Bike setup #1: Osprey Packs Escapist 20 backpack, Everything Bags, handlebar roll, frame bag, panniers and trunk bag on rear rack.

Bike setup #1: Osprey Packs Escapist 20 backpack, Everything Bags, handlebar roll, frame bag, panniers and trunk bag on rear rack (click to enlarge).​

Editor's Note: Inspired by the #everythingisaero mantra, our resident tech head dared answer the question that no dared ask before him: Which bikepacking setup is most aero?

This article is to answer the burning question of how aerodynamic bikepacking gear is. Most people think that aerodynamics don't matter when you are only going 12mph, and they would be correct. But studies have shown that if the wind is blowing 72% of the time it is a headwind. And riding 10mph into a 15mph headwind is the same aerodynamically as riding 25mph.

The testing was done on a fat bike, since that was the only mountain bike I have that has a rack. Since I don't have an wind tunnel or a power meter my only real choice for testing was coasting down a hill. One of the things that I was worried about the testing was that when I added gear to the bike it would add weight which would also increase the force accelerating the bike. Especially since just about all of the items needed something in them in order to hold their shape. I tried to find the lightest things to put inside the bags that I could. I also decided to weigh about 219 lbs with my gear on, which makes the weight of the bags less important. I drew the line at filling the tires with water.

Bike

Medium Mukluk Ti with Husker Du/Knard on Marge Lites. Tires inflated to full hard psi

Instrumentation

Garmin 810 set to record data at 1 second intervals

[TD]
Equipment List

  • Bedrock Bags Entrada with pocket handlebar roll
  • Old Man Mountain Phat Sherpa rear rack
  • Cleaveland Mountaineering Everything Bags
  • Arkel XM-28 panniers
  • Revelate Designs frame bag
  • Arkel Tailrider trunk bag
  • Bedrock Bags Coconino seat bag

[TD]
Bike Setup #1

  • Osprey Packs Escapist 20 backpack
  • Panniers
  • Everything Bags
  • Trunk bag on rear rack
  • Handlebar roll
  • 23.6 lbs. weight
  • Frame bag

Bike setup #2: Everything Bags, handlebar roll, frame bag, seat pack, backpack. Bike setup #3: Everything Bags, handlebar roll, frame bag, seat pack, backpack. Bike setup #4: Frame bag, seat pack, backpack.

Bike setup #2: Everything Bags, handlebar roll, frame bag, seat pack, backpack. Bike setup #3: Everything Bags, handlebar roll, frame bag, seat pack, backpack. Bike setup #4: Frame bag, seat pack, backpack (click to enlarge).​

[TD]
Bike Setup #2

  • Everything Bags
  • Seat pack
  • Handlebar roll
  • Backpack
  • Frame bag
  • 22.9 lbs. weight

[TD]
Bike Setup #3

  • Handlebar roll
  • Backpack
  • Frame bag
  • 18.4 lbs. weight
  • Seat pack

[TD]
Bike Setup #4

  • Frame bag
  • Backpack
  • Seat pack
  • 14 lbs. weight

Bike setup #5: Frame bag.

Bike setup #5: Frame bag (click to enlarge).​

[TD]
Bike Setup #5

  • Frame bag
  • 1.9 lbs weight

[TD]
Bike Setup #6 and #7

  • Nothing
  • 0 lbs weight

Continue to page 2 for Setup notes and graphs »



Setup notes

When I ordered the Cleaveland Everything Bags I still had the stock pre-recall Mukluk fork and it had 3 braze-ons so the bag would have bolted right on. I ordered P-Clamps so I could put the bags on my full-suspension bike. When it was time to do the test I had not gotten the correct size P-Clamps for the new fork, so they are not attached in an approved manner.

I wore the backpack on my back, it wasn't attached to the right crank arm.

I sat full upright on all of the runs, just like I was simple pedaling along. Except for #7, which I did in a full tuck. Hands next to the stem, elbow aligned with the knee, everything I normally do on a road bike. But here I also used the dropper post, which eliminates the stay on the seat or get ridiculously forward by dropping down in front of it dilemma.

Elevation plot of the testing

Eleavation Plot of Testing

(click to enlarge)

Testing Velocity

Testing Velocity

(click to enlarge)

I would pedal up to 20mph and then start coasting when I went by a marker on the side of the road. The red trace is a tuck run on a road bike.

Graph 1

(click to enlarge)

XY positioning at the top of the hill. The red trace is when I stopped at the marker I was using to be going 20mph and start coasting. After I took the data I realized I didn't know where that was so I had to mark it on a separate trip.

Graph 2

(click to enlarge)

I was just going to use the terminal velocity of the runs, but looking at the data I could see that wasn't going to work. The combination of different weights for the setups, not being at the exact same speed at the top of every run, and just the way the GPS records data meant that the terminal velocity was not that indicative of differences in the way the bike was packed. I could see that tucking worked and that was about it.

What I did next was calculate the force exerted on the bike at each point on the hill. Force = 9.8 x Mass x sine (arctan (slope)). Dividing the force by the mass of the bike gives the projected acceleration. That can then be compared to the calculated acceleration. The difference between the projected and calculated acceleration contains the number that we are looking for. Projected acceleration is Force/Mass.

Projected Acceleration - (Rolling Friction * Velocity) - (Aero Friction * Velocity3) = Calculated Acceleration. I was going to do some low speed testing on hills using different tire pressures and different bikes to try to calculate the actual Rolling Friction, but haven't gotten around to it yet. I just guessed at a value and it seemed to work pretty well. Changing the value changed every Aero Friction result but didn't change their relationship with each other.

(click to enlarge)

This is the Projected Acceleration, Calculated Acceleration, and the Fit of the Projected Acceleration to the Calculated Acceleration. This is from run #1 and has a Rolling Friction of .01 and an Aero Friction of 0.000190689. All of the data looked about this noisy, this one is about the worst as far as the fitting of the first 10 seconds.

Projected Acceleration Graph

(click to enlarge)

Continue to page 3 for more graphs and the conclusion »



Here is the graph of the Aero Friction coefficients. Run 0 is a tuck run on a road bike. Run #1 is not surprising the drag leader. I don't really understand how taking off the Everything Bags increased the drag, I guess the bags moved the air away from the rider legs. I'm not surprised that taking off the Frame Bag and Seat Bag increased the drag.

Table of coefficients

Table of Coefficient

(click to enlarge)

A breakthrough

When you try to put your car key in your jersey pocket while wearing a pack sometimes it doesn't make it into the pocket. This is what I found at my rig when I got back after run number 4. Which answer makes this picture the most embarrassing?

A) That it happened in the first place.
B) That I went to all the trouble to take a picture of the key and then stood with the key in my shadow so that you can't make it out.
C) That I didn't just not mention it instead of taking a picture.
D) That you can see from my shadow that I wear a helmet mirror.

Shadow

Conclusions

I really do think that a frame bag and seat bag help aerodynamically. The GPS really doesn't work for this. Next years test will involve actual accurate measuring of distances, chalk marks, and a high speed video camera. Or, I'll just ride my bike and drink beer.

Happy April Fool's everyone!