Luggage - High or Low on a Cruzbike?

[Gromit]

Conventional bike wisdom (diamond-frame) seems to says that luggage should be kept as low as possible.
Does this advice apply to the Cruzbike? Discuss?

Why am I asking this question? I went with the conventional advice that low is better on my Sofrider and mounted a pannier rack on my rear swinging arm. I bought a pair of panniers and a rack top bag as well.
I mainly ride my Cruzbike for pleasure rather than commuting to work. I rarely use the panniers as my day ride kit fits easily into the top bag. Recently I started to think about reducing the weight of the bike by getting rid of the rack and hanging a bag off the seat instead.

I therefore had a look back through some earlier forum threads and found an interesting one about seatback-mounted, Fastback Double Century and Radical Design Solo Aero bags.

In the middle of the thread, I found these words:-

Hotdog said

Quote: It probably would be better if the bag were slightly higher, it would look at bit neater if it didn't bend round under the seat base and would be marginally more aerodynamic (though lifting the load C of G higher is less good).

John Tolhurst replied

Quote: Its a small effect - but I would suggest more good. The relatively high C of G on the cruz compared to low racers is important to its ridability, as it gives you more time for your balancing reactions and so allows them to be timed with the pedal stroke. Sometimes the timing is not there, and you have to manhandle the bike to react when you want it.

Hotdog replied

Quote: Very true, moving less than 5kg by less than 10cm isn't going to make much difference to anything, and in any case lower centre of gravity isn't necessarily better. As you said, too low (like a low racer) and balance gets twitchy.

The discussion then moved back onto the specifics of how to mount the Double Century bags and the discussion on C of G got dropped.
IMHO It is interesting topic. What do you other folks think? Higher or Lower?

 

[JonB]

I have driven like a year with a backpack in my basket and other stuff. I have driven 2 days with stuff in my new low mounted pannier. The height difference is something like 20-25 inches.

With the high basket carrier i often felt very wobbly wobbly if it was heavy loaded. The reason is possibly a combination of a deflated rear wheel, but also that the rack under the basket moved from side to side. Imagine balancing something heavy ontop of a long pole which you only support from underneeth. It is not easy. Most of the time i didnt feel much of a problem, maybe also because i changed the rear tire and now has a schwalbe maraton with high pressure. The old tire was the one it came with, and maybe i didnt inflate it as much. With the basket, the load was centralised over the path the wheels took.

With the low side mount i feel no wobbling, even with a heavy load. But i do feel that the load is not centralised over the wheel path. Normally my load will be half, because i will only bring one laptop. I expect to get used to the unbalance, i did today after 20 minutes of riding. I plan to test with panniers in each side.


I do not yet feel confident to answer your question, as i only have 2 days experience with the low mount. I developed it because i heard the same about as low as possible, and i did not have a rear rack that allowed me to mount panniers under the basket. I feel more secure since the panniers is nearer to me than they would be on a rear rack. I feel i will notice if it falls of, or if someone steals it. ( not that i have ever been robbed, and Copenhagen is a nice place, but hey, i like my laptop thank you. )

 

[Gromit]

Interesting thoughts Jon. I wonder if you are compensating for the offset weight distribution of the bag in the same way that you might do if you were riding in a strong crosswind. Of course in a crosswind, the area of the bag presented to the wind might also have an effect on your leaning.
Regarding the higher top of your unsuspended rear rack. I wonder if the wobbly feeling would go away if the rack was attached to the suspended part of the frame higher up. Like John Tolhurst's child seat for example.

 

[JonB]

Gromit wrote: Interesting thoughts Jon. I wonder if you are compensating for the offset weight distribution of the bag in the same way that you might do if you were riding in a strong crosswind. Of course in a crosswind, the area of the bag presented to the wind might also have an effect on your leaning.

Wind affect should be the same since the size of the bag is the same. But maybe it matters if the bag is on the side of the rear wheel or between the front and rear wheel? Maybe.

Gromit wrote: Regarding the higher top of your unsuspended rear rack. I wonder if the wobbly feeling would go away if the rack was attached to the suspended part of the frame higher up. Like John Tolhurst's child seat for example.

I think that Johns is less wobbly. But i dont agree that the reason i feel it is because my rack is unsuspended. I think the reason is that i bought the cheapest rack i could find. Something like $30. I also think that it doesnt help that i have the Freerider handle bars which further puts the connection way front of the rack.

 

[JonB]

i might have found the reason for being wobbly wobble and ratling. The base mount of the rear rack was cracked in the right side just milimeters above the cruzbike frame. Luckily the broken part was a slider made for fitting the rack to different size wheels, so i only had to slide it down and drill a new hole. So far no noises, but i havent tried loading weight onto the rear rack since this fix.

 

[Gromit]

I'm pleased that you may have found the answer to your problems Jon.

So has anyone else any opinion on whether luggage should be mounted high or low on a Cruzbike? :?:
I'm still after advice on whether to remove my swinging arm mounted rack and attach a bag to the seat back.
What about any aerodynamic advantage in having a seat back bag in your "wind shadow" rather that two pannier bags hanging on the pannier rack and hence below seat height?

 

[JonB]

Gromit wrote: I'm pleased that you may have found the answer to your problems Jon.

So has anyone else any opinion on whether luggage should be mounted high or low on a Cruzbike? :?:
I'm still after advice on whether to remove my swinging arm mounted rack and attach a bag to the seat back.
What about any aerodynamic advantage in having a seat back bag in your "wind shadow" rather that two pannier bags hanging on the pannier rack and hence below seat height?

what i ment was that keeping the weight high might not have been what made my bike wobbly wobbly.

since a rear fairing does influence your top speed at the same watt, you will probably be better off mounting stuff in your "wind shadow". But you are moving it up, which makes the bike harder to handle.

 

[John Tolhurst]

If the luggage moves side to side at all and if it is placed behind you, then your body's inertia becomes a pivoting point for the whole bike. In effect, the tail wags the head, so makes the bike feel very wibbly wobbly.

 

[Gromit]

johntolhurst wrote: If the luggage moves side to side at all and if it is placed behind you, then your body's inertia becomes a pivoting point for the whole bike. In effect, the tail wags the head, so makes the bike feel very wibbly wobbly.

John T
I assume that the above is your response to Jon B.
Do you still reckon that luggage is best placed higher rather than lower on a Cruzbike? As in the quote from you which I copied from another thread? See my first post in this thread.

 

[John Tolhurst]

I don't think there is a single right answer, Gromit,

If you want good aero, you must put the luggage behind the seat.

If you want to carry a real lot of weight, put it under seat to reduce the inertia around leaning into and out of corners

If you want optimum weight balance and aero, behind the seat and shift your seat forward (but without luggage you centre of gravity will be a bit far forward)

If you are on unpaved roads, weight under the seat and as far forward as possible without impinging the steering of the front wheel.

My sofrider with child seat on the back has perfect balance and is highly maneouverable - my seat is moved forward and without weight in the back, I can lift the rear wheel on an emergency stop.

If I were touring, I'd try to get it all on the back, and may then run pvc piping under the seat on each side, from the front of the seat right out to the back and carry water bottles in them.

You can also study the solutions of the two guys who are doing world tours on cruzbikes.

 

[chiefdan92]

This is my commuting setup

I have my water bag slung behind/under the seat and the racktop bag has integrated panniers to carry my clothes since I commute every day rain or shine (not much rain in Fresno! But it is getting cooler.)
I have not noticed it being top heavy, though If I don't make sure the waterbag is tight I can feel it move on a left turn!

I have a q-beam rack that attaches to the seatpost. You just have to make sure you don't loosen the rear shock too much, or it drags on the tire!