Parcours Gravel Wheels - 650B vs 700C

Unlike most triathlon bikes, we offer 700c or 650b wheels with our Ventum bikes, but how do you know which are best for you?  Our exclusive UK wheel partners, Parcours.cc, explain the difference.

What is the difference between 650b and 700C wheels?

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Generally speaking, there has only ever been one wheel size to consider for most road cyclists – the 700C.  Ever since the mid-1980s, this has generally been considered as the "standard" wheel size by most road bike designers, at least in part due to the influence of the leading male Time Trial cyclists.  However, as mountain bikers will happily tell you, a "standard" wheel size is often not the best option for every ride or rider.

To help with a little background, let's quickly dive into the history of bike wheels as a whole...

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Right up to the early 1900s, early bikes manufacturers often specified their own bespoke wheel size for their frames.  It was only when Dunlop introduced the pneumatic tyre, that standardised sizing became important.  Wheel manufacturers wanted to allow their riders to fit a tyre from a third party, and the two parts had to fit together.  To make the fit secure, tyres and rims were produced to standardised Bead Seat Diameters (BSD) - the inner diameter of the tyre.

Bead Size Diameter (BSD) for 700C or 650B wheels

But as wheels sizes were being simplified, the terminology used to described them stayed confusing, using the outer diameter (including tyre width) instead of their BSD.  The French sizing system uses the nominal outside diameter (700mm where road wheels are concerned), accompanied by a letter to indicate tyre width (C - a thinner 28mm tyre).  Over time, the number of standards used by road bike manufacturers gradually declined, eventually leaving only 700C as the road "standard".

Over the past few years, another the 650B wheel size (outer diameter 650, with a wider 'B' tyre) has gained popularity in road cycling, having proven its value with mountain bikers as a 27.5".  

Simply, a 650B wheel has a BSD of 584mm whereas the 700C is 622mm, so the wheel itself is 38mm smaller in diameter.

Should I Choose a Smaller or Bigger wheel?

Do I need a 650B or 700C wheel on my Ventum Bike?

There is no 'right' or 'wrong' when it comes to wheels.  The size of your wheel and the size of the tyre will affect how your bike handles, as well as altering the overall riding experience.

Smaller Wheels = Wider Tyres

At first glance, a 700C wheel fitted with a 28mm tyre will have the same total diameter (678mm) as a 650B wheel running a 47mm tyre.  But crucially, the 47mm tyre will have a roughly 2.5 to 3 times more air volume, enormously affecting how the wheel rides.  The wider tyre will enable lower pressures, which increases both ride comfort and grip.  Lower pressure means the tyre can deform more around irregular surfaces, offering a smoother and more confident ride.

Smaller Wheels = Different Handling

Alternatively, if you compare the two wheels fitted with tyres of the same width, the overall diameter of the 650B will be much smaller.  This will therefore impact the ride you get, as the smaller wheel reduces the fork trail and wheelbase, which in turn gives more responsive handling.  

Another consideration is gearing.  Because the smaller wheel moves the bike a shorter distance for each wheel rotation, gearing will feel slightly easier with the 650B.

On occasion, the larger 700C wheel has been claimed to "rollover" larger bumps and obstacles more easily. You unquestionably see this cited as a factor in mountain biking when deciding between a 26er and a 29er. However, it's more nuanced with a 650B vs 700C choice, as you'll see below.

Smaller Wheels = ...Same Weight?

The 650B wheel will be lighter than the 700C option simply because it is smaller (assuming there are no other differences in rim design).  But don't forget that a wider tyre will almost certainly offset any weight saving and may even weigh more! 

The smaller wheel will require also smaller spokes, resulting in a stronger, more robust wheel.

Smaller Wheels = Smaller Riders

The above reasons are assuming that all riders can effectively ride on a 700C wheel, but in reality smaller riders and smaller frames would do well with a 650B wheel regardless of riding conditions.  The smaller wheel improves clearance between the foot and front tyre (most noticeable on sharp turns) and makes it much easier to get a good handlebar and cockpit position on smaller frames.

Is the Wheel or Tyre More Important?

650B or 700C wheel for Ventum Bikes

Whilst changing your wheel size can make the above differences to performance, it really all depends on the tyre size that you fit to the wheel.  Shrinking the wheel gives the tyre more space, enabling riders to tailor performance to the terrain they're riding on.  Essentially, almost all of the differences you'll feel between wheel sizes are down to tyre choice.  The main reason you'll want to choose one wheel size over the other is to let you run the tyre size that you prefer whilst also supporting handling characteristics suitable for your bike rides.

Is a 650B wheel or a 700C wheel right for me? 

700C wheel on a Ventum One Triathlon Bike

The Ventum bikes are all able to run with either a 650B or 700C wheel, as they run on disc brakes rather than caliper and have good frame clearance, so the choice is very much yours. 

Choose a 650B wheel with a 47mm tyre for:

  • Gravel trails, rougher off-road riding on light singletrack and mostly unpaved surfaces!
  • Looser surfaces where grip is a must
  • Sharp, snappy handling

Choose a 700C wheel with 28mm tyre for:

  • Lighter off-road riding, including rides that will also include paved roads or tarmac,
  • "The best of both worlds", combining road performance and endurance with off-road versatility
  • Riders over around 5'5" tall.

Choose a 650B with a 28mm tyre for:

  • Lighter off-road riding, including rides that will also include paved roads or tarmac,
  • "The best of both worlds", combining road performance and endurance with off-road versatility
  • Better handling for smaller frames
  • Riders under 5'5" tall.

Above all, it comes down to personal preference.  We build your Ventum bike for you, to your spec, so whether you choose triathlon, road or gravel, the wheel choice is yours!  And with our UK-Exclusive partnership between Ventum and Parcours, we have the perfect wheel for you. 

 

Note:  The 650B wheel is not the same as a 650C wheel, which were previously used on smaller road frames, but are now very hard to find.  Whilst they are a very similar size, the Bead Seat Diameter is different thanks to the French sizing system, so the two aren't interchangeable!  650B is also sometimes called 'Road Plus'.

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About Parcours

Parcours is a British company with a goal of making aerodynamics more affordable.  They offer an impressive range of road and off-road aero-wheelsets, delivering tangible benefits without costing the earth.  Build your Ventum with an option for Ronde, Strade or Alta 650B wheels, or talk to us to find your ideal wheelset.