Author Topic: weight limits on bikes  (Read 7003 times)

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Offline whittierider

weight limits on bikes
« Reply #15 on: August 05, 2008, 05:18:50 pm »
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I believe the only weight limits I've seen in cycling is mostly on carbon fiber road bikes and/or front forks.

I've only heard of weight limits on aluminum, and I've heard first-hand from several 350-pounders on these forums on carbon fiber, with no issues.  The new Boeing jetliner is mostly carbon fiber and grosses at about a half a million pounds; so it's definitely up to some serious load-carrying capability.

http://www.velonews.com/tech/report/articles/3270.1.html has some info on carbon forks' strength and durability.   When asked about the strength and durability of their CF forks, Reynolds responded, "...Our fatigue testing would indicate that well built composite forks are far superior to metal forks with cycle counts running hundreds of thousands of cycles rather than tens of thousands.  These tests are also run at much higher loads than metal forks can withstand further demonstrating the durability of composite materials."

True Temper says about their carbon forks, "...But our production forks are stronger than that, often going into the 20-25K range and beyond at loads 0f 360-405 lbs."

As an anecdote, the only fork I've seen broken on the road was an aluminum one.  The 180-pound rider hit something at 20mph and broke both fork blades clean off.  Our son's broken collar bone yesterday came from hitting a car at 25mph that failed to yield on left turn in front of him.  Although we will have the carbon frame and fork thoroughly inspected, so far it looks undamaged.


bobbirob22

  • Guest
weight limits on bikes
« Reply #16 on: August 05, 2008, 05:35:31 pm »
thanks jay ill keep that in mind. im a noob when it comes to bicycling but on my exstensive search of the net ive found most bikes do have weight limits mainly 250 lbs and 300 lbs capacity. i weigh over 350 so i need a very sturdy bicycle. ive found one at landrider that can hold 450lbs but has the auto shift mechanism which i dont like at all. ive read many threads in other forums on a similar topic as mine and most ppl just say to get any mountain bike frame with wide tires. think thats what im going to do since i cant afford the mazama. as for carbon fiber bicycles i dont know anything about those  but im glad you told me about the cracks, makes sense , that could lead to serious injury especially on a donhill slope going 30 or 40 mph and having the frame break into pieces. nightmare!! but because of my weight i would chance facing the same event on any bicycle which is why i need the toughest frame i can find. that would make some people think steel frame but like whittierider said the steel frames have become thinner in recent years in order to compete with other lightweight frames. ill keep searching the net and emailing them to try to find a bike for my weight but im not having much luck and the ones i do find are anywhere from $3000 to $8000 way to exspensive for me at the moment.

ROBERT JENKINS

bobbirob22

  • Guest
weight limits on bikes
« Reply #17 on: August 05, 2008, 05:51:42 pm »
I've heard first-hand from several 350-pounders on these forums on carbon fiber, with no issues    

thats what im seeing a lot of to on other forums and in my net searches.  maybe thats the direction i need to go.
 
The thing with CF is that you can get microcracks that are almost invisible leading to catastrophic failure and shearing of the fork/frame.

however this does worry me some but by testimonies ive read most agree that carbon fiber is really tough and rugged material lighter than steel but just as strong if not stronger. a micro crack as he says can occur anywhere on any bike especially in weld seams leading to breakage. that a chance that all bicyclist face no matter what the frame type. all i know is most of the big guys out there are going with carbon fiber and i havent seen a complaint yet.

ROBERT JENKINS

Offline whittierider

weight limits on bikes
« Reply #18 on: August 06, 2008, 02:57:40 am »
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The thing with CF is that you can get microcracks that are almost invisible leading to catastrophic failure and shearing of the fork/frame.

Such "microcracks" however will come as a result of impacts and abuse, not mere fatigue like what killed my nice steel frame.  There are things you can look for in your constant vigilance, such as the cleaning rag getting snagged when you wipe a part of the bike that should be smooth and glossy when you clean it.  In the link I gave above, Easton says, "Most of the time any damage to a fork from a crash will be visible. Cracks can be seen."  About their Alpha Q forks, Bill Hull of True Temper writes, "The failure mode is not catastrophic.  A broken fork will crack near the crown and allow more movement.  It will feel "soft" because it will flex more under braking.  The rider will see cracks on the outsides of the crown.  The rider can ride home and remove the fork without danger."  I couldn't tell you from experience, but my research gives me confidence you won't get from hearsay and from the myths left over from the early efforts of carbon that were almost laughable.

For the heavyweights however, you also need to be careful about handlebars, stems, and maybe seat posts as well.  Handlebars, especially aluminum ones, can break, and that's never pretty.  A very bike-knowledgeable man I have frequent contact with, who's a racer and a dealer, recommends replacing aluminum bars after any crash.  Race Face used to have a handlebar test article on their website showing the carbon bars to be far less likely to break.  They've revamped the website and now I can't find the article.

This message was edited by whittierider on 8-5-08 @ 11:06 PM

bobbirob22

  • Guest
weight limits on bikes
« Reply #19 on: August 06, 2008, 12:16:08 pm »
thanks for all your posts youve helped a lot! i dont know much about bicycles and i think the last time i rode one was about 8 years ago, your imformation has been very helpfull.

ROBERT JENKINS