EB13: Shimano Hydraulic Road Bike Disc Brakes – Tech Details & First Ride Impressions
Shimano gave us a short ride opportunity to test out their new hydraulic road brakes on the latest 11-speed Ultegra Di2 group. On the ride, we had access to Dave Lawrence, their road product manager, and questions and braking were done hard and fast. Here’s what we learned:
First off, our bikes were using preproduction units, so take all this with that minor caveat. They were quite polished and probably look exactly like what you’ll see at the end of the year when parts start shipping.
The calipers are based on XT mountain bike brakes. As in, they basically are XT mountain bike calipers. This let them get a group on the road without starting from scratch, and it let them take advantage of the finned IceTech pads and trickle down Freeza rotor design to maximize cooling. They’re so confident in the combination’s ability to shed heat that they’re spec’ing 140mm rotors for all. As long as you use both the finned pads and Freeza rotors, there’s no rider weight limit.
They used their older brake hose that has a bit more flex, so it’s intentionally mushier than the current XT-level MTB hoses. So the on/off of the full engagement is less severe. That means you’re less likely to lock up the wheels unintentionally because it’s purposely lacking the bite of their trail brakes.
Because these are just the initial offering, it’s likely higher end units in the future could see a sleeker design with the hose running to the inside of the caliper.
Like their mountain bike brakes, it’s a one-way full bleed. Push fluid in from the caliper and out the top of the shifter. It’s all lined up so gravity and rising air works in your favor. Just below the bleed port is the reach adjust, and below that you can see the silver ServoWave rollers. Unlike on mountain bikes where ServoWave changes the rate of pad movement, it’s used here to simply provide a consistent lever feel throughout the stroke.
All of these adjustments are accessed by removing the silver top cap.
Free stroke adjustment is under the hiod on the inside and controls how much lever pull you have before the pads make contact with the rotor. Back the bolt out and the pads will make contact quicker. This could be the key adjustment to getting the direct braking feel most riders will likely want.
First, the good: Hood ergonomics are every bit as comfortable and sleek as the normal mechanical parts. Lever feel is super smooth, and modulation of braking power was pretty good.
I say *pretty* good because there were some potential issues with these preproduction units that resulted in a lack of full, confident braking power.
The rear brake lever in particular moved through a lot of space -about 60% of its throw- before making pad contact, then needed plenty more pull before it started feeling powerful.
Shimano’s tech rep felt it and thought the hydro fluid might be a little low, hence the amount of pull before rear braking really kicked in. A fresh bleed might fix it. He said these units just came in and they were building up the bikes quickly in order to have them ready for us.
The next initial concern was a bit of prolonged retraction on the front. At the start of the ride we had a few fast descents into corners, which required hard and/or consistent braking. That, coupled with the 100° desert heat, might have built up enough heat to keep the pads slightly close to the rotor for a few seconds. When I let go of the lever, I could still hear the pad making contact, and the noise faded away as the pad retracted over the next 1-2 seconds.
Given Shimano’s confidence in the thermal management properties of the equipment, the more likely cause was simply that the new seals inside the caliper needed to break in so they’ll retract faster. That means the issue would disappear as the brakes wear in a bit. They say this happens in mountain bike brakes, too, you’re just less likely to hear it.
About the power: I was hoping for more. I’d sprint then grab as much brake as I could without skidding, and it took a little too long to reign in the speed or come to a complete stop. A lot of the possible issues and fixes mentioned above would probably remedy this, but personally, I think I’d prefer the power and feel of a 160mm rotor, at least on the front. I rode a 140mm rotor on the rear of my mountain bike for years before switching to a 160mm, and the difference in power/feel I experienced there is what I believe was needed here, too. Keep in mind, I’m 6’2″ and about 190lbs kitted up.
So, at the moment I’d err on the side of trusting Shimano’s experience in making some of the best mountain bike brakes available and say these issues will be resolved on production parts. Several other editors on the ride said they really liked them, so it could have just been my setup. But that raises some very important concerns about making sure the factory or bike shop also has to set things up properly.
I’ll finish with this: I’m very much looking forward to testing a production set on my own bike. With a 160mm rotor.
A few notes on integration of the hydraulic brakes into an existing Di2 system:
You can put these new Di2 hydro levers and brakes on an otherwise 10-speed Di2 e-tube setup. The rear derailleur communicates to the shifters to tell them how to function. You would just need to update the software in the battery to make it all play nice together.
You can also mix and match 11 speed Dura-Ace and Ultegra, which would let you add a wider range cassette to an otherwise DA system or just upgrade a few parts at a time.