Frame flex

[khe killah™]

Just wondering how many of you suffer frame flex and if so what frame are you riding...

On my drive side when my crank is parallel to my chainstay i have 7-8mm of clearance but my chainstay has massive chips from the crank arm hitting it! Pretty sure this happens when im up in the time machine. My old RIP had exactly the same chips, so the frame is flexing alot! I also found sometimes it feels as though it's twisted slightly or the headtube angle change's very slightly. There are no cracks or ripples or signs that it's gonna break but where the tubes crossover im sure it twists after a big whip but then relaxes after a few minutes...

Anyone else have similar issues

[Topsey]

My old KHE Tantra flexed like buggery, Im pretty sure its the use of thin tubing. My Zion Focus is solid as rock but its a good 3/4lbs heavyier!

[stuntnuts]

For me it seems like it's the cranks that flex into the stays when the bike crashes on it's side and the pedal hits the ground first.

[SNOOP]

^ This dude has it. Whats going on, is your crank arm flexes and comes into contact with your frame.

If your bike were flexing that much, to actually make the frame contact the crank.. Instead of the other way around... The frame would of probably broke by now from work hardening itself in those particular areas.

[khe killah™]

Yeah, never thought of that... What a dumb ass! Lol

Still, the front end still feels like it twists and the headtube angle changes... That tube crossover is where my old frame bent.

[EZChris]

on my old st martin i could physically flex the rear end with my foot with the bike flat on the ground - due to lack of lower bridge on the chain stays.

[mare]

^ This dude has it. Whats going on, is your crank arm flexes and comes into contact with your frame.

If your bike were flexing that much, to actually make the frame contact the crank.. Instead of the other way around... The frame would of probably broke by now from work hardening itself in those particular areas.

completely wrong statement!
this problem is caused by the frame flexing not cranks. those r way too short to flex that much. that hapens when pedals hit the ground before pegs and not from timemachines. i had that problem on my mankind alive because tubes have way to thin wals. i have no problems with that with my razzia frame.

[sakis]

i have that problem too with flatware frame and profile cranks..

[cunners]

grind the backs off, works a treat

[khe killah™]

grind the backs off, works a treat

Crankless... lol

[SNOOP]

^ This dude has it. Whats going on, is your crank arm flexes and comes into contact with your frame.

If your bike were flexing that much, to actually make the frame contact the crank.. Instead of the other way around... The frame would of probably broke by now from work hardening itself in those particular areas.

completely wrong statement!
this problem is caused by the frame flexing not cranks. those r way too short to flex that much. that hapens when pedals hit the ground before pegs and not from timemachines. i had that problem on my mankind alive because tubes have way to thin wals. i have no problems with that with my razzia frame.

Hmm.. Maybe for you, but I checked today. There is noway my frame is flexing from a timemachine to hit the crank arm so hard, that it dents it. Noway.  But I did notice I can stand on my crank arm with the bike laying down and almost get contact. So this just leads me to believe if dropped/ force down upon in that way.. It will contact hard enough to dent.
Also riding the first gen mankind alive.

[metalbmxer]

Ok I am chiming in. I have personally seen a demonstration of frame flex by pressing one's foot on the seattube area while holding on to the handlebar. Here's the kicker--it was from the welder himself explaining that non-heat treated frames last longer because the flex dissipates force that would normally fatigue the welds on a heat treated frame.

[pwh4130]

They are all going to flex a bit but it sounds like adding a spacer on your spindle would help.  You need more that 2mm clearance between the CS and the back of the crank arm.  Also, with frames with low standover, you are going to get more flex.  Smaller triangles=not as stiff.

[tod miller]

Ok I am chiming in. I have personally seen a demonstration of frame flex by pressing one's foot on the seattube area while holding on to the handlebar. Here's the kicker--it was from the welder himself explaining that non-heat treated frames last longer because the flex dissipates force that would normally fatigue the welds on a heat treated frame.

This.  If frames, bars...etc., didn't flex, they would all be snapping!  Every frame flexes, and every crankset will flex to some degree.  The dents in the chainstays is probably a combination of both, especially when dropped.

[tod miller]

They are all going to flex a bit but it sounds like adding a spacer on your spindle would help.  You need more that 2mm clearance between the CS and the back of the crank arm.  Also, with frames with low standover, you are going to get more flex.  Smaller triangles=not as stiff.

+1