This genius hacked together Shimano Di2 and SRAM hydraulic brakes because he could

What do you do when the bike industry doesn’t make components to suit your specific needs and desires? If you’re design engineer and pneumatics specialist Paul Townsend, you make your own, hacking together parts from competing brands.

Paul commented on our feature about road tech dead ends (which featured hydraulic rim brakes) with a photo of his unique SRAM-Shimano hack, and we had to learn more.

Back in early 2016, the road groupset market looked very different to now. Shimano had yet to launch its Dura-Ace R9170 disc-and-Di2 groupset (the non-series R875 levers and matching brakes were the sole hydraulic/Di2 option), and SRAM’s Red eTap HRD was still months away too.

Paul wanted hydraulic rim brakes on his road bike but he wasn’t happy with the Magura calipers at his disposal.

There were good deals available on SRAM’s levers with hydraulic rim brakes and he was a fan of Shimano Di2 shifting, so he decided to combine the two in a unique DIY mashup.

Paul’s levers combine Shimano Di2 shifting with SRAM hydraulic braking.Paul Townsend

This involved transplanting the brake lever and shift button assembly, plus associated electronics, from a set of Di2 levers into SRAM hydraulic road lever bodies.

The SRAM hydraulic system remains intact but is operated by a Shimano lever blade, while shifting is entirely Di2-based.

I put some questions to Paul to learn more about his extraordinary setup: how he did it, his background and an engineer and what might be next…

Before we go on, we should point out that modifying your braking system in any way carries a risk of serious injury and we don’t recommend it. Modifying components will usually void any manufacturer warranty, too.

What is your background and where did you acquire the skills for this kind of component mashup?

Hacked levers front and side view
The hacked levers look like a finished product. You’d never know they’re a DIY special.Paul Townsend

I’ve been into biking since the eighties when I was studying mechanical engineering at Coventry Poly. I had a Diamondback Topanga and a Mick Ives cyclocross bike back then.

I’ve gone through loads of bike builds and custom setups and have been a design engineer and pneumatics specialist for way too long now. I’ve also modified cars and bikes for years.

I had a Canyon Ultimate back in 2013 and have always liked tech, so first I fitted it out with a Shimano Ultegra 6770 Di2 external wired groupset.

I then upgraded the brakes and tried the Magura RT6 hydraulic rim brakes, which were frankly crap, and a pain to install and set up.

I’d already made a clutch derailleur for my cyclocross bike and put my Formula RR clone disc brakes on it with Di2 shifting. It worked fine, but at about this time the SRAM HydroR hydraulic rim brakes and levers were on offer for a ridiculously low price at Planet-X.

Having researched how the SRAM stuff went together, and knowing the space needed for a Di2 module, I picked up a set of the HydroR rim brakes for about £100. I subsequently bought another four sets for me, a mate, and a guy in the US.

I’ve also made hubs and Gravity Research Pipe Dream-style v-brakes for my cyclocross bike in the past, and loads of other bike mashups since.

Can you explain the thinking behind your Di2/HydroR levers? What was your motivation and what did you set out to achieve?

So the thinking was: hydro disc brakes have loads of feel and a light-ish lever action. The Maguras were a pain and butt ugly, so if I wanted hydro rim brakes for my road bike then SRAM was an option, but l liked Di2.

How hard could it be to combine the two? The SRAM lever bodies have a big empty hole when the shifter mechanism is removed, so the answer is: it’s dead simple.

What were the hurdles you had to overcome to get the levers to work? Did you have to fabricate any new parts?

I bought some second-hand 6770 Di2 shift levers as 11-speed Ultegra 6870 Di2 was the new thing and loads of people were mistakenly selling off 6770 levers to upgrade [mistakenly, because 6770 can actually be made to work with 6870 derailleurs]. I think I paid about £50 for a pair of levers.

My setup uses the existing pivot hole in the Di2 brake lever, and pushes with both the metal of the original Di2 lever and a plastic rapid prototype (3D-printed) part onto the brake’s master cylinder, so structural strength wasn’t going to be an issue.

I cut the excess off the top of the 6770 Di2 lever and machined it flush, then bonded on the sintered rapid prototype nylon part.

Modified Shimano lever blades with extra 3D-printed part
Paul cut down Shimano’s lever blades and added his own 3D-printed part to make them fit.Paul Townsend

I reamed out the holes to make the bores smooth and to size. With a lick of paint, or in this case nail polish in Shimano grey-green, I was ready to assemble everything.

This arrangement doesn’t use the stock lever return spring or E-clip to secure the shaft, so the shaft is drilled and tapped to take a countersunk screw that has a head larger than the pivot pin. Once the lever body is slightly countersunk as well, the head sits flush.

A conical return spring was added to the brake master cylinder shaft to give a return force for the lever.

The only mod I did after that was to add a small cross-section O-ring to the old E-Clip groove of the pivot pin, to stop a slight rattle from the brake lever blade.

The Di2 cable runs in a groove in the underside of the 3D-printed plastic head of the brake lever, so it’s retained and can’t get snagged or wear.

The only mod to the SRAM parts, once all the shifter mechanism was removed, was to file a groove to run the Di2 cable. The Di2 module is secured with a block of foam in the space left behind.

I also run a hacked sprint shifter system, with old Dura-Ace 7970 Di2 switches wired to the electronics module from a SW-R600 climbing shifter switch, all wired to the left lever. The wires are extended to allow a neat plug-in solution and, as I run a Canyon clone integrated bar-stem setup, the Junction ‘A’ Di2 box is in the stem.

The brakes have titanium hardware and light brake block holders to give an all-up weight for the shifter, hose and caliper of 375g for the front and 390g for the rear, as installed on a 52cm frame.

SRAM hydraulic rim brake with aftermarket pad holders
Even the brakes are lightly customised for a small weight saving.Paul Townsend

Was it a success? And would you do anything differently with the benefit of hindsight?

Yes, I would say it’s been a success, I sold a set to a guy in Hong Kong who shipped me SRAM Red and Dura-Ace to do this mashup too.

I sold another setup to a guy in Australia for his TT bike and a third to a guy in the US, so that covered all my costs.

It would have been a bigger risk if I had paid full price for everything. Also, I can always return the SRAM parts back to stock mechanical shift with no issues.

Maybe I would give the lever a stronger return spring, and I did need a dab of thread-locker to stop the reach adjust from changing during a ride because I’d unscrewed the brake adjuster fully, stripping the original thread-lock off.

re you working on any new hacks?

Yes, I’ve got some new climbing and sprint shifters underway, and I’m looking at a different arrangement where the front shift will be a secondary lever like the thumb paddle on Campagnolo shifters.

The initial idea is right-hand upshifts and left-hand downshifts, and I’m still playing around with what lever blades to use.

I could stick with the flattish SRAM brake lever blade or use a Campagnolo one, then retain the SRAM lever blade for the rear derailleur shifts and the new lever for the front derailleur shifts.

This should mean no chance of mis-shifts, even with gloves, which can be an issue in winter with Shimano’s standard setup.

Thanks very much to Paul for answering my questions and supplying images. For more of his hacks, follow him on Flickr and Instagram, or read his posts on the Weight Weenies forum under the username motorapido.

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