Road Fan

So I agree that weight has effects that are different from shock. Which problem are we worried about - bruising your butt, or bending of your frame or fork tubes? Does the torquing of the tubes due to hard pedaling have any effect on inelastic damage to steel frame tubes? I suspect it does not, hence the lack of concern for frame weight loading "in the old days."

Any good theory of frame strength and durability needs to consider what happens in modern times, and what happened all the way back to the 1920s or so (whatever that was). I think everyone with some experience has seen (or maybe even caused ... ) damage due to bike abuse, such as jumping Peug UO-8s through forest trails.

Trakhak

It would be difficult to refute that compelling argument.

Looks like you're in a fightin' mood today, judging from your posts.

To clarify: I said that the majority of customers buying racing frames in the mid-'80's were fit racers. Racing frames: frames plus forks, ready to be chased and faced and to have components installed and wheels built.

If you were thinking that I mean complete bikes with drop bars and sport touring geometry, or even racing geometry, that would explain your objection.

Road Fan

Many cyclists in the 1970s (yes, you were talking mid-'80s, when lighter tubesets were available) bought the best frames they could to have the best bike they could, to enjoy the ride. Not many in my circle were into organized road racing, but there were a wide range of high-end frames on the Chicago streets wearing Campy Record groups, Fiamme tubular rims, and Clement Selle Main tires, of cotton or silk. Some shops like Turin had a racing program, and some known riders and builders came out of them, but that was the exception. Not too many were coached by any coach, must less known coaches of racing teams. The guys' weights ranged from 135 (me, for example) to 7" taller, and a lot more girth. Some were football team members. NOT a crew of racing snakes. I knew riders who loved racing bikes, not racers.

Now maybe we were not the majority, I'll give you that one. And there were a lot of Schwinn Varsities and Continentals and their direct competitors from France and Italy also on the city streets. And maybe many in my crew did not have the ability to regularly smoke a guy on a UO-8 while riding a Fiorelli or Legnano. The Fiorelli did not make one a racer, it made you a wannabe, and it was a sign you loved the feel of a great bike. And could not necessarily afford a Cinelli.

I didn't work in a bike shop for more than a short time, so I didn't see much in the way of broken frames at all, besides my job was to assemble new bikes to put them on the sales floor. One in my crew was a Super Course which had the seat tube separate from the BB shell at the lug. I also saw that on a Raleigh Record, then a gas-pipe bike with bottom end components, not quit as good as a Varsity IMHO.

So, my experience is mainly from the early '70s, that few riders and even shop owners were very savvy about weight "ratings" for bikes. If it's different in your experience, a decade later, so be it. Your statement seemed too much like a generalization, hence my reaction.

Other aspects of the thread were bugging me, too, like all the generalizations about how the strength of carbon fiber layup works. I have a pretty strong formal background in metal structures as part of my general engineering coursework, (but I'm an EE, not and ME) and about 7 years working in the 1980s and 1990s on projects which used carbon composite tubing. It was pretty obvious to the design team in my cadre of spacecraft designers that strength depends critically on the details of how fibers are chosen, combined and bound together to form a structural tube, and it's not at all simple to draw conclusions about tube properties based on fiber properties and simple matters of construction.

If some composite-specialist bike frame designers have presented any in-depth papers on how to estimate expectations about mechanical properties of carbon frames I'd love to see it. My more recent work is not connected to any of this. So I can see where I think the viewpoints in BF discussions are too simplified, but I can't offer any quality information to add to the carbon-steel comparisons.

Trakhak

I was talking about the mid-'80's because that's roughly when the practice of buying and building up racing framesets became much more common (as these things go) than it had previously been.

But my experience with racing bikes began when I got my first tubular tire-equipped bike, in 1964---a Helyett Speciale track bike. Rode it (unsuccessfully) in the Nationals later that year at the urging of the local bike shop owner in New Haven, who apparently knew I was the only 13-year-old boy in Connecticut with a track bike who was a registered ABLA rider. That was my first ABLA race, in fact.

There were a couple of kids from Chicago lined up next to me in the mass-start race in the Kissena Park velodrome. I complimented them on their gorgeous orange Paramounts with orange Clement Seta tires. In return, they jeered at my big fat Dunlop 10-oz. tires. If I ever wondered whether I'd forget that humiliation, the answer is: apparently not.

When I started racing, everyone in New Haven who owned a bike with tubular tires (i.e., all 25 or so of us, including Yalies) knew everyone else with tubulars. Very different from Chicago, which was a hotbed of bike racing culture even then, 10 years before your involvement. Even in my backwater town, I'd heard of Chicago's track specialists Jack Disney and Roger Young. Not surprised that the early '70's bike boom had guys in Chicago coming out of the woodwork who weren't typical svelte racer types---especially given the easy access to the Northbrook (?) Velodrome.

The only guy I rode with in the mid-'70's who fit that description, though, was an ex-college football player who was, he said, determined to slim down from his linebacker build---developed courtesy of the steroids his coach gave him---so that he'd have a shot at living past the age of 50.

Still, in the '60's and even through the '80's, throughout the U.S., the real racers, the pin-on-a-number riders, averaged below 180 lbs, and probably closer to 150 to 170. I was a pretty good all-arounder at my 136 lbs. That said, the gradual swing away from mostly road races to mostly criteriums during those decades meant that riders with (moderately) heavier builds became increasingly competitive.

Road Fan

Congrats on the loss! Last winter I was 210/215, now pretty steady at 190-195. But as you say, I have not had a problem with good quality lugged frames, even with 7/4/7 standard tubing. It's high-strength (TrueTemper OX-PLAT), but not stiffer than say, 531.

Road Fan

Thanks for the props on my "compelling argument!" ("Um, no") --- Lol!

So our experience was different. You actually raced, so congrats for that. I didn't race or hang out with racers, I was into the bikes and frames. I pedaled out to the Northbrook Velodrome once but hadn't brought enough $$ to get in and besides the biking route was not particularly safe, so I didn't continue going there, about 15 miles of 45 mph traffic, including trucks. My involvement with high-end bikes began about 1968 when I bought my Rossignoli road bike. I didn't get others after that - went off to college in '71. I continued riding, but still no racing. Besides, school cost a LOT. The Turin guys weren't sure exactly where the Rossignoli came from (other than Cicli Rossignoli in Milan) because it appeared to be NOS in a warehouse near Chicago - Ochsner? The shop received the bike built, but they thought the warehouse built it. Component selection was great for the period before my teen years, but odd for 1968.

When I worked at Ford Electronics (automotive electronics) I met an engineer who helped his neighbor with technical improvements and issues to his track bikes - the rider was a hulking gent who raced short-distance sprints and was able to bend frames and chainsets on start-up. He had frames custom built with frame tubes rather stouter than the norm for lightweight road frames of the late '80s/early '90s. He pressed some ungodly big weights, so yes, I know there are some big gents riding some races. He was probably using the Bloomer Park track, back in those days.

Again, my cohort were not racers, we were enthusiasts over racing bikes, and riding them as far as we could. Perhaps we were more like the British Clubmen of the 1940s and 1950s, than any formalized regime of cycling.

Troul 

for my personal reasons, I limit weight to an estimated amount determined off the max PSI the rear tire is labeled to hold. If the tire says max 75 PSI, yet for the rider's weight it should be NLT 100 PSI, then it's time to change the tire size or go with a different bicycle. The later would be the case if the existing frame is unable to support the increased tire size.

YMMV

base2 

Troul may be on to something. If the tire or rim max pressure must be exceeded in order to meet recommended tire pressure (15% drop) recommendations. Then it stands to reason that is the upper limit on weight in any circumstance.

For myself, on my WeinerBike SL® () that is certainly the case with the Stan's Grail CB7 rims. Due to hoop stress, 25mm tires have a pressure requirement not to exceed 85psi and 38's are not to exceed 50psi. Per the Silca calculator at 85 kilos, I am right at the maximum. Though every other component on the bike has a 100-110kg weight rating.

The frame (of WeinerBike) itself is, interestingly enough, not all that light at 1949 grams in a size 58. There are loads of lighter custom steel frames out there from Columbus XcR or Spirit tubing. Even production frames like the Bianchi Pinella.

The challenge is at some point ride quality and/or longevity starts to suffer. For a strong or heavy rider a frame built to the absolute minimum for an average rider will be too noodley to ride. The stress from manufacture or material imperfections will start to manifest during the frames anticipated lifetime. So that is the lower bound for frame performance is derived from. For this reason general production frames tend to be over built for the heaviest, strongest riders encountering the worst possible situations.

Simply put: Within reason, the frame isn't where the bicycles weight rating comes from. It's a variety of factors with the limiting factor being the wheel in some way.

cyccommute 

Go back and read post 10. Every “weight limit” I’ve ever seen on bicycles falls into the category of being a blanket weight limit. Trek’s weight limit is but one example but it applies to all of their bikes in all materials. If the weight limit is the same for aluminum or carbon, it’s not really an engineering limit but more of a lawyerly limit. In general, the bike isn’t going to collapse or crumble to dust if the weight limit is exceeded.

base2 

I don't disagree. I was seeking to put a finer point on where an actual limit would be derived. In my specific case, the weakest link is hoop stress. I then used that as a jumping off point to discuss the specifics for other components (the frame) at or near their actual limits and the "why" behind why the general limits are what they are. (Ride quality & longevity)

The Lawyer limit is even broader and could probably (within reason) be completely disregarded with the understanding of component life cycle limitations and personal responsibility of associated risk assumption.

The Lawyer limit sort of misses the point. The OP's question was where the bikes weight limitation, not the corporate liability limitation comes from.

ScottCommutes

Realistically, there isn't a weight limit on any component of a bike. Rather, there is a continuum from too heavily built all the way down to it cracks when you sit on it. In between, you've got the various ranges like "fast", "slow/heavy", "noodily", fatigue cracks at stress points, etc.

If a racer is sponsored with unlimited financing (and not considering weight restrictions), he wants to cross the finish line (first) with components too fatigued to ever be ridden again. The rest of us pay a weight penalty to get some decent reliable life out of our stuff.

Road Fan

Yes, I think the word "asplode" does not apply here!

Road Fan

As I understand it, the Lawyer limit means that because we warned you it could break and provided you with the information that it could break if used above the limit of xxx pounds, if it broke at a loading greater than xxx pounds, it's not our fault and you can't sue us because we told you we do not intend that it will survive such "careless abuse." We did not commit that it is impossible to break it at a load less than xxx pounds, but we are prepared to argue that whatever you were doing when it broke, it was beyond limits and hence it's not our fault.

The lawyer limit says nothing about whether the bike has any degree of safety, or will be safer with bigger tires or the carbon seatpost replaced with steel, or any other fix. It's not information which tells you how to or how not to use your bicycle, it's just a groiund rule that enables the lawyers who are expected to protect the company in case of a lawsuit to do their jobs and protect the company - not we the riders.

You can still make those arguments that "I better put fatter tires on it" but they won't help you in court. They MIGHT help you survive a road event, but that's not the concern of Trek or any other manufacturer.

Trakhak

Rossignoli---that rang the faintest of bells. Don't think I've ever seen one. Looked them up, and discovered that they're still in business!

Your engineer friend's neighbor sounds like a bodybuilder customer who came in the shop in 1983 or so, asking if we had any bikes that wouldn't feel like overcooked spaghetti under him. I reasoned that a Cannondale would be his best shot, and sent him out on a test ride.

He came back and bought it on the spot. When he came in for his free tuneup a couple of months later, he said, "You get any other big guys in here---give them my number. I'll tell them to buy a Cannondale."

Our local pro bike shop in the small town of New Haven must have been an anomaly in the mid-1960s, when most bikes were sold by Montgomery Ward and Western Auto.

I wish I'd thought to ask the owner how he happened to carry so many real racing bikes. I remember lusting after them, up on the racks: Atalas, PX-10s, Frejuses, Legnanos, Schwinn Paramounts, Raleigh Competitions. (He was also a Raleigh dealer, but it would be a few years before Raleigh introduced the Professional to their lineup.)

British Clubmen---that's how I picture the ideal road riding experience. I won a few races over the years, but I never enjoyed racing all that much. Putting in the miles with friends was the best back then.

Road Fan

In Chicago we had Western Auto and Monkey Ward as well, as well as bike shops focused on Columbia, Huffy, and other gaspipe bikes.

The Clubman approach is what I'm shooting for now. I'm even building up an old 1952 Rudge Aero Special, the Rudge clone of the Raleigh Super Lenton of that model year, Raleigh's top of the line in that year. I don't have a crew here in Ann Arbor, so my plan is just to start riding indoors and transition to outdoors as the weather comes up. Meanwhile the Rudge needs a rebuild for its Sturmey Archer FM gearhub, and possibly a change to the 5 speed. Install brakes, 'bars, saddle, generator (bottle type) and lights (some kinda B&M) and a rear support for my Carradice saddle bag. Oh, and some fenders. I changed to alloy rims and the truing/tensioning are done. Saddle will be either a B17 or a Ideale 92, left over from 1985. My overall riding interest is 50/75 mile rides on our new Border to Border Path, which goes from east to west end of our county - should be just abot right for the loop. Maybe we'll see about some brevets or something bigger later.

I've also replaced the Raleigh Industries cottered crank with a TA pro-5 vis, 48 teeth. It's getting a 18 tooth sprocket in the back and a new ¼" chain. It'll be essentially a new drivetrain on a 70 year old frame and hubset., but much newer Super Champion 27 x 1 ¼" rims and tires.

cyccommute 

In terms of weak links the first and foremost is the spoke. Think of any other load bearing parts of the bike that can fail and the spoke is the one that fails most often. It’s also the smallest member of the load bearing parts of a bicycle.

A distant second could be the rim but rims don’t fail all that often. Axles…especially freewheel axles that aren’t supported out on the ends…could be the distant second as well. A very, very, very distant 3rd is the frame itself.

It’s actually quite remarkable that something as thin as a 2.0mm piece of wire will take the weight of the bicycle and, more importantly, the bicycle rider. A structure that weighs in around 2 kg can hold many times its weight and still function as a structural member.