So you've decided to get yourself a roadbike. You've gone online and you've done a bit of research. Amongst the myriad of bike brands, models and offerings, a consistent trend is apparent. Every one of those bike brands have 2 or 3 bike models and they look slightly different from each other.... or at least that's what you think.
You're right though. Most bike manufacturers do offer 2-3 different models in their line up. Trek with the Madone, Domane and Emonda, Specialized with the Tarmac, Roubaix and Venge and Giant's Defy, Propel and TCR. And there are differences between the models.
Essentially, the three bikes belong to three distinct (or not so distinct, as we'll explain later) categories. The three categories include Aero (Aerodynamic), Endurance and Lightweight. Each of these bikes are built differently, with different geometry, tube shapes, stiffness and compliance to suit the needs of the different types of riding that they are purposed to serve. So first, we'll talk about the different categories and the needs for each category.
An S-Works Roubaix
We'll start with Endurance bikes. Endurance bikes, or sportif/gran fondo bikes, are designed to do one thing - ride long distances. This means endurance rides. There isn't an official distance as to what is considered endurance riding but generally endurance rides are from 100 miles onwards. If you think that 100 miles is pretty do-able, google 'ultra endurance' and you'll understand what we're talking about.
Since this category requires a rider to ride long distances and to be on the saddle for long hours at a time, comfort is of course the first priority. Comfort is achieved through different ways on a bike. First and foremost, the geometry on an Endurance bike is 'slacker' or 'less aggressive'. This means that the rider is seated slightly more upright while riding. This of course is at the expense of aerodynamics, but while endurance events are still race events, when you're doing those kind of miles, comfort > speed anytime. The wheelbase of an Endurance bike is also usually slightly longer than an aerodynamic or lightweight bike. This essentially means that this bike is more stable and less twitchy. This isn't necessarily a bad or good thing. Endurance riders ride over very long distances and very rarely have to carry out manoeuvres like breaking off a group or overtaking a rider in a last minute sprint. Therefore, 'twitchiness' or how fast the bike reacts may not be of utmost importance.
Comfort is also achieved through compliance. Compliance in cycling is a complicated science and is still an area where bicycle manufacturers are thoroughly researching (we could go into the details between vertical and lateral stiffness but it gets abit confusing very quick and we'll leave that for another day). A major consideration many cyclists have in choosing a road bike is a bike's stiffness. Stiffness is achieved through various means - shape of tubing, design of the bike, materials used. A stiff bike is more efficient, in the sense that all the energy you put into the bike while cycling translates into power moving the bike and no energy or power is lost. A less stiff bike, or a more compliant bike, will flex slightly under your weight and power so any power you put into the bike cycling or pedalling will be slightly reduced as some power is lost in the flex of the bike. With this information, you might think "why not just get a stiff bike?". Well, stiff bikes generally ride harsher. Where you transfer power onto your bike and it translates into the bike moving on the road, the road will also 'transfer' its 'feedback' to you. Bumps, pebbles or even bad road surfaces feel a lot worse on a stiff bike than a compliant bike, where a compliant bike flexes and absorbs those small impacts while the stiffer bike just translates all those rough surfaces to you.
Parts and components are also generally built to be more compliant, comfortable and durable, which means they're possibly not the fastest, quite compliant and comfortable and heavier to withstand the abuse from the absolute volume of riding.
This is precisely why Endurance bikes are usually built more compliant. As mentioned above, comfort is a top priority and therefore every bit of an Endurance bike is built with comfort and long distance riding in mind, of course at the expense of some other attributes such as speed and aerodynamics.
Examples of Endurance bikes: Giant Defy, Trek Domane, Specialized Roubaix, Wilier Cento10NDR
Wilier's new Filante SLR
Aero (aerodynamics) refers to the category of bikes that are built primarily for optimum speed. There are a few key factors that contribute to speed - power transfer, stiffness, and aerodynamics. These beasts of bikes can often be seen used by sprinters in the pro peloton. There are a couple of characteristics on an Aero bike.
The geometry of an Aero bike is 'aggressive', 'aero' or 'race-y'. Lower front ends, shorter stacks, slightly longer reaches. This means that the rider is positioned such that he is bending forward a lot more. This allows the rider to achieve better aerodynamics, ensuring that minimal power is lost to drag. The geometry of an Aero bike also ensures its reflexes are faster and is more 'twitchy', meaning it manoeuvres faster. This is to allow riders to pull off last minute maoeuvres to overtake other riders in sprints and breakaways.
Aero bikes also generally have... well... aerodynamic tube shapes. These tubing shapes are usually not circular or wide and are designed to cut through the air better. These shapes also generally produce a stiffer bike, which is another important factor in Aero bikes. Stiffness is achieved in Aero bikes through frame design, tube shapes and frame material and material build up. Generally, with Aero bikes, the stiffer the better. This ensures that no power is lost when transferred from the rider. Of course, for most of us non-professionals, stiff may still be good but a bike is only as good or as fun as it is bearable. There will always be a certain amount of pain involved in cycling (haha), but too much pain makes you not want to ride your bike. And there's no point in having a fast bike that isn't ridden.
Components are usually geared to being as stiff and as aerodynamic as possible. This means deep profile rims, bladed spokes, aerodynamic cockpits. There might be a weight penalty with that much material but weight isn't top priority in Aero bikes. Aerodynamics and stiffness are.
Also, as cyclists ourselves, we think it is worth mentioning that you can only feel the benefits of an Aero bike at a certain level of skill, experience and fitness. A lot of road cycling is in the fine margins and the speed gains on an Aero bike is marginal. These marginal gains may mean a whole lot to professionals who push cycling to the human limit. But for us weekend warriors, it might be difficult to see the benefits of an Aero bike, especially if most of your riding is spent at cruising speeds with your friends.
We mention this because you then have to weigh the benefits against the disadvantages. Aero bikes can be extremely uncomfortable in some cases, especially if you're only starting cycling, as the ride is harsh and the cycling position requires flexible muscles and will tire you out faster. Essentially with an Aero bike, you're opting for the marginal speed gains that you might or might not be able to enjoy (due to perhaps a lack of fitness) and a less comfortable and harsher ride. If you feel that you're pretty fit, flexible and want to enjoy and experience the speed gains of an Aero bike, we say go for it. Otherwise, you might want to think twice.
Examples of Aero bikes: Trek Madone, S-Works Venge, Giant Propel, Wilier Filante SLR
Giant's Award Winning TCR
Lightweight bikes are also usually marketed as 'Race' or 'Climbing' bikes. These bikes are usually built with one key thing in mind - weight. A lightweight or a race bike is what you'll see professional cyclists ride on their races. They can be stiff, they can be compliant, they can be aero - these are all up to the bike manufacturer and how they design their bikes. But weight is always the top consideration in the design of these bikes. Lightweight bikes are generally great all-rounders. You could simplify it by saying that Lightweight bikes fall between Aero and Endurance bikes.
Components on Lightweight bikes tend to be lighter. They may not be the stiffest and/or the most durable and robust, but they are usually very