Shimano XT M8020 Brakes Review
Updated: Mar 5, 2020
What it is: Shimano 4-piston 'trail' brakes, combining the power of a Saint caliper with the modulation of XT levers, providing greater and more balanced power delivery than the standard 2-piston brakes.
I have run a few different brakes over the last year since ditching the Guides that I had been running for ~2 years. The first change I made was to the M8020s, because they claimed more power, firmer bite, better reliability, less fade, and easier bleeding...if you listen to the internet, anyway.
What I found was that these brakes offer some of those benefits, but still lacked overall power for heavier riders on steep terrain, along with some design deficiencies and fade issues.
Given that the lever is your main point of contact, I think it's worth starting on and talking about a little bit.
For the XT M8020 lever, it's the same lever as the M8000 lever. In fact, I'm fairly sure the idea to offer these brakes to the market came from riders combining XT levers with Saint calipers. It's pretty cool that all the Shimano products are cross compatible, I will give them that, but I found the lever design to be inadequate for several reasons:
The entire lever flexes at the clamp under heavy braking. You can watch the entire lever body move under minimal pressure.
The freestroke adjustment does something (you can open/close it during a bleed and see fluid levels change), but what it actually accomplishes is beyond me. It's nowhere near as useful as the SRAM contact point adjuster on the RSC/Ultimate brakes
I am not a fan of the ergonomics of the lever design, but this is a preference issue.
There is a lot of slack at the lever between full extension and the point the pads start to bite
Lever feel varies in cold temperatures presumably due to mineral oil thickening
Bushings in the lever will wear eventually and cause a minor amount of lever flop, although not as much as the Guide R/RS levers
Overall, I didn't have any reliability issues with the lever, mostly nitpick or preference issues. The main problem I had is, no matter how many brakesets or bleed processes I tried, the lever feel is inconsistent below 40f, but I'm not sure that's an isolated lever issue rather than one due to the whole system.
Cold Weather Inconsistencies and Bleed Processes
At first, the inconsistency at cold temps was a dramatic difference and I had significant issues with the levers pumping up. While riding, if I grab the lever once, it feels normal, but an immediate second pull of the lever results in a much earlier bite point and firmer lever feel.
After some experimentation, I blame the bleed process I had been using. The process I started with was one I observe many riders do: Attach the bleed cup to the lever, pump the lever until air stops coming out, then cap it off. Essentially, this is topping off the reservoir, but it doesn't involve the use of a bleed block.
The problem with this process is that the reservoir is designed to have some air in it and 'bleeding' in this manner overfills the system, unless the pads are pushed in far enough that there is space for the pistons to fully retract or a bleed block is used. The flaw with this method reveals itself in colder temperatures, because the mineral oil thickens and the pistons retract slower, which is compounded by being overfilled and not providing space for the fluid to retract.
That's my theory, anyway, based on observation of the piston behavior, experimenting with different bleed techniques, but also noticing that the problem seems to diminish as the pad wears. I could be mistaken, but this issue was significant enough to me that I spent fair bit of time trying to resolve it.
Once I stopped this 'bleed' technique, I found the issue mostly resolved itself, but it was still there. So if you plan on using these brakes in colder temps, you can expect rapid pulls of the lever to feel different, even if it is slight.
Not really much to say here, except the extremely annoying pad noise that comes from the finned pads rattle and popping around. I've had brakes that squeal under power, but the noise coming from the pad moving around in the caliper is absolutely irritating. I'd ride some fast/chunky trails and the pad would be shifting around in place, popping and snapping, it made my bike sound horrible and got old real quickly.
Apparently, going to non-finned pads eliminates this, but I never bothered to try it.
Other than that, the large pistons seem to move easily and there is plenty of space for the rotor when aligning, even with new pads.
The position and design of the bleed nipple is a bit concerning, though, as it seems like it'd be prone to getting dirty if the cap falls of, which it will eventually.
On the Trail
Coming from the Guide Ultimates I had previously, there are a few benefits to these brakes, mainly in the power delivery and consistency.
Being heavier, I found the Guides heated badly on long descents and they lacked power unless you ran the brake lever pretty far out. I found the power provided by the M8020s really helped reduce arm pump and allowed me to brake later than I would have before. I tested these with XT rotors front and rear, with a 203 up front and 180 in the back.
The M8020s modulated fairly well, definitely not as well as the Guides, although part of the Guide brakes 'good modulation' feels more like a lack of overall power and bite to me. I'm sure the Guides are sufficient for lighter riders, but the M8020s were a huge improvement in overall power and resistance to fade.
So I found the brakes powerful and well modulated compared to the Guides, but that's where my favor for them stops. I covered my complaints earlier, but I overall felt the power still wasn't there for the bike and terrain I am riding. If I was 20-30lbs lighter or on mellower trails, I'm sure they'd work out a lot better, but I think for heavier riders on steep terrain, something with more power is still recommended, even with bigger rotors.
In part, I think this has to do with the late delivery of power. The lever stroke has a lot of slack in it at the start, the pads don't start biting down on the rotor for a while, which means you essentially have dead, useless stroke in the lever that could be putting more power down. It seems to get more dramatic as the pads wear, although only a small bit. I really wish that slack was not there and power delivery was more even and consistent like with the Codes, because it effectively means you have to run your levers much further out to compensate for the slack feeling in the lever.
So they improved my riding and felt better than the Guides, but I think I'd recommend something more powerful for heavier or more aggressive riders.
So who would I recommend this to?
If you find brakes like the Guides or M8000s lack a bit of power, but want something with slightly more bite and good modulation, these work great. If you are lighter or on mellower terrain, they work really well also.
For heavier riders, steeper terrain, or if you find the Guides or M8000s are a wide margin off on the power you want, these aren't going to be a major improvement and you'll still find yourself outrunning them.
vs Guide RSC/Ultimate: The SRAM brakes have more meaningful adjustments, mainly in the contact point adjuster, they also use DOT fluid (which is love or hate it seems). I feel the lever ergonomics and clamp design on the Guides is better. The M8020s are more powerful, with similar modulation, and feel better on the trail. You can expect a much more powerful feel from the M8020s once they start to grab, with a fairly significant power ramp up as you pull the lever. They both make noise, the Guides tend to squeal when wet and the M8020s use finned pads that rattle around. The Guides are more consistent in the cold temperatures.
vs Code RSC: The Codes provide a lot of the benefits of the Guide brakes, with considerably more power and bite. They aren't really in the same category as the M8020, probably closer to the Saint, but I went from the M8020 to the Codes and felt it was worth comparing them. The Codes feel better in every way: more power, better lever feel, less fade, no pad rattle, but may be a bit overpowered for light riders or trail riding. The contact point adjustment makes this somewhat of a non-issue, but I'd only run Codes if you needed a dramatic increase in power. For heavier or aggressive riders, the Codes would be a better option.
vs. Hayes Dominion A4: Similar to the Codes, these brakes aren't really in the same category, but I felt it was worth comparing them still since heavier riders may find themselves torn between a 'trail' brake like the M8020 or something more enduro/DH oriented. Similar to the Codes, overall power of the Hayes is much higher, but the lever feel on the Hayes feels closer to Shimano, although the use of bearings means it's a smoother lever stroke and the slack is shorter in the Hayes. The Hayes use DOT, which I prefer, but some do not, and manage heat better, although the bleed process is slightly more difficult. The Hayes use a much better lever design and are all around engineered better, they also come with both pad compounds, but they are more expensive. I haven't tried the A2s, but if budget wasn't a concern, I'd default to the Hayes over any of the Shimano offerings currently.
Inexpensive compared to similar options
Enough power for aggressive trail riding
Mineral oil is less toxic, won't damage your frame, and has a longer shelf life
Better power and fade resistance than other 'trail' brakes on the market I've ridden
I've found caliper alignment to be easier with the Shimano brakes
You can reach out to Shimano support over the phone
Lack power and heat management for heavier riders or enduro/AM/DH style riding
Mineral oil will cause any moisture that gets into the system to pool at the caliper, resulting in less heat management
Shimano mineral oil can be expensive and harder to find than DOT 4/5.1
Lever flexes under heavy braking
Lever is inconsistent in cold temperatures
Finned pads rattle in the caliper
Shimano does not offer rebuild kits for levers or calipers, problems with either require full replacement