Review: Ashima PCB Pistonless Hydraulic Disc Brakes

This review has been a long time coming. We’ve blown through two pre-production sets before receiving a third, production-level set of brakes, which we’ve tested under a number of riders over the past eight months. The first set leaked out of the box and never worked. The second set worked fine until we shipped them to Zach, after which they lost pressure and failed after a few rides. This last and final (and the only production version) set seemed to finally cure the ails that plagued them.

For the uninitiated, Ashima’s PCB (PanCake Brake) is a completely different design from other hydraulic brakes. The caliper uses diaphragms to hold the pads rather than pistons, so technically there are no moving parts other than the lever and plunger. This saves weight and simplifies the design – these are the lightest brakes we’ve ever had come through our doors – but it also gives the brakes a feel unlike any other we’ve ridden.

Is that a good thing? Read the full review and find out…

WHAT’S IN THE BOX?

To be fair, we never received our test sets in production retail packaging, and in most cases they arrived from overseas in a heavily beat up box…which might explain some of the issues with the early versions. The final production version weighed in at a very light 197g front and 213g rear.

They also come with their very light AirRotors and the appropriately sized mounting brackets.

This is within 1g of the pre-production versions we received, and that’s with an ever-so-slightly longer cable for the rear:

One of the issues with the early sets was that we had to run the rear cable on the wrong side of the steerer tube. See that, along with the weights for each size rotor and mounting bracket in our original “Unboxed” post. Since that post, Ashima has started offering sets for both hardtails and full suspension, presumably with longer hoses for the FS kits. Measurements aren’t listed online, but I can say that the sets we’ve tested would not have fit a full suspension 29er bike. Each brake also comes with spare parts (banjo, hose fitting, tools, etc.) to help you make repairs or shorten the hose.

Price is about $169 per wheel, available through J&B Importers for the U.S.

HOW THEY WORK:

The hydraulics push directly into a diaphragm that doubles as the seal for the brakes. There’s a hard, flat surface on the visible section of the diaphragm to push the pads evenly and firmly.

An exterior “pipe” carries fluid from one side to the other and aids in cooling. We never noticed any fade on long downhills. Note the pin that holds the pads in…grab it good when pulling it off or it launches into space and is impossible to find. A normal cotter pin would be preferable.

The master cylinder puts the vacuum diaphragm cover on the inside edge, forcing the hose to come in from the side, which means the backside of the cylinder body. The body itself is made of an “engineering grade” plastic to save weight. The lever blade is pretty comfortable and easy to grab, and a small allen key adjusts reach. That’s the only user adjustment offered.

The hose banjo on the back of the master cylinder forces a big gap between it and your shifter body. I was able to compensate somewhat by using SRAM’s adjustable trigger on their X0 shifters, but it still cocks it backward more than normal and requires a bit of compromise. The shift lever placement was something we quickly adjusted to, but worth mentioning if you’re ultra-particular about your setup. You could get around this by running them Moto or buying the Euro versions (flip flopped front/rear placement), which would put the banjo facing forward.

HOW DO THEY RIDE?

TYLER’S REVIEW: I spent the most time on these brakes, about six months on the 2nd pre-production set and about the same or a bit longer on the production set.

Hmmmm…how to describe these. I feel I need to preface the next section with this: The brakes absolutely work, and for the right person, they’re probably just right.

If you’ve felt the rock solid engagement of Shimano’s new XTR brakes, these are the polar opposite. The Ashima’s squish into action with a very soft lever feel. If you ever had SRAM’s old 9.0 thermoplastic lever mated up to some Avid SingleDigit brakes on a hardtail, the feel is very much the same…it’s mushy all the way to the end, even after the wheel is locked up and you’re skidding. It’s just that there’s a bit of a disconnected feeling between the lever and the pad.

What that translates to in terms of braking performance is a rather smooth progression from start to finish, with more lever pull required to lock up the wheels, but you can definitely lock them up. On the trail, that means you’re less likely to scrub off too much speed too quickly unless you’re doing an Oh S&*t grab. For racers, that could be just the ticket as you’re saving energy in the long run while still being in full control.

Ashima’s rep, Wayne, says they’re great for DH, too, but personally, I think the power is more in line with XC riding. I’ve raced them, and the bike’s been ridden by myself and others in wet, cold, hot, dry, mountains, rocks, dust and dirt, and the performance never waivered. Also, I never had any squeal throughout the entire test period.

So, would I recommend them? If the placement against your shifters doesn’t bother you and you’re looking for something super lightweight, then they’re worth a shot. It doesn’t take long to get accustomed to the brake feel and performance. The rotors themselves are pretty great…light, stiff and haven’t seemed to warp any over time (I’ve used the same rotors from start to finish on this review, including on other bikes with different calipers).

Now, all that said, a couple of days before writing this review I found the rear brake lever like this:

This didn’t happen during a ride, so either it fell against another bike in the garage (likely) or my kids tried to hang from it (equally likely). Either way, it’s not wanting to go back in, so short of sending this back for repair, the rear brake is gonzo. Even if it could, a full bleed would be required to get them working properly again, so if this happened on the trail, you might be in trouble. So, I hadn’t thought of it during the review, but a breakaway lever feature like on Avid’s levers would be a welcome addition.

ZACH’S THOUGHTS: I think the first thing that anyone should consider before purchasing a set of Ashimas is the brake feel. The Ashima PCB has one of the strangest lever feels that I have experienced, but I must say they work.

Obviously, my pair were pre-production, so everything has be taken with a grain of salt, but I have been told that even the production models feel… squishy. Unlike most disc brakes that have a very positive engagement point when the pads contact the rotor, the Ashimas engage very quickly, but never firm up. Ashima states that this is due to the fact that they are a pistonless system, and therefore rely on a flexible membrane that expands when you pull the lever. As the membrane expands, it pushes up against the pad, which then contacts the rotor. The harder you squeeze, the more power it delivers, but it always feels muted at the lever.

Eventually I got over it, even while running an Ashima on the front and a Shimano XT on the back (my rear brake wasn’t any good from the get go, but Ashima has stated that the set that I have are pre-production, and had known issues which have now been fixed). Out on the trail, I found the power to be quite sufficient even with a 160mm rotor up front, in lieu of my normal 180. Modulation was actually incredibly good with a very light feel at first, which could ramp up in an extremely controllable fashion. All in all, from a performance stand point I was fairly impressed. Considering these are basically a radically new design, they work pretty well, and it seems that Ashima is keen on making sure the final product is up to par, which brings me to some of the downsides of the brake.

While the performance was good for the most part on the trail, my front brake squealed quite a bit while riding in the wet. In the dry the brakes were quiet and happy, so this leads me to believe it is a wet condition issue, not a pad or rotor issue. I also had some issues with the pad rubbing on the rotor, but since this generation’s issues have already been fixed, it is a moot point.

My biggest gripe with the Ashima PCB? That would have to be the alloy rotor bolts. Yes, they’re ano red, they look great, and they’re light, but alloy bolts have no place on a rotor. Even worse than the fact that they are made of very soft alloy, is the fact that they utilize a T20 Torx fitting. This is obviously smaller than the standard T25 Torx that almost every other company uses, and one that up until that point, I hadn’t seen used on a bike before. After finding a T20 bit in a set of Dewalt Torx bits I had at home, I made sure to install the rotor bolts without Loctite, and torqued them to 4Nm with a Park Torque wrench per instructions. Installation was a breeze, and I really didn’t think anything of it until I tried to remove the rear rotor. While attempting to remove the rotor bolts on the rear, I managed to strip one of the alloy bolts. Now, if I was going to strip it, I would expect to do that installing it, not removing it. I can honestly say that in my nearly 10 years of wrenching, I have never stripped a rotor bolt, and while as they say sh*t happens, if I was that careful and I stripped one? I’m guessing many home mechanics would be cussing and throwing wrenches (as long as they found a T20). You can see by the pictures that it was not stripped after it was installed, and the carnage afterward, after Dremeling a slot in the bolt to use a flat blade to remove it.

The only other real issue has to do with how you position your controls on your bar. Rather than having the brake line attach to the front or side of the master cylinder as most companies do, Ashima uses a banjo fitting that attaches to the bottom of the MC. This is great, looks really clean, and allows fine tuning of the hose angle, but like Tyler mentioned, it could be an issue with shifter placement. The bezel that surrounds the banjo fitting sticks out quite a bit from the MC, which I found to prevent me from angling the levers down as far as I would have liked. I suppose to get around the issue you could simply flip flop the levers and run the brakes upside down, but this would require removing the hoses and swapping them, and most likely require a bleed. This didn’t present itself as a huge issue for me, but it could be quite annoying depending on what angle you run your controls.

Speaking of bleeding, the Ashima features one of the easiest bleed methods I have seen. Unfortunately, it requires a specific bleed kit, and I was unable to get one from Ashima after multiple requests. So, in order to try and bleed my set I had to improvise. Eventually, I figured out that a Magura Bleed fitting would work for the bar with a couple extra o-rings to seal it up, and an Avid fitting that was ground down would work OK. Basically, all the bleed entails is connecting a syringe with DOT fluid to the lever, and connecting the empty syringe to the caliper as a catch can, and pumping the lever while adding fluid. It really was pretty simple, and their video made it seem even easier with an actual bleed kit.

Overall, the Ashima PCB is a fairly well thought out brake, if not without a few flaws. The performance is there as long as you can get over the lever feel, and for anyone looking for a fairly light set of brakes that are unique, they’re not a bad option.

NOTE: It’s worth mentioning that each production set gets it’s own testing and paperwork showing power data, and Ashima seems really keen on listening to feedback, as evidenced by the progression of features and fixes since we first started testing these. It’s great to see a company listening and improving throughout the year rather than just waiting for arbitrary model year releases.