# How is the max load in the bike specifications defined?

In a bicycle description I see "laden weight" of 130kg. So I assume this is weight of the bike itself plus the rider's and of what they carry on themselves. In my case the bike itself is 11.6kg, so the rider and their cargo would have to be under 118kg.

I am sure I do not exceed it, but is that enough to estimate the max load or the pressure on pedals should be also accounted? Say with a drop-bar bike it is possible to make pressure that would make it notably over the rider's weight depending on their legs' strength.

• Don't overthink it. The max load is equivalent to the gross weight of your car (fully laden), which is a stationary measurement. Bicycle manufacturers won't necessarily honour the warranty if you started your journey with a static weight over 130kg Oct 14, 2023 at 12:50
• @Noise am on the verge of demanding the frame replacement according to warranty, just wanted to ensure it was not a my fault due to some misunderstanding... Oct 15, 2023 at 12:11
• You'll be fine on that point. There's alot of hot air in the answers! Hope you reach a satisfactory conclusion quickly. Which brandname are you dealing with? Oct 15, 2023 at 18:39
• The question was about the definition only, so I am a bit surprised by such a lengthy discussion here :) Oct 16, 2023 at 12:49

I don't think we consumers really know how the maximum weight is defined. Perhaps someone in the industry will contribute, or perhaps someone with engineering background can say how these specifications are usually generated.

It's possible to simulate the loads on a bike with finite element analysis (the aerodynamic equivalent is computational fluid dynamics). The problem is that you need to simulate the real world closely enough to be relevant to real life experience. This doesn't mean that you have to simulate everything 100% accurately, but rather that it's a complex task. Also, you don't necessarily know all the loads going into the bike. You could simulate static loads on the bike, but dynamic loads might introduce a lot more variables - e.g. what are the size and depth of the potholes the rider hits, how often do they hit a pothole, what tire pressure were they running and did this cushion the blow, etc. And yes, the rider's power output is also worth considering, and it clearly will vary among riders of the same weight. If you are 118 kg (260 lbs), you're probably not a strong cyclist, but if you had a threshold power of 3W/kg (pretty good aerobic fitness), that's 354W going into the bike at threshold, and much more in a hard effort. I would be surprised if cheaper bikes got extensive FEA to generate maximum weight specs.

I suspect that to at least some degree, the limits are set by prior experience plus some guesstimation on the part of the engineers or product managers. The manufacturers probably had previous similar bikes fail. They may have been able to get an approximate idea of the rider weights from the warranty reports. If you added a safety margin to that, that's one way to estimate a maximum weight.

Basically, that weight limit is an estimate. The manufacturer might deny a warranty if you are heavier and you break something on the bike, or break the frame. But the bicycle won't hit a pothole and crumble to dust if you have 131 kg total weight on it.

For heavy riders, I think I've heard that the wheels often break first. If they do, it is probably worth getting a strong set of wheels built by hand by an experienced builder. You would be looking at, for example, a 30mm aluminum rim and 32 or 36 spokes, whereas OEM disc wheels on performance bikes are often 24 spokes front and rear (although they're usually 30mm-ish aluminum rims). You would definitely want to add a bigger tire if it fits the bike - more tire = more cushion = less shock transmitted to the components.

• As quite a heavy rider who often carries stuff and has had a child seat, 32 spokes front, 36 rear seems good, and hand-finished wheels might be worth it. I broke a machine built 32 spoke rear. Oct 14, 2023 at 15:10
• Spoke count isn't nearly as important as rim choice, in my experience. 32-hole MTX33s are my current rims of choice, and my system weight probably peaked at around 190kg. I've had no problems hitting potholes or curbs. Plus, with 36 hole rims you are limited to terrible Shimano hubs that use loose bearings, not counting exotics like White Industries Oct 14, 2023 at 23:22
• Even if we define and simulate the loads perfectly, how many load cycles do we need the bike to survive? One pot hole, two pot holes, 1000 pot holes? Oct 15, 2023 at 10:24

The manufacturers have to have some standardized reference (gross weight) and then make some assumptions on what usage it should withstand with some margin.

I'm guessing landing jumps on non suspended bikes is the intended use case that dwarfs other requirements with regards to strength of a frame/fork. You can easily and realistically double and even triple that strain by increasing the weight of the rider (50-150kg), thus doubling/tripling the required minimum strength of parts. Where as not even Usain Bolt runs the 100m in half/third the time of a reasonably fit person. The power output of riders is also more smoothly applied than sudden ladings on pavement.

In short, static weight is critical to engineer safe bikes properly. And since people want light bikes, manufacturers don't want to oversize frames/forks to handle any infrequent rider weight. Wearable parts will probably wear faster with a stronger rider, but this is not as critical from an engineering point of view.

System weight limit is, in my opinion, produced ab rectum. The typical reported max weight for most bikes is 136kg, because that is what ASTM demands. However, I believe that most bicycle parts don't have a weight limit, and most of the rest have weight limits that exist mostly to provide a safety margin when riding badly or crashing.

The general limiting factor of a complete bike, in my experience, is the wheelset. In the wheelset the limiting factor is generally the rims, unless it has less than 32 spokes per wheel. Having started riding bikes at 180kg, I've only ever seen clearly weight-related failures in rims and saddles.

Other than that, and excluding weight weenie parts that don't come stock on bikes anyway:

• The frame and fork are built to have a safety margin when overloaded by hitting an unseen pothole or casing a jump. This safety margin erodes as system weight increases - even within the limits set by the manufacturer. The more careful you are, and the better your rough terrain technique is, the less this limit matters.

• The stem and handlebars are equipment that "cannot fail", meaning a failure is almost guaranteed to cause a crash, so they are generally extremely overbuilt. I'm not aware of any stems or handlebars that had a reported weight limit; I suspect it would be absurdly high.

• The load on the seat post depends on its extension more than the rider's weight. A 65kg rider riding a race-fit frame (the smallest frame that fits) can have 30cm of seat post exposed, producing the same bending load on it as a 195kg gorilla with 10cm sticking out of a touring frame.

• The crankset carries static load and power the same way. I've heard that 2000w is about 1250N average load on the pedals, with the peak higher. That's equivalent to an extra 127kg while coasting.

• Pedals aren't a part of a complete bike as sold, but the same argument applies to pedals while putting down power. However, I'm aware most titanium-spindled pedals have posted weight limits - a titanium replacement of a steel part with the same dimensions will be noticeably weaker, and titanium is more notch sensitive than steel.

• Saddles shouldn't carry the rider's weight over rough ground anyway. Merely pedaling doesn't really load the saddle, most weight is on the feet. Of course, everybody misses potholes occasionally.

• The tires do not hold up the rider's weight - the air inside them does. Very narrow tires are still suitable for heavy loads - just not on rough terrain, since the pressure required to support a given weight increases as tires get narrower and loads get greater. Excessive pressure ("inflating to max psi") causes more damage to rims. Insufficient pressure causes pinch flats.

The more skillfully and gently you ride, the less applicable weight limits are. Avoiding unnecessarily standing out of the saddle, not overinflating your tires and using your knees and elbows as shock absorbers when going over bumps are the most important techniques in this regard. The general public, of course, cannot be expected to ride skillfully, and weight limits reflect that.