Thursday, April 12, 2012

Weight Distribution Mysteries

Loaded Rivendell, Rockport MA
One thing that continues to mystify me about frame design, is how different bicycles react to weight distribution. Over the years, I've really found this aspect of a bicycle's handling to be a wildcard. My Rivendell Sam Hillborne is built like a typical mid-trail touring bike, which, it is said, makes it optimal for carrying heavy loads in the rear but only moderate loads in the front. However, I prefer to ride this bike with an enormous handlebar bag, and it does very well with it. It also handles well with a saddlebag and panniers, but interestingly the handlebar bag - with the same amount of weight in it - does not appear to affect speed at all, whereas the saddlebag does a bit. If I am going on a fast ride, I remove the saddlebag but do not bother removing the handlebar bag. All of this is just fine with me, because I find it far more convenient to keep my stuff in the front for easy access. But it goes against my understanding of the way a bicycle like this is supposed to react to weight. 

Francesco Moser 2.0
Then there is the Moser racing bike, which reacts badly to any weight I put on it at either end. The front gets twitchy with even a small bag attached. And with any saddlebag larger than a tiny wedge the bike feels distinctly rear-heavy. A few times I've affixed a mid-sized saddlebag so that I could carry my camera, and it felt like trudging through mud compared to the speed this bike is normally capable of. On the other hand, a full water bottle on the downtube (the bottle weighing about the same as my camera) has no effect, and neither does my own weight gain when I stuff my jersey pockets with all the things I would have otherwise kept in a bag.

Riding bikes like this has made me understand why some cyclists chose to ride with backpacks instead of baskets or panniers - some bicycles simply do not handle well with weight on either end, but do fine when the weight is part of the rider. This is one reason the argument "If you want to lighten your bike, lose some weight" does not make sense to me. You cannot simply take the combined weight of a bicycle, its accessories and its rider, and assume the handling and speed will be the same as long as the total remains the same.

My first city bicycle - a Pashley Princess - came with a huge front basket, but it did not handle well for me when I put things in the basket. Eventually I removed it and attached a set of rear folding panniers instead. With that configuration the bike handled much better, and faster. When I carried weight in the rear, I could detect no difference in speed, even with a full load of groceries.

Bella Ciao, Fastrider Pannier
On the other hand, the Bella Ciao city bike I now ride - while faster than the Pashley overall - is more sensitive to weight in the back. The handling doesn't change, but I can feel a difference in speed depending on how heavy the load I am carrying is. 

With pretty much every bicycle I've ridden over an extended period of time so far, I've noticed some sort of relationship between weight distribution and handling, and it is not always a logical one - or at least not obviously so. I am sure there are lots of factors contributing to these effects, and these factors are just too nuanced to be obviously discernible. It's interesting to figure this stuff out in the process of getting to know a bike. 

39 comments:

  1. To carry the little extras on the Moser you will require domestiques.

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  2. jaysus don't tell me that is how much stuff you usually carry on the Riv! or is it camera equipment?

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    1. We went on vacation last summer, by bike and train. That is 2 weeks worth of stuff on the bike. Here's more about it.

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    2. It seems to me that the photo is from the annual North Shore jihad when in the interest of science, the Cohibitant graciously allowed V to haul most of the weight.

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    3. Oh come on, don't start with that again.
      I WANTED TO!!!

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    4. I remember that post. It might have been the first time I felt compelled to reply. What was it that PT Barnum said? ;>)

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  3. "I've noticed some sort of relationship between weight distribution and handling, and it is not always a logical one - or at least not obviously so."

    Oh it's totally logical to me, but I'm not saying why because it might offend someone who has a bike that doesn't do a certain thing.

    I missed out on the banana hammock & low trail festivities.

    "The banana must be carried on a 650b for superior handling!"

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  4. Ridden with handlebar bags, back packs, panniers, front low riders and sometimes all together :) Indeed, weight front, back, low, high, secure, less secure, changes the ways in which the bike feels/handles. With only the one bike, however, I've learned to get used to each variation and have never found any unsafe. Mostly, it just felt different than my expectations and my expectations adapted.

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  5. After hearing about it from others, I finally tried my Rivendell Atlantis with low-rider front panniers (on a Nitto/Rivendell Big Front Rack) carrying most of my touring load. As promised, they had a wonderful effect on handling. The bike felt like it was riding on rails, it was so steady, yet it was not hard to steer. If you haven't tried front low-riders yet, you may like them on your Sam Hillbourne.

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  6. I think there's more at play here than just bike geometry differences. Wheel size, tire pressure, center of gravity, and the way in which the bags are secured, all make a difference in how the bike handles. (Bags that are allowed to sway or move contribute to a sense of instability). But of course, geometry must also a role.

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  7. I would think that overall bike weight relative to load weight would be a consideration also.

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  8. Frame material is significant too ... your Moser is built from thin-wall steel tuned to carry little more than an average male, and the rear stays may be particularly sensitive to an "unusual" load. The Pashley on the other hand is built from thick steel pipe, you can hang whatever you like on it and it won't notice.

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    1. But isn't the Moser built from Aelle tubing, which is straight guage .9mm stuff and actually quite stiff? Not only that but hers is a small frame which would add to stiffness relative to a larger frame like the one I have. I have a similar Moser with Aelle tubing in a size 61. With a small bag on the back, a VO baguette bag full of tools and more, I can't even notice it; the same load on the front makes for a very annoying ride. Aside from size there are other differences - I have a 5mm taller fork (from another bike) and my handlebar is pretty high. I think geometry plays a larger role than material, but I do think material can play a role. Many modern and old timey randonneur bikes made for front loads are/were made light with thinner walled tubing than Aelle.

      -- Rolly

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    2. Aelle is 0.8mm straight.

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    3. Yes it is built with Aelle tubing, the specifics of which I am not sure about. However, it is "tretubi" - so who knows what the chainstays and fork are. Well, I am sure someone knows... And it can't be too bad, because the bike is light.

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    4. Here: www.equusbicycle.com/bike/columbus/columbusoldfullcat/big/10columbuscat.jpg

      Late 70s Columbus catalog.

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  9. I think @somervillian is on the right track. Pneumatic trail definably contributes to front end stability. There is a very good reason most low trail randonneuring bikes use large volume tires instead of skinny low volume ones. The friction of the tires contact area keeps the wheel going strait, which is why high trail bikes with a front load feel more unstable at low speeds. I think it's interesting that in the BQ review of the Grand Bois city Jan says he prefers high trail geometries for very heavy loads like a stack of magazines. I'm assuming that's because you need the stability to keep the bike strait and you aren't concerned with wheel flop. With that kind of load you would never take your hands off the bars like you might with a smaller handlebar bag.

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    1. Careful with your theorizing there. My bike (which has huge balloon tires on it) is much more prone to no-hands front-end shimmy when the tires are a little low, and I am pretty sure it is related to the contact patch.

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    2. Interesting. I turned a Surly Steamroller into a porteur style city bike and fabricated my own rack for it. I'm sure it's high trail. I like how it handles with heavy loads but it is a two handed affair, sometimes allowing for just one hand if it's a lighter load (had a full size empty beer keg on it once; carried three bike frames another time; a load of angle iron that made the stem and everything else flex! Will never do that again; a 2-4 or case of beer is great to carry). I've been curious about the difference a short trail set up would make.

      -- Rolly

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    3. Man, longtime reader of the blog but never felt the urge to post before - now here I am three-time-posting, an indication, I guess, about how fascinated I am with geometry, loads and effects on handling - thanks for exploring these topics and providing the forum for such discussions.

      I find the Jan Hein theories/ideology interesting becasue I think my favourite snow-riding bike of all time (when I was messengering) was a track bike that I'd put a big-rake fork on - possibly discovering short trail by accident. It had the best front end traction in snow and didn't go all crazy with a box on the bars.

      My experiment to explore this low trail stuff further (I stopped messengering in 2005 and became a welder) has been converting a LeMond Alpe D'Huez racer into a short trail randonneur bike. I moved the seatstay bridge higher and put canti bosses on it for tire clearance and then pondered the front end for a long time. I made a fork re-raker to convert a cyclocross fork but then found an old Reynolds 531 touring fork that was closer in height to the original yet has more rake. I measured the trail at around 40mm but that may be a bit inaccurate. However the bike handles great with a 6 pack strapped to the front rack. I'm just getting a handlebar bag made by a friend and will have to see how it handles once it's done and I can load it up. This blog post makes me want to get an accurate trail measurement and maybe even try that fork re-raker (yikes, and maybe wreck that 531 fork... there'd be tears in my beers). The chainstays are 41.5mm which I believe is in the rando realm.

      The bike also handles great with a loaded 11 litre saddlebag (and also ok when full of beer) and so these latest blogs, comparing the Riv to the Sojwhatever-I-forget, your Royal H and the loaded bike stuff, have been interesting to me.

      -- Rolly

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  10. The Bella Ciao has lighter stays than the Pashley. That's why it has a nice ride. Load capacity and comfort are a direct trade-off.

    Weight in jersey pockets is suspended weight. Suspended by the springs in your arms and legs. For handling purposes the bike thinks the weight is all you.

    Water bottles firmly mounted and mounted low aren't felt much. You might feel a difference with long bottles. If you did two behind the saddle where they sway and wobble you would feel it.

    The biggest mystery to me here is how the SH can carry massive loads at all and still be a bike anyone rides for fun. The best guess I have is that a lot of the ride is comes from the special tires.

    I've had some race bikes that calm down a lot with wider tires. Some race bikes not affected at all. What Somervillain and Somacisco say is on track. Try the Moser with Cerfs or Parigi-Roubaix and see what happens. (The latter mounts easier.) The bike will ride very differently and very much better whether it creates carry capacity or not.

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    1. I've had the Moser fitted with 28mm Panaracer Pacelas before its current incarnation and when it was a fixed gear. It was indeed calmer, but still didn't like weight in the rear. But in its present state (with a rear brake) it won't fit anything wider than 25mm.

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    2. Are you sure? If the frame clears the tire....
      Older Veloce brake arches would clear, I don't look at new stuff much.
      There is no rule you can't run a 25 rear and a 28 front.
      Fixed & free handling could be different.
      And it could be a fruitless experiment.

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    3. Oh yes I am sure. I do not really feel the need for 25/28mm tires on this bike to tell you the truth, and for the kinds of riding I do on it I am just fine using my jersey pockets. But it's interesting to know what it is and isn't capable of in various configurations.

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  11. One of the things I love about beefy-bracketed carbon fiber is that it is not as flexy under load.

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  12. The LHT behaves very well with just back panniers. But, it is positively regal when I load it for touring with large back panniers, and smaller low-riding front panniers (totalling a third of the weight). It's as though a magic combination has been dialled in and the stability of the ride is so much better than it is even without a load.

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  13. I would just like to add that my Sam Hillborne isn't really affected by a handlebar bag (sackville barsack) or rear loads. I generally keep the handlebar bag on the bike even on fast rides with the club. I use 38mm Pari Motos for tires. Great bike.

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  14. There is no doubt that trail and stiffness matter, but I still think that the weight of the bikes is important also. This is true both objectively and subjectively. You ride a heavy bike differently than a light bike, so the same addition will have a greater effect on the balance of a light bike and you are going to notice changes to the light bike more. Teasing apart the weight factor from the other factors would require some pretty complex testing. I think.

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  15. "Hit me, hit me"...

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  16. I'm in the market for a new bike. Reading this post about the ability of a Sam Hillborne to carry so much weight is quite helpful. I'm especially pleased to read that you have a large handlebar bag (an Ostrich - which I also own / plan to use on my new bike) on your Sam all of the time.

    All of this is making it hard for me to resist making that call to Rivendell World Headquarters!

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    1. Yes, my standard way of riding the Riv is Ostrich in the front and nothing to balance it out in the rear; bike handles fine. Note that this bag needs both a front rack and a decalleur to be stable.

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  17. >My Rivendell Sam Hillborne is built like a typical mid-trail touring bike, which, it is said, makes it optimal for carrying heavy loads in the rear but only moderate loads in the front. However, I prefer to ride this bike with an enormous handlebar bag, and it does very well with it.

    Yes, "it is said." Perhaps it is not so wise to accept things you read online and in 'zines as fact. I have ridden all kinds of bikes, from early pneumatic tire safeties to a bike with rando geometry built a few years ago. What "is said" does not match my experience, or yours, apparently. A lot of what is being trafficked in the steel bike realm just now as "real research" about bike handling is based on human perception within tiny samples that would not pass muster with any scientific journal or conference, not on measurements with repeatable, controlled inputs eliminating the possibility of unconscious bias. We will need a cycling robot in order to do real science on this aspect of bike handling. Maybe not far off in the future! Even then, the conclusions may not matter to human performance, perception, or pleasure.

    Many Rivendell owners ride with front loads and report none of the problems or suboptimal handling "it is said" this arrangement causes. Has the designer of your bike written anywhere that the design is optimal for carrying heavy leads in the rear but only moderate loads in the front? Photo evidence from his web site suggests that he and his friends often carry substantial loads on the front of Rivendells. In truth, the idea that mid or high-trail bikes such as Rivendells are optimal for carrying heavy loads in the rear but only moderate loads in the front is pushed frequently by commercial competitors of Rivendell with a vested interest in selling the accouterments of the rando style bike.

    One thing Grant Petersen definitely wrote, in the Reader after riding his experimental, variable trail fork, is that it is hard to make a bike that is not fun to ride.


    >the handlebar bag - with the same amount of weight in it - does not appear to affect speed at all, whereas the saddlebag does a bit.

    Is this measured, or your perception? Measured or not, how do your expectations, unconscious or otherwise, affect performance? Can you repeat your input identically, in order to assess this perceived phenomenon over a series of trials? Where's that robot when we need it?

    I use the baggage that works for me and that I like, on a bikes with low trail, mid, and high. It works fine on all choices. Having extensive experience on bikes across a broad range of front-end geometry, I regard the trail dogmatists as so many medieval theologians counting angels on the heads of pins. My riding buddies who are scientists (employed as scientists, present their research in conferences and journals they do not control, submit their work to review by peers they do not get to pick) concur on this matter. The human motor on the bicycle is elusive to science and engineering. That opens the door to myth and lore, debate and dogma.

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    1. Your comment appeared in a weird location (as a reply to another, unrelated comment), so I took the liberty of reposting it here without editing it in any way. Hope is okay.

      "Perhaps it is not so wise to accept things you read online and in 'zines as fact"

      Absolutely. That is why I wanted to try the hbar bag. Some Rivendell owners I knew told me they loved having a front load, others said the opposite. Could depend on the bike model and how they have the bars set up to. I took a chance and it worked out great.

      Regarding the handlebar bag vs saddlebag affecting speed: It is my perception, measured non-scientifically, based on how well I can keep up with the same person/people on the bike. Indeed where is the robot when we need it.

      It is fun to speculate, especially for science types, but I agree that experience is the only thing that matters.

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    2. Maybe not elusive to science and engineering, but rather not funded, as far as I know, except a couple distinct unrelated studies (like the self-righting bicycle) I recall seeing/reading about.

      Wouldn't it be nice if MIT (or, you know, somebody) got a grant for human-propelled vehicles lab in the amount of--oh, let's not skimp on things--NN million and matching endowment funds for... Okay, I need to stop dreaming. :)

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    3. Well you joke but they get grants for things like "the Copenhagen wheel". It's all in how you spin it. So to speak.

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  18. Spoke count on the wheel set being used, center of gravity of the load, and the age of the bike need to be factored into the equation as well. Just a guess, but a twenty plus year old bike with standard diameter tubes, minimal spoke count wheels will feel whippy in comparison to a freshly built Riv with O/S tubes, psuedo compact geometry and 36 spoked wheels. Another factor in regard to loaded handling characteristics and fork trail is the fact that fork trail deminishes as wheel and tire diameter increases. The difference between a 32mm tire and a 42mm tire may effectively shorten fork trail by as much as 5mm to 10mm (depending on head tube angle, actual wheel size (650B vs. 700C, 10mm is a larger percentage on 584mm e.r.d. vs. 622mm e.r.d. rims), which may cross the "just noticeable difference" line, whereas the Moser is stuck in the 23mm to 25mm tire range with hardly any difference in trail and therefore handling, other than the friction created by the slightly larger contact patch of the 25mm tire.

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  19. I don't quite understand what you mean by speed. Are you suggesting that the top speed of your bike varies with where you put the weight? I can understand this if the aerodynamics are changed but I can't see what difference the weight placement itself will make. Handling is another matter and obviously weight placement will affect it.

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  20. I generally keep the handlebar bag on the bike even on fast rides with the club.adipex online I use 38mm Pari Motos for tires. Great bike.

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