Shimano Deore XT BL-M8100/BR-M8120 Disc Brake and Lever [Rider Review]

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Not long ago, Shimano launched a 4 piston option for their XT line of disc brakes. For years, XT brakes were only 2 piston and already super powerful, but with this new 4 piston caliper, Shimano made them even more powerful. Our friend, Allan, just reviewed both the 4 piston and 2 piston brakes. See what they think!

Overview

I’ve run Shimano brakes on my bikes for years. That said, about a year ago I got a great deal on a new hardtail. The only negative is that it came with brakes that were not Shimano. The deal was too good to turn down, so I bought the bike.

The brakes, as it turned out, were not horrible and functioned well - at least for a while. Over this past winter, the rear brake become progressively mushy and despite multiple bleeds, new pads, re-bedding, sanding, etc. I just could not get them to function the way I wanted. I decided it was time for an upgrade so to speak!

I ride two bikes: a hard tail XC and a full suspension Enduro bike. The Enduro bike came with Shimano XT8100 brake’s they have functioned perfectly well. The only thing I would have liked was a little more modulation on the super steep chutes that are ever present on my local trail system.

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Having heard nothing but positives from local riders who were running 8120’s I was thinking of an upgrade. Riding a couple of bikes equipped with 8120’s on demo days sealed that decision.

But, what to do with the perfectly serviceable 8100’s? Enter failing hardtail brakes, I decided to transfer the 8100’s to my hardtail and upgrade the Enduro bike to the 8120’s

Installation
I put the front and rear XT 8120 brake kits in my shopping basket. But, I needed a couple of accessories to finish the job. I really dislike cluttered handlebars so a new i-Spec EV compatible 12 speed XT Shifter, this eliminated one clamp. I use a Wolf Tooth dropper lever but needed an adaptor to make it work with the XT i-Spec EV brake. Next the brakes on my XC bike did not come with a Shimano Disk Brake Adaptor spacer, so all that stuff also went into the basket. .

The Shimano 8100 and 8120 share a common brake lever, and given that the Enduro bike already had XT 8100 brakes all I needed to do was take the 8100 calipers off and replace them with the 8120’s. Installation including centering, bleeding and bedding took less than an hour start to finish. The new levers and the 8100’s went on the XC bike, the longest part of this install was feeding the brake lines thru the frame.

If you plan on doing this, you will need Shimano Disc brake bleeding funnel and a few other items including Shimano Mineral Oil.

The next day I was at my local trail system dropping into a double black with multiple steep chutes.

The brakes operated flawlessly.

Modulation was fantastic, beautifully progressive. Sadly, that was the day before all the Corona Virus restrictions kicked in, I have not been back on my Enduro Bike as all our parks are closed.

Shimano Tech

Shimano has a technology built into their M8100 brake levers called Servo Wave. Servo Wave causes the pad to move to the disk surface quickly this results in an aggressive initial bite which becomes progressive as the levers move closer to the bars, if you really get into the brakes the bike stops like you’ve hit a wall..

Final Thoughts

The M8100 Caliper with its two-piston design has noticeably better modulation. My understanding is that the smaller piston engages first followed by the larger. This results in improved modulation and progressivity. Other riders might consider upgrading to these calipers for their raw stopping power and as I mentioned they have that in droves, but for me the increased modulation and progressive nature of the XT8120 is where it’s at. Although the 8120 are positioned as Enduro / Downhill brakes, I believe aggressive trail riders might also benefit from these brakes, they are definitely overkill for an XC rig.
Both bikes as well as their rider couldn’t be happier, highly recommended!