- Not all grams are the same.
- You might be saving weight, at great cost, in the wrong places on your bike.
- If it turns, you need to make it lighter.
All cyclists, both mountain bikers and road riders, obsess about bike weight. You might pay in Rands, but riders really care a lot more about grams than anything else.
Lighter bikes are theoretically faster and require less effort to pedal. That means you can either set new personal bests, on a lighter bike, or ride at the same speeds with less effort.
The tricky bit about bike weight is that not all grams are the same. That might sound like a ridiculous contradiction, but it is true.
For on and off-road riders to benefit most from any lightweight of their bike, it is important to understand the concept of rotational weight.
Those grams that matter most
The weight categories on your bikes can easily be divided into two groups: components that rotate and everything else. The latter category is your frame, seatpost, seat, cockpit (handlebar/stem), brake levers and callipers.
Where any lightweighting budget is spent for best effect, will be on the rotation components: wheels, tyres, cranks, pedals and the moving bits of your drivetrain. These are all components that have to be rotated by your energy output. If they are replaced with lighter parts, you invest less energy to keep them spinning on a ride, increasing speed and reducing effort – especially when climbing.
Bike builders and experienced riders know the value of lightweighting in the right places, and that is usually not the frame. Most novice riders will compare frame weight as the basis of their decision, but this is a fallacy.
There is a much greater gain to be had, from spending money buying lighter rotating components, than an ultra-lightweight frame. Lighter wheels and tyres are by far the biggest potential win, as they are the largest rotational components on your bike.
Avoiding the frame fallacy
If you are on a budget, don’t spend it on a lighter frame or carbon-fibre handlebar. Get lighter rims.
A good thought experiment is to imagine two mountain bikes, both weighing 12kg. The bike with a lighter frame, but heavier wheels, will feel slower than another 12kg mountain bike with a heavier frame, but light wheels – despite both bikes having the same overall mass.
If you are going to invest in making your bike lighter, start with the wheels. And then the drivetrain. A lighter frame should not necessarily be your first upgrade.
When selecting lower rotational mass components for your bike, always apply the engineer’s logic that says you can have two of the following things – light, cheap or strong – but never all three. Make your decision accordingly.