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-   -   How Hard to Inadvertently Bend Steel Frame? (https://www.bikeforums.net/bicycle-mechanics/964219-how-hard-inadvertently-bend-steel-frame.html)

skamen 08-05-14 05:44 PM

How Hard to Inadvertently Bend Steel Frame?
 
This is probably a ridiculous question but I'm wondering how hard it is to inadvertently bend a steel frame. I have a Surly Long Haul Trucker Deluxe (the one with S&S couplers) and I jumped a bit to quickly put all of my weight (about 150 lbs) on the top tube to see if there was enough air in the bike tire. I'm guessing that I'm being overly paranoid but is there any way I would be able to bend the top tube by quickly putting my weight on it? There's no distinct bending in the frame but I'm wondering how I might go about checking for minor bending. Thanks!

Dream Cyclery 08-05-14 06:00 PM

You can use a level to check, but I doubt that you bent your frame by sitting on it. Surly frames are tough.

gl98115 08-05-14 06:07 PM

Put a straight edge up against the top tube at various orientations. A ruler should do.

HillRider 08-05-14 07:22 PM

Unthread the coupler nut in the top tube, then start and tighten the nut again. If it unthreads and rethreads smoothly, the top tube is still straight.

zukahn1 08-05-14 07:28 PM

I doubt you could bend better quailty strait steel gage frame icendentally. I have crashed sinilar frames into curbs at 20miles an hrs that held up fine. And I no others that readily ride them down stairs no issues.

FBinNY 08-05-14 07:38 PM

The human eye is amazingly sensitive. If you sight down the tube like a ***** you'd be able o spot any bend.

But I'd be amazed if you discovered a bend. These tubes are extremely strong, and are much easier to dent then bend.

zukahn1 08-05-14 07:48 PM

Yes look close I have never seen a bent tube that did not have at least one fairly visible ding or flaw. But Don't look to close becease you will see a lot of flaws on nearly any lesser production bike that don't realy matter.

Dan Burkhart 08-05-14 08:21 PM

I dunno about bending the tube but quickly putting your weight on the top tube with that part of the anatomy that is normally poised over it, YIKES!

RandomTroll 08-06-14 12:29 AM


Originally Posted by skamen (Post 17009935)
I jumped a bit to quickly put all of my weight (about 150 lbs) on the top tube to see if there was enough air in the bike tire.

I recommend a pressure gauge.

I broke the braze, where the seat tube connects to the bottom bracket, of a steel frame about 20 years ago. The nice thing about steel is how easy it is to fix. I don't think I'll have as easy a time fixing a break in my aluminum frame.

Looigi 08-06-14 08:32 AM


Originally Posted by skamen (Post 17009935)
... I jumped a bit to quickly put all of my weight (about 150 lbs) on the top tube to see if there was enough air in the bike tire....

A bit OT, but I don't understand this method checking tire pressure. How does it work?

Sixty Fiver 08-06-14 08:35 AM

My brother in law drove his Surly LHT into the back of a car at close to 30 miles per hour... he bent the fork beyond belief and only put a minor bend in the frame.

Overbuilt is an apt word when it comes to describing how tough these frames are.

Wilfred Laurier 08-06-14 09:01 AM

i have been around or above 200 lbs since i was a teenager
and me and a friend used to race down a certain hill sitting sidesaddle on our top tubes
of a much lighter steel frame than a lht

i am not saying it was a good idea
just that you have absolutely nothing to worry about

ThermionicScott 08-06-14 11:04 AM


Originally Posted by RandomTroll (Post 17010934)
I recommend a pressure gauge.

Or pinching the tire as a bare minimum... jumping on the bike makes no sense -- if it doesn't pinch-flat, you have enough air? :lol:

Reynolds 08-06-14 11:32 AM

It's extremely unlikely you can bend a good quality steel tube like that just by putting your weight on it.

fietsbob 08-06-14 01:04 PM

Ive inadvertently ridden over a concrete wheel stopper block which was across one lane of the street ,

at night in the dark .. (inadequate lights)

went over it, didnt end up on my face , but the downrube suffered a rumpling bend. from the fork coming back.


I imagine once the S&S coupler is disconnected bending the tubes is relatively easy ,

because of the leverage of the length of the tube.

RandomTroll 08-06-14 06:36 PM


Originally Posted by ThermionicScott (Post 17012114)
Or pinching the tire as a bare minimum... jumping on the bike makes no sense -- if it doesn't pinch-flat, you have enough air?

You have strong fingers. I can't tell the difference between 100 and 70 psi with my fingers. I'll pinch when I'm on the road and worry I've a leak, but at home I measure.

Thermionic? Isn't that an out-dated super-power, now that transistors have replaced tubes? I never saw your comic books.

ThermionicScott 08-06-14 07:40 PM


Originally Posted by RandomTroll (Post 17013359)
You have strong fingers. I can't tell the difference between 100 and 70 psi with my fingers. I'll pinch when I'm on the road and worry I've a leak, but at home I measure.

Right, I measure at home, too. There's a gauge built into the floor pump, so why not.


Thermionic? Isn't that an out-dated super-power, now that transistors have replaced tubes? I never saw your comic books.
LOL, I do like vacuum tube guitar amps. ;)


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