Priority Bicycles Eight and the Road Plus Revolution

Sell me a good bicycle, and I’ll take it apart! The Priority Bicycles Eight is a great bike, and I am the Dr. Frankenstein of bicycles. None of my bikes remain stock, and this month seemed a good time to have a go at the Road Plus revolution.

Road Plus is about running wider tires at lower pressures. But wider tires are taller tires, and there’s little room for taller on commuter frames. Solve that problem with smaller-diameter rims! Then buy wide tires to fit those rims, and their corresponding height will compensate for the loss in rim diameter. Bingo! Wider tires having the same outer diameter as stock. 

New parts! Because bicycles are like LEGO-brand brick sets. 

New parts! Because bicycles are like LEGO-brand brick sets. 

Wheelsets are expensive, so I raided my Haro Beasley single-speed mountain bike for its 650b rims. These have a 584 mm bead-seat diameter that is 38 mm less than the stock wheels on the Eight. 

For tires, I went with a set of Horizon Road Plus tires from WTB. These are 650b tires having a 47mm width and a tall enough profile to be a drop-in replacement for most 28-30mm tires. Stock tires on the Eight are 32mm—close enough! 

Road Plus tires against the stock tires. The Road Plus tires are a few millimeters less in radius.

Road Plus tires against the stock tires. The Road Plus tires are a few millimeters less in radius.

The Eight is belt-drive, and the Haro is chain-drive. Naturally, the sprocket interface on Shimano’s Nexus hub (the Eight) is incompatible with the Shimano-compatible hub from the Haro. Naturally. Because, this is the bicycle industry and stable standards are apparently the enemy. So I threw down for a belt-sprocket having a nine-spline, Shimano pattern fitting my hub from the Haro.

Standard interface. This belt sprocket fits any common, nine-spline hub.

Standard interface. This belt sprocket fits any common, nine-spline hub.

The rest was easy. Keeping to the stock tooth count on the sprocket meant that I didn’t need to adjust belt tension. The wider tires fit nicely into the frame with plenty of clearance, and surprised me by fitting the stock fenders. I did need to realign the brake calipers, because rotors on different wheelsets tend to vary by some fractions of a millimeter in their distance from the centerline. 

Fender clearance. You can run these tires with the stock fenders.  

Fender clearance. You can run these tires with the stock fenders.  

What did I say earlier about belt tension? I lied—sort of. I did end up having to adjust tension. Running the bike single-speed means that I am putting more than usual stress onto the belt when pedaling up hills. And the belt is now mildly misaligned front to back due to my wheel swap. The belt was slipping, and I’ve added some tension to combat that. 

Done! Except that before riding I zip-tied the shifter wire to the chain stay to prevent it flopping around loose -- because the bike is now single-speed. For this photo, I just had the wire tucked around the fender stay.

Done! Except that before riding I zip-tied the shifter wire to the chain stay to prevent it flopping around loose -- because the bike is now single-speed. For this photo, I just had the wire tucked around the fender stay.

The wider tires improve confidence when leaning into corners. That was the first thing I noticed as I pedaled the reconfigured Priority Eight out of my drive into the street. Next is a feeling of increased smoothness on pavement as the lower-pressure tires absorb minor surface irregularities. (I’m running the Horizon’s at 30 psi versus 60 psi for the stock tires). 

Motivating my Road Plus experiment is a particularly shabby stretch of asphalt that I often ride in the downhill direction. Hitting that one stretch of road on the stock tires and their higher pressures while going fast downhill is jarring and the bike bounces around, whereas the wider tires and lower pressures make that descent manageable – still bumpy somewhat, but no longer in excess.

Then it snowed!

Stay tuned. Studded tires are in the wind. New fenders too.