What happens when a mountain bike takes inspiration from a trophy truck?
The BREWser: an experimental belt-drive, gearbox, 190mm front and 184mm rear travel bike with a 62.5-degree head tube angle.
Adam “Prosauce” Prosise, the mind behind the BREWser, is a machinist at REEB Cycles who describes his riding style as “smashing into things.” He grew up dirt jumping and racing BMX in Iowa with his two older brothers, and he says Rule Number 1 was ‘keep up.’ Now, he’s a regular on the Big Mountain Enduro circuit and consistently places in the top third of the pro field on bikes he built himself.
The BREWser is a collaboration between Adam and a handful of willing friends: Chris Sulfrian, who taught Adam framebuilding; Tyler Brady, who helped with suspension kinematics; Steve "The Space Cowboy," who helped with engineering and aesthetics; and Pinion Gearboxes and Gates Carbon Drive, who helped figure out the whole belt-drive gearbox situation.
4130 Chromoly/7005 Aluminum Frame Construction
Pinion P1.12 gearbox, 600% range
Gates Carbon Drive belt system
RockShox ZEB 190mm 29” fork
Super Deluxe shock variation
Industry Nine Grade Hydra wheels. 29” F/R
Industry Nine stem 32mm
RaceFace Atlas Bars 35mm x 820mm
TRP DH-R EVO brakes. 223mm F, 203 R
Vittoria Mazza Enduro 2.6” tires F/R
OneUp 210mm dropper
HT Components pedals
Seat tube: 450mm
Effective top tube: 680mm
Effective seat tube angle: 76 Degrees
Head tube angle: 62.5 degrees
Head tube: 125mm
Axle to crown: 606mm
BB Drop: 23mm
Weight: "Doesn't matter where we're going." (It hasn't been weighed.)
The BREWser was built to be low-maintenance and indestructible, so the belt-drive and gearbox options were no-brainers for Adam, who fell in love with gearboxes a few years ago when he tried one at a bike park. REEB already builds belt-drive and gearbox hardtails, so Adam had friends in the right places, and the fact that the gearbox only needs an oil change every 10,000 kilometers fit right in with his vision for the bike.
Settling on the BREWser’s geometry was a bit more of a process. Adam has dialed in his preferred geometry numbers on several race bikes over the last few years, and has found that for him, longer and slacker is the answer. As he pushed the geometry a bit farther on each of his versions of REEB’s full suspension bike, he rode faster and faster until he and his coworkers had to redesign the rocker link to take more abuse. In designing the BREWser, Adam took the geometry numbers from his favorite bike, including his preferred 62.5-degree head tube angle, added a bit of chainstay length, and created a long-travel monster.
As for the material, the aluminum and steel combination was inspired by a trophy truck Adam saw at the Baja 1000 that had a raw Chromoly 4130 chassis with machined aluminum swingarms. Since Adam was already on a path of reducing unsprung weight by eliminating the derailleur and cassette, it made sense to keep the swingarms light and made of aluminum. The steel front triangle made for high strength and relatively easy fabrication.
The most difficult part of the design was making sure there was enough belt clearance on the chainstay and that there was enough travel in the belt tensioner for a full 180mm of travel. Luckily, Adam said, Pinion had a full CAD package of information about those components, so with some extensive modeling and a bit of luck, it worked out.
The result is a bike to rival the Grim Donut.
The BREWser is about as custom as it gets.
I have a soft spot for raw metal bikes. This one has a gorgeous industrial look.
This bike has just the right amount of flair.
When it all came together, Adam was blown away by how dialed it felt, he said. He takes pride in everything he makes, but he's glad he didn't waste everyone's time, given that he leaned on a variety of people for help with the project. He wants to thank everybody who believed in the BREWser, and also those who didn't.
The BREWser in its current form likely won’t ever be for sale, Adam says, because those numbers are not for everyone and aren't the most marketable. Still, it is being used to develop a similar but less out-there REEB frame that we’ll likely see in 2022.
In the meantime, look for Adam on the BREWser at Big Mountain Enduro races, the TransBC (pending access to Canada), and any rowdy trails near you.