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Prototype Rose Root Miller 27.5+ trail bike digs up longer, slacker design

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This prototype Rose Root Miller shows where their current 29er trail bike is headed. Thanks to a new Boost rear end, it makes the switch to being a 27.5+ bike that’ll also work with 29er wheels, and they’ll offer an upgrade kit that includes a set of both hoop sizes so you’ve got everything you need to swap back and forth.

The new design also bumps travel from 130mm up to 140mm, and they’ve made a few other changes around the frame to make it quieter and more capable…


Up front, the top tube reach is 15mm longer and head angle is 1.5° slacker. That allows a shorter stem without cramping the cockpit and gives it the modern long/low/slack geometry that’s sweeping the industry. They also moved the internal cable ports from the front of the headtube onto the sides of the downtube, adding locking clamps to keep the cables from rattling inside the frame.


Another locking clamp at the BB lets you pull the housing/hose tight and clamp it down, preventing slack that could otherwise make noise. The exit path is on top of the bottom bracket and lines things up for minimal crimping or bending during suspension movement. That also keeps it away from the ground and eliminates the loops from before. The original’s PFBB30 switches to a BSA threaded bottom bracket.


Seat tube went a little shorter for better standover and so you can use a longer dropper.


If you wanna run a front derailleur, it’s compatible only with Shimano Side Swing parts. They’re using the new metric shock sizing and production bikes will get the bearing mounts at the shock’s lower eyelet.

The main pivot upgrades to conical bearings, which helps eliminate play and provides a stiffer system. A new downtube protector will come stock.


Max tire size is 27.5 x 3.0, or about a 29 x 2.25. Available around Eurobike this August.


Also working on a 150mm travel version that’ll be a dedicated 27.5″ bike (not Plus) and fit a max 2.6″ tire.



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7 years ago

Slowly but surely the MTB world is heading back towards BSA threaded BBs. All those millions of ‘my brand new bike is creaking like an old rocking chair’ warranty claims must be having an effect.

7 years ago
Reply to  J N H

For aluminium frames the weight and manufacturing cost savings of PFBBs aren’t that big. So especially for trail/AM/enduro bikes it makes sense to go back to BSA. For carbon frames I think pressfit will continue to rule as the manufacturing is cheaper and simpler without the metal inserts. It also saves a few grams.

7 years ago
Reply to  Mikey

Tell that to Santa Cruz and Ibis.

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