Words: Mike Blewitt                                                             Photos: Paris Gore, Sterling Lorence

Is 12 gears just a matter of keeping up, or getting ahead? Shimano's oldest mountain bike group set, Deore XT, was updated in late May. With SLX being redesigned as 12-speed and XTR M9100 launched in May 2018 Shimano now has 3 major group sets offering 12 speeds and a huge 510% range cassette. But it's a whole lot more about just having the range.

The Shimano Deore XT group set is the world's oldest mountain bike specific group, and one that has seen many innovations across its history, including being the first group set to have V-brakes! The new M8100 group has gained just about all the options and new tech from the range-leading XTR M9100 group set released 12 months prior. SLX is now also available in 12-speed as M7100.
Shimano organised a product launch in the Pacific North West of the USA, right in Bellingham, Washington to be precise. This corner of the US is known for craft beer, the Cascade Mountains, coffee, aeroplanes, permaculture and to a lesser extent some exceptional mountain biking. With pro riders Bryn Atkinson and Jill Kintner calling it home, you know it has to be pretty good.


This would be the first ride on Shimano's 12-speed Deore XT for much of the world's mountain bike media. And given the delays on delivery of full XTR M9100 group sets, Shimano knew they really had to hit a home run with Deore XT M8100 – which in part is why they released SLX M7100 12 speed at the same time. The good news? Shimano had Deore XT groups ready to send to bike stores, with SLX group sets ready a few weeks later.

XTR, Deore XT and SLX – what's the difference?
The great thing about Shimano's top three mountain bike group sets all being 12-speed is that the features are really similar across all three. All three group sets offer direct mount chainrings for 1x dedicated drivetrains. They all have 2-piston and 4-piston brake options. All group sets have a 10-51 and 10-45 cassette option. All group sets use Hyperglide Plus for faster and more secure shifting up and down the cassette. The iSpec EV mounting system is standard, and the new hub design is the same across all of the group sets.


Where things change are in materials, manufacturing processes, ergonomics, shift action and some of the finer options like chain ring sizes, derailleur cage lengths and chain line options.
The myriad of options within a group set means you can build a 2x12 touring mountain bike, or an enduro race rig with the same group set. Sure, some parts might change like brakes and chain ring configuration, but the idea is that you can have the same level of quality and performance no matter what the riding you want to do is. But here are the key differences within the main components.
XTR is the boss of the shifters, being able to up and down shift multiple gears at once, with an instant action and two way release – where you can upshift with a thumb or forefinger. Deore XT has similar actions and still has a firm feel so you're not likely to accidentally shift. SLX is a lot softer at the lever and while you can have two way release, you can't shift more than one gear at once.


They all come as a bar mount option, or iSpecEV. XTR M9100 has the greatest amount of adjustment with iSpecEV. There is a Mono shift lever for 2x options in each group set. It uses a push to shift and push to release action.
All three group sets have a 2 pot and 4 pot brake system. The XTR one differs a little as the M9100 lever does away with the ServoWave feature. For Deore XT and SLX, the levers are the same between the 2 and 4 pot brakes – just the callipers change. All levers share the new mount which moves the clamp inboard for a stiffer lever.

All the 4 pot brakes will be stronger than the 2 pot versions, and they are designed to deal with a lot of heat. All the brakes have faster piston retraction, and the brake systems have greater modulation. The XTR M9100 2-pot brakes are by far the lightest option if that's what you're after.


The rotors have similar tech with Ice Tech Freeza on XTR in 140-203mm sizes in centrelock, The Deore XT rotors come in the same sizes, same tech, but without the black anodising. SLX rotors remain the same.
So there's a bit of a change here. While there are two cassette sizes in each group set, you can only get a short cage (GS) derailleur in XTR M9100... for now. They all use oversize pulley wheels, Shadow Plus design with an adjustable clutch and the have a bump guard to keep them quiet even on rowdy terrain. The main SGS derailleurs from XTR to SLX do get heavier due to materials, but the function is the same. The higher end units tend to last longer being built with better tolerances as well.


There are specific derailleurs for 2x setups for Deore XT and SLX, and that means there is a 3rdoption for XTR for 2x setups. XTR also has a few chain device options for 1x group sets.
For front derailleurs, all models are Side Swing, with clamp, E-type or direct mount options. XTR has better materials but there's very little difference between Deore XT and SLX.