This is all high-end stuff though: SRAM's discs are only for the top-end Red groupset and a full set will cost you £850 RRP for the levers and callipers. It seems that Shimano's will be based around the Di2 electronic groupsets which have plenty of space in the lever for a master cylinder but again that's top-dollar gear.
So what are your options further down, if you have mechanical shifters? Well until recently there were two: run mechanical disc brakes, or use a converter system (Hope V-Twin or TRP Parabox, for example) to convert cable pull to hydraulic push.
The Hy/Rd is a refinement of that second solution. The cable runs all the way to the calliper, and the hydraulic master cylinder and pots are all bolted on to the frame or fork as one unit.
After a month or so testing these brakes in all conditions, I'm happy to say that they're about the best-performing brakes I've used with road levers. They're more powerful and controllable than rim brakes and easier to set up and maintain than mechanical discs, and they win over stem-mounted converters in their simplicity with no noticeable loss in performance. Here's a rundown of what's good about them.
Ridiculously easy, in fact. I swapped out Avid BB7s for the Hy/Rds and a bit of cable outer trimming was the only thing that required anything other than a 5mm Allen key.
Setting the brakes up is a doddle. There's a knurled wheel that screws a bolt into the lever arm to lock the brake open, and once locked you can pull the cable nice and tight to make sure there's no play in the mechanical system. Then you unlock the lever, loosen the mounting bolts, pull the brake on hard, tighten the bolts and let go. That's pretty much it. The self-centering hydraulics will take care of pad positioning like they do on your Mountainbike.
Adjustment is taken care of by the open hydraulic system: the rotors run free on my test bike with a barely discernible gap to the pad, the way you wish you could get your mechanical discs to sit but never can.
As the pads wear they move in, so the only real maintenance is changing the pads when they're finished. In a cyclo-cross environment, when a muddy race can shred a pair of organic pads, the constant pad adjustment is a major benefit over mechanical systems.
Since the hydraulic system is completely enclosed there's no reason to suspect it'll need to be bled unless you manage to boil the brake fluid, which I don't reckon is possible given the field testing I've been doing.
I found that the default position gave a bit too much lever throw but there's a barrel adjuster on the calliper to take up any remaining slack. However, you need to be careful with that; pushing the pistons in too far can affect the brake's ability to self-centre. I found the lever throw more of an issue in the drops, with heavy braking pulling the lever quite close to the bars.
TRP say that you can also use the lever lock to stop your pads getting pushed together when you take the wheels out (in transit, for example) but you'll have to be really sure you'll remember to unlock them at the other end if you don't want to end up in a hedge.
These brakes are more powerful that rim brakes and nearly all mechanical discs I've tried. That means it's easier to lock the back wheel up and the first few times you use them you'll skid to a halt. But the practical upshot of all that power is that braking is easy once you've adjusted your filter: less lever force for the same amount of stopping.
That means better control and more confidence on descents. It means that you don't have to go down onto the drops to be sure you can grab enough brake to haul yourself up at the end of a big road descent, or on a technical cyclo-cross run.
To everyone that thinks they don't need more powerful brakes, I'd say: try more powerful brakes. They're better. Like modern dual pivots are better than those old Weinmanns you had on your road bike in the 80s. In terms of performance, it's progress.
Mechanical discs work much better with a high quality, compression-free cable outer and these Hy/Rds are the same: if your outers compress, the brakes will feel spongy. Fit the best cable outer you can afford. Our brakes ran mostly on a Pinnacle cyclo-cross bike with mid-level Jagwire cable housings and we had no issues, but top-quality housings would no doubt give a slightly improved lever feel.
One of the main benefits of discs on a mountain bike is that they're out of the mud and grime. The same is obviously true for cyclocross. On the road the mud's not so much of an issue, but wet rims can seriously affect braking, especially on carbon rims. Discs have a smaller surface area than rims, they don't pick up water from the road and they run much hotter, so braking performance in the worst weather is miles ahead of rim brakes.
If you want to run carbon rims then you'll get the same braking performance, obviously, and with no rim brakes eating into whatever rims you choose you can expect your wheels to last longer.
A lot of the talk around road discs has been to do with heat build-up and in the interests of science I've done my best to cook the Hy/Rds by dragging them on long and steep descents, one brake at a time.
It's possible to induce a bit of heat-induced brake fade if you drag a single brake down one of Bath's many hills and then try and use it to stop at the bottom, but it's fairly predictable fade and once you're using both brakes together it really ceases to be an issue at all. Even with a bit of fade you're still applying much less pressure on the levers than you would with rim brakes.
Heat transfer to the actual calliper unit is minimal. Even when the rotors are piping hot the hydraulic system is barely warm. TRP uses a Bakelite piston to insulate the hydraulics against the braking heat and it seems to work. I haven't tried firing myself down an alpine col in the high heat of the summer with these brakes, but I wouldn't have any qualms about doing so.
TRP Hy/Rd brakes are powerful, easy to set up and adjust and they work well in all conditions. What's not to like? Well not much, really.
The lever throw to the bite point is a bit longer than would be ideal, and not that adjustable, but it's still acceptable. In terms of weight (198g per wheel not including rotor) they're not all that different to a set of BB7s and they don't stick out anywhere near as far, giving you more heel clearance.
TRP reckons they could be made a bit lighter, and I'd like to see them do a bit of work on the look, which is currently a touch agricultural; fine for a cyclo-cross bike but a road bike wouldn't wear these as easily as it would the Red hydraulics or TRP's new Spyre mechanical unit.
As a first iteration of a new product, though, TRP has more or less nailed this one. At £110 RRP per wheel you'll be seeing these on bikes at Shimano 105 level. Look out for them, because they're worth having.
Currently about the best braking performance you can get from a road lever. Not perfect, but definitely progress.
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Make and model: TRP Hy/Rd mechanical interface hydraulic disc brakes
Size tested: n/a
Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?
The latest iteration of our industry leading efforts to bring hydraulic performance to the developing road/cross disc market, the HY/RD is an OPEN hydraulic system that is FULLY compatible
Tell us some more about the technical aspects of the product?
-True 'plug-and-play' compatability with ALL existing cable actuated systems
-Hydraulic reservoir provides automatic pad wear adjustment
-Works with ALL cable actuated road levers
-TRP's own ultra-grippy semi-metallic pad that is Shimano compatible allowing for further customization
-Available in black ano with polished cap or polished with black ano cap
-140mm or 160mm rotor options will work for both front and rear
-All mounting hardware included
-140 versions include our L2 (140F/160R) IS to PM adapter
-160 versions include both L2 and L3 (160F/180R) IS to PM adapters
-Post mount to post mount adapters available separately
-Weight: 195g/caliper per wheel
Tell us how the product performed overall when used for its designed purpose
They're the best performing brakes I've used with a road lever
Tell us what you particularly liked about the product
Braking power, consistency and modulation
Tell us what you particularly disliked about the product
Slightly agricultural looks
Did you enjoy using the product? Yes
Would you consider buying the product? Yes
Would you recommend the product to a friend? Yes
Age: 40 Height: 190cm Weight: 102kg
I usually ride: whatever I'm testing... My best bike is: Genesis Equilibrium with SRAM Apex
I've been riding for: 10-20 years I ride: Every day I would class myself as: Experienced
I regularly do the following types of riding: commuting, sportives, general fitness riding, fixed/singlespeed, mtb, Mountain Bike Bog Snorkelling, track
Dave is a founding father of road.cc, having previously worked on Cycling Plus and What Mountain Bike magazines back in the day. He also writes about e-bikes for our sister publication ebiketips. He's won three mountain bike bog snorkelling World Championships, and races at the back of the third cats.