Originally Posted by
sfrider
Wheels, tires, and hubs matter more the slower and beginner you are because at slow speed on level ground you're mainly facing rolling resistance, and beginners lack the power to take on big hills. The faster you ride, the more air resistance takes over. On long climbs power to weight dominates, and your body weight will pretty much determine how hard that will be since as a beginner there won't be a lot of sustainable power. Still, 1-2mph is 1-2mph and it's not that hard or expensive to get a frame, wheels, and tires to check that box; you can then focus on developing power and losing weight (if the latter is a factor) without any excuses.
1-2 MPH.
A $20 pair of Latex tubes will do more for you than $2000 carbon fiber wheels. Tires will provide the greatest gains. Hubs don't matter. Aerodynamics impede your speed more than rolling resistance even at beginner speeds.
Assuming 75kg bike plus rider, 0.004 Crr, and 0.3 CdA which is low for a new rider 15 MPH is going to cost you 19.7W in rolling resistance and 55.3W in aerodynamic drag.
Rolling resistance is linear with speed, so 1 MPH is another 1.3W and 2 MPH 2.6 W.
Aerodynamic drag increases with its cube, so 1 MPH increases power overcoming drag by 11% - 12W. and 2 MPH 44% - 24W.
Wheels hardly make a difference assuming your starting point is a modern 25mm+ deep alloy rim, not an actual rectangular box section rim..At common apparent wind yaw angles better wheels usually save under 1.5W at 20 MPH and 4W at 30, with the difference increasing to 3.5W and 12W respectively using bad contemporary alloy wheels in atypical crosswinds.
Better tires will get you 10-20W at 20 MPH, an aero jersey 5-10W over race fit, latex
tubes 2.6–6.6 W but require inflating your tires daily instead of weekly.
Multiply tubes and tires by .75 to get the effects at 15 MPH, and wheels/jersey 0.4 for 7.5 - 15W tires, 2-4 for jersey, 2-5 tubes.
A training program can get you 50W or more but the question was about equipment.
Wheel makers measure at 30 MPH where drag requires 3.4 times the power to overcome as it does at 20 MPH. They often compare against the venerable Mavic Open Pro which was slow 20 years ago. They sometimes use atypical crosswind situations.
At 30 MPH (700 W on a drop bar bike without someone blocking wind) Tour Magazine measured 11 W between best and worst wheels, which is 3.2 W at 20 MPH and 1.4W at 15 MPH.
November Wheels measured good alloy wheels doing 2W better at low angles of attack than the 45 mm Zipp 303 with a 7.5 W maximum spread at higher angles which is only 2.2 W at 20 MPH. The HED Belgium+ was within 4 W at 0 degrees with a worst case 12 W departure becoming 1.2 W and 3.5 W at 20 MPH respectively. $2000 Zipps do less for you than a $25 pair of latex tubes.
November Wind Tunnel Testing the Al33, XR31T(FSW3), and other alloys. Front wheel only, with rear aerodynamic gains minimal because it’s in the turbulent air coming off the pedaling rider’s legs. Note the apparent wind angle distribution - most of the time the wheels would have a 4 W extreme spread (1.2 W at 20 MPH). Airspeed is 30 MPH. Divide by 3.375 for 20 MPH power.
Typical weight changes produce negligible effects. Their speed difference isn’t measurable on flat ground. Improvements uphill are proportional to the total change. 500g lighter wheels save a 70kg rider on a 9kg bicycle just 25 seconds an hour climbing in the mountains - 0.7% faster, which is a 1.75 W savings for a rider producing 250 W.
Rotating weight doesn’t matter at a steady speed, and is still negligible accelerating.
If that 500 g was where the rubber meets the road it would count double accelerating for up to 1.3% of total kinetic energy. However, accelerating that rotating weight from 0–20 MPH takes only 2 (kinetic energy rotating + in a straight line) * 0.5 kg * (8.9 m/s)^2 / 1000 kj / j = 0.079 kj which is what you spend covering 12 feet at 20 MPH requiring 35 kj / mile.
In practice the effects will be lower because most of the weight savings is closer to the axis of rotation from things like swapping a steel freehub for aluminum.