Intro:
I've tried various iterations of Shimano brakes over the years and had mixed experiences. The one model I never really had a chance to get and try were the Saints, which have been often recommended over the years especially in the wake of SRAMs problematic Guide offerings, which I'm convinced pushed many users to Shimano.
I finally got a chance to get a pair several months ago and put some time in on them, so I thought I'd offer a few thoughts. I will caveat that I didn't spend my usual minimum of 3-4 months on these, rather a few 100 miles at most. I think I was able to get a good idea on feel, but not so much long-term durability. Point being, I'll only cover what I could observe and the period of time I spent on them wasn't as much as I prefer.
I'll spare too much detail on things heavily discussed elsewhere, these have been out for a long time and there are a lot of details on them. My main goal in covering these is to compare them to modern offerings like Dominions, Hope T4 V4, and others I've tried.
Overview:
The Saints are Shimano's downhill brake, with four large pistons in the caliper and finned pads.
The brakes, as with all Shimano brakes, use their proprietary brake fluid that is mineral oil based.
The lever has a fairly short lever blade, reach adjustment, and some form of contact point adjustment, which I've never found to work on any Shimano brake. The lever clamp itself is fairly stout and even pulling heavily, I can't really discern much significant flex. The lever pivots on some form of bushing or pin with no bearings, something I really wish every brake would move away from, because wear inevitably causes play here. The lever length isn't terribly long, but it's not excessively short either, being typical Shimano style lever blades.
The caliper contains four pistons, which seem to extend and compress fairly smoothly. The pads insert from the top and are held in with a pin. Important to note that the hose banjo rotates laterally instead of vertical like many brakes, which means the hose may kink depending on the direction it needs to go. Many other brakes use a vertically rotating banjo so you can straighten the hose out during installation. This isn't a functional issue as far as I can tell, but it does look kinda disorganized.
The reach adjuster is easy to use and smooth, but reach adjustment is limited if you run your levers close to the bars. Even with it all the way adjusted out, the lever is further from the bar than some other brakes I've used. This is a preference thing, but I like my levers close to the bars and I couldn't get them as close as I'd like.
I will make one note on the clamp, it's a lot more stout than previous iterations of Shimano's brakes, which I had flex issues with. It makes sense they adopted these for the newer lever designs and it's one of the stiffest lever clamps I've used.
Service:
These are probably the easiest brakes to bleed on the market, although there are several techniques for doing so, ranging from using two syringes to just letting fluid drip down (gravity).
One thing I would caution against is the often suggested "lever bleed", where you attach a cup to the lever and pump the blade until air stops coming out. This isn't bleeding anything, it's overfilling the master cylinder and severely aggravates wandering bite point problems people have with these brakes. I do not understand why this is such a common practice, as it makes the brakes feel profoundly worse due to the fluid not having enough room to retract especially with temperature changes. As far as I can tell, it's also not recommended by Shimano in any service manual either and following the recommended bleed process reduces issues most people have with their brakes.
At any rate, bleeding is easy whatever way you do it and the use of mineral oil makes it slightly less volatile than with DOT, however that doesn't mean the fluid is safe for you to get in your eyes or on your skin either. Yes, I know blahblah123 on the internet told you that you could, but the fluid material safety sheet says otherwise. They may have a base of mineral oil, but there are other additives and solutions in the fluid and they aren't all safe.
Hose shortening and install are easy, same as most brakes, there isn't much to mention there. If you can cut the hose properly, you can install these easily.
Shimano brakes can't be rebuilt, so fixing issues with the caliper or lever means whole replacement, which is wasteful, but they also aren't the only brakes that are like this.
Riding:
I historically have not liked Shimano brakes. No, it's not due to the "on/off" feel or "lack of modulation", neither of which I think are a thing, rather it's the wandering bite point the closer ambient temps get to freezing. It is absolutely infuriating to grab your lever twice and have no clue where the levers are going to bite. I also feel that their brakes are largely poorly engineered compared to their peers, previous iterations of XT brakes had flexy levers (not an issue here) and other problems that make me wonder what their testing process is like.
All that being said...I didn't hate these. The power availability is good, not the best, but good. They engage reasonably quickly with moderate freestroke and I couldn't get them to fade, even though I tried. The ramp up is intuitive and fair when the bite point isn't jumping around (more on this later). They also didn't have the "peel your face off" power I expected or was told they would, the power was more in line with modern brakes like Dominions or MT7s. That's not a bad thing, but there are more powerful brakes available now, so I guess it depends on what your comparison points are. If you compare to something like Guides or Codes, then the power at a given lever stroke is higher, but compared to options like Dominions or V4s, not so much. In any case, there is enough power even for my weight, but they aren't the most powerful either.
I was getting along with these brakes really well, to the point I thought I'd leave them on my bike, surprising myself. That was this past fall, however once winter hit, that all changed. While I was able to largely reduce the wandering bite point on the rear, it was still present and it was really annoying. I was sad to see these brakes suffered from the same problem and, ultimately for me, that's why they are coming off. Brakes should engage consistently at the same point unless exposed to unreasonable conditions (negative temps or excessive heat), it's disorienting when they don't and that's my biggest issue with these.
When the temps were warmer, these brakes were great. I would have almost no complaints over the form or function of them, but sadly, I ride year round and dealing with a bite point jumping around just wasn't something I could deal with. You could possibly adjust your brake technique to avoid this, as it only manifests itself when you make two rapid pulls of the lever one after another, but I don't really feel like that's something I should have to worry about either.
One thing I will note here: the "modulation" of these brakes is fine and I don't see where they are "on/off" any more than any other brake system. I think a lot of people equate a lack of power with modulation and that's a huge misconception. I hear people talk about how SRAM brake offerings modulate well, but they also lack overall power or require a really long lever stroke to obtain the same power due to linear power delivery. The Saints aren't going to throw you off the bike if you grab slightly too hard, the power ramps up really intuitively and they are easy to control when the bite point is consistent. Even when it wanders, it's not as dramatic of a bite as people seem to indicate. So who would I recommend this to?
Being blunt: for enduro and DH, there are better, more powerful options available today at a cheaper cost, lower weight, and improved serviceability. Brakes like the Dominions, Hope T4 V4, Radic Kaha, and MT7 will all provide equal or better power with greater consistency or adjustment.
Sadly, the cost of these in comparison to better options just leaves me wondering what the point is. They aren't awful brakes, eliminate the bite point problem and I'd probably keep them, but there are options offering more for less now and I don't see where these are a good value proposition for anyone unless you are just stuck on using Shimano brakes for some reason.
That doesn't mean they are bad, they aren't necessarily, but as I will discuss shortly, other brakes do the same thing better and are cheaper.
If you get a good deal on them and can deal with the bite point issues, I found myself liking these more than I thought. It took me a while to find them at a price I was OK risking it with, knowing about bite point problems and my history with their brakes. Otherwise, I'd suggest something else.
I guess to summarize, these are the best brakes of 2014. In fact, I'd go as far as to say that they are some of the best brakes up until 2020 when the Dominons came out. Once the Dominons landed, other options became available that I feel offer better feel, improved serviceability, better consistency, and more or equal power.
Comparisons:
This is the meat of what I wanted to get to with this one. How do the M820s, which have been on the market a while now, compare to other options?
vs. Hayes Dominion A4: The Dominions use a similar lever size, in that it's on the short side (compared to Radic or Hope). I ran Dominions for years before going on the great brake experiment and found they were more powerful, more consistent (no bite point wandering), and smoother than the Saints are. They are also fully rebuildable and include two pad compounds in the box, along with a unique multi-function bleed block. Their lever pivots on a bearing and there is no hint of vertical flop, they also remain consistent across bleeds even when it's been too long. The downside is largely in the bleed process, Dominions bleed well, but not as easily as Saints and not as cleanly. Some people also don't like DOT fluid, which Dominions use. Overall performance on the Dominions is far better, but some maintenance tasks are more tedious. I'm also not a huge fan of the two bolt clamp used on the Dominion levers, I find them irritating. Finally, I find I need roughly the same lever distance from the bar on both brakes, which is a bit further than I'd like, but still OK. The Dominions are largely superior and are generally my goto for most people when they ask what brakes they should buy, small nitpicks aside, I find them superior or equal in every way.
vs. Hope Tech 4 V4: The latest iteration of Hopes brakes are fantastic, they are easy to bleed and work on, less messy than the Dominions albeit still using DOT fluid. The lever is longer than the Saints, which can make for some weird cockpit organization, but otherwise creates a lot of leverage to reduce strength needed to put power down. The contact adjuster and bite point both work well with good range. The power exceeds that available to the Saints and it comes on much smoother, although the Hopes have a bite point that feels less firm than the Saints, which could be good or bad depending on preference. The Hopes also use a hinged lever with bearings on the lever blade, again, both very nice. The new Hopes are some of my favorite brakes of those I've tried, they are smooth, consistent, and VERY powerful. The downside is their cost, they are considerably more expensive, so they aren't a budget option.
vs. Magura MT7 Pro: Probably the closest relative to the Saints of those I've tried here, although they improve the formula a bit. I admittedly am just now experimenting with these, so I haven't had a ton of time, but the power engagement seems similar although the lever feel is way more consistent (no wandering bite point) and solid feeling. There are a lot of pad options straight from Magura and I really appreciate that they use thicker rotors, something Shimano would do well do adopt. I found the MT7s easy to bleed and work on, but some indicate otherwise and there are a lot of reports of bleeds being a problem. Both use mineral oil based fluids. The MT7s use a composite lever body, which some report problems with, although I haven't had issues yet and most seem related to crashes or not following instructions. I prefer the clamp on the Saints and the use of a singular pad on Shimano brakes makes pad changes slightly easier. The lever feel remains very consistent over time and doesn't require a ton of hand strength to pull power down, although with the Performance pads, it comes on a little later than with Saints (marginally though). The MT7s also give you several blade choices, as they can be changed. Overall, if Shimano brakes weren't prone to wandering bite points, it would be a more difficult decision, but the greater consistency of the MT7s makes me feel they are the better choice. Magura customer support is also more available and I've yet to hear any complaints about dealing with them, whereas Shimano is basically impossible to get anything from.
vs. SRAM Code: In short, these have less power and more fading issues than the Saints do, but a better lever feel and "modulation". The power delivery ramps up slower on these brakes than the Saints, which IMO is more suited to lighter riders or those who like to run their levers really far from the bar. I got along ok with these, but over time found myself wanting brakes that engage faster and fade less, which the Saints both do. I would readily take the Saints over these, even with the bite point issues.
vs SRAM Maven: The Mavens have a bit firmer lever pull, but much better overall power and engagement. The contact point adjustment on them actually works, but the power comes on a lot faster and stronger than Saints. They both use fluid with mineral oil as a base, but I found the Mavens cleaner to bleed despite requiring more specific tools. The deadstroke on the Saints is a bit lighter, but the Mavens can be feathered easier once they do engage and provide more overall power. The Mavens are hideous, though, and the lever size/position will make cooperation with other controls more challenging. I think users of Shimano brakes will find a lot to like with the Mavens and I generally prefer them to the Saints, but the aesthetics and cockpit organization issues are a major downside to the Mavens.
Pros:
Easy bleed process
Rigid lever doesn't flex under heavy load
Plenty of power that engages easily and quickly
Power is easily managed and adapt to
Widely available pads and fluid
Numerous pad options
Hinged clamp makes install a lot less tedious than other clamp mechanisms
Cons:
Lever does not pivot on a bearing, over time this will result in vertical slop
Caliper banjo doesn't rotate vertically, causing excessive hose to hang out and possibly kink when installed
Can't be rebuilt
Finned pads rattle over time
Wandering bite point in cold conditions even when bled properly