November Bicycles is a brand that’s built their business on selling open mold frames and rims, but that’s about to change.
Shown above is a solid plastic rapid prototype of their new Rail aero rim, the first proprietary design from the company. What makes this interesting is the level of testing done thus far to ensure it’s worth the trouble of producing something new…and what they’ve learned about aerodynamics, watts and real world time and energy savings. The best part is, they’ve put it all out there, making for some great reading.
Of course, aerodynamics are just one part of a rim. The other, particularly for a carbon clincher, is the braking surface and the tech that’s gone into making sure it’s safe and sound. Roll on for the run down…
Beyond aerodynamics, they wanted something that rode smoothly and comfortably. So, it’s 52mm deep with an 18mm inside width at the tire bead hook at 25mm at the top of the brake track. In their words, they wanted something “optimized for every part of the race course”, which they found in the NACA 0024 profile.
Before we get to the aero testing, which sheds a lot of light on the standards of testing, let’s talk brakes. Here’s what November’s Dave Kirkpatrick told us:
“The first part of the equation is to raise the temperature that the rims can stand before they weaken and fail. Carbon is basically impervious to heat, but the resin isn’t. To a large degree, resin properties have existed on a continuum where resilience and heat tolerance are at odds with one another; high temperature resins have been too brittle for use in wheel applications, but resilient resins have been too heat intolerant. Our rim manufacturer is fortunately high enough up on the food chain that their resin suppliers are paying attention to the issue and addressing it. The new production (which has already gone into effect on the rims we buy from them) uses a resin that is rated to 180°C, or about 360°F. They’ve increased the resilience of the heat tolerant resins. We’ve also given the manufacturer a realistic weight target, allowing them to build the rims with enough meat to withstand life on the road.
“The other side of the equation is the heat that gets generated in the first place. We’ve done a lot of research into brake pads, and there are a lot of good brake pads out there compared to what was available just recently. SwissStop’s new Black Prince pads (Ed: reviewed here) are pretty tremendous at generating less heat. We’re sending some wheels to Switzerland, since SwissStop has a great setup for testing brake pad/rim interaction. That testing will confirm that both the rim and the pad are working hard to make heat much less of an issue than it’s been in the past.”
Kirkpatrick added that the combination of good rims and good brake pads means you can stay off the brakes longer, which means less dragging, which ultimately means less overall heat generation to begin with.
Now for the aerodynamics:
Using their own FSW 23 as a benchmark, they sent all of their wheels plus a pair of Zipp 404 Firecrest (58mm deep) to A2 Windtunnel for testing. This chart shows the time saved over a 40km time trial if you held 30mph, averaged for all AOA (Angle of Attack, or Yaw) wind angles. The Rail prototype tested just two seconds slower than the Zipp wheel, but what makes that pretty remarkable is it’s a shallower wheel and it was built with 24 spokes versus Zipp’s 16. Production Rail wheels will only have 20 spokes, so our hunch is it’ll close that gap a little more when it’s carrying fewer sticks and has a polished carbon finish rather than rough plastic.
Two things worth noting, one plus, one minus. The gap gets even narrower when you bring it down to real world speeds (see chart below), which makes the Rail even more attractive. The unknown and potential negative is rim and total wheel weight…it might be a good bit heavier than the Zipps.
What I found most interesting about November’s test data from A2 was the minimal differences in drag and energy savings when speeds are more like what you and I are riding. At 20mph, the energy savings across most of the wheels is arguably statistically insignificant. At 25mph, it might make a hair of difference.
November Bicycles’ blog has a very detailed analysis of the numbers and more from A2, including a head-to-head test of the same wheel built using Sapim’s Cosmic and CX-Ray spokes to see if bladed spokes really make a difference. Spoiler alert: Like the wheels, speed is the key to getting much advantage out of the more expensive bladed spokes. The story is carried across several blog posts on their site, but reading from the top down (reverse chronological order) won’t ruin it.