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Question:

Why bike frame (often) breaks at top tube/head tube ?

( Mine and ) some other aluminum ( $1000+ bikes) frames got broken at top tube 2-3 inches before head tube joint.What kind/type/direction of force is causing it???I can not speak for the others but.I'm 175lbs,all stock parts.Suspension front fork 80mm.No abusive riding,mostly commuting and long haul trips with backpack or seat post-clamp rack (bags never exceeded 30lbs.)I can almost understand drop-out zone frame cracks/breaks at the back.but this thing where the tubest are largest,welding seems strongest - that's way beyond me.

Answer:

There is a reason why the tubes are large in that areaThere is a lot of stress on the top tubeThe fork acts as a lever, the bottom of the head tube is a fulcrumWhen you hit a bump in the road, the fork legs are pushed backwards and the top of the steer tube is pushed forwardThe fork and wheel form a very long lever, and the forces at the top tube are much larger than the force pushing back the wheelThe shorter your head tube, and the longer your fork legs, the bigger the force along the top tubeThe result is that the tube can crack
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Fox news will have a field day, and there will be a little re-training or some new added to the SOPs for the day!
Again? Mexican military invades US all the time, and it has gone on for at least a couple of decadesMex govt repeatedly interferes in US sovereignty, and that has gone on at least since the Clinton Admin, tooThat worthless POS, BO, is completely clueless as to what 'sovereignty' is or means, so he's not about to tell Mex stuff it! Which is exactly what they need to be told! Mex is an enemy, and needs to be treated as suchThat Stinker, BO, will never defend US bordersIt is up to citizens to demand Congress act appropriately, defend the Constitution and defend the borders and the citizens of the US.
Hmm, that's interesting,,,I find it hard to believe the Mexican army doesn't have access to a GPS device, or a map,,or at least one soldier that would recognize the border when they got closeI also don't think the cartels would be stupid enough to try anything that bold, even if they got across the border they would have to realize they would all be shot shortly after entering the U.SWe don't play thatThen again, maybe the soldiers were deserting, trying to get away from the cartels.

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