Power to weight... better performance with load on back vs bike?

[mrmacmusic]

Silly question perhaps but I'm curious – should you expect a difference in performance between carrying a load on the bike in panniers or on your back in a rucksack?

I had my fastest ever commutes on Friday by quite a considerable margin – I shaved 2 minutes off my best ever time, which was 7-8 off my average for the past month or so. My rack and panniers hadn't been re-fitted following derailleur surgery (i.e. reduced bike weight), but I was carrying my usual load in a rucksack (i.e. increased "rider" weight).

My legs haven't increased in size overnight, but I was very surprised with the time difference... climbing was a bit easier too despite the fact that the overall weight – rider+bike+load – was essentially the same.

Thoughts?

 

[Pauluk]

Centre of gravity? Weight moving away from the drive axle towards the front?

 

[MrJamie]

Maybe a backpack is more aerodynamic as well as the reduced weight from not having the rack fitted.

 

[Sittingduck]

More comfortable to have a pannier but I reckon I'm quicker and obviously better balanced, with a backpack.

 

[MacB]

Even a marked improvement would only see me move from really slow to slow...so I'll stick with a non-sweaty back

 

[gaz]

I'm going to be commuting for the next week with a backpack instead of using my trunk bag.
And i'm going to be using my carbon roadie rather than my single speed alu commuter.
I'm expecting to be quicker for several reasons, removing weight from the bike being one of them.
I'm also expecting to be more uncomfortable due to the backpack and a sweaty back.

 

[taximan]

I think it depends on how much weight you want to carry. A heavy bag on hour back raises the centre of gravity and must affect stability especially at low speeds.

 

[asterix]

As a practised cycle tourist, I don't think that 'weight on the bike' makes you any slower than 'weight on the back'. What does make a difference on a tourer is the wind resistance of pannier, especially noticeable when descending when it becomes difficult to exceed 60km/h. But then that's carrying a volume of 60 litres or more.

 

[MattHB]

Maybe a backpack is more aerodynamic as well as the reduced weight from not having the rack fitted.

Enormously so. The effects of any headwind are multiplied by panniers. I used to ride with them a lot.

 

[screenman]

We have had some pretty quick weather of late.

 

[defy-one]

I've noticed i'm quicker with a rucksack,but my back was sweaty,shoulders hurt and lower back was stiff for days after.
The rack & panniers are staying!

 

[mrmacmusic]

Interesting comments, thanks

Maybe I shouldn't have been surprised that it felt easier riding the lighter bike despite the fact that the overall weight was the same. I hadn't considered the aerodynamics perspective, and that's bound to be having some bearing on matters – there was a strong headwind this morning and my commute was noticeably faster with the backpack compared to the pannier.

 

[amaferanga]

It's not weight, its aerodynamics.

 

[GrasB]

It's not weight, its aerodynamics.

No & yes.

Certainly shifting weight onto your back makes climbing easier when you attack the climb. I assume this is more to do with the amount of energy lost moving the bike from side to side when standing up, it doesn't seem to make much difference if you gently ride up the climb.

You're right though, there's also a big aero advantage over conventional panniers. However if you do panniers right with attention to aerodynamics you can make really nice gains there, especially if you're on a 'bent.

 

[Cubist]

Perhaps the bike felt better for not looking like a pack mule and decided to behave like a bike again................