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I truly do believe that certain bicycle frame materials should have weight limits. I know for certain that Trek has set weight limits upon both its racing bikes and hybrids. I'm most certain that other bicycle companies have weight limits too.

IMO, these weight limits should be strictly adhered to, due to possible or potential injury to which overweight cyclists may be subjected. Morbidly obese cyclists, should be forbidden by law to ride CF road bikes and most aluminum framed bikes should be excluded, as well.

IMO, some overweight and all morbidly obese cyclists should be primarily restricted to steel frames, only. Even at that, some of these steel frames should be specially designed for this particular group of people. Otherwise, safety becomes an issue, almost by default.

Companies like Surly, Salsa, and SOMA, need to more closely address this issue.
 

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My carbon frameset Colnago has a weight limit of 300 pounds. That includes the rider and all components. I have seen several riders that are at that weight or over that are riding carbon bikes. I just don't want to be there when the frame fails.
 

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Not sure we need laws governing this, typically what something is rated at and what it fails at are two different numbers. Drywall screws for instance are rated for 180 pounds but won't fail untill 360 pounds. a 300 pound ladder does not collapse at 301 pounds. I'm sure there is some built in leeway in the bike numbers as well. Is there any data supporting material failures due to bikes being overweighted (rider and gear)?
 

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I don't see a need for laws either. As far as steel frames go, welded frames and forks may be plenty strong, but brazed stuff is going to fatigue faster and have lower limits for weight. How much faster and how much lower weight limits? I couldn't tell you, I'm not an engineer.

Carbon fiber has less impact resistance than steel, aluminum, or titanium, but it's plenty strong. It's a certifiable aerospace material and has been put into some of the most expensive devices made. Carbon frames are engineered to work as bike frames, whether or not they'll support a 500 lb rider is almost inconsequential, because of the very few people that would be doing so.

I too used to be skeptical of carbon fiber as a frame material, but I've seen the kind of testing they put frames through at different bicycle manufacturers and I've changed my mind somewhat. It is still fragile in certain ways, but so is aluminum. The trade-off is weight, and for the vast majority of serious riders, lightweight materials help sell bicycles.
 

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Frickle Frack
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It could also be from these bikes sold at the big box stores. Being made over in China and Taiwan the frame tubing is much thinner in order to bring the price down on the "off the shelf" bikes. They set a weight limit on them because if you are too big then you will most likely break the thin wall tubing and it could be a liability issue.
 

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It could also be from these bikes sold at the big box stores. Being made over in China and Taiwan the frame tubing is much thinner in order to bring the price down on the "off the shelf" bikes. They set a weight limit on them because if you are too big then you will most likely break the thin wall tubing and it could be a liability issue.
I'm sure the tubing is thicker, to bring the price down.

Steel is cheapest when it comes to price/strength. Titanium would be the ideal material for a crazy-strong bike, but not very affordable for what very well be a transitional bike for the clyde looking to lose weight.
 

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Not sure we need laws governing this, typically what something is rated at and what it fails at are two different numbers. Drywall screws for instance are rated for 180 pounds but won't fail untill 360 pounds. a 300 pound ladder does not collapse at 301 pounds. I'm sure there is some built in leeway in the bike numbers as well. Is there any data supporting material failures due to bikes being overweighted (rider and gear)?
I sure that most weight limits are well under what they will actually break at and are mostly for litigation purposes against the manufacturer. If a 350 pound rider should happen to break a carbon frame with a 300 pound weight limit within the warranty period, they can come back and say, he exceeded the weight limit and therefore are not responsible for the replacement of the frame or any other damages. That being said, I also believe that any frame will eventually become fatigued at the joints after repeated years of overweight people riding them. The road vibration and the excess weight will eventually break them down.
 

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Frickle Frack
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I'm sure the tubing is thicker, to bring the price down.

Steel is cheapest when it comes to price/strength. Titanium would be the ideal material for a crazy-strong bike, but not very affordable for what very well be a transitional bike for the clyde looking to lose weight.
When I buy steel tubing in bulk for roll cages it is .120 wall. .059 wall tubing is half the price but less overall strength. Less mass = less money. I could very easily build the cages out of .059 but id be afraid of a lawsuit, not if it fails but when it fails. From the outside you would never know the difference and I can almost guarantee that the box store brand bikes use thinner wall tubing than the premium lines as a cost saving measure.
 

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When I buy steel tubing in bulk for roll cages it is .120 wall. .059 wall tubing is half the price but less overall strength. Less mass = less money. I could very easily build the cages out of .059 but id be afraid of a lawsuit, not if it fails but when it fails. From the outside you would never know the difference and I can almost guarantee that the box store brand bikes use thinner wall tubing than the premium lines as a cost saving measure.
You're comparing apples to oranges. Premium tubing is drawn thin and then heat treated. It costs more to make the thinner tubing for bicycles.
 

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First to the OP, what is your problem with fat cyclists? Your post toes the line of being insulting and derogatory toward people who are overweight. Why don't you just come out and say what you probably mean? Are you sure you don't mean fat people should not be riding bike because you think they look disgusting doing so and you don't want to see it when you are riding? Your post is kind of coming across that way.

For the record, I am a fat cyclist. I have no illusions about my weight. I don't wear the form fitting bike cloths, but am able to wear..... Wait a minute on second thought why am I explaining myself and justifying me riding a bike to someone like you OP? I don't have to do that. I don't need any sort of approval from you just because I'm fat guy who rides bike and you don't like it. The bottom line is if you don't like seeing us ride don't look at us when we do.
 

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Second, My bike, a Vision R40 recumbent is cro-moly frame. While I am a fat cyclist I have NEVER had a problem with the frame failing on me for any reason. My bike is almost 11 years old and has over 10,000 miles on it. I have replaced both rims. But not because of my weight. The front cracked on the side wall/braking surface from NORMAL wear and tear after about 9 years. The rear developed stress crack around the spoke holes, again after NORMAL wear and tear after almost 10 years. The original rims were 32 spoke. the new rims are both 36 spoke.

I did have the original aluminum seat frame replaced with a custom built cro-moly one. The shop that did it used the original for the correct geometry. I did this because I got tired of the vibration from the aluminum frame caused against my back. Cro-moly absorbs road vibration much better than aluminum.

My point is my cro-moly frame has never failed for any reason, least of all because of my weight.
 

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I used to work for a steel company so i know a bit about weight limits and failure rates of metal. First the reason why weight limits even exist is insurance liability. If metal fails and it is due to the weight limit being exceeded of there is a weight limit for that product, such as a bicycle frame, the manufacturer cannot be held responsible in civil court. However it depends on where the failure occurs. For example at a joint or not. If it does fail at a joint it depends on how the joint is held together.

But it the failure occurs say in the middle of the top tube, the question is going to be why. Was there a dent in the material, causing a weakness? What was the condition of the paint of finish on the material? as there corrosion of any kind?

There are a lot of variable that factor into metal failing. It is impossible for manufacturers to reasonably think of them all.
 

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Materials are only part of the strength of a bike. My Diamondback Strongbox framed MTB has a hydro formed frame that's thin yet strong.
Plus there's the tensile strength of the materials. A guy at a bike repair shop told me he saw stainless steel spokes break a lot on the cheap bikes. But not on the better brands.
And like John-V pointed out there's fatigue. A bike that would pass the test at the point of sale might not pass the same test a few miles down the road.
 

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I'd be interested to see reports of obesity-related bicycle or component failure. I've seen some very heavy people out cycling, both in person and in online reports.

I'm all for getting the obese on bikes from the fitness and happiness standpoint. That would fall apart quickly in the face of evidence it's significantly unsafe due to the likelihood of equipment failure, though.
 

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As far as I'm aware most of the regular brands test frames to comfortably accommodate riders up to around 280lbs. I don't see it as a problem.
A bigger issue for frame breakage is the age of the frame.
Personally I've broken one aluminium, one (cheap) titanium and three steel frames and I only weigh 170. They were all old items..
 

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Now you all have me thinking. I have a Diamondback Podium 2 I got in 2007. I am 250 lbs, 6'3'' and not obese. I don't ride 20 miles or more like you hard core people do but I do ride aggressively with hard pedaling and interval training. I am wondering my weight to bike ratio. I don't want to buy another right now. It has an aluminum frame.
 

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Spin Spin Spin
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Woohoo, 8yr old resurrection......beyond obvious laws of physics, we all ride what we ride, how we ride and where we ride however often or not at our own choosing, risk and reward. Manage one's own needs and wants.
 

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I think we can all agree that we need more laws .... if less management is better ....micro-management must be better still. (Hmmmm ..... )

As a fat cyclist riding carbon and 24-28-spoke wheels (the Horror) I can assure everyone that fat cyclists do not give a fornication about all that.
 

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Now you all have me thinking. I have a Diamondback Podium 2 I got in 2007. I am 250 lbs, 6'3'' and not obese. I don't ride 20 miles or more like you hard core people do but I do ride aggressively with hard pedaling and interval training. I am wondering my weight to bike ratio. I don't want to buy another right now. It has an aluminum frame.
By definition 6’3” and 250 is obese. For the information you entered:

Height: 6 feet, 3 inches

Weight: 250 pounds

Your BMI is 31.2, indicating your weight is in the Obese category for adults of your height.
 

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Spin Spin Spin
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Solid billet titanium frame is the only call.....with concrete rims.
 
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