A couple of weeks ago I took my bike on it's maiden loaded voyage, some 70 miles from Austin, TX to Palmetto State Park over concrete, asphalt, chipseal, and dirt road (more on my blog - www.work2ride.com)

The gear weighed about 34lbs and I had it balanced left to right (was able to ride easily no handed) and 70% in the rear 30% in the front. The issue with flex in the frame that I had was when I stood to pedal the lateral flex in the frame was noticeable enough that I didn't want to tempt fate and bend the frame, so I stayed seated.

I was also able to reproduce the feeling in the frame when I wobbled the handle bars from side to side (not turn) while riding. Is this normal for loaded touring frames or should I worry about it?

The good news is otherwise the bike handles great even at 30mph+ downhills, no shimmy or shakes at speeds or turns and can't reproduce when not loaded. I also tested moving the weight distribution rear to front to what I guess to be about 60/40 or 50/50; moved the heavy blue bag to the front rack.

Next I plan to try without the blue bag at all and put everything in the panniers.

here is my direct experience with flex:

On any of my standard diameter tubing frames with "square" geometry like your bike ( for example, 1985 trek 620, 1984 specialized expedition, 1982 Kuwahara Custom) the frame will laterally flex a bit as you describe when loaded. Many (including me) feel there is a balance between comfort and "noodliness" of the frame, due to vertical flexiness

The bike frame will not bend, so dont worry about that... but it will "spring" from side to side, especially when climbing or pedaling hard. This can be a good/fun thing on fast road touring, but more of a hassle when slowly climbing or offroad (IMHO). Occasionally when pedaling very hard, the crank arm might even hit the frame a tiny bit, or the chain will rub on the derailleur due to BB flex... nothing to worry too much about- just sit back and feel strong

Really, the only way to circumvent this lateral flex side effect, (assuming same load and riding) is to build a frame from oversized diameter 'OS' tubing. I have two 26 inch wheeled bikes: a Roberts roughstuff and a Tout terrain Silkroad both build form OS columbus and/or reynolds steel. In addition these bikes have compact geometry, which also adds to their stiffness. Neither of these bikes will flex laterally, and they are therefore more surefooted beasts of burden, but they can be harsher to ride. I make up for that by using 40-50mm tires at lower psi, thus retaining stiffness while at the same time maintaining dampening of road vibrations.

You should be proud of that bike, it looks great. (ditch the boat-anchor surly front rack though )

posi, interesting that you have a Kuwahara, rare bikes. My old touring bike is a 90 or 91 Kuwahara Caravan, quad butted. My experience with that bike (which I did all my loaded touring on) is similar to what you describe. I'm not a big guy, nor particularly strong, so I dont recall ever seeing the crank move too much, but compared to my aluminum bikes, it is clearly more flexible and one can definitly feel it when pedalling hard. What is clear is that I am nearly always seated, and while one can clearly see and feel how more flexible it is, it still has a nice nice ride. My modern alum cross bike is somewhat more harsh, but not overly so, and is more flexible than my older alum mtn bike that I use with slicks (curved rear stays versus straight ones on the Rockhopper)

I would say that what you are describing Ul, and positron, is probably fairly common. Its hard to say without seeing it how it compares to our bikes, and I understand the concern given that you made the frame and this trip was the first time with some weight on it. I dunno, the fact that you can ride no hands with 35 lbs on it, and it doesnt exhibit any funny business with handling or at speed, would make me think that all is fine.
I guess you could try to compare it to some other steel bikes of similar style, you know, by holding bars and seat with hands, put foot on bb and push abit to see the flex? Kind of like comparing downhill skiis. Would this show a big difference from frame to frame? I don't recall where you did this build, but if it was nearby, I guess the best person to ask would be the frame fellow who did the course for you.
If you werent umpteen 1000 kms from here, Id show you my bike...

All in all, I think Positron summed up things pretty accurately. very good way of putting it and very much close to my experience also.

I shall go and read of your first trip to see how it went.

oh, how was the saddle?

cheers
ps, shorts and t-shirts?? man you guys make me sick (I was on the trainer watching Kung Fu Hustle tonight and it is only -12C tonight)

What you're describing is pretty much what I've experienced with several touring bikes - only I got the shimmy, sometimes at slow speeds (12-14 mph). This only happens with a load. I think this flex only sets up as an actual shimmy if you happen to hit the natural resonant frequency of the frame in some way (with your riding position, weight, load distribution, wheel size, speed - there are too many possible variables to even count here). If you're lucky then you get the flex but no shimmy, if you're unlucky then you get the shimmy as a special added bonus. Sounds like you're relatively lucky, so that's a good thing. However, I personally wouldn't want to have that type of flex on a touring bike, even if it didn't come with shimmy. Reason being, I want such a bike to feel nice and solid underneath me, I don't want to feel like I have to coddle it, or worry about 1 lb being positioned just right here or there. It's a work horse, it should be able to just take the load (in my opinion).

The way to increase the stiffness of the frame is to use oversized tubing - I think that's part of the reason why my Co-Motion Americano is so strong, and I don't see the same flex on this bike at all. It's rock solid, and funnily enough I don't seem to get the shimmy either - so I believe that even if I am close to some resonant frequency, the stiffness of the frame helps to damp it down so it can't get started. I think of the flex like a big pendulum - you might not be able to bend that frame with your hand normally, but if there is a natural flex with a load then that gets it started, and the resonance just reinforces it. So stiffness helps keep it from even starting.

I had a really bad flex and shimmy on my 1998 TransAm bike (a British Raleigh Randonneur) and in Yellowstone I took a day out to try all sorts of different combinations of load distribution. I found nothing seemed to make any difference. Who knows why that was happening... you may be luckier, if you can find a certain way of packing that stops the flex, but I think it's probably simple: You have a flexible frame. Short of building a new frame with oversized tubing, you can't really change that. In my view, touring bikes need to be built much more beefy than normal road bikes, but for some reason many "touring" bikes are made with standard diameter tubing, and they will flex. I guess for many people, they don't notice it or they happen to not get the shimmy, so it's not worth changing. Maybe I'm in a very small minority with my experience - I must be, otherwise they would have changed the standard designs before now.

A good, quick test is to load the bike up with front and rear panniers (and bar bag if you use that), then hold it by the saddle and try shaking it side to side. If it's just too flexy then you'll be able to feel it under your hand, it's just obvious that the frame is flexing side to side.

Neil

My Jamis Aurora was flexy... my Norvara Randonee not so much. Neither bike did I worry about bending. Flexing... sure.

Even my TCR that has a gigantic bottom bracket and down tube will flex some. Think about the shape of a frame and it's pretty much impossible to get rid of... all you can do is lessen the amount.

This has been a big issue for me, namely because I like to stand often when I ride.

I came to the same conclusions as the other posters: the only way to cut down on that "whippy" feel on a loaded bike is to have a super sturdy framed bike. My 25" Trek 520 does not fit the bill. With a load, that bike is all over the place.

I almost bought a Thorn Nomad since they are supposed to be very sturdy, but I tried a Burley Nomad trailer and it solved all my problems in that particular area. The bike rides almost like it's unloaded when towing the trailer, no frame flex at all. I can work it as hard as I want and it's solid.

Adventure Cycling Association offers a pretty good tutorial on touring frames and bike choice which addresses teh idea of frame flex... For example, that's why the top tube on many touring frames is so hefty.

https://www.adventurecycling.org/reso...e_Schubert.pdf

Does a titainium frame flex more than steel or aluminum?

I would just caution the OP that if this was your first loaded tour on that bike you may still be adapting to the bike and no changes may be needed.

A few years ago I flew my LHT to a winter tour. I was carrying a light load, but hadn't been on a bike a lot due to the Canadian winter for a few months. My initial ride was so unstable I feared something was wrong with my bike and I would have to call off the tour.

A week later [having made no changes] I was riding one handed on the white stripe at the egde of the road opening a package of pastries with my teeth and one hand while enjoying the scenery. Same bike, same load, same rider, but I had some time to get in sync with my bike again.

Initially I found riding a loaded bike while standing was awkward and flexed the frame a lot. In relatively short order I adjusted to it and no longer found it to be a problem. The adjustment just seemed to happen with no conscious effort so I am not exactly sure what adjustments I made.

Interestingly enough after a couple months on the road, riding an unloaded bike while standing took a bit of readjustment, but that was a matter of minutes as opposed to a longer adjustment in the first place.

The impression I've gotten from listening to framebuilders is that the tubing diameter is much more relevant to frame stiffness than the material itself. In other words it's possible to build a stiff steel bike, or a flexible aluminum bike. I think one reason people tend to associate aluminum with a harsh ride is because most aluminum bikes happen to have oversized tubing (maybe due to the material not being as strong as steel). In fact, though, you probably don't actually want a very flexible aluminum bike, because aluminum has a finite lifespan when it comes to flex, unlike steel, so perhaps that too is why most aluminum frames are built quite stiff.

As for Ti, I would assume that it's also possible to build a very stiff or very flexy titanium frame. It's all in the geometry, and a good framebuilder would be able to make it with whatever characteristics you want/need for the application.

Likewise, I don't think lugged vs TIG welded makes any practical difference to the stiffness - you'll see huge discussions about this flame-worthy topic on some forums, but as far as I can tell the technical consensus seems to be that if you're blindfolded (not a good idea on a bike, but metaphorically speaking) then you can't tell the difference. Again, the geometry and tubing type and diameter make the biggest difference. Tubing type - some steels are harder, e.g. Reynolds 853 is very hard, which allows the framebuilder to use thinner tubing without compromising strength. So there are obviously some choices to be made with materials, depending on application.

Neil

I think most of what we feel as flex is really explained by the steering geometry and interaction with the tires. The bottom bracket does flex, no doubt about that, but I don't think that is the most significant reason that the bike feels like it is flexing.

I saw shimmy was mentioned. Shimmy is a rigid body motion of the wheel/frame and does not involve vibration modes of the frame. We measured the first natural frequency of a frame and it's significantly higher than what you see in shimmy. Shimmy generally seems to be exacerbated by having weight further back on the bike, you have to take that into consideration while touring.

I think it would be very interesting to take a touring bike that shimmies under load, and build a version of it that is exactly the same in all respects (as far as possible), but stiffer with oversized tubing, and see if this version still shimmies. It would be important to keep all the other variables the same - tires, components, racks, load distribution and rider. This would be good experiment, has anybody done it?

Shimmy is very complicated, it has many variables that figure into it, but my intuition is that the stiffer frame will help to stop the inherent flex in the frame setting up the resonant wobble that eventually becomes shimmy. I may be wrong, of course, but I chose my Americano because of its extremely oversized tubing and strong design, and my theory seems to have been borne out so far. That bike has the biggest chainstays I've ever seen on a bike, and the rest of the tubing is also larger diameter than any other steel bike I've seen. I can stand up while pedaling the Americano up a hill, with a full load, and there is not a trace of frame flex. It's just rock solid, the way a fully loaded touring bike should be... and no trace of shimmy. That said, I think I have read maybe one or two comments from people talking about getting slight shimmy on their Americano, so maybe it ain't that simple.

I don't think it's fully understood yet. Ask any bike builder if they can guarantee that their bike won't shimmy and they will likely demur, because it's impossible to predict with any certainty (at least with our current level of knowledge).

Neil

it's normal in touring bikes made with regular road sized tubing that are loaded up. The fact that handling was good going fast and there's no shimmy is all that really matters. There's some flexibility in wheels/tires that can also contribute to the side/side flex you are feeling.

If you wanted nearly zero flex you get a frame with heavy oversized tubing, put on wide 26" rims with heavy sidewalls and never ride it without a heavy load.

You can make any bike shimmy,depends on how you load it.

Try shooting an arrow backwards,everyone knows the heavy part likes to be in front,same with bicycles.Hang a 10# weight,10ft of the back of your bike and let us know how it handles

The more weight you can put in front/down low,the less chance of shimmy,simple physics.The heavier the back of the bike,the more it wants to be in front.

In a perfect world,our panniers would be under the bottom bracket.But since there's not room for them there on most bikes,we must compromise.For the best handling,the rear load should be as low as possible and as far forward as possible.On the front,the load should be as low as possible,and centered with the front hub as possible.Centering on the hub decreases the effect of the extra weight being thrown around either foward/behind the axle.Adding weight in front/behind the front axle adds the FEEL of more/less caster angle(trail for bike people) depending.Weight in front of the axle will make it feel heavier/sluggish because you are actually lifting the weight as you turn,weight behind the axle makes it feel lighter/snappy,because the weight is helping you turn.

All of that said,your still adding weight to the ends of the bike,so it's never going to feel like a "regular" bike,no matter how it's made.

My poor old Shogun gets 60-70% of the weight in front.Sleeping bag,tent,water,anything heavy,goes in the front.Clothes,kitchen,food in the back,and the lightest/bulkiest sleeping pad and tent poles on the top of the back rack.

Cannondale touring bike. Problem Solved.

Yes 'what is ... "normal" ..

My 'one off ' touring frame does not shimmy at all , even with a silly load..

but to achieve that I built it around 2.. 3/4" .049 wall tubes
from a CAT/HPM cargo Bike, Jan helped me put it together..

the tubes are side by side as a top tube,
though they also form the rear triangle as well,
bent at the rear and again at the top of the seat tube.

added bonus the long frame pump sits between the 2 top tubes
so It wont fall off when I hoisted my Bike.

I do have curiosity about whether using a widely ovalized tube 1.125x2.25"?
using thinner wall tube would do the same .. bottom tandem 'Boom Tubes " come to mind..

Tube oriented horizontally for the top and vertically for the downtube..

most factorys use round tube , as its what is most common,
and easier to sell, as people are used to seeing it for 100 years.

my silkroad is made from columbus zona oversized asymmetric double-butted tubing. The downtube is ovalized vertically up near the headtube, and horizontally down near the BB... This design is very similar in theory to the tandem boom tubes you mention.

At some point you are making the tubes more dent prone as you thin them out and make them larger diameter... I think OS tubing is the best 'durable' compromise.

OP, the flex isnt a 'problem', rather, it is a feature which is sometimes more or less desirable.

I saw a caravan a while ago, cool bike. did yours have the chrome fork?

I wanted a Kuwahara BMX ever since I saw ET as a kid, so when I saw this touring frame used, I had to pic it up. No model name, but it is a really nice handbuilt frame with thinned out longpoint lugs, 4 spoke holders, and a braze on for a BB dynamo. Nice features like a lugged brake bridge and suntour GT fork ends too. It is built from Ishiwata 022, and has a low (38mm) trail with 27 x 32mm tires. Turns out to be one of my favorite bikes for sure- I guess they were more common up in Canada, but for all my searching, Im pretty sure mine is a one-off bike.

One experiment with $20000 worth of test equipment is all that is required to prove your intuition wrong in this case. Below the first resonant frequency of a structure, you will not get any vibration in the structure itself. It acts as a rigid body -- you're just shaking the frame back and forth with the fork/wheel. So changing the tubing would have no effect until you made it into a wet noodle. The wet noodle wouldn't ride well enough to even consider as a bike.

It's clear to me that a bicycle is a very complex system of interacting variables (the whole thing - wheels, racks, bags, rider, speed etc) which has some kind of resonant frequency that can result in shimmy. Anybody who has experienced shimmy knows this - it's a self-reinforcing resonance which can quickly grow out of control if you're not careful. And it's also clear to me that the stiffness of the frame seems to affect the way this system resonates - people talk about stopping shimmy sometimes simply by pressing one knee agains the top tube, which dampens down the side-to-side wobble. Just treating the bare frame like a giant tuning fork and making conclusions based on that about the more complex system, seems overly reductionist to me (no matter how much your equipment cost).

Neil

What you say about the first resonant frequency of a structure is true, but you can change that resonant frequency by changing the stiffness or mass of the structure. As a very simple example, imagine a vibrating string. If you put the string under more tension (analogous to a stiffer frame), that will raise the first resonant frequency. If you increase the mass of the string (analogous to putting a load on the bike), that will lower the first resonant frequency. A bicycle is a much more complex system than a string, but I am unaware of any system where the first resonant frequency is not increased by increasing stiffness and decreasing mass.

I suspect that when you load a bicycle, you can lower the first resonant frequency to the point where it can be excited by the rocking motion when you ride out of the saddle. If you build the frame out of a stiffer material, you can raise that resonant frequency back above that range.

interesting about yours. Now I recall, I bought it in 91. It is a greeny colour, will look at frame badge again to see the exact steel, but I do recall it say quadruple butted. No, fork is not chrome. Has 2 spoke holders and spokes on chainstay (never used them, wheels have held up very well overall) I recall also that it was a new model in 91, rated as a very good balance of cost/quality at the time, was also the most expensive bike I had bought (maybe $600?) and had middling to good equipment (LX derailleurs etc--which work fine still) Replaced bb at some point for a sealed one, headset, but rest with good maintenance held up well all in all. I dont think they sold them for more than a few years, and so you really dont see them around at all. The previous Caravans were blue I think, but again, they were fairly rare even then. Oh, it came with Biopace--yuck, changed that out after the first season due to knee issue.
Here it is, seat from my cross bike and regular pedals, but at least you can see how it looks. Interestingly enough, the wheelbase and chainstay length are the same on the Kuwahara as my cross bike.
___________

The points everyone is bringing up are very interesting. For me, the main issues are how (as someone said) there are so many factors that can cause shimmy. Ive only had it happen once, but messing around with position of load got rid of it. As for amount of flex--who knows what is too much. I have had motorcycles and have had head shaking (and even tank slappers) when racing on track, but on bike, really only had a weird shimmy once when touring. It was definitly an oscillation-amplication thing going on which moving cargo around ended up curing (later that same trip, hit 50mph on a descent and all was serene and unflustered)
Again, to UL, if your bike is handling well, I figure that is the important thing.

re Cannondale tourers, I rode a friends Cannondale (from about 10 years back) and yes, they are rigid suckers. Too much unloaded for my tastes, but I could tell that loaded it would be nice. I am tempted to try my alum cross bike with front and back bags loaded this summer, just to see how it compares to my tourer. I suspect that it will be fine, going from how it feels when I have two panniers of groceries on it.

In recalling my touring bike, I suspect too that I would prefer a stiffer tourer if I were to ever think of getting a true "touring bike" again.

booger--funny but my experience has been the opposite, I prefer a lighter front end, for less heavy steering and turn in etc.

I experienced considerable flex when carrying rear panniers only on my Trek 520, enough to be disconcerting when descending bumpy, potholed and curvy backroads. Besides frame flex I also suspected that flex in my rear rack was making a contribution, but definitely putting weight behind the rear axle will exacerbate any flex issues in a frame. The flex was still there but not nearly as bad when loaded evenly front and rear as the bike was designed. Very comfortable, controllable and a good compromise with unloaded comfort.

I eventually moved to a Cannondale T2000 and as others have mentioned it is a dream when loaded.

I would add to this discussion that a super stiff frame is not much fun to ride. Given that some 120lbs riders are touring with 30lbs of gear and some 300lbs riders and touring with 100lbs of gear the amount of stiffness needed in touring bikes varies quite a lot. I've owned a number of different touring bikes ranging from noodly to ultra stiff. I didn't love the ones at either end of spectrum and settled on a middle of the road stiffness touring rig in the Surly LHT. Which makes sense given I weigh 175lbs and tour with 30lbs of stuff.