How much flex to expect from my bike?
 

http://bikeforums.net/attachment.php...hmentid=181291Hello everybody,

My wife and I just came back from a 3 day mini tour, our second all in all, and the first thing I noticed when I got on the bike fully loaded, was that it flexed quite a bit.

It kept bugging me the rest of the trip, and the bike's front never ceased feeling twitchy and unstable.
It is a Marin Kentfield, Old Man Mountain rear and front racks, Mavic A319 wheels. As far as the load goes, I had Arkel T42+T18 bags (front and rear), plus a sleeping bag on top of each rack. I didn't weigh the gear, but I would be surprised if it was more than 35 lbs.


So, as I said, the first thing I noticed as soon as I got on the bike was that if I apply the slightest pressure on the handlebars, the top tube/headtube would move about 1/2 an inch in each direction.
I don't remember feeling this on our first tour three years ago, but then I was in much better shape, a lot stronger and a lot more used to the bike.

Is this something that is normal on a proper touring bike, or is it just because the bike is a cheap city hybrid and not really suited for fully loaded touring?

Thanks,
Emil

The movement you describe is not normal and not safe. Could be the stem needs to be tighten or replaced, or it could be a cracked frame. Take it to a mechanic to diagnosis.

Looks like the frame is a bit small on you based on how much seatpost you have extended above the seat tube, the fact that you can stand over the bike and clear it by almost 12" it looks like.

I have a bike that is too small for me that does the exact same thing you mentioned with flexing. I imagine you're going to have flex simply due to the leverage you're applying to the extended stem/handlebars. You might be able to find a stem that is a lot more rigid, but the best solution would be to get a frame that fits you better.

This is a great excuse to bike shop ;). My touring bike allows a mere 1.25" clearance -- but it's more than enough and it is such that my seatpost extends only 2" out of the frame and my bars don't need a lot of extension to maintain a level position with the saddle.

Huh...Interesting...I thought this bike fit me perfectly. You're right, I do have the seatpost and the stem at their maximum height. Didn't think of that.
And you're right, I'm only using this thread as an excuse to bike shop. Just need a few more replies to present before the wife. :-)

youre going to get many responses that may or may not have anything to do with addressing your problem. Assuming all parts are tightened etc., it is normal that a loaded bike will have some lateral flex in the frame. some people dont mind this, others do. If you want less flex, a bike made from larger diameter steel tubing will be better for you...

I definitely didn't like this feeling, so maybe steel is the way to go.

A question that I have often pondered regarding bikes being sold too small - doesn't riding on a bigger size bike necessarily push the handlebars further out? If so, doesn't it, at least partially, negate the effect of the taller head-tube on the larger sized bike on handlebar height?
I read this, among other places, on the Rivendell site, and was somewhat confused. Bike's are being sold too small, so handlebars end up lower than is optimal or desirable. Okay, but doesn't the longer TT force you to extend further forward and cause discomfort?

Also, TurbineBlade - come to think of it, it's a bike with a sloping geometry - standover and seatpost extension are bound to be higher, on this kind of bike, no?

My Jamis Aurora flexed quite a bit when standing, it was built with 520 tubing. My Novara is built with the same 520 tubing but a much larger downtube. It is worlds stiffer when I get out of the saddle and pedal.

The Aurora felt like it was wagging it's tail when standing during a climb... and I prefer to stand more than most so I really notice it.

I have had this problem on several of my touring bikes - first on a British Raleigh Randonneur back in 1998 when I did my TransAm, then again with a Novara Safari which got in 2008. It seemed to me that the frame itself was definitely flexing. Since then I did some research and ended up looking at the Co-Motion Americano, because those frames are made very stout, with oversized tubing which increases stiffness. Sure enough, no trace of flex on that bike (I have one now, and love the ride).

It's my opinion that a bike made for loaded touring should be stiffer than one that is made to be ridden primarily unladen, due to this flex issue. I also think that oversized (large diameter) tubing is an important aspect of getting this stiffness. However many people use "normal" bikes that don't have oversized tubing or particularly stiff frames for loaded touring without any issues, so it's obviously not quite that simple - maybe they just don't notice the flexing.

I also think that the rider's height and body proportions affect the way they sit on the bike, which can then affect handling (e.g. having relatively longer legs and shorter reach (arm/torso combination), as I do, means I tend to put the seat up higher on off-the-shelf bikes that are short enough to fit me in the top tube, thus putting my weight higher and further back over the rear than usual).

Basically if you notice frame flex, then try out something like the Americano - you'll definitely see a big difference, those bikes are rock solid, probably the strongest frames out there bar none. If you are ever looking at buying a touring bike, then make sure to test ride it fully loaded before purchase. Ask the bike shop if it's ok to fit your own racks and panniers - any good shop will let you do this. Then you'll be able to tell right away if you're getting that flex or not. I will never buy another touring bike again without being able to test ride it fully loaded first. This might be difficult with a custom builder, but they should still be able to provide you with a representative test bike - it might not fit perfectly, but at least you'll be able to get a sense of how it handles the load. In fact, you don't even have to ride it to get a rough sense - just load it up, then hold it by the saddle and shake it side to side. If the frame is flexing, then you'll feel it.

Frame material is not the main predictor of frame flex, but rather tubing diameter. Some aluminum frames are very stiff - e.g. the Cannondale touring bikes are famously rock solid under load. Most aluminum frames use oversized tubing, but not all - my Novara Safari was aluminum, and it flexed a lot.

The important tubes seem to be the top tube, down tube and chainstays. On my Americano the top tube is 1 1/8" in diameter, downtube is 1 1/2", and the chainstays are 1 1/2" tall.

Neil

in all honesty, i doubt people are going to come across many shops are going to let a rider mount up racks and panniers to a bike for a fully loaded test ride. not to mention even having suitable touring bikes to test ride in the first place!

there are many bikes out there aside from the americano that will be stiff...

basically any bike made with oversize tubing will be loads better. also, compact frame geometry will help due to the smaller (stiffer) triangles at play. My TT silkroad is very laterally stiff (columbus zona OS tubing) as is my roberts roughstuff (reynolds 851 and columbus nivacrom OS tubing). my Kuwahara and specialized expedition are both much more flexible - standard gauge 531 (or equivalent ishiwata 022). They also have traditional 'square' geometries, so even though there is less seatpost showing and smaller stem length, they flex more. one way to see this is to load the bike, grab the stem and wiggle side to side to generate wobble without letting the wheels move at all....

that said, flex isnt a bad thing (provided the bike doesnt shimmy at high speed) its more of a preference. I prefer stiffer rides for most loaded riding.

The shop here in Eureka that had my Rocky Mountain Sherpa was quite happy to let me put my own racks on and take it for a test ride. I really think that any bike shop which is serious enough about selling touring bikes to actually have them in stock will understand completely the desire to test ride fully loaded. As long as it's your racks, where's the harm?

I was actually surprised at how many touring bikes I found in stock here in Eureka CA. Sport and Cycle had the Sherpa, Henderson Bicycles had a Trek 520 in the window for a while with full racks and Ortliebs, Pro Sports had the Salsa Fargo, and Adventure's Edge in Arcata had the Jamis Aurora. Pretty good selection, I think! They all seemed very open to me taking their bikes for fully loaded test rides. It's all part of the sale - you just need to reassure them that there won't be any damage to the bike in the process. If a bike shop won't let you do this, then I would find another bike shop, to be honest - a touring bke needs to be test ridden with the type of load that it is going to be used for, because everybody knows that a bicycle handles very differently when loaded up. I have purchased too many touring bikes now that seemed great riding around the parking lot unladen, only to find that they wobbled like a wet noodle and shimmied under load. Never again.

Neil

Well if my Novara did what you are talking about Neil... I would take it back to REI and get a full refund. Seems about the best way to deal with most stores carrying next to zero touring bikes in stock in my area. If I drive an hour I might be lucky to find a LHT'r.

So if I buy a Co-motion and I don't like it down the road do I get to return it if I can't mount my racks for the test ride? Just curious :)

For some reason that didn't really occur to me. I do love REI's returns policy, but I think part of the reason I didn't do that was that I had already made a few modifications to the bike by the time I realized it shimmied. I honestly don't know if they would take it back after those changes... and I wouldn't want to abuse their extremely generous returns policy. I ended up selling the Safari once we moved to Medford OR, to someone from San Francisco who was going to use it for commuting in town - a perfect application for that bike, I think.

When I was living in St Louis and wanted to get a Long Haul Trucker, I made an overnight trip up to DeKalb IL to see Tobie DePauw at North Central Cyclery (he was great, very patient, highly recommended). That was the closest dealer that had those bikes in stock. I think it's well worth at least an overnight trip to do that, given how important it is to find the right bike that fits you for long distance touring.

Ironically, I ended up selling the LHT in favor of the Safari. I think I was too hasty in that decision. I based it on many unladen test rides around Forest Park in St Louis. Without a load, the Safari was definitely a very perky bike, and felt better than the LHT, so I chose the Safari. I think I also didn't like the toe overlap on the LHT, which wasn't a problem with the 26" Safari. But this was all part of my learning experience - now I know better. The LHT didn't feel as lively, but that's completely the wrong criteria for choosing a loaded touring bike. I was pretty dumb in making that choice, in retrospect. But you live and learn.

I dunno, go ask Dwan! They were very nice to me, though, and let me do a loaded test ride on one of their stock bikes - as recounted here:

http://www.crazyguyonabike.com/doc/co-motion-visit

Neil

Sold your LHT!! Man I love mine ;). It's not some magic bullet though - many other touring bikes would probably have made me happy too.

Don't people typically rant that aluminum frames tend to be much stiffer than steel ones? I know this is a slippery idea, and tube diameter/geometry/construction makes more of a difference than the type of frame material.

I'm still hung-up on the actual size, but it's so common for people to use smaller frames with extra long posts and stems these days that bikes are seemingly never called "too small" anymore. I would still venture a guess that even a much stiffer frame, with that much post and stem hanging out would be pretty "flexy".

And like others said, flex is personal. My LHT had a *bit of flex in the bb/crank area until I installed an SLX triple crank -- stiff as can be, and now I'd say that even standing and cranking up hills loaded isn't "flexy" -- it's fine to me!

Maybe indirectly. It's likely that the machine built wheels that came with the bike have low spoke tension. I've improved the feel (responsiveness, stiffness) of most bikes with cheap wheels by bringing them up to proper tension.

BTW, judging from the size of your panniers, unless you're packing marshmallows, I'd suspect that you're carrying at least 45#, not <35#;)

You should size a bike by the effective TT taking into account bar and stem preferences. I only look at stand over last. My LHT has zero stand over clearance and I have never had an issue of body to frame contact - including riding on soft surfaces.

If you have unusually short legs some models of touring bikes may result in the correct TT being combined with a stand over so high it doesn't work. In that case there are companies like Thorn that offer short and long top tube frames. This also allows folks who want to use drops or riser bars to tweak their fit to work without really long or short stems.

I wouldn't want to ride a touring bike that was so stiff that it didn't flex at all. OTOH riding a noodle with 4 panniers gets old fast.

First I'd ensure you racks and panniers are securely mounted to the frame. If they are not then a lot of your handling issues could be from them vs. the frame.

If they are solid you may want to also look at your weight distribution. Ensure it is even side to side. Then look at how it is loaded front to back. Experiment a bit to see if moving the weight front to back changes how the bike handles.

If none of that works you can either get a trailer or get a new bike depending on what seems more attractive to you. A 2 wheel trailer [ie. Burly Nomad] doesn't exert any twisting forces on the frame so your bike should handle fine.


I had a MTB I loved, but with 4 panniers on OMM racks it was a noodle and not any good to tour on. Unloaded or lightly loaded with slick tires it served as an awesome urban assault commuter. I decided to buy a Surly LHT and have it enjoyed it a lot.

That does sound like a loose headset.

As for other flex. I've got a reynolds 531 frame with 700 wheels, and I was surprised when I first rode it how spongy it all felt, esp with front panniers affecting a certain sway.