The UCI, cycling’s international governing body, has a rule stating that bikes must weigh no less than 6.8kg to prevent teams and bike manufacturers from building bikes that are too light and fragile to withstand the rigors of professional racing.
There were once times when pro cycling teams mocked the rule as being outdated because, with our current technology, bike manufacturers can easily make carbon fiber bikes that weigh far less than 6.8kg while still meeting the EN ISO 4210-6 safety requirements.
In fact, pro teams used to artificially add extra weight to their bikes to meet the 6.8kg weight limit rule.
However, new generations of Tour de France bikes are now significantly heavier than they used to be. The average bike in the pro peloton today weighs around 7.2kg. Why?
In this article, we’ll discuss why road bikes are getting heavier and why that’s not necessarily a bad thing.
What Is The Average Tour de France Bike Weight?
Based on videos of GCN and CyclingTips who regularly weigh Tour de France bikes every year, aero bikes weigh upwards of 7.5kg. But most importantly, bikes that the Tour de France pros use in mountainous stages weigh from 7.0 to 7.3kg. This is far above the UCI weight limit of 6.8kg.
Looking back to 2015 and earlier, lightweight bikes are so much lighter. Trek Emonda, for example, which first launched in 2014 and weighs 4.6kg was the lightest production bike at the time. Then there are the first and second versions of Cannondale SuperSix Evo Hi-Mod that weigh less than 6.8kg even without the highest-level components.
Of course, you can’t race them in UCI-sanctioned races, but these bikes were the norm. Even if you can’t race with them, everyone can buy these bikes.
Clearly, manufacturers know how to actually make lightweight bikes that are safe to use. At one time, they just decided not to.
Despite today’s weight inflation, though, apparently, Tour de France riders are getting faster than ever. So, what happened there? Why are lightweight bikes getting heavier and why are these new-gen heavy bikes faster than the old lightweight ones?
The Advantage of Aerodynamics
Because carbon fiber technology advanced so quickly and bikes were getting so light, the UCI did have a second look at their 6.8kg regulations a few years ago. Ultimately, they decided to keep the rule in place.
Because of that, pro teams artificially added extra weights to their bikes. This is often in the form of heavier components or leads taped to the frame or wheels. This brings the bike up to the minimum weight limit.
Later, companies realize that instead of adding dead weights, which gives pros no advantage during the race, they might as well add weights that do make them faster.
With the help of wind tunnel testing, bike companies have been able to design bikes that are more aerodynamic than ever before. Other than the thicker frame tubes, features such as integrated handlebars and stems, hidden cables, and deep-section wheels, all of this help reduce drag and make the bike faster.
Because of all these features, aero bikes are significantly heavier than lightweight bikes. And this is the first reason why we’re seeing the start of inflation in Tour de France bike weights.
The Rise of All-Arounder Bikes
But aero bikes aren’t new. For a while, pros have been switching between lightweight bikes for mountainous stages and aero bikes for flat/sprint stages.
They thought because aero bikes are heavier, they wouldn’t be able to climb as well as lightweight bikes. But as it turns out, that’s not always the case. As long as pros are able to ride above 30km/h, aero properties will always be more important than weight. Even on the longest and steepest mountain like the Alps the Huez, grand tour riders can still hold an average speed of 20km/h where some aerodynamic properties still matter.
So there’s a sweet spot between weight and aero, which gives birth to all-arounder bikes. They are essentially climbing bikes with some aero optimization, giving them a little bit of extra weight but can climb faster than pure climbing bikes on most hills because of the aero shapes.
The Specialized Tarmac is one example of an all-arounder bike. It’s not the lightest in the market, but with some aero features, it’s one of the fastest bikes you can buy.
Optimized for aero and equipped with deeper-section carbon wheels, most of these lightweight all-around bikes weigh from 6.8 to 7.5kg.
The Age of Disc Brakes
The final reason for the current state of Tour de France bikes is the rise of disc brakes. Disc brake bikes are heavier than their rim brake counterparts, but most top-level aero and all-arounder bikes come equipped with disc brakes now.
Not only the calipers and disc rotors themselves are heavier, but the fork, frame seat stay, chain stay, and wheels of a disc brake-compatible bike must also be reinforced and be made heavier than their rim brake counterparts to compensate for the higher stopping force.
All combined, a top-level disc brake road bike is said to weigh about 500g more than a rim brake bike of the same model.
But all these weights are not for nothing. Sure, rim brakes vs disc brakes preference is still a very controversial topic even today, but there are some clear advantages of disc brakes that make almost all pro teams ride exclusively disc brakes today.
With disc brakes, you can slow down from a high speed with better reliability, and as a result, pros are more confident in going on a higher-speed descent. Disc brakes also have better compatibility with tubeless tire setup, which has a lower rolling resistance compared to standard butyl or tubular setup.
The use of disc brakes also allows wider rims and tires, which can lower rolling resistance and add comfort. These will surely add weight, but looking at how pro peloton has been continuously increasing their tire width from 23mm to 28mm today, the swap must’ve been worth it.
Is Disc Brake the Biggest Contributor to Weight Inflation?
Aero and disc brakes are surely the main contributors to why Tour de France bikes are now heavier than 6.8kg. The disc brake has been blamed as the reason why bikes today are so much heavier than older rim brake bikes. But is that true?
To answer that, we need to look at road bike manufacturers who still give a choice to customers whether they want a rim brake or disc brake bike.
The best example of this is the Pinarello Dogma F since it’s one of the new-gen bikes that still have a rim brake option.
In a video on the YouTuber GC Performance’s channel, he weighed the Dogma F rim brake bike in size 53 with a Campagnolo Super Record EPS groupset and Princeton 4540 wheels with White Industries hubs. The total weight without pedals is 7.19kg.
In another of his video, he weighed the disc brake version of Pinarello Dogma F. Same paint job, same size, same groupset, but heavier wheels (Princeton 4550, slightly deeper than the 4550). The weight? Also 7.19kg.
What happened there? Why is the rim brake bike not lighter than the disc brake variation?
If we looked at CCache.cc’s road bike groupset weight comparison table, it turns out that there are only 107 grams of difference between Super Record EPS rim brake vs disc brake—without the brake fluid which can weigh from 50-100 grams per bike. So, in total, the difference between the disc brake and rim brake groupset is 200 grams or less.
This difference can easily be offset by the small weight variations that normally occur during the frame and components manufacturing process. So, maybe what we’re seeing is a disc brake frame and components that happened to be lighter than the rim brake. But, seeing that they have the exact same weight, the actual difference in weight between disc and rim brake bikes might not be that significant after all.
How Much Does “Aero” Add Weight?
So, now that we know disc brakes add more or less 200 grams to a bike, how much weight do aero profiles contribute to added weight?
The easiest way to find out is by measuring two bikes, one with aero profiles and one completely without. The two bikes must be of the same company and same generation so that we know they use the same carbon layup.
The two bikes that come to mind are the Specialized Tarmac SL7 and Aethos.
The Tarmac SL7 is the perfect example of an all-arounder bike. It eliminates the need for Specialized’s dedicated aero bike, Venge, from the market and pro peloton because the Tarmac SL7 is not far-worse in terms of aero, yet it is significantly lighter.
The Aethos, on the other hand, has absolutely zero aero optimization. The Aethos is made to be a lightweight frame, all the tubes are rounded without a single hint of aerofoil profile.
The Tarmac SL7 is no doubt the faster frame, but the Aethos is lighter. But by how much? If we compare frame weights, the Aethos is 570g and the Tarmac SL7 is 800g, both in size 56.
Right away, you can see that making a frame more aero adds 230g.
As a complete bike without pedals, the Tarmac SL7 is 6.9kg and Aethos is 6.2kg. The difference gets bigger because the Aethos is equipped with a lightweight integrated handlebar and stem, and a much shallower rim depth.
As you can see, aero profiles add 700 grams and disc brakes add up to 200 grams to the bike. There are also minor factors like wider rims and tires, threaded bottom brackets, and electronic groupsets. Combined, these are the reason why today’s road bikes can be more than 1 kilogram heavier than older ones.
How Much Does Weight Affect Speed Anyway?
Road cyclists are obsessed with weight, so you might be curious about Tour de France bike weight in the first place. But how much faster is a lighter bike?
Everything else being equal (they are usually not), a lighter bike is not measurably faster on a perfectly flat road. That’s because on a flat road, gravity doesn’t work for or against you and the bike weight only contributes to the small increase in rolling resistance. Considering the weight difference between the lightest and heaviest road bikes, which is not actually not that significant once we started adding the rider’s weight, this can’t practically be measured when you’re on a flat road.
Cycling uphill on steep gradients, though, you might be able to feel the difference.
On a 3% gradient, a 70kg rider with a 6kg bike will need to exert 193 watts of power to go at a speed of 20 km/h. If we increase the bike weight to 9kg, the rider will need 199 watts to go at the same speed.
A 6-watt of difference with 3kg of bike weight isn’t much for most people except people who compete at the highest level of competition like the Tour de France.
The power difference gets bigger the steeper the gradient is. For example, on a 7% gradient, the same rider with a 6kg bike will need to exert 368 watts of power to go at a speed of 20 km/h. If we increase the bike weight to 9kg, the rider will need 381 watts to go at the same speed.
So the difference is now 13 watts at a 7% gradient compared to 6 watts at 3%.
If you put a more comparable bike weight, for example, a 6.8kg UCI-limit bike vs a Tour de France bike’s average weight of 7.3kg. The difference going up a 7% gradient hill is only 2 watts at 20 km/h.
If you’re interested in experimenting with the numbers yourself, you can use this calculator.
Unfortunately, it’s impossible to check if the weight and aero tradeoff is worth it because you will need a wind tunnel to measure how much all the aero frame and components make you faster. The closest thing we can make a judgment on is by looking at Tour Mag’s aero test comparisons.
For example, Giant TCR Advanced 2019, a pure climbing bike with very minimal aero considerations, scored 227 watts at 45 km/h in a wind tunnel. On the other hand we have the Specialized Tarmac SL7, an all-arounder, scored 210 watts in the same setting. A 17-watt difference at 45 km/h, which is probably around 5-10 watts at 30 km/h.
So, realistically, the heavier aero/all-arounder bike can save you about 10 watts on a perfectly flat road but make you slower by 2 watts going on a very steep uphill. For people competing in the highest level of the sport, this tradeoff might be worth it.