Cool Tool Tuesday #8: The best tools for installing hydraulic disc brakes
Hydraulic disc brakes offer a number of major performance benefits in terms of control and system bike design. However, they are without question a more complicated component than the old mechanical rim brake, and for that, new knowledge and tools are required. If you don’t know your mineral oil from your DOT, or how a disc rotor attaches to a wheel, then start with our endless FAQ to disc brakes.
As with most Cool Tool Tuesdays, this article is really aimed at those who either work on bikes for a living or wrench on personal bikes as a hobby. Very few of the tools mentioned here will be needed if you plan on letting someone else work on your brakes (no shame in that).
Tools related to disc brakes are a surprisingly massive topic and it quickly became apparent that to do it justice, I needed to split it into two articles. This first feature focuses on tools related to installing disc brakes, routing hoses, and trimming them to length. The following feature will be more mainstream-applicable with a focus on bleed tools, caliper alignment, piston cleaning, and more.
And given brakes are often all you have for stopping, I’ll give a quick safety warning that hydraulic brakes are not a component you should be messing with until you have a high level of mechanical confidence. A bad bleed, a loose brake hose, or even just a wrongly installed brake pad can quickly put yourself and others at great risk.
OK, on with the show.
Mounting levers and calipers
Mounting of brake levers and calipers almost always requires just a handful of general-purpose tools. Shimano brakes tend to require 4 and/or 5 mm hex keys, while SRAM is often a mixture of 5 mm hex and/or Torx T25.
In most cases, you can use whichever hex or Torx key you prefer. However certain frame, lever, or caliper designs can call for some more specialist types of hex key styles, a topic I’ve covered in depth before. Some of my preferred specialist hex and Torx key options include a fine-tooth ratchet and bit socket for fast threading of most caliper bolts. I like offset stubby keys for brakes with weird-shaped calipers that don’t allow easy direct-path access; short bit-ratchets for when frame clearance is an issue surrounding the caliper; and a cross-handle (aka flag-drive) for flat-mount brakes – a tool that offers a handle small enough to not interfere with the spokes of the wheel.
Torx bolts tend to cause people more issues than hex, especially the shallow T25 bolts used by SRAM on their road brake calipers. Here I recommend investing in a good quality T25 tool, namely from PB Swiss, Wera, or Wiha. My go-tos are the PB Swiss PB 1407.25-150 cross-handle (actually a P-handle) and stubby offset PB Swiss 2411-25 – both of which offer a wonderfully secure fit.
Almost all brake brands recommend the use of a torque wrench, a topic that will be covered in a future Cool Tool Tuesday. And while I work on that, I can say for disc brakes you want a torque wrench that falls somewhere between the 2-20 Nm range (many are often 3-15 Nm, a great range for bicycles).
The bigger problem is the sometimes-tricky tool access on certain hydraulic road brake levers or access to the caliper bolts. For this I often find that a set of 100-150 mm long hex bits (such as those from Vessell or Wera) can often be the solution. However, there are rare times when the lever design may force you to forego the torque wrench in order to ensure a perfect fit between the tool and fastener.
Mounting brake rotors
Disc brake rotors come in two common forms: six-bolt and Centerlock. Our endless FAQ to disc brakes has more information about rotors.
Six-bolt rotors are almost always held in place with six T25 bolts, often with a shallow head design that rewards the use of good quality tools (see the recommendations above). Those wanting to speed up the process often reach for an electric drill or small impact driver with a T25 bit. I personally use a Wera T25 50 mm Impaktor bit in a Milwaukee M12 Fuel (M12 FID). Just note that I never use the impact feature for final tightening, that is always done with hand tools.
Centerlock rotors are far quicker to work with and are held in place with a lockring that’s not unlike that of a rear cassette. There are two common styles of these lockrings – internal serration and external serration (I’m purposefully ignoring the original Shimano Saint lockring; hiss to that).
Internal serration lockrings use a regular HG-style cassette lockring tool (aka, Shimano style). The only catch is that modern thru-axle end caps often sit quite far out on the disc side and so you need a lockring tool that can clear this – something many old lockring tools fail at. Frankly, almost any new lockring tool sold by a respectable tool company should do the trick.
Meanwhile, I prefer the fit and feel of the Abbey Crombie (Shimano) for this task, and if a torque wrench is needed, then the Abbey Crombie Socket is my go-to as it has a square drive and deep clearance.
External serration lockrings use the same 16-notch 44 mm bottom bracket tool as needed for almost all 24 mm threaded external cup bottom brackets. For this, you have the choice between spanner or socket-type tools. I covered the best options and my preferences for this style of the tool in part two of my ‘building a cycling tool kit’ feature.
Brake hose routing
It’s rather rare these days to get a hydraulic disc brake, zip-tie the hose onto the outside of the frame, and then trim the hose at your leisure while being able to ride the thing in the interim. Rather, the process of installing a new hydraulic disc brake (or replacing a hose) can be rather intricate as a great number of designs now require you to internally route the hose through at least one portion of the frame.
Routing hoses and cables will absolutely earn its own dedicated article in future, but for now, I’ll offer a few quick tooltips specifically for hydraulic hose routing. And depending on the frame you have or how built up it is, it’s quite possible you won’t need any specialty tools at all. Instead, an old spoke bent into a hook, a flashlight, or perhaps even some needle nose pliers may be all you require – if that.
However, if you do need to blindly route a hydraulic hose, then an internal routing tool can be a real time-saver. My favourite versions of these are effectively a gear cable with a magnet on one end, and a threaded barb on the other. The barb is threaded into the open end of the hydraulic hose, and from there you can use a magnet to guide this special cable through the frame. Or if you’re replacing an existing brake hose, it’s often as simple as threading the barb into the end of the old hose, pulling the hose out while leaving the routing cable in place, and then switching the threaded barb to the new hose before pulling it back through in reverse.
Park Tool, IceToolz, and Pro all offer kits worth owning that can achieve the above and more. None are perfect, and frankly, there are situations where I’ll swap between them all. The Pro is the best one for Di2. The IceToolz is the best for frames with ultra-tight hidden bends. And the Park Tool is the pick for frames with tiny entry/exit ports. If I had to pick just one, it would probably be the IceToolz, but that opinion may quickly change if you give me a bike with tiny cable ports.
A far cheaper alternative is the SRAM Reverb barb connector. This is a tiny double-sided barb that’s designed to ease the replacement of hoses. I have used it before with the addition of some dental floss and a vacuum (the vacuum sucks up the dental floss through the path you’re trying to route) to help pull a cable through a frame. This was in the early days of problematic internal dropper-post routing.
This easily lost SRAM tool is cheap to acquire, but just know that it typically grips into the end of hoses with about as much holding strength as a knock-off iPhone charging cable.
Cutting brake hoses
Bicycle hydraulic hoses are typically made with a combination of Teflon, nylon, and sometimes kevlar, too (metal-braided hoses also exist, although these are rare these days). These plastic hoses are always best cut with an ultra-sharp blade, or better yet, a blade-based hose- or cigar-cutting tool.
Those who reach for the Bowden cable cutter or diagonal cutter (as is normal for gears or mechanical brake cables) will typically find themselves with a squished bit of fragmented or jagged hose – not good. Electrician scissors are another I’ve seen people use, and a sharp pair will indeed leave a smooth cut with little effort – but in my experience, it’s often at a slight diagonal angle whereas you should be seeking a square cut. Meanwhile, a super sharp pair of plastic flush cutters can do the job, but it’ll pinch the hose a little out of shape. This isn’t a total deal-breaker but better results can be had.
Cutting hydraulic hoses can indeed be done with a fresh box cutter or similar thin-bladed knife and a cut-safe surface beneath. However, a dedicated hose-cutting tool makes the task simpler, especially when you need to cut the hose in the tight confines of an integrated road handlebar or with the bike in a workstand. Here there are a myriad of options with cutting results that rank from fair to ‘that was so smooth I don’t think it worked’.
At the very cheapest end of hose-cutting spectrum is a basic sprung plastic tool that you squeeze the jaws together on; something that can be sourced from AliExpress from as little as US$1.50 (not kidding). However being mostly plastic I’ve found these tools can flex, allowing the blade to go out of its guided groove, and then cause tool failure. I wouldn’t rule out this style of tool, but it’s important to not buy the cheapest one. Those sold by Magura or ZTTO are pretty good for casual use. I guess you do get what you pay for.
Spending more likely opens you up to better-built hose cutters, or even some tools that merge the hose cutter and barb press into one. I’ll come back to this latter option in the next section.
Spending a little more on a dedicated hose cutter will likely have you looking at something like the Jagwire Sport hose cutter or SRAM Hydraulic hose cutter (they’re the same). These little tools are compact, cut well, and are surprisingly durable. They are all a home mechanic needs, however, for frequent users, I’d suggest stepping up to a tool that has a stiffer body that will help ensure the repeatability of cuts.
The next step up is another product that Jagwire and SRAM each offer: the Pro cutter. This is effectively the Consumer cutter on steroids with a flex-free metal body that helps ensure the cutting blade won’t twist with the hose. This cutter is easily good enough for the professional user, but of course, there are even better options.
My previous top pick was the Knipex 90-20-185, a plier-style hose cutter designed for snipping through plastic tubes far larger and far tougher than what a bicycle requires. This cutter is super durable and makes light work on any hose. Yep, that was my previous top pick.
The new top dog is the Jagwire Elite Cutter. Why? Because it cuts perfectly straight, does it with ease, and all while fitting into tighter spots. The Knipex wins in absolute blade durability, but the Jagwire at least uses common and readily available craft blades.
Needle driver / hose barb install
Once you’ve got that hose freshly cut, you’ll need some form of compression fitting on the end of it. Commonly these compression fittings consist of two pieces – the barb and the olive.
SRAM’s system involves threading a special barb into the hose with a small Torx key. It’s a simple idea and one that requires no hammer or special press tool. And the latest version then has the compression olive reverse thread onto the barb – a super smart system.
A few readers may be familiar with the Jagwire Consumer barb tool that has the ability to thread in the older version (T10 versus T8) of these SRAM barbs. I certainly used to use one of these when SRAM brakes were still Avid, but have since learned it’s something to be avoided given the pitch of the tool thread is mismatched to the pitch of the threaded barb.
Almost all other brake systems use a press-in barb. The old school approach for these barbs is to find a way to hold the hose safely and securely, and then use a hammer to knock the tiny barb into the hose. And as barbaric (intended) as this sounds, Shimano still provides two little yellow blocks (top right of the image below) with its brakes and hoses to aid in holding the hose for this very method of installation. These little blocks are best accompanied by a small vice or some pliers (Knipex Pliers Wrench FTW), but I’ve never found them particularly awesome for the task. Meanwhile, there are some pliers on the market (Park Tool for example) with centre holding holes that can be used for this purpose, too.
That said, I prefer the new school approach – a dedicated barb press tool. And oh do I have some thoughts on the topic!
A hose barb press tool does exactly as the name suggests – it presses a barb into the end of a hose. And it does that by firstly firmly holding the hose and secondly providing a way to drive in the barb on a straight path. And while the purpose of this tool sounds simple, it’s amazing how many tools fail at the first part due to not offering a way to adjust the hose clamping tension. For example, the Jagwire Sport Needle Driver Insertion Tool and Shimano TL-BH62 (also features a cutter) are both great compact options when new, but over time they’ll begin to let the hose slip and there’s no easy way to fix them.
Meanwhile, the Park Tool HBT-1, Jagwire Pro Needle Driver, Tektro/TRP Hose Cutter and Barb Press, ZTTO Needle Tool Driver, and LifeLine Pro Hydraulic Hose Needle Driver all offer ways to control the holding force on the hose. All of these tools do what they need to and you can’t really go wrong with any of them. That said, I do have my favourites.
For those seeking a tool that’s extremely high on value, super compact, and good for occasional use then check out the TRP Hose Cutter and Barb Press (also sold under Tektro branding). This US$15 tool does everything it needs to, and even cleverly uses a snap-off box cutter blade for the cutting. My biggest criticism is that the barb press works at an angle, so care needs to be taken to ensure you don’t let the hose kink through misuse.
Those wanting something a little more fool-proof or better for ongoing use in the workshop should check out the Jagwire Pro Needle Driver and the ZTTO Needle Driver Tool. The Jagwire Pro Needle Driver is the most efficient option going, but it’s substantially larger than most (especially given there’s nothing holding the handles closed). Meanwhile, the ZTTO tool is actually an AliExpress type of item, but I’ve been really impressed by the form factor and functional design.
Brake hose compression nut spanner
Once the hose is trimmed and the barb/olive is installed you’re ready to secure it to the caliper or lever. All popular brake systems use a hose nut for this task (often 8 mm), and some can be a little prone to rounding off when using a simple open-end spanner at the required torque.
The solution to this is a tool from the automotive and motorcycle world – a flare nut spanner. These tools effectively hold onto a nut with a similar surface area to a six-sided socket but do so while being able to slip past the hose.
There are a few options from cycling tool brands that are easy to source and competitively priced. Park Tool’s MWF-3 is a new option that can also be used with a torque wrench. Meanwhile, the Pedro’s Disc Wrench includes a slot for truing rotors. Both are great options that I keep returning to after trying fancier options.
One tool I’m still waiting for is a high quality 8 mm ratcheting flare nut wrench. Cheap options can be sourced from AliExpress (pictured on the right above), but they have a habit of jamming in annoying ways. Meanwhile, the good quality ones only start from 10 mm sizes. I’m mentioning this simply in the hope that someone makes one.
These hose compression nuts often carry recommended torque values, and it’s especially a good idea to follow them when you’re threading into a composite Ultegra or Dura-Ace lever body. Your existing torque wrench should work for this task, but you’ll need a way to adapt it to the 8 mm hose nut. Crowfoot flare nut wrenches are designed for this very task, and you’ll find one included with SRAM’s Pro Bleed kit, built into the Park Tool MWF-3, or alternatively, Pedro’s offers a nice and unique option that works with a 1/4” square drive for not much money.
Just try to avoid the more commonly found 12-point crowfoot flare nut wrenches; these are more likely to round the nut at final torque. Whatever Crowfoot tool you use, just be sure to keep the tool at 90º to your torque wrench to ensure accuracy without having to get really tricky with math.
Another option for using a torque wrench is Magura’s slotted hex nut socket which has a regular 1/4” hex bit end. I found something similar from Uxcell on Amazon. Mine has been pretty good, but I’ve heard mixed reports over the quality control on them.
Australian-based pro mechanic Brad Kelly offers a few useful tips.
Facing / frame prep
OK, so your brake is now fully installed on the bike. However, you simply can’t get it set up to not rub unevenly on a portion of the caliper or have a disc brake that wears brake pads unevenly. It’s all too likely that your brake caliper mounting point is not perpendicular to the wheel axle. Sometimes it’s paint build-up that causes this, other times it’s because the frame manufacturer failed to check alignment at all. The following tool arguably only exists because of poor industry manufacturing tolerances. No it shouldn’t need to exist, but that doesn’t change the fact that it is quite commonly needed.
The professional solution is a disc tab facing tool that has the sole purpose of removing frame material until the disc brake mount is perpendicular to the axle. This process only needs to be done once to the problematic frame or fork, and from there it’ll be great for its lifetime. However, these facing tools typically cost hundreds of dollars, feature wear components, and the process can be somewhat advanced. For the vast majority, it’ll be a shop-only tool.
Those interested in a disc tab facing tool will need to be careful to not buy into a tool that has limited compatibility. Many of the well-priced options can do older IS and post mount style facing, but are not equipped for newer flat-mount facing.
There are three popular professional tool options that work across all three common caliper mounting types, and these are the Park Tool DT-5.2, VAR CD-14500, and Cyclus Dual Disc Mount Facing. A new lower-cost option is the SuperB TB-DB10, one that I haven’t used, but appears to be a cheaper copy of the Park Tool DT-5.2. Just be warned that the cutter is said to be unsuitable for use with steel, which points to a softer construction.
The Park Tool DT-5.2 was the first tool on the market to offer flat-mount facing and remains the most adaptable at fitting into impossible frame corners. Like most of Park Tool’s this one comes with clear instructions, easy access to spares, and there’s now a carbon-specific grinding bit, too. That’s all fantastic stuff, but it’s also the fiddliest to use.
Cyclus and VAR both offer facing tools that cut both mounting tabs at the same time, a design approach that saves time, is more likely to ensure accuracy, and is just simpler to use. However, the VAR is known to occasionally suffer compatibility issues with low-clearance chainstays, while the Cyclus has limited axle sizing compatibility.
Both of these tools offer improvements over the Park Tool DT-5.2, but a number of professionally equipped workshops are finding that there’s occasionally still a need for the unsurpassed compatibility of the Park Tool. Meanwhile, Park Tool’s customer service is pretty tough to beat.
With that all said, there are still times when a frame design won’t work with a disc tab facing tool (Cervelo’s latest frames just have a flat surface for the brakes as opposed to raised mounts, for example). Some mechanics have resorted to careful use of sandpaper or files on such rare occasions. Such an approach takes huge patience and a good eye.
Finally, there are a few simpler facing tools on the market such as the IceToolz Shuriken which works only with post mount. I’m not at all a fan of this style of tool because it does nothing to align the caliper to the axle.
More to come…
This is just the first part of my deep dive into disc brake-related tools. The upcoming second part will cover the things more applicable to ownership of hydraulic disc brakes.
Note: A number of the tools mentioned in Cool Tool Tuesday are not sold through traditional cycling channels and can be hard to find, which is also kind of the point of the series. Access to the tools covered will be easy for those in Europe and the United States. Use a search engine to find the products mentioned.
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