline QT where Loic was smashing laps) is that it's all part of the data harvesting. With info on brakes and suspension they can tell exactly what's happening to the suspension/bike under braking.
  • 7 2
 Sounds legit!
  • 4 0
 @AJBarlas: well, the someone was a guy riding with Loic. We stopped to talk to them at the top of the gondola - the bike looked part super computer. I should clarify that I have no clue if the above gadget in the pic has anything to do with that, but they were definitely getting telemetry data on brakes and suspension combined.
  • 6 0
 @AJBarlas: but would you go as far as to say it was "2 Legit?"
  • 5 4
 A lot of the work they are doing with the custom progressive links is to fine tune how the bike handles under breaking. Most FSR style bikes are neutral under breaking in theory and tend to "stand up" a bit when riders brake and the weight shifts forward. Loic's Lapierre did quite opposite and would squat a bit under breaking.

With the suspension telemetry they have been using a few years now it would make sense to now also be adding the effects of braking into the equation.
  • 21 1
 @davetrumpore: Most riders hit the ground when the bike is "breaking". If the bike was braking...well, now...it'd be slowing down.
  • 4 0
 No sorry, I had a dream about this. Its Specialized's entry into the ABS brake game. Just imagine! :-) n
  • 1 0
 inb4 floating brake kits :p
  • 33 3
 Weed pipe
  • 13 1
 ABS? Smile
  • 6 1
 That's what sprung to my mind but that would be pointless on the rear as sometimes a skid is needed. Would be cool on the front tho Smile
  • 9 5
 ABS is a rather chunky bit, even for motorcycles so it ain't that. While it could work for the front brake for amateurs, it is completely useless for the rear.
  • 1 0
 On motorcycles you can find a slotted metal disc on the front wheel with a sensor attached to that which is, of course, electrically powered. Unless they're using a completely different kind of sensor, it's probably not ABS.
  • 3 1
 Everyone knows what plumbus is
  • 6 1
 I'd guess it's a pressure transducer to measure the amount of braking and compare it to the suspension movement. The caliper mount has a threaded hole that could be used to mount a temperature sensor measuring the caliper. In my opinion it wouldn't be very valuable to know the temperature of the oil that far from the caliper, there's a chance that oil never reaches the caliper at all...
  • 1 1
 " there's a chance that oil never reaches the caliper at all..."

  • 3 2
 @bogey: the volume of oil in the line is greater than the total volume of oil displaced by a full stroke of the lever. Most of the oil in the brake system never actually gets inside the caliper. I agree it is 100% definitely not a temperature sensor. Would be useless.
  • 11 2
 it loic like he crashed and scratched the lever
  • 5 0
 Measuring hand pressure, force and duration or what I would call measuring the riders fear level.
  • 2 0
 Next evolution of this? www.pinkbike.com/news/first-look-brake-power-meter-prototype-interbike-2016.html

They were aiming to release in the middle this year so would be about time. Although given the inventors links to Giant I thought it would appear on one of their bikes first.

Been waiting for braking telemetry, I'm just a data junkie wanting their next fix.
  • 3 0
 Actually, if you put a sensor in that caliper mount, you could measure wheel speed.
  • 1 0
 The hole in the caliper mount may be to mount a tiny shield prior to production to cover it up visually before production. Sometimes with these companies, the science is just to keep a secret.
  • 3 0
 Has Protour been notified? I have the nappy rash cream on standby guys, I've got this. #CaptButhurt
  • 2 0
 I'd bet on pressure transmitter. Not an exact match, but really close, only $810 for you DIYers.
  • 4 2
 R&D team want to show that they are doing something whilst they have everything done long time ago.
  • 1 0
 Telemetry. Relationship of brakes and suspension platform Or it could be used with GPS to analyze the run in unheard of details for the team.manager
  • 1 2
 The angle of the sensor seems not correct for measuring temperature, it is directed at the disc, so maybe measuring disc temp or disc speed. But since the sensor is no longer there, it probably didn't give interesting data...
  • 2 0
 Looks like their testing a new type of Condom to keep Bruni's fluid at bay....
  • 1 2
 I'd guess that this specific part on the brake hose circuit is a kind of bladder, this one is here to maintain constant pressure in the brake hose when the fluid heat is raising during braking. For the caliper adapter, it's either to install a temperature sensor close to the disk or a proximity switch to monitor influence of suspension on the wheel during braking period.
  • 2 0
 Perhaps an extra reservoir to increase fluid & reduce brake fade? Made one for a set of Hope DH4's once.
  • 2 0
 Why is spesh going to other company's for brakes and suspension? Did spesh and sram get into a fight?
  • 2 2
 Extra brake fluid reservoir of when the brake heat up the fluid needs somewhere to go, so that it doesn't trigger the brake.....????
  • 2 0
 Ahhh brakes... and that thing for sure will just make him go slower...
  • 1 0
 hahaha....right, for stop and go Big Grin
  • 1 1
 It's possible Specialized is disappointed with Bruni's recent performances and want to make sure he's not using his brakes too much.
  • 2 0
 Now I want calipers machined to look like a hippo opening its mouth.
  • 1 1
 The hole in the brake mount could be for an inductive sensor for an ABS-system. But because it's actualy not in use they removed the sensor to hide it.
  • 1 0
 To be honest what does it matter your run of the mill rider wont need or afford whatever it is
  • 1 0
 Where does that 3rd line connect?
  • 3 0
 Read it again, it looks like you are suggesting data logger. I would imagine its pressure, which they can translate to braking force. Perhaps testing new levers to see if there is an improvement. Extra braking force may warrant reinforced brake mount.
  • 1 0
 They are measuring brake Jack......Roure
  • 1 1
 I do like the idea about ABS. your rear wheel doesnt block, i.e. your suspension gets less influence.
  • 1 0
 This is without a doubt a fluffer valve !
  • 1 0
 could be a brake booster, but what ever it is doesn't look UCI legal.
  • 2 0
 SWAT storage
  • 1 0
 I didn't realize he even used brakes
  • 1 0
 It's an extra reservoir to increase psi
  • 1 0
 It is a Red Herring. No one spotted what he's done to the ........
  • 1 0
 Blah.....it is all just there to try and skew him down Razz
  • 1 0
 That brake caliper looks like a hippo eating the rotor...
  • 1 0
 Brake mount looks like a heat sink
  • 1 0
 Think he's running ABS with that pressure transducer..
  • 1 0
  • 1 0
 its a double piggy back
  • 3 3
 Braking = loosing. No need for this fancy sh**, to figure it out.
  • 1 2
 Hay que ser idiota para esperar el abs en una bicicleta de montaña. Idiots!!
  • 1 1
 Its the first ALBS for a bike. No more skidding on the trails , children.
  • 1 0
 Bruni uses brakes??
  • 1 0
 It's not a toomah!
  • 3 3
 ABS obviously!
  • 4 1
 Nup. To make ABS work you need a polewheel, a proximity to count the polewheel as it rotates, an ECU to collect the input from the proximity and calculate loss of traction (loss of deceleration in this case), and a relief valve (modulator) to then be told to increase/decrease oil pressure by the ECU connected into the brake line. Too heavy, too cumbersome, too many bits to mount on a bike.
  • 1 5
flag Wouldhaveletmego (Mar 29, 2017 at 6:48) (Below Threshold)
 @handynzl: for a vehicle, yes. But that setup would be much smaller for a bike. No larger than a di2 battery.
  • 3 1
 ABS has no place on a mountainbike. It is there on passenger cars to allow the driver to panic, hammer the brake and still steer. It doesn't give you the biggest deceleration, but it limits the deceleration to the level that you can still steer without losing grip. It doesn't make sense on a mountainbike (let alone the rear wheel) as the terrain varies so quickly that the ABS system can't anticipate (whereas the rider can).
  • 2 0
 @Wouldhaveletmego: what @handynzl didn't mention is that you also need a pump and oil accumulator for ABS systems to function, otherwise you can reduce caliper pressure but you can't reinstate it once the wheel starts spinning. Those pumps are a lot more powerful than your Di2 battery can run, they need to be able to build about 100bar in ~0.5 seconds.
  • 1 0
 @handynzl: you must be fun at parties
  • 4 0
 @gabo2112: Ain't no party like a mechanical engineer party
  • 1 2
 It's probably ABS braking and traction control. Duh.
  • 2 5
 maybe ABS System????
  • 1 4
 It's an ABS system.
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