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I'm about to increase my daily commute from 5 km each way to 10 km each way. I've been using a MTB converted to a commuter for years. Given the extra distance, regular evening head wind, and aging body, I'm considering getting a road or cyclocross bike or for better efficiency.

I usually commute with a large backback full of clothes, towel, laptop, lunch containers, etc. My question is, would the aerodynamic gain of switching to a road bike be negated by the backback? If so, would panniers or some other solution be better in terms of drag?

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    Here is a partial answer: a backpack is better than panniers but worse than a saddlebag bikepack. youtube.com/watch?v=wdfB5fbVHck What's missing from this is the size of the advantage for going to a road bike from a MTB. Typically, however, road bike tires have lower rolling resistance, are lighter, and have lower aerodynamic drag than MTBs so with the same cargo-carrying location the road bike will have lower drag. – R. Chung Sep 17 '19 at 23:46
  • You should also consider comfort, handling, and convenience. If you put panniers on a bike that wasn't really designed for them, the bike will handle like a pig. I say this from experience: I switched recently from carrying one pannier with about the same load as you to leaving some stuff at work (I scored a locker) and carrying the rest in a small backpack--it's a much better setup for me. – Adam Rice Sep 18 '19 at 0:32
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    On the actual question of aero drag, there's a wattage estimator. Using myself as an example, at 17 mph, an MTB takes 155 W, a road bike on the drops takes 121 W, and a road bike on the tops takes 160 W (!). This is holding tire type constant. So if you ride on the drops, you could still burn 20 W on panniers (as per that GCN video) and be ahead of riding an unencumbered mountain bike. – Adam Rice Sep 18 '19 at 1:10
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    Not posting it as an answer since it's not about your question, but I prefer panniers to backpack because: 1) it saves me a sweat mark on my shirt 2) it lowers my center of mass. – L.Dutch - Reinstate Monica Sep 18 '19 at 6:01
  • @AdamRice: "handle like a pig" is a bit of an exaggeration. Hauling some clothes and a laptop or similar light loads is going to be nearly imperceptible for how just about any bike handles. – whatsisname Sep 18 '19 at 19:49
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Your very question has actually been answered by GCN (below) and Specialized and has been partially answered in What's more aerodynamic on flat bars: backpack or pannier?

Essentially the in order of fastest to slowest:

  1. Large saddle bag (i.e., bike packing bags)
  2. Back pack
  3. Pannier

By far the panniers will be the slowest option as you are hanging the bag out in the full wind. Backpacks are pretty fast, but do affect wind transferring over your back. If you don't have a lot to carry bike packing bags are the fastest option as they are tucked away the most.

Over the last 2 years I have switched completely to bike packing bags and a fast road bike for my 45 km commute (2 way) and probably save close to 10+ minutes per day.

One thing not tested in the videos is a front roll bag. I have good luck with that setup as I think it acts a bit like a wind fairing for your upper legs which do cause a lot of air disturbance.

What's The Best Bag For Commuting By Bike? Saddle Bag Vs. Panniers Vs. Backpack

What's The Best Bag For Commuting By Bike? Saddle Bag Vs. Panniers Vs. Backpack

Screen capture with the actual data with a suspect y-axis scaling... Come on Emma your are a PhD scientist!

Wattage cost by bag type

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  • Rider_X, at what speed did they measure the 20 W drag increase for the panniers? Unfortunately I cannot watch the video again right now. What is more, its best to include all relevant in the body of your answer anyway. We may compare drag of a road bike and a mtb at the same speed to answer the actual question (partially). – gschenk Sep 18 '19 at 22:21
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    @gschenk from a screen capture it looks like 40.3 kph was the test speed. This means a pannier would add ~ 6%? to the effort required to ride at that speed. Now before everyone freaks out and says it’s an unrealistic speed, and therefore useless, the relative difference between the setups will remain the same at different speeds as your drag is directly proportional to your effective frontal area, which is affected by bag position. – Rider_X Sep 19 '19 at 2:48
  • Perfect, thanks! So a large saddle bag is the way to go. – horeobs Sep 19 '19 at 3:26
  • @horeobs Yes, if your only interest is reducing your drag. Large saddle bags have other issues, such as how much can be stored, removal and transport of your items at your destination and where to mount a tail light, which can be important if you commute during low light. That said, I still prefer it over panniers. – Rider_X Sep 19 '19 at 16:24
  • Fitting a notebook might be difficult for most notebook/saddlebag combinations. Rider X, did you find ways to fix those issues? Or did you accept the drawbacks? – gschenk Sep 19 '19 at 21:58

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