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When Shimano introduced their 12-speed lineup, they didn’t go all-in like SRAM. They still offered a 2x option, with a 10-45 cassette. But, ’cause they could, they offered a mid-cage derailleur for 1x riders who want to optimize their bikes for quick shifts, quiet descending and maximum ground clearance. And it was likely going to be a niche market, as it was only available at the XTR level. Today, Shimano introduces an XT mid-cage derailleur, and it makes sense. For decades, tiny little short-cage derailleurs have been the calling cards of aggressive, gravity-focused and park bikes. Bikes where derailleurs don’t necessarily have the greatest life expectancy. Those opting for the 10-45 cassette on a 1x drivetrain because they’re too fit to need a 51t ring, or live somewhere too flat can still go for the boutique XTR option, but the rest of us can save almost $150, enough to buy a spare XT derailleur.
Also, more cranks are getting more chainline options. On a bike with Boost spacing, the dominant chainline (the distance from the chainring to the bike’s center line) is 51 millimeters. Then came Super Boost 157, which is nine millimeters wider, bumping out the optimal chainline by 4.5mm to 56.5. That’s available too. But because our industry can’t just leave well enough alone, what about bikes that need a little extra meat around the bottom bracket but aren’t Super Boost? The Canyon Spectral 29, for example? That’s where the 55mm chainline comes in. It’s only been available in SLX or XT, but it seems there’s a chance it’ll get more popular, so Shimano expanded it to Deore and XTR levels.