In this article, we’ll be discussing a Handlebar Integrated Master Cylinder Assembly by SRAM, US patent 11066121. The publication date is July 10th, 2021 and the filing date is May 29th, 2020. This patent is granted as novel.
This document is incredibly detailed — way too much for an article. I’ll try to keep this high-level so you’re not bored out of your mind. And before you come at me with “Magura did it, how can SRAM do it” — this is fundamentally and technically different. Just because the general idea is the same, the method is new.
And, again, I can’t believe I have to keep saying this to other full-grown adults, but please just cite this if you use the research for your own website.
Brief Summary (tl;dr)
SRAM appear to have come up with their own integrated braking system, similar to Magura’s MCI system that was released a few years ago. This system places the master cylinder inside the end of the handlebar, where a cable-type mechanism is pivotally connected to the brake lever linkage. When the rider pulls the lever, the linkage puts tension on the cable, which pushed the piston at the end of the handlebar/master cylinder through a slot in the master cylinder assembly. The handlebar and master cylinder will hide behind the grip, so everything will have a super clean look. Importantly, it looks like the lever is rotationally adjustable, but not in/out adjustable.
We can’t talk about this idea without referencing Magura’s Cockpit Integration (MCI). I wrote about the latest development here, which relates to a more adjustable, integrated, braking system with a nifty little barb. Their newest idea expands on the first iteration by adding a small level of adjustability to the brake lever, which was the primary complaint about the first one, though none of you actually rode it – you just like to bitch about stuff.
Ultimately, integration is the new buzzword for the bike industry. Everything is getting integrated, from tools to storage to water bottles (Shiv). It makes for a clean appearance and, at times, more convenient. Though you can argue that integration like brake levers may be less convenient, but that’s the mechanic’s problem, right?
The intended novelty here is pretty legalese. SRAM say the fluid cylinder is partially inside the handlebar and the force applicator is partially outside the handlebar. Additionally, they say the force applicator is a ‘pull rod’ and is ‘under tensile load when the actuator is actuated’. The attorneys had to add that second part to narrow the scope because this was too close to this one from Campy, back in 2014. Campy’s looks like a linkage assembly, not a pull rod under tension, so this addition is what got this application granted.
SRAM have a pretty good problem statement, though I think it’s probably more about aesthetics than anything else. I’ve said this before, but the bike consumer doesn’t give a shit about how anything works. As long as it looks good, we’ll buy it. Riding is all about appearance, not actually riding.
“How can my wife spend $500 on a new purse?”
*Buys a Zeb when my Lyrik is perfectly fine*
‘…the brake hydraulic hoses are positioned within a handlebar of the bicycle to improve the aesthetics of the cockpit, reduce weight, improve aerodynamics, and reduce the risk of catching the brake hydraulic hoses on trail side brush or obstacles.’
Here’s a line from SRAM stating a huge advantage of this system compared to other integrated braking systems. Their goal is to provide the exact same features as a typical braking system we’re all used to.
The master cylinder assembly of the present disclosure provides the same rider facing features as externally mounted master cylinder assemblies of the prior art.
Few hours later edit: Adding some new stuff relating to adjustments. It’s pretty adjustable.
The master cylinder assembly of the present disclosure provides the same rider facing features as externally mounted master cylinder assemblies of the prior art. For example, the master cylinder assembly of the present disclosure provides a variable mechanical leverage rate, reach adjustment, dead-stroke adjustment ( e.g., lever contact point adjustment), and a range of mounting angles of a lever of the master cylinder assembly relative to the handlebar.
Also, adding this line, where SRAM note the location of the hole in the handlebar is strageically placed as to not be in a ‘strength critical’ area:
Unlike configurations of the prior art, in which a number of holes are added to strength critical areas of the handlebar to allow for hydraulic hose exit, in the present disclosure, the hydraulic hoses exit the handlebar through a single hole through the handlebar outside of the strength critical areas. The single hole through the handlebar outside of the strength critical areas of the handlebar does not compromise the structural integrity of a safety critical component, the handlebar.
FIG. 2 shows a high-level view of this system. The components you need to know are the master cylinder 152, force applicator 154, support 156, and actuator 158. This took me an embarrassingly long time to figure out wtf was going on with this, but here it is. The rider obviously presses the brake lever, the linkage 192 pivots around connector 195, and the force applicator 154 is pulled at connector 195 which pushes the piston inside the handlebar. I’m pretty sure the force applicator is on both ends (top and bottom) of the bar and is pulled at two places.
So, the actuation is actually outside the handlebar. The force applicator wraps around the end of the braking assembly/master cylinder, which is inside the bar, and compresses the piston, which then compresses the brake fluid. My amazing artwork below should clear up my ramblings.
Let’s talk about the most important part — the feature that will make this either a complete success or a horrible failure: Adjustability. I’ll try to answer this as best I can. As far as rotational adjustment, the brake assembly is separate from the handlebar. So, the whole reservoir/piston/etc. should be able to rotate relative to the handlebar. As a result, the lever/grip should also rotate.
As far as inward/outward adjustment, that may be more difficult. The system relies on the force applicator pushing the piston inward. If you moved the lever inward, the force applicator would preload the piston. If you move the lever outward, there would be a lack of tension on the piston, so the stroke would be dead until it tightened up. It appears as though the in/out position of the lever is based on the grip length. FIG. 27 shows the grip with an extension and flange, which should keep the lever in place.
So how do you fill the ressy? FIGs. 20 – 23 show the process. First, you’ll remove bolts 235 and 240. Now the grip and the lever will slide off the handlebar. FIG. 21 shows the grip and lever assembly removed.
At this point, everything should be loosened, and you’ll pull the master cylinder 152 out of the handlebar. You’ll also pull the bleed sleeve 362, as well. Then, you’ll move the bleed sleeves back toward the bike to expose the bleed port 364. You’ll then do your normal bleeding procedure.
FIG. 15 shows how your shifter or brakes will attach to this new brake. This is pretty self-explanatory.
So, where do the cables go? FIGs. 41 – 44 show some examples:
Edit: The location of the hole is shown in these figures. It’s located ‘…outside of the strength critical areas…’
FIGs. 30 and 33 show another example of the same idea. The lever pulls a ‘rod member’ 428 to move the pushrod, which closes the piston. I’m not sure what the material of that rod member is, but it’s got to be something malleable, but not elastic — probably some kind of plastic.
Is this cool? You bet your buttons. Will it work? No idea. I’ve said this before, everything I write about is new, not better. At the risk of being skewered in the comments, I’ve had very few issues with all of my SRAM stuff. If this is built/designed with the same care and precision, I have no doubts that this will work. And let’s be real, it’ll definitely look better. Cables are so 2020.
But, it seems as though SRAM have, at least, addressed one aspect of adjustability, which is a big deal in my opinion. The overwhelming criticism of Magura’s MCI was the lack of adjustability, which is only partially addressed in the last patent. If someone can come up with a fully adjustable, integrated brake lever, I think it’ll be a success. SRAM are close with this one.
Lastly, this is an incredibly creative idea, and honestly, I’m a huge fan of the attempt. I would love to see the final product. In fact, I’d love to take a walk through SRAM’s R&D department and peak at the other crazy ideas they’re cooking up. Based on the ideas coming out of this place, it looks like a super fun place to think and create. I’m sure there will be some SRAM employees that’ll scoff at this, but they must incubate a great work environment to constantly come up with heaters like this.