A Useful Review: Shimano Deore XT M8100

For as long as there have been production mountain bikes there has been Shimano’s Deore XT group. Few products in cycling can so thoroughly lay claim to setting the standard as Deore XT. For the entirety of the group’s existence we can say that it has shifted as well or better than everything else on the market. It has stopped as well as anything else, and better than most. It has been light, though certainly not the lightest group for some years, but it has been a model of reliability and durability.

I’ve been riding the new 12-speed Deore XT for a few months now and only as I sat down to begin writing this review did I realize something. Deore XT is the only group, road, mountain, gravel or other that has never disappointed me. There were a couple of Dura-Ace efforts that fell short, a few Ultregra ones as well, and the same thing on the mountain side, except for Deore XT. There’s never been a brake that was worse than the previous one, not better. Nor has there been a shift lever that didn’t operate as well as the previous one. Every single time I’ve gotten on the new Deore XT group, I’ve been blown away.

The first thing I want to say about the new drivetrain is that compared to a great many other 1x systems on the market, Deore XT has very little drag. Keeping high tension on the chain doesn’t make a drivetrain run smoother. I’m surprised they don’t do more to call this out.

The combination of Linkglide and Hyperglide+, which boils down to all the shaping that goes on with the cassette teeth have made for the smoothest-shifting MTB group I’ve ever used; granted, I still haven’t spent significant time on the latest iteration of XTR. I recently dropped into a short, steep gully and had to downshift like crazy to ride out and the rear derailleur moved across four cogs like a knife across warm butter.

The 10-51 cassette is a marvel for how well it shifts, how great its spread is, and how light it is. It also cracks me up that Shimano decided to literally one-up SRAM.

Shimano’s nomenclature can get arduous, but even so the geometry of the Deore XT Shadow RD+ is such that despite all the rock I ride through, the Shadow design is such that the derailleur parallelogram has yet to pick up a scrape. The same cannot be said for this editor. It’s nice to see them use the 13-tooth jockey wheels in the rear derailleur cage in order to shorten it. It’s an idea they introduced in the Dura-Ace triple group circa 2003. It was a great idea that seemed like it should have caught on. There’s less friction in the larger jockey wheels and they will wear more slowly; those two reasons alone are good enough, but shortening the cage is a fine achievement.

Shimano is producing two different brakes for Deore XT. There’s a standard 2-piston caliper, as well as a 4-piston caliper for those tackling their descents with maxxed out verve. I’ve been riding the 4-piston brakes and this is the first 4-piston brake I’ve ridden that felt to me like it could be modulated. The others I’ve ridden were so powerful that they seemed binary: either on or off. Modulation wasn’t a thing. But with the Deore XT 4-piston caliper and 180mm rotors, I can scrub just a bit of speed, or grab a big handful of brake if I need to not move anymore. Shimano says this new brake features faster pad retraction, and that may be providing a small part of my love for the 4-piston unit. Not only will it stop on a dime, it’ll leave three cents change.

The Deore XT Ice Technologies Freeza rotor does a fantastic job of dissipating heat; I’ve never had a problem with the Deore XT brakes fading on a long, technical descent. And while I’m not sure this is the sort of thing they want to brag about, I find these rotors the easiest to true.

The levers have a terrific shape to the lever itself and the mounts feature enough material that I’ve never felt the levers flex under hard braking, something that has nearly always been an issue with XTR.

As good as carbon fiber wheels have gotten, a good aluminum wheel still has a place in this world. As good as carbon fiber wheels have gotten, if I want bulletproof reliability, I still choose aluminum wheels. That may be a bias on my part, but I’ve yet to have a Shimano wheel leave me high and/or dry.

Regarding weight, I’ll say that it matters to a point and then unless someone is racing at a reasonably high level, a rider is unlikely to notice in a way that hurts their performance. That said, these are, at just under 1kg for the rear wheel and a nick over 800g for the front wheel, lighter than than many sets of road wheels just a dozen years ago. I’ve managed to prang a rim on a rock, but neither cut the tire nor dented the rim; I couldn’t even find the spot on the tire when I got to the bottom of the descent. That the rims are all tubeless now corrects the one fault their wheels had for too long, which was not being tubeless compatible.

I’ve ridden MTB pedals from all of the big manufacturers. I’ve yet to ride anything else that approaches the flawless entry of the Deore XT pedals. Like so many components Shimano makes, the pedals seemed unimprovable 10 years ago. I’m riding the trail pedal, which is nearly 100g heavier than the XC pedal (438g to 342g), but offers more platform for standing on the pedal even if the cleat hasn’t engaged.

I’ve studied the differences between this pedal and others that I’ve ridden to try to understand why the pedal catches on the first try. I can’t come up with a reason why the balance of the pedal would be different than with others, but the cage of the pedal has slightly chamfered edges. The other detail the makes this such a superior pedal is that I’ve never experienced a release cone wrong. I’ve had pedals not release because they were wet, or packed up with mud, or the cleat caught at an odd angle or was harder to release for some unknown reason. The Deore XT pedal releases the same way, with the same amount of force, every time.

The Line at the Bottom
Talk of improved transverse shear stiffness and the like can make my eyes glaze over like zombie’s. I respect that Shimano needs to quantify the improvements they make to each group. One cog, a few teeth and two extra brake pistons doesn’t say much about the amount of engineering that went into this group. But that other end of things where talk turns to grams saved and stiffness increased can be silly because often times those improvements don’t rise to a high enough tactile volume that they break through someone’s threshold of perception. The threshold of perception is the amount that something must change by before someone perceives that there is a difference.

I mention this because other than those most notable and noticeable changes, I can’t point to any one thing Shimano did to make this group superior to its predecessor—which was a fine group in its own right—but this Deore XT group is distinctly better. How much better? What I can say is this: Deore XT is what to buy when someone wants real quality that will last. This is what goes on the bike that someone is investing in. This is the group someone can put on their bike and not worry about. With Deore XT Shimano has created one of the best arguments for quality in the bike industry. One ride on this group will cause someone to shake their head and say, “I get it.”

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