Frame flex

[si_c]

Was on the way home from the shops yesterday at a set of lights on a slight downhill, so had the brakes on full. Was tapping my foot (flat pedals) on the left side and noticed that the bottom bracket was being deflected about half an inch to the right.

It is a steel frame, and I know that steel flexes, but I was surprised at how visible it is. I'm not worried, but I was surprised as I wasn't tapping particularly hard. How much flex is normal / expected on a frame?

 

[Smokin Joe]

Depends on the frame. The better the quality of material and builder the less flex you'll get, but as you say steel does flex more than other materials.

What frame is it?

 

[Tim Hall]

And how much of what you saw is down to the tyres "squirming" under the sideways load?

 

[screenman]

Or the wheels and tyres.

 

[Yellow Saddle]

Your bike, like most multispeed bikes, has a built-in frame flex indicator. It doubles up as a front derailer. Does the frame flex so much that you cannot get rid of the grind no matter how you trim the FD? Probably not, therefore the frame flex is minimal. Drink beer, ride bike, ignore flex.

 

[si_c]

It's an old peugeot HLE frame, not the best quality I'll readily admit but it's lots of fun, comfortable to ride and I haven't noticed any flex while riding, just noticed it when stopped yesterday. Could well be down to a bit of wheel and/or tyre flex, I'm gonna pop out later, so will try to replicate

Like I said, I'm not even remotely concerned about flex, I was just surprised as to how much there was when stopped and was curious as to how much steel, and for that matter other materials, can flex. I would have thought that there would have been less at the bottom bracket given that it is the confluence of two triangles.

 

[ayceejay]

Just to be sure why not check the condition and tightness of your head set?

 

[si_c]

Just to be sure why not check the condition and tightness of your head set?

I already checked that, the headset is new, done just over 500miles, I tightened it up a week or two ago, and it's still tight, I checked that when I got home, just in case.

 

[Citius]

Unless your frame is actually broken, it won't be flexing that much.

 

[Gravity Aided]

I think sometimes, when we see something flex a bit, we see it greatly magnified, because it is worrisome. Still, I've never known HLE to be particularly flexy, more like rigid to a fault. Columbus is what always worried me, at least on my Schwinn Passage, which had a checkered career in psychlocross before coming to me, a rather heavy rider who made it back into a touring bike. You could grab the saddle and handlebars on that and see it flex.