Plus-size tires are one of the hottest trends at Sea Otter this year, and Specialized has launched two mountain bikes designed around the 27.5+ size: the Fuse and the women’s specific Ruze. Both bikes feature the company’s all-new “6Fattie” 27.5+ plus-size tire.

The 6Fattie tires are 27.5 inches in diameter and three inches wide, offering riders the ability to run lower tire pressures than on traditional, 2.1- to 2.4-inch mountain tires. The combination of the wider tire and lower tire pressure increases the contact patch with the trail—up to 69 percent, says Specialized—giving the tires significantly more traction.

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With matching, slack 67-degree head angles, and relatively short 433mm chainstays for snappier handling, the Fuse and Ruze hardtails are made for more aggressive trail riding. Three builds are available for the Fuse and Ruze: Pro, Expert, and Comp. The Fuse comes with a 120mm fork, while the Ruze got a 100mm fork to keep the stack lower. The Ruze also features an angled top tube to achieve a shorter reach and lower standover height.

Gloria Liu

To accommodate the extra-wide tires, Specialized designed a unique “diamond chainstay”: In order to provide enough clearance for the 3-inch wide tire, while maintaining enough stiffness for quick handling, the chainstay “splits” to go up and over the widest part of the tire.

Also to accommodate the new tire size, these are dedicated 1x frames: The Pro models get 1x11 drivetrains, the Comp and Expert builds get 1x10. All versions get wide-range gearing, with 11-42 cassettes. All Fuses and Ruzes come with dropper posts—Pro builds get the new, 12-position IRcc Command Post by Specialized; the less-expensive models get Tranz X droppers.

Related: Redesigned Specialized Camber Hits a Sweet Spot

Gloria Liu

To provide enough sidewall support for the wider tires, Pro builds have Roval 38 alloy rims, which have a 38mm internal width. The lower models get WTB Scraper rims with a 45mm internal width.

Pricing on the new plus-size mountain bikes is to be announced; we’ll update as soon as we have them. Look for a longer-term, in-depth review of the 6Fattie tires soon.

Gloria Liu Contributing Writer, Bicycling & Runner’s World Gloria Liu is a writer-at-large, and formerly the features and gear editor at Bicycling.

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