My bike always feels slower when I use the pannier, but it's worth it to get the weight off my back.

The weight doesn't matter although the aerodynamics do. Speed differences and a little back-of-the-envelope calculations suggested a 20% CdA increase from my one Arkel Commuter pannier.

That said it's MUCH more comfortable than a backpack and entirely worthwhile.

Out of the saddle the weight is more noticeable on the frame but you get used to that.

Aerodynamics suggest that if the cargo is "drafting" off your body, you'll be faster (argument for the rack); different riding positions will cause different 'drag spots', enabling areas off the rider's back that are aero-efficient (argument for the backpack).

A lot of the replies here have to do with perceived comfort, and this has an effect, as well. A more comfortable rider, at the same intensity, will produce a smidgen more power, simply because he/she isn't diverted by DIScomfort.

AANNNN-NNDD, of course, there's another alternative, where it is that I land...it's an interesting mental exercise, but I really don't care. Simply, I prefer the weight on my back, where I can use it as my own, as body weight for body English. Faster is irrelevant to me, as "faster=less ride time" for a given journey. I'd just as soon be on the bike a little longer.

I think the backpack is noticeably faster, but I still use the rack nearly all the time, because it's a LOT more comfortable. I'm commuting or running errands, not racing; I'm willing to sacrifice a little performance in exchange for a dry back and an absence of soreness in various areas.

I will be finding out very soon. I just bought a rear rack and am waiting for it to come in. Ive been commuting with a backpack for about 2 years and its finally getting to me. Light loads are okay but heavier loads put a strain on me and my backpack smells heavily of back sweat haha.

I have a cycle computer that I got for Christmas and have been timing my rides with it so I have good data with a backpack just need to see what its like for a rack. With backpack average moving time is about 35min for 9.2 miles with an average speed around 16mph based on my cycle computer. Wind is the biggest factor for me when it comes to speed, with 20-25mph sustained for most days. I ride in the drops if that counts for anything..

Ill chime back in when I get more data riding with the rack when it comes in.

Well I'm back with some data. I was only able to do this commute 4 times with the backpack on the rack so far, so keep that in mind when I make my claims. There has also been a lot of storms in the area which have changed my typical riding conditions, wind speed and direct have not been constant with all 4 rides. Ok so for the first ride 39min, second 35min, third 34min, and fourth 37min. For the first ride I was being cautious with the rack and getting used to riding with it so that could attribute to my slower ride, the fourth ride was against an untypical strong headwind; but these time are still under my slowest time with a backpack on back. These times where pretty common of what I do with a backpack on back, though maybe a tad bit slower total time.

Though overall ride time may have increased slightly which would need more trials to confirm there are several notable differences between the two riding system. With the weight on the rack handling changes significantly, acceleration is a lot slower but top speed seems unaffected, it is less maneuverable, however the bike is more stable and there is less bike movement when pedaling hard and out of saddle. The main benefits I see for my riding conditions, flat terrain with high winds, is a 2-3 mph increase when battling headwinds. Also with the weight off my back I am more comfortable when riding and can focus more on my pedaling. My ride also is more enjoyable now and I seem to be less fatigued after riding than usual.

So my consensus is that riding with a backpack on a rack has no significant difference in total ride time than with a backpack on back, more testing is needed to confirm this claim. Against a headwind the rack is notably faster, but with a tailwind I think backpack will win because it catches more wind. I have no data for hills so can't apply that here. For me I say the rack makes the ride more enjoyable for my conditions.

I can't say which is faster, but when I had a rack I liked the weight distribution much better with the load on the rack.

A backpack can tire out your arms and back. Instead of the entire weight being supported by a rack, your muscles also have to carry the backpack. Your legs need to move the same weight, regardless. A backpack can be more convenient, cheaper, lighter overall and more aerodynamic than a rack and bag, but on balance, a rack and bag wins, when considering the sweat factor.

When I put my backpack on the rack (tie it with bungee cords), I feel faster on good terrain, since there's less weight on my back.

When riding aggressively on bad roads (or off road), backpack on the back is the quicker, better solution.

When putting panniers - slightly more air drag, feels slower than any of the previous scenarios - whether on good, or bad roads. But it is the most convenient solution when it is raining and I need to carry spare clothes.


Backpack on the back is always heavier and swetier though.

I think it all just comes down to personal preference; on my old bike I had panniers and a racktop carrier (for my laptop) from the start, and only carried a small Camelbak pack on my back. When I bought my new bike, I hesitated about putting a rack on it at first (it looked so sexy sans-rack), and tried loading everything into one of my sleek hiking backpacks. I found it to be much less comfortable, and ended up with a stiff back and such at the end of my ~22km (one-way) commute. I'm back to a rack now and loving it!

I mix it up between backpack and rack mounted trunk(actually a plastic rubbermaid type container with lid) for my 20 mile round trip commute. I definitely feel like the backpack is faster and more fun up to a certain load, maybe up to about 15lbs. Beyond that the comfort level goes down to much to be fast. I don't think aerodynamics are to much of an issue for me because both the trunk and the backpack are mostly blocked by my body. If I could stand more weight on my back my guess is that the backpack would always be faster. I would think that having excessive downward force directly over the drive wheel slows the bike more than well distributed force. I'm sure this is something that could be figured out fairly quickly by somebody proficient in physics. Bicycle physics seems very interesting to me, but it's one thing to think its interesting, and a whole other thing to sit down with a physics book and figure it out.