Frame flex? Will it break?
 

Hi.

I have a 2006 Trek pilot 1.2 with carbon front forks and an average weight alu frame.

I've recently started training for a bike tour by riding my bike with full 40l panniers. (if the pandemic doesn't shutdown my plans).

The problem is that the frame seems to flex a small amount side to side noticeable on the top tube when the panniers are fully loaded. Is this normal? It can make the bike 'shimmy' as you ride and if you are not smooth at slow speed you can see the bags causing the frame to flex side to side. My concern is for the 500 mile tour.

Is this flex when the bike is fully loaded just a side effect of a heavily loaded bike? Would this type of flex go away if I were to invest in a steel specific touring bike designed for carrying loads? Could my light rack be exaggerating the effect? Will this type of flex break the bike frame?

I'm probably over reacting, but ideally I'd like this thread to put my mind at ease.

If it were me, I'd get a steel frame for loaded touring. Steel may flex too; but the stress cycle for steel is effectively infinite, while in the case of aluminum, flex WILL eventually lead to failure.

I would guess that personal injury lawyers probably have access to a data base of bicycle types solved in lawsuits, if so, the types of bikes involved would probably be listed.
Good luck

In the seventies my buddy and I toured all over the Midwest using Pletcher racks. Highly flexible we could always feel the load out back swinging the bike side to side when pushed. Not a big deal, and happily put thousands of miles on those things without trouble. Frame flex will happen regardless of material it is made from, and I seriously doubt the modern alum frame flexes more than the Schwinn Super Sport I used or the Torpado my buddy used, or the Viscount another fella used back in the day.

Ride with confidence as your modern bike is very capable of handling the job.

Cheers. I know it was a bit of a silly question to be able to answer as no one can know for sure.

I guess for now I'll still do the 200km tour on my commuter bike and if I still enjoy touring after this first small bike touring trip invest in a surly disk trucker if i can get one this year if I still enjoy bike touring and want access to something with front racks and potentially a more relaxed geometry.

To the bike shop!

This reminds me of my paper route bike from Sears carrying 70 editions of the Sunday paper. That bike was not safe.

However, if your carbon or aluminum breaks and you are a long way from a shop you may be in serious doo doo. However, a steel frame could possibly be welded by someone close by.

Your bike isn't designed for loaded touring. Some of the flex you feel is caused by the compact rear triangle which puts the load farther back than it would be on a proper touring bike which would have longer chainstays along with more robust tubing. With any bike, or any car as well for that matter, rearward weight bias results in less stable handling. Riding your road bike with a heavy load on your rack is a bit like driving a rear engine VW from the 1960's. That weight gives you great traction at the expense of stability as you go faster

Had you posted that your aluminum frame felt excessively rigid rather than excessively flexible, everyone would have solemnly agreed with you and urged you to buy a steel touring bike.

Experienced touring riders would tell you that the best solution would be to install a front rack and divide the load between the front and rear, regardless of whether the frame is aluminum, carbon, or steel..

Not me. 10,000 heavily loaded touring miles on a Cannondale that didn’t flex.

Two things, as someone said, your bike isn't designed for loaded touring, so no I would not recommend using that bike for that unless you go ultralight.
Second thing, steel bikes can flex as well, and again as someone mentioned it can flex and not hurt the frame any, however when loaded a flexing frame can become a handful especially if descending rather fast, but there is a cheap way to fix that is to buy a Tubus Cargo rack, this rack is made of steel and it's rated for 88 pounds, why a steel rack instead of the usual aluminum rack? Because a rack bolted to the rear will actually act like a sway bar does for a car, it will stiffen up the rear triangle, however aluminum flexes and thus does little for stiffening up the rear end, but the Tubus steel rack being made of steel is a lot stiffer, plus that particular one is rated for 88 pounds which makes the steel stronger than lessor steel racks thus improving the ability to stiffen up the rear triangle even more than a standard steel rack.

Yes that rack cost more than an aluminum rack, but if that 500 mile trip you want to do has any fast descents you'll be glad you got a steel rack. Plus if you plan on doing any more tours the steel won't weaken at the welds like aluminum will over time with all the weight jostling up and down and back and forth as you ride.

Your probably thinking you can't do the tour because you can't afford another bike, well you can still do it by one of two ways. One is to go ultralight, it's not as comfortable, at least for me it wouldn't be, but you're only going 500 miles so you could bear it that long, just google how to ultralight tour on a bicycle. You could still get a steel rack for your bike IF the bike has those bosses added for that, but I would keep the weight low. The other option is to find a used vintage touring bike on Craigslist or Facebook Marketplace, you can find those for around $250, and if it hasn't been abused and been take care of they're great bikes, of course you would still need the rack, and you would have to check out everything on the bike to make sure it's tour ready, if a shop did that expect to spend about $125, just tell the shop what you will be doing with the bike so they go over it better.

If you go used just make sure you google the make and model, some bikes were called touring bikes but the low end components they put on I wouldn't recommend touring on one. Bikes like the Schwinn Traveller, the World, or the Schwinn Le Tour have the implication that they can be used for touring, but I wouldn't do it, however the Schwinn Le Tour Luxe and the Schwinn Voyageur series are the top bikes for touring on, and in the case of the Voyageur sort of easy to find used for little money. Trek 520, 620 and 720 were very good too; those Treks generally go for a bit more money then the Schwinn for some unknown reason, both brands were equal in that department if you ask me.

It may be that trying to buy ultralight camping gear may cost you more then buying a used bike! something to consider.

If you've never ridden a bike with a significant load, I suspect what you're feeling is normal and would occur with almost any bike as bikes really tend to feel more flexible and less stable when you load them up. That being said, bikes designed for loaded touring handle it a lot better than everyday sport bikes and the effects you're noting would be lessened, especially if the bike has front racks. Lessened, not eliminated.

As to whether it is a frame strength/fatigue problem, I'd say probably not, at least for a single tour. Over time and tours, you might start to have more serious issues though. But you could probably make do with this bike for a single tour. I would do everything you could to lighten the load and get weight lower and forward though.

- Mark

If you have the truly all aluminum one it should do ok, if you have the carbon stays which popped up around then I wouldn't trust it, the joints are strong but not meant for what you're doing. Ultra light camping equipment will help as suggested and is better quality if you buy the good stuff but in my experience a long haul trucker would be cheaper.

https://cimg9.ibsrv.net/gimg/bikefor...edc1f84c20.jpg
You just need the proper jersey

I went to my local bike shop the other day and they said not to worry about it, probably because I was buying a new bike. One of their customers had done a massive ride on the same bike without problems so I think I'm good. The frame is 14 years old now so I'm sure if it was going to break, it would have failed by now.

I just wasn't really used to seeing fully loaded frame flex on a bike, but I have heard it's a normal thing. But I'm still getting a touring bike because I want a bike built for the job and since I was hospitalized years ago on a mountain bike crash I'm finding I need a more relaxed position for anything over 50miles or 7 hours as the neck starts to hurt like hell otherwise. Basically, even with small things it didn't leave any room for emergency food rations and it's a bit disconcerting riding a fully loaded bike that you can lit the front end with your little finger because it's so light.

This thread and my own personal testing did convince me to buy a new bike though and I think when we're allowed to go touring again I'll be much happier on a surly disk trucker and the current bike will remain the good old faithful daily / commute bike.

From my own personal experience I'm glad I did some equipment testing before actually going touring and riding the miles I would need to ride and carrying all the stuff I'll need. Plus I've been riding more and further and using the bike more and enjoying riding more,

Hopefully get the new bike before I can go on the first week long tour, otherwise I'll put old faithful to good use.

That's not how aluminum works. But regardless of the frame material, if you load the panniers, then grab the saddle and move the bike side to side quickly, and if you feel 'wiggle,' it's probably the rack flexing, not the frame.