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Shimano XT gets new racer’s rear derailleur, XTR & Deore cranks add Super Boost option?

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A new Shimano XT 12-speed derailleur and two new XTR & Deore cranksets sound like a huge development. But in fact, it’s more about iterative updates that offer more Shimano drivetrain options for mountain bikers looking for their perfectly dialed mountain bike setup…

Shimano adds new XT derailleur, XTR & Deore crankset sizing options

Shimano adds new XT derailleur, XTR & Deore crankset sizing options
new XT derailleur, XTR & Deore-level cranks

Every mountain biker wants their bike perfectly set up for their style of riding, so Shimano has a few new size options in the 12-speed MTB pipeline to get your setup dialed. A shorter medium cage XT rear derailleur means not only saving just a few grams at the derailleur, but also plenty more in the smaller 10-45T cassette for those mountain bike racers looking for a tighter gearing spread. Meanwhile, talking about specific chainlines doesn’t really sound cool, but who doesn’t want to talk more about Boost & Super Boost options for top-tier XTR or always-affordable Deore?

New Shimano XT M8100-GS medium cage derailleur

New Shimano XT M8100-GS medium cage derailleur
Shimano XT M8100-GS medium cage derailleur

The new shorter, medium cage rear derailleur is said to offer more ground clearance for aggressive riding while delivering the same fast & precise XT shifts, even smoother suspension action with decreased unsprung drivetrain weight. Whether you are pushing through more technical terrain or an XC racer looking for lighter weights & tighter gear spacing, an M8100-GS derailleur offers a solid option when paired with the smaller 10-45T 12-speed cassette.

The Shimano XT M8100-GS medium cage derailleur sells for 105€, and is 28mm shorter than its 115€ long-cage SGS sibling, and both about 1/3 cheaper than XTR.

New Shimano XTR M9125 55mm chainline cranks for Boost or Super Boost?

New Shimano XTR M9125 55mm chainline cranks for Boost or Super Boost?
Shimano XTR M9125 crankset

The idea for the new 55mm chainline cranks is to better fit the latest frame designs and “more progressive riding styles” – meaning improved chainstay and bigger tire clearance possibilities. Fitting in between Shimano’s standard 52mm Boost chainline and their wider Super Boost 56.5mm, is the new 55mm adding more options than ever. The industry has generally settled on 52mm for Boost 148 and 56mm for Super Boost 157, but individual frame designs can still cause clearance issues.

So curiously, Shimano calls the new 55mm crank options Boost-compatible. And the 445€ Shimano XTR M9125 crankset looks to keep the same 168mm Q-factor of the narrower chainline M9120 cranks. The new size is available in 165, 170 & 175mm lengths, with 30, 32T, 34 & 36T chainring options.

New Shimano Deore-level M6100 series & MT512 55mm Boost/Super Boost cranks

New Shimano Deore-level M6100 series & MT512 55mm Boost/Super Boost cranks
Shimano Deore M6120 crankset

Deore M6100 series already has the full 52mm (172 Q), 55mm (178 Q) & 56.5mm (181 Q) cranks. So now the non-series MT510 gets those same extra options…

New Shimano Deore-level M6100 series & MT512 55mm Boost/Super Boost cranks
Shimano Deore-level MT512 crankset

The new ~85€ MT512 is a Deore-level alloy crank available in 165, 170 & 175mm lengths with 30 or 32T chainrings.

Long-term forecasted availabilities!

The rub in all of these new components is global supply chain tightening and long wait times for delivery. Even though Shimano is telling us about these lovely new size options now, we’re going to have to wait. The new XTR cranks will be available in June 2021, but the Deore-level crank and medium cage XT derailleur aren’t expected until early 2022. Yikes.

In the meantime, if you want the full breakdown comparing all of Shimano’s 12-speed MTB groups, we explain the tech and what’s different from group-to-group here.

Bike.Shimano.com

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tech9
2 years ago

Dang… Still no di2 12spd. 🙁

TimE
TimE
2 years ago

pretty underwhelming and straight out of the 2000’s

Ol' Shel'
Ol' Shel'
2 years ago

52mm chainline is basically perfect for 157/superboost. Only go wider on chainline of you’re getting tire/chain interference. The conspiracy theorist in me (and with the bike industry, standards conspiracies are true!) says that they’re only pushing 55mm chainline so that they can make your current frame obsolete when they introduce the new Super-duper Boost standard.

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