Author Topic: Effects of different weight distributions  (Read 1565 times)

quixoticgeek

  • Mostly Harmless
Effects of different weight distributions
« on: September 04, 2019, 02:10:47 pm »
I'm thinking for really hot weather I want to add more water carrying capability to my bike.

I'm pretty much already at capacity for what I can fit on the bike in terms of saddle bag, frame bag, top tube, and stemcells.

The only space I really have left is the front fork. I could fit a bottle cage onto the back side of each fork blade, so they are sort of angled back at about 45°.

Thing is, I'm wondering how much adding 2kg to the fork, just above the axle will effect the handling of the bike. What if I move it up a bit? How will things change as I drink one bottle and then the next?

And just to preempt some answers: No a bladder is not an option. No I won't fit a rack. No I won't be using panniers.

J
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Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Re: Effects of different weight distributions
« Reply #1 on: September 04, 2019, 02:21:53 pm »
Ask me next week and I'll be able to tell you how I get on with my Gorilla Cages, which are much larger than bottles but probably lighter, being stuffed with clothes and similar. FWIW Gorilla themselves recommend 1.5kg per side but there seem to be other systems with higher maximum weights. In the old days with panniers on a front low-rider rack, it certainly made the steering a bit heavier and slower with a greater tendency to flop when stationary, but nothing that was destabilising.

I do remember a chap on a 200km audax last year who had one bottle on his l/h fork, with a long hose to drink from while he rode, but nothing on the r/h fork at all. He seemed to cope fine with that imbalance – but he was a rather tall man (with a very upright position too) so the weight will obviously be a larger percentage for "most" people.

a bottle cake
Christmas cake with brandy?  :D
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Kim

  • Timelord
Re: Effects of different weight distributions
« Reply #2 on: September 04, 2019, 02:26:01 pm »
It'll be a lot less significant than front panniers[1], and those mostly affect handling when the bike isn't self-balancing (ie. when stopped and when wheeling).  The steering will probably feel a bit weird for 5 minutes until you get used to it.  I'd certainly try it.

(Obviously there's a risk of shimmy, as when adding or removing weight anywhere on the bike - you have to suck it and see.)


AIUI, higher-up mass makes the bike marginally[2] more stable when in motion, lower-down mass makes the bike easier to manhandle.  Perhaps counter-intuitively, the latter is more useful than the first.  At least on a loaded tourer - you're presumably carrying less in total than a traditional tourist would carry in a pair of rear panniers.

If you're going off-road, getting things as far away from the undergrowth as possible is highly desirable.


[1] If you haven't used front panniers, then it's probably worth pointing out that a weight mismatch of a kilo or so isn't a big deal, and the bike's still rideable with a single pannier (though the steering feels a bit weird).
[2] When in motion, the weight of the rider dominates.  When being wheeled, the luggage is much more important.
To ride the Windcheetah, first, you must embrace the cantilever...

quixoticgeek

  • Mostly Harmless
Re: Effects of different weight distributions
« Reply #3 on: September 04, 2019, 02:29:17 pm »
It'll be a lot less significant than front panniers[1], and those mostly affect handling when the bike isn't self-balancing (ie. when stopped and when wheeling).  The steering will probably feel a bit weird for 5 minutes until you get used to it.  I'd certainly try it.

(Obviously there's a risk of shimmy, as when adding or removing weight anywhere on the bike - you have to suck it and see.)

Shimmy is the sort of thing I'm worried about. I find descending scary enough as it is, without having to worry about unexpected handling issues at high speeds.

Quote
[1] If you haven't used front panniers, then it's probably worth pointing out that a weight mismatch of a kilo or so isn't a big deal.

I've used them, many many years ago... On a slower , heavier, much more loaded tourer. Before I learned the art of just not taking as much crap with me...

J
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frankly frankie

  • I kid you not
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Re: Effects of different weight distributions
« Reply #4 on: September 04, 2019, 02:32:14 pm »
Sloshy bottles though, not just static weight.
Diffferent people like different distributions.  When Nick Sanders cycled round the world he used front panniers and no other luggage.  (Mainly so that his luggage was always in his eyeline.)
It's not dark yet but it's getting there.

Kim

  • Timelord
Re: Effects of different weight distributions
« Reply #5 on: September 04, 2019, 02:36:47 pm »
Sloshy bottles though, not just static weight.

True, but if that's a real problem, swap with some other luggage?


Quote
Diffferent people like different distributions.  When Nick Sanders cycled round the world he used front panniers and no other luggage.  (Mainly so that his luggage was always in his eyeline.)

Upright bikes in general benefit from a bit more weight over the front wheel, at least on road.  It's putting weight on the steering axis that's the problem, in as much as it's a problem.
To ride the Windcheetah, first, you must embrace the cantilever...

Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Re: Effects of different weight distributions
« Reply #6 on: September 04, 2019, 02:39:44 pm »
If the bottles are full, there shouldn't be much sloshage.

Are we talking 2kg in total – presumably 2 bottles of 1 litre each – or 2kg to each fork – say a large PET bottle on each side? (Not that I think the answer will make a huge difference TBH).
sideways bounding monkey lounging under fruit tree

Kim

  • Timelord
Re: Effects of different weight distributions
« Reply #7 on: September 04, 2019, 02:41:45 pm »
It'll be a lot less significant than front panniers[1], and those mostly affect handling when the bike isn't self-balancing (ie. when stopped and when wheeling).  The steering will probably feel a bit weird for 5 minutes until you get used to it.  I'd certainly try it.

(Obviously there's a risk of shimmy, as when adding or removing weight anywhere on the bike - you have to suck it and see.)

Shimmy is the sort of thing I'm worried about. I find descending scary enough as it is, without having to worry about unexpected handling issues at high speeds.


Shimmy's one of those resonance things you can't really predict.  Not least because you'd have to model the rider's muscle tension in response to TEH FEAR.

But it's only a problem if it happens at Awkward Moments.  (When lightly-loaded I can induce a shimmy on my tourer at ~10mph by unloading the weight of my arms from the handlebars in a way that I wouldn't normally do.  It's dramatic, but harmless.  Goes away as soon as I hold the bars properly, doesn't happen with full luggage, and disappears at higher or lower speeds.)
To ride the Windcheetah, first, you must embrace the cantilever...

Re: Effects of different weight distributions
« Reply #8 on: September 04, 2019, 02:53:59 pm »
I used the Many Thing Cages on my forks when I rode Bikepacking Trans Germany in July. I was carrying bivvying things on the forks, so perhaps 500g on each. I can't really say I noticed any difference with this setup, definitely I had no issues either when riding or when navigating any of the frequent hike-a-bike sections.

Worth noting is that the top bikepacking riders don't tend to use forks for carrying things as it is less efficient aerodynamically. For the speeds that I ride and the nature of my bikepacking routes (hilly and technical), this is not a real concern for me. It might be more of a factor for you, especially when exposed on the road. But 2 bottles will be more aero than the larger bags I was carrying.

Karla

  • car(e) free
    • Lost Byway - around the world by bike
Re: Effects of different weight distributions
« Reply #9 on: September 04, 2019, 02:59:32 pm »
IIRC your bike is a MTB frame which has a very high BB and a low top tube, so you can't fit normal frame bottles.  That might be a good place to start.

quixoticgeek

  • Mostly Harmless
Re: Effects of different weight distributions
« Reply #10 on: September 04, 2019, 04:33:21 pm »
Sloshy bottles though, not just static weight.
Diffferent people like different distributions.  When Nick Sanders cycled round the world he used front panniers and no other luggage.  (Mainly so that his luggage was always in his eyeline.)

Good point. Tho the free surface effect on something with an area of 0.0043m³ isn't going to be that massive is it?

With 3 identical bottles, one on the stem cell (current location), I was thinking, drink that, when empty, swap with one on the fork, repeat. Which would limit free surface effect, but would maximise imbalance...

If the bottles are full, there shouldn't be much sloshage.

Are we talking 2kg in total – presumably 2 bottles of 1 litre each – or 2kg to each fork – say a large PET bottle on each side? (Not that I think the answer will make a huge difference TBH).

2 x 1kg bottles. Was my thinking. If I'm more than 3L away from a water source, I've made one hell of a navigational mistake... or I've been an idiot and entered RttR...

I used the Many Thing Cages on my forks when I rode Bikepacking Trans Germany in July. I was carrying bivvying things on the forks, so perhaps 500g on each. I can't really say I noticed any difference with this setup, definitely I had no issues either when riding or when navigating any of the frequent hike-a-bike sections.

Worth noting is that the top bikepacking riders don't tend to use forks for carrying things as it is less efficient aerodynamically. For the speeds that I ride and the nature of my bikepacking routes (hilly and technical), this is not a real concern for me. It might be more of a factor for you, especially when exposed on the road. But 2 bottles will be more aero than the larger bags I was carrying.

Yeah. Except most top bike packers don't tend to need such a small frame as me. My thinking of mounting the bottles so they are set back behind the fork, rather than to the sides of the fork, was to minimise aero penalty.

IIRC your bike is a MTB frame which has a very high BB and a low top tube, so you can't fit normal frame bottles.  That might be a good place to start.

I've read this multiple times, and I still can't parse what you're trying to suggest here.

Are you suggesting I should be getting a different frame?

BB drop is 73mm, which is the same as the croix de fer, and 1mm lower than the datum...

The top tube is quite low, making for a small frame triangle. I can't actually fit 2 bottles in there even if I removed the frame bag. And there isn't enough space between the seat post and the top tube to fit a bottle in here, even if I could find a suitable way to fit a bottle cage here. I did consider it. I also considered the amount of stand over height I have, and amount of space between top tube bag and front of saddle. With feet on the ground, top tube bag touches crotch, saddle pokes me in the bum. Not sure there's space for a bottle...

On this years TCR I had a couple of the soft water bottles (pouches like platypus things), which I just bungeed to the aero bars. It kinda worked, but I only had 2.4l in total.
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Karla

  • car(e) free
    • Lost Byway - around the world by bike
Re: Effects of different weight distributions
« Reply #11 on: September 04, 2019, 04:56:08 pm »
Yes I'm suggesting a different frame.  Okay your BB height is normal - I'm misremembering from a picture you posted a while back - but your top tube is definitely very low.  If you had a normal height top tube you could fit bottles in the main triangle like most people do, thus obtaining extra capacity.

Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Re: Effects of different weight distributions
« Reply #12 on: September 04, 2019, 05:54:26 pm »
As if on cue, J. Random Commuter has just ridden past with one front pannier and no other luggage. Of course, that pannier might be empty for all I know.
sideways bounding monkey lounging under fruit tree

bludger

  • Randonneur and bargain hunter
Re: Effects of different weight distributions
« Reply #13 on: September 04, 2019, 06:00:05 pm »
I am guessing you've already filled your handlebars up with gubbins. But I've always liked the retro bottles-on-bars look.



For myself on hot long rides I get a 2l bottle of water and secure it to the top of the saddlebag with bungees, and use it to top the actual bottles up.
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Kim

  • Timelord
Re: Effects of different weight distributions
« Reply #14 on: September 04, 2019, 06:02:24 pm »
As if on cue, J. Random Commuter has just ridden past with one front pannier and no other luggage. Of course, that pannier might be empty for all I know.

I did at one point have a front pannier on one side and a D-lock on the other.  That worked fine.
To ride the Windcheetah, first, you must embrace the cantilever...

Cudzoziemiec

  • Solar powered, tea fuelled cycle-wol
Re: Effects of different weight distributions
« Reply #15 on: September 04, 2019, 06:18:40 pm »
Those retro steel water bottles with cork caps are, of course, bang on trend now and also tapping into the no-plastic look!
sideways bounding monkey lounging under fruit tree

Re: Effects of different weight distributions
« Reply #16 on: September 04, 2019, 06:25:14 pm »
Dune suit.
L'enfer, c'est les autos.

Re: Effects of different weight distributions
« Reply #17 on: September 04, 2019, 06:40:41 pm »
I tried gorrilla cages at one point. They were poorly suited to the diameter of mmy forks, which had no bosses. I didn't like how easy it was to knock them into my wheels and so removed them. This was on a mtb with suspension fork, your bike may be more sensible.

If you're shuffling luggage about, i found a 1.5l bladder in a frame bag worked ok.


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Re: Effects of different weight distributions
« Reply #18 on: September 04, 2019, 06:46:44 pm »
I’d be worried about them (or perhaps the empty cages) being sucked into the front wheel. Every after market bottle cage system I’ve encountered wants to pivot.

I have some Salomon soft water flasks which are good for carrying an extra litre in jersey pockets.


Re: Effects of different weight distributions
« Reply #19 on: September 04, 2019, 08:45:06 pm »
Maybe make your existing bottle cages bigger.  Blackburn do a cage which would carry 4 kg (if your frame bosses would take the weight - my surly takes two happily) https://www.ribblecycles.co.uk/blackburn-outpost-cargo-cage/

quixoticgeek

  • Mostly Harmless
Re: Effects of different weight distributions
« Reply #20 on: September 04, 2019, 09:19:34 pm »
Maybe make your existing bottle cages bigger.  Blackburn do a cage which would carry 4 kg (if your frame bosses would take the weight - my surly takes two happily) https://www.ribblecycles.co.uk/blackburn-outpost-cargo-cage/

What bottle cages? I don't have any bottle cages fitted.

 
I’d be worried about them (or perhaps the empty cages) being sucked into the front wheel. Every after market bottle cage system I’ve encountered wants to pivot.


I can mount bottle cages solidly, using screws, so that shouldn't be a problem.

J
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http://b.42q.eu/

Re: Effects of different weight distributions
« Reply #21 on: September 04, 2019, 09:37:43 pm »

I can mount bottle cages solidly, using screws, so that shouldn't be a problem.


If you've a couple of bosses on your forks then that's much easier. As mentioned above, I've got a pair of Gorilla cages somewhere downstairs that aren't being used - if you'd like. like this

Re: Effects of different weight distributions
« Reply #22 on: September 04, 2019, 09:47:04 pm »
you can get bottle cages which are designed to accommodate outsize bottles, eg fuel bottles, such as the 'bike buddy' cage. These can be made to hold a 2L bottle of water.

Fastening stuff onto the fork blades with band-on clamps is basically a daft idea.  It ain't great even with braze-ons, but without it is practically suicidal.

cheers

bludger

  • Randonneur and bargain hunter
Re: Effects of different weight distributions
« Reply #23 on: September 04, 2019, 10:03:50 pm »
I've seen lots of people do a decent job with some old inner tube to protect the paint and jubilee clips. So long as you don't use a hydraulic torque wrench to stick them on I don't think it'd be suicidal, products like http://bikepacker.com/gorilla-cage-system-review/ seem to do the same thing.

My bike uses a 100% carbon fork.
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quixoticgeek

  • Mostly Harmless
Re: Effects of different weight distributions
« Reply #24 on: September 04, 2019, 10:15:09 pm »
If you've a couple of bosses on your forks then that's much easier. As mentioned above, I've got a pair of Gorilla cages somewhere downstairs that aren't being used - if you'd like. like this

Thanks, but I have a pair in the spares box. I use them in winter when I need extra warm kit. My sleep matt (exped down mat winterlite) goes on the right hand side, and my Paramo Torres jacket goes on the other side.

you can get bottle cages which are designed to accommodate outsize bottles, eg fuel bottles, such as the 'bike buddy' cage. These can be made to hold a 2L bottle of water.

Fastening stuff onto the fork blades with band-on clamps is basically a daft idea.  It ain't great even with braze-ons, but without it is practically suicidal.

I'm not after carrying more than 1 normal 1L bike bottle on each side. So normal bike cages will work.

The fork on my Vagabond has mounting bosses for a rack mid way up the fork, and another boss by the drop out. I use a wolftooth BRAD[1] between the mid fork boss, and the drop out boss. I then attach the double bottle cage adapter[2]. The Gorilla cage goes on the front, and a bottle cage goes on the back. I've used this in winter with approx 600g in the front, and a 500ml nalgene bottle full of water on the back.

It looks something like this:



It works well, even off road, but I was careful to balance the weight round the fork.

My question here stems from what happens if the weight is all behind the fork (i.e. just the bottle cage, without the gorilla cage full of warmth in front of it). The BRAD setup allows me to move the weight up and down a bit. How would moving the weight relative to the drop out effect the handling of the bike?

In anger, with too much crap on the bike (taken on the banks of the Rhine):



J

[1]https://www.wolftoothcomponents.com/collections/b-rad-system/products/b-rad-bottle-relocation-and-accessory-device
[2]https://www.wolftoothcomponents.com/collections/b-rad-system/products/b-rad-double-bottle-cage-adapter
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