Wassup guys!

My chain rubs my FD whenever I stand up and mash on steep hills. I adjusted my FD properly, it never rubs otherwise.

I'm 240 lbs and I ride a Schwinn Fastback(the one in my signature). It's an entry level bike, so it comes with low level components to say the least.

So my question is, what's most likely to flex? The frame or crank?

There is always flex in the bottom bracket. It's made more noticable when you are are a big guy pushing big gears. How bad is the rubbing? Does it derail the chain or just click?

Have a look at this (look under "clicks"):

https://www.jimlangley.net/wrench/keepitquiet.html

and where is it rubbing? (which part of the fd)

Thanks guys.

It's the chain rubbing the cage of the FD. It's just a noise, it didn't derail or anything. And it never does that except when I mash up a hill.

The rubbing itself doesn't bother me, I'm just worried that all those flexing could cause metal fatigue.

In my experience, long before you flex the frame so many times mashing up hills that it becomes structurally unsound, you will be riding a different bike. (Truth is, you will be riding your fourth or fifth bike before that bike is fatigued like that. And at that point, the bike will be under some delivery guy bringing you pizza.)

Welcome to the Clyde club.

yep that happens to many of us Bigger folks Esp with steel bikes.

I have a surly cross check and My bike often enough will auto shift when I start mashing due to bottom bracket flex I keep the cable well greased.

As for your FD that happens to lots of people Clyde or not , many times the FD just needs a better tuned adjustment.

Or get FD that has a greater swing range Thats what I did I went from a Deore LX (older) and installed a Plain Jane DEORE instead.

The plain jane Deore had more swing than My Deore LX so now I can move it away further when Im on my top ring.

"John"

Happens to me too. I usually have to gear up or the chain starts slipping as well.

slipping chain is something different. Is it slipping around the chainrings, the gears in the front? If so, you should check for chain stretch first. (Google it but basically you count 12 links of your chain and measure pin to pin. It should be within +/- 1/8 of an inch.)