Sram Red etap HRD
Sram’s wireless etap has shifted to the next level. Now it comes with disc brakes
Sram’s etap shifting simply had to be impeccable. Sram was in the crosshairs of every sceptic who wished to shoot down the wireless shifting concept, waiting to pounce on any tiny glitch. But the glitches didn’t come. No one’s gears started going haywire as they rode near a mobile phone mast. No one had their gears hacked. Shifting was solid and reliable, even in pouring rain, covered in muck and filth on a winter ride. Sram had delivered a superb product.
I’ve used etap for months now and can hardly fault its performance, which is why I was keen to find out how it would be affected by the addition of hydraulic disc brakes.
On paper, etap HRD should be a simple marriage of Sram’s already proven Red HRD (Hydraulic Road Disc) callipers to the etap shift levers. With much less internal gubbins in the etap lever body compared to the mechanical version, it appeared Sram’s engineers had a straightforward task ahead. But nothing is ever that easy.
Starting from scratch
‘etap HRD (Hydraulic Road Disc) is an all-new design. It’s not like the Red HRD at all,’ says James Alberts, Sram’s brake product manager. ‘The calliper has a lot of new features to do with pad clearance and heat management but also ease of set-up and servicing. We’ve worked really hard on the controllability of the braking. You don’t
want a brake that hits you with all its power at once. You want feel, so you can control it. For that we had to work a lot on the piston ratios – the size of the piston at the lever, the rate it pushes fluid through the system, to the size of the piston at the calliper and how much it moves the pads.’
Before I could test Alberts’ claims, I had to attach the system to a bike, which was much easier than I thought it might be. The hose-cutting, hydraulic connections and bleeding were all simple processes. Sram calls it Bleeding Edge Technology, meaning the internal architecture has been altered to change the way the fluid flows in order to reduce the chance of trapped air. It’s still not quite as slick as Shimano in that department, but it’s a big improvement over Sram’s previous convoluted methods.
Setting off on a ride, I immediate noted how similar the etap HRD levers felt to the mechanical versions. The etap HRD hood is 4mm larger, but I struggled to notice. The slim design felt good in my hand and it’s visually a big improvement over the original Red HRD hood shape.
Also pleasing was the lack of pad rub when riding hard out of the saddle – the bane of so many disc bikes. Sram claims a pad clearance of 0.4mm each side, which doesn’t sound much but during set-up there’s daylight between the pad and rotor, so as long the hub and axle hold the rotor firmly in place, you can ride in silence.
The size of the rotor affects both the available braking force and its ability to dissipate heat. Sram recommends a 160mm rotor, but after just a short period of testing I opted to flout its advice and switch to a neater 140mm.
In terms of performance the HRD levers delivered just as promised. The braking force comes in a progressive manner. Initially slow to react (a good thing), the modulation through the middle of the lever stroke is well regulated before ramping up to a force that’s well beyond anything my 67kg bodyweight requires.
Boiling point
Heat management is a big concern for disc brakes. The etap HRD callipers have a number of specific features designed to reduce heat build-up. Alberts assures me these callipers run cooler than anything in the past.
‘The calliper has a wider opening to increase airflow for improved cooling. The aluminium pistons are thermally insulated and there’s a stainless steel heat shield that sits between the brake pad and the calliper body, both of which reduce the heat transferring to the fluid, reducing its temperature by 35°C in lab tests.’
With other hydraulic set-ups (including Sram’s Red HRD) I found that if I dragged the brakes on a long descent it was possible to get enough heat in the system that the brakes would rub for a while as the fluid expansion pushes the pads closer to the rotor. I couldn’t induce the same effect on the etap HRDS, which suggests the claims about improved heat management are true.
Combined with wireless shifting, the flat mount etap HRD calliper and 140mm rotor combo on this Cannondale Super Six Evo is the neatest and cleanest solution for a road bike I’ve seen to date. The next step will be to get rid of the brake hoses too for the ultimate clutter-free bike. I’m not sure how they’re going to manage that, but I’m sure Sram is working on it.