Is it worth upgrading my bike?
If you mean buying a faster frame, usually not, and certainly not first. On our figures a £2,500 time trial frame saves around 20 watts, which works out at 0.008 watts per pound spent. Shaving your legs saves around 5 watts for the price of a razor, which is 0.62 watts per pound. That is about 78 times better value.
Most riders buy speed in almost exactly the wrong order. The frame and the wheels are the expensive, visible parts, so they get bought first. They are also the two worst-value things on the list. What you wear and how you sit are cheap and unglamorous, and they are where nearly all the easy watts are.
What a pound actually buys
| Change | Watts saved | Cost | Watts per £ |
|---|---|---|---|
| Shave your legs | 5 W | £8 | 0.62 |
| Clean and wax your chain | 6 W | £25 | 0.24 |
| Add clip-on aero bars | 25 W | £120 | 0.21 |
| Aero overshoes | 6 W | £35 | 0.18 |
| Skinsuit instead of a jersey | 12 W | £230 | 0.052 |
| Time trial helmet | 8 W | £250 | 0.032 |
| Deep front wheel | 6 W | £700 | 0.008 |
| Dedicated TT frame | 20 W | £2,500 | 0.008 |
| Full disc wheel | 5 W | £1,200 | 0.004 |
The frame does save the most watts of anything on that list. It just costs so much that the saving is close to the worst value available. If your budget is £2,500 and your goal is speed, you could buy the frame, or you could buy clip-on bars, a skinsuit, a TT helmet, aero overshoes, a waxed chain, fast tyres and a razor, save considerably more, and still have most of the money left.
How much is a watt actually worth?
At roughly 40 km/h, 10 watts is worth about 45 seconds over 40 km for a rider holding around 250 watts. Treat that as a rule of thumb for flat riding, not a promise. The number shrinks as you slow down, because air resistance rises with the cube of speed. At 32 km/h the same 10 watts buys you noticeably less time, and tyres and chain matter relatively more than aero kit.
When a new bike is worth buying
There are real reasons, they are just not usually watts:
- Your current bike will not take what you want to fit, such as clip-on bars or wider fast tyres.
- It does not fit you, and no amount of aero kit fixes a position you cannot hold.
- It is worn out, or you do not trust it.
- You want it. That is a perfectly good reason to buy a bike. It is just not an efficient way to buy speed, and it helps to be honest with yourself about which one you are doing.
The honest caveats
These figures are indicative. Most come from published wind tunnel and rolling resistance testing, and some are our own estimates, which are flagged in the tool and listed on the sources page. A wind tunnel resolves to roughly ±2.5 W at 40 km/h, so anything smaller than that is below what testing can reliably separate.
They are also generic. Savings depend on your position, your speed and what you already own. Someone already in a skinsuit gains nothing from buying another one. That is why the tool asks what you are currently running and works out the upgrade from there, rather than comparing you to an imaginary beginner.