How to choose road bike geometry

Differences between road and sportive bikes explained

There’s an incredible diversity of road bikes to choose from these days. But before you even start to narrow down brands and equipment options there’s one very basic question you need to answer.

Are you worried about where you finish, or whether you finish – and therefore do you need a ‘race’ bike shaped for speed or a ‘sportive’ bike shaped for comfort?

What are the real differences?

Bike geometry is the blanket name given to all the different tube lengths that go to make up a bike, and the angles they join at. It’s the blend of each part that creates the overall handling and fit character of the bike and it’s amazing how 10mm there or a fraction of a degree here can make a noticeable difference.

Sportive bikes: heads up for comfort

The most immediate guide to bike type and fit is the height of the head tube. You can move the stem and bars up and down by adding or removing spacers under the stem or even by changing to a different angle stem.

However, taller head tubes (160mm or longer on a 56cm frame) naturally mean a higher cockpit position and therefore more upright posture than a shorter head tube (140mm or lower). Sitting more upright places less strain on hands, wrists, shoulders, neck and spine and creates a more relaxed ride but obviously creates more aero drag, which slows you down.

Because you’re sitting up taller, many sportive bikes also use a shorter top tube so you’re not stretched forwards. You’ll often find slacker steering angles (nearer 72 than 73) and wheelbases (towards a metre on 56cm frames) on sportive bikes. This means that they naturally run straight rather than twitching about, which can get tiring.

As the fork steerer inside the head tube is longer it’s more prone to flex, and that’s often amplified by deliberate softening of the fork blade and lengthening and/or thinning of the rear stays for extra comfort. Factor in that your weight is further back from the front wheel, and that handling as well as power delivery feedback can often feel more vague on sportive bikes. It adds up to an ideal recipe for cruising comfortably within your limits rather than pushing the pace.

Rose's new Xeon Team GF 3100 sportive machine classically features a tall head tube, slackish head angle and slender, kinked seatstays

Race bikes: head down to hammer

In contrast race bikes push rider weight low and forward for better aerodynamics and more front wheel traction. This demands shorter head tubes and longer top tubes that stretch the rider out, flattening the back and reducing frontal area to minimise drag. This also lowers the centre of gravity and puts more weight through the front tyre for cornering grip, creating a naturally more aggressive ride character.

Traditionally race bikes will often have steeper, twitchier steering angles and longer stems to enhance that aggressive feel further. Add shorter, stiffer rear ends and the increased use of deeper, often more rigid feeling aerodynamic tube shapes and you’re looking at bikes that are very fast and efficient, but potentially unforgiving on longer rides.

Canyon’s new Aeroad is a prime example of an aggressively focused race machine

Blurring the lines

While geometry is a good baseline for judging the character of a bike there are lots of unseen aspects that you’ll only realise from reading reviews such as the ones on BikeRadar or by riding the bike yourself. For example, some short and upright bikes such as Scott’s CR1 are surprisingly stiff, responsive and agile – and some long and low aero race bikes like Ridley’s Noah have a distinctively floated distance friendly ride.

Machines such as Giant’s brand new Defy Advanced or Cervelo’s S3 blur the lines between long haul comfort and aggressive responsiveness too. Swapping spacers or stems is obviously an option for any rider wanting to change their position and bike shop fit systems can help if you’re not sure what ‘right’ feels like in the first place.

The bottom line is that there are more better fitting, faster and more comfortable road bikes available now than there ever have been before. Keep reading our tests, try as many bikes on your shortlist as you can and we guarantee your riding future will shape up pretty well.

Related Articles

Comments

Back to top