Caerus Posted January 31, 2011 Posted January 31, 2011 With the way a carbon bike is built, a mortice & tenon join is used and then glued together. If youre too constantly put weight & pressure on here, I doubt people that do this sit on the top tube slowly without putting undue force & pressure around a joint, the joints & frame will eventually crack. I very much doubt they test for that sort over a prelonged period. I stand to be corrected, but I'm baseing this on fibreglass models & moulds Ive made.
Wannabe Posted January 31, 2011 Posted January 31, 2011 Are you not the clown who recently broke your seat tube, and yet you are still man-handling your new bike by sitting on the top tube? That is pretty naughty of you!If the shoe fits, wear it. And yes, like I said, Foxy's post got me thinking and I will desist post haste.
Harry Potter Posted January 31, 2011 Posted January 31, 2011 With the way a carbon bike is built, a mortice & tenon join is used and then glued together. If youre too constantly put weight & pressure on here, I doubt people that do this sit on the top tube slowly without putting undue force & pressure around a joint, the joints & frame will eventually crack. I very much doubt they test for that sort over a prelonged period. I stand to be corrected, but I'm baseing this on fibreglass models & moulds Ive made.Sure, but now their is a BIG difference between carbon and fiberglass The yellow sticker on the carbon Giant frame in the window at the LBS reads "DO NOT CLIMB ON ANY PART OF COMPOSITE FRAME"
numbnuts Posted January 31, 2011 Posted January 31, 2011 Look at F1 cars they are made to handle loads of G forces, but one bump from the wrong angle and all you see is wheels flying. So they are designed for high power stop and go,hard cornering but not for wheel rubbing with other cars. So are carbon bikes mtb or road designed to sit on the top tube?
Caerus Posted January 31, 2011 Posted January 31, 2011 (edited) Sure, but now their is a BIG difference between carbon and fiberglass The yellow sticker on the carbon Giant frame in the window at the LBS reads "DO NOT CLIMB ON ANY PART OF COMPOSITE FRAME" The fabrication process is almost the same, structurally of course they are not the same. Either way I would not sit like that, it will eventually cause a problem with the joint becoming compromissed, if it doesnt crack there it will eventually crack somewhere else. The frame was designed for weight distribution over the entire frame. Not for someone to sit for long periods on the toptube. It may be carbon, but can break very easily as well. Edited January 31, 2011 by Caerus
covie Posted January 31, 2011 Posted January 31, 2011 you are going to have to show us some scientific evidence of that being the case. not just the thumbsuck you're presenting here. and ja haa, like hairy said, look at the two okes in the pic, maybe 200newtons max on the toptube i could think that MAAAAYBE the spesh shiv tt bike might have this problem but most bikes will take that abuse. infact my superlight has that kinked top tube that fits my ass purrrfectly, oh so comfy. Makes sense to me, a bike is desgned for spesific stress points, sitting on a welded or carbon hinged top tube, cannot be good for the bike, its not designed to handle a 100kg of down presure on those joints. Sit on your top tube at your own perril, and remember to whine and moan like a girl when it breaks at the head tube or seatstay, and then tell everyone what a crappy design that bike was.
bikemonster Posted January 31, 2011 Posted January 31, 2011 Are you serious please don’t be rude to me I was not telling you anything Foxy, I don't know atraut personally, but I know a bit about the Hub, and a little about how people work: much of the time, unless a post specifically calls a person rude names, there is no belligerence. Put it down to to mis-communication. When you read a Hub post, you miss any subtlety that may be there. F'rinstance, my post may look like condescension, when all I'm trying to do is defuse a small situation. That is all.
Elvin Posted January 31, 2011 Posted January 31, 2011 LOL... Sitting on the toptube wouldnt do any harm. Felt reluctant the first time when I got my bike cause it feels like plastic, but really, I wouldnt worry about it
Shebeen Posted January 31, 2011 Posted January 31, 2011 Just realised my windsurfing mast is carbon. Going through the washing machine of wavesailing they do eventually break...but it takes a lot of abuse. Way more than bakkies botha could ever do by sitting
'Dale Posted February 1, 2011 Posted February 1, 2011 Great question asked by the thread originator...Makes me think a bit. The earth sucks me down at 74 kgs - not too much stress if a percentage sits on da tube.... Gulp, I hope...
Tokyo Posted February 1, 2011 Author Posted February 1, 2011 Great question asked by the thread originator...Makes me think a bit. The earth sucks me down at 74 kgs - not too much stress if a percentage sits on da tube.... Gulp, I hope... Think about how little Newton/meter you can torque a seatpost clamp stem and handle bar to on a carbon frame
bikemonster Posted February 1, 2011 Posted February 1, 2011 Think about how little Newton/meter you can torque a seatpost clamp stem and handle bar to on a carbon frame Nm, torque, is a twisting force. The twisting force on the fastener creates a clamping pressure on the seat tube. The small number of the torque on the fastener says nothing directly about the pressure on the tube.
The Drongo Posted February 1, 2011 Posted February 1, 2011 After spending a cool R60 000 on my dream S-Works, all I need is for Foxy to come along and tell me what to do with it! WTF, mind your own business Foxy, if it cracks I will source the replacement frame from where the original came from, and that is definitely not your wallet (team manager or not)! atraut We got your little boast - thanks. Were you perhaps the chap who some lady politely asked 'where your helmet was' the other day? Relax buster.
The Drongo Posted February 1, 2011 Posted February 1, 2011 (edited) Nm, torque, is a twisting force. The twisting force on the fastener creates a clamping pressure on the seat tube. The small number of the torque on the fastener says nothing directly about the pressure on the tube. But you got her POINT, didn't you Doc? NO? If you OVER TORQUE, you OVERCLAMP! Good carbon is as strong as aluminium peeps. Move on. (goes to get popcorn) Edited February 1, 2011 by The Drongo
Danger Dassie Posted February 1, 2011 Posted February 1, 2011 Mind you, it doesn't help to delete the original post starting the thread either. Sitting on a top tube, I've never seen or heard of a breakage like that occuring. Would have to be from an impact.All things being equal, if it breaks a carbon frame, it'd break an alloy one. Sit away, live life on the edge....
Mish100 Posted February 1, 2011 Posted February 1, 2011 I got a sl3 and weigh about 98kg and never ever thought sitting on the top tube would be a problem Anyways if it breaks its insured
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