Answers to the most common questions across all 10 calculators — tyre pressure, rolling resistance, gear ratios, power vs speed, hill climb & VAM, aerodynamics CdA, FTP zones, calories and training load TSS.
Road tyre pressure depends primarily on total system weight (rider + bike), tyre width, and whether you're running tubes or tubeless. A common starting point for a 75 kg rider on 28mm tyres is approximately 80–90 PSI rear, 70–80 PSI front.
The front tyre always runs lower than the rear because it carries less weight (roughly 42% vs 58%). Running them at the same pressure is a common mistake that leads to a harsh ride and slower rolling on the front wheel.
Use our tyre pressure calculator for a precise recommendation.
On a typical road bike, approximately 42% of the total rider + bike weight rests on the front wheel and 58% on the rear. Since pressure is proportional to load (via the contact patch area), the front tyre requires less pressure to achieve the same optimal contact patch shape.
Running equal pressure front and rear would mean the front tyre is over-inflated for its load, resulting in a smaller contact patch, reduced traction in corners, and a harsher ride.
Yes — tubeless tyres can typically run 5–15 PSI lower than tubed equivalents. The main reason is the absence of an inner tube, which eliminates pinch flat (snakebite) risk. With tubes, too-low pressure allows the tyre to bottom out and pinch the tube against the rim.
Tubeless also benefits from sealant, which self-seals small punctures, giving additional confidence at lower pressures. Many gravel and MTB riders run surprisingly low pressures tubeless (as low as 18 PSI on 2.4" MTB tyres) that would be impossible with a tube.
This is one of the most counterintuitive findings in modern cycling science: wider tyres do not necessarily have more rolling resistance, and on imperfect surfaces they can have less.
A wider tyre at lower pressure has a contact patch that is short and wide, versus a narrow tyre at high pressure with a long and narrow contact patch. Both can have similar total area — but the wider tyre's casing deforms less aggressively, and the rider absorbs less vibration energy from road imperfections.
On perfectly smooth surfaces, narrow tyres at high pressure still win. But real roads are never perfectly smooth, which is why 25–28mm tyres have largely replaced 23mm for road racing.
Road tyres lose 10–15% of their pressure per week through normal permeation through the butyl rubber tube, even without any puncture. Check before every ride if you want to be precise, or at minimum weekly for road riders.
Tubeless tyres hold pressure better and may only need checking every 2–3 weeks, though this varies by tyre and rim seal quality. MTB tubeless should be checked before each ride, especially in cold weather when pressure drops significantly.
Linearly — and understanding this is fundamental to comparing it fairly against aerodynamic drag. The rolling resistance braking force (F = Crr × mass × g) is completely constant — it doesn't change with speed at all. Power = force × velocity, so rolling resistance watts rise in direct proportion to speed.
Concretely: going from 35 to 40 km/h increases rolling resistance watts by 40/35 = 14.3%. Going from 20 to 40 km/h exactly doubles rolling resistance watts. There is nothing exponential about it.
Compare this with aerodynamic drag, which scales with velocity cubed. Going from 20 to 40 km/h increases aero drag power by 8× (2³ = 8). This is why at 40 km/h in a hoods position, aerodynamic drag accounts for roughly 85–90% of total resistance, and rolling resistance only 5–10%. Tyre selection matters — but position and aerodynamics matter far more at race speeds.
Yes — and the direction surprises many riders: wider tyres have lower Crr at their respective optimal pressures, not higher. This is measured, not theoretical.
A wider tyre at lower pressure has a contact patch that is short and wide. The casing deforms more gently and returns to shape more efficiently. A narrow high-pressure tyre has a longer, narrower contact patch where the casing bends more sharply — slightly higher hysteresis loss per rotation. Based on Bicycle Rolling Resistance drum-test data, a 45mm tyre at optimal pressure has roughly 6–7% lower Crr than a 23mm tyre at its own optimal pressure.
The bigger real-world effect is what Jan Heine (Bicycle Quarterly) terms impedance loss: on anything other than billiard-smooth tarmac, an over-inflated narrow tyre transmits road vibration to the rider rather than absorbing it through casing flex. That vibration energy comes directly from your forward motion — it's effectively additional rolling resistance. Wider tyres at lower pressure eliminate this. Our calculator models the width effect with a (25/width)^0.10 factor fitted to BRR published data.
Yes, under-inflation is significantly worse for rolling resistance on smooth surfaces, and our model deliberately uses different penalty coefficients in each direction. This is one of the most poorly-understood aspects of tyre physics.
Under-inflation forces the casing to deform excessively on each rotation, dissipating energy as heat in the rubber. The penalty grows steeply — a tyre at 70% of optimal pressure can have 12–16% higher Crr. Our model applies a 40% Crr increase per unit of pressure ratio deficit.
Over-inflation on smooth tarmac produces a slightly smaller contact patch, but the casing still deforms efficiently and the Crr increase is small. Our model applies only a 5% increase per unit ratio on road surfaces. However, on rough surfaces (gravel, MTB), over-inflation prevents the casing from conforming to irregularities — vibration energy loss dominates, and we apply a 20% penalty per unit ratio. This is why the optimal pressure on gravel is not "inflate as hard as possible."
Practical implication: being 15 PSI under-inflated costs you significantly more watts than being 15 PSI over-inflated on smooth tarmac. On gravel, both directions matter equally.
Crr (Coefficient of Rolling Resistance) is a dimensionless number representing the rolling braking force as a fraction of the wheel's normal load. A Crr of 0.004 means the tyre exerts a braking force equal to 0.004 × its load weight on every rotation — about 3.3 N for an 84 kg system.
Typical values from Bicycle Rolling Resistance drum testing and published manufacturer data:
At 30 km/h for an 84 kg system, the difference between Crr 0.003 and Crr 0.006 is about 6–7 watts. Over a 4-hour ride this is real — but a 10 cm improvement in riding position returning 30W in aero drag savings dwarfs it.
There is no sharp cutoff, but the crossover happens earlier than most riders expect. A rough breakdown for a standard road position (CdA ~0.32, Crr ~0.004, 84 kg system):
This is why tyre selection matters most for: slow climbing (low speed), heavier riders (higher F_rr), MTB (high base Crr), and long-distance endurance (cumulative effect over hours). For criterium racing at 45 km/h, the difference between a Crr 0.003 and Crr 0.005 tyre is less than 5W — less than the noise in a power meter reading. But that same 5W sustained over a 6-hour gran fondo adds up to real fatigue and calorie burn.
For steep climbs (6–10%+), most riders need a gear ratio of 1.0–1.5. This means combinations like:
A ratio of 1.0 at 70 RPM on a 700c wheel produces approximately 12–14 km/h — a comfortable climbing speed for most riders on moderate gradients. Use our gear calculator to find the exact speed for your combination.
Research by Lucia et al. (2001) found that professional cyclists self-select 80–100 RPM during sustained efforts. This range minimises muscular fatigue by reducing the force required per pedal stroke, at the cost of slightly higher cardiovascular load.
Beginners often default to 60–70 RPM (pushing big gears). Training cadence up to 80–90 RPM is one of the highest-impact efficiency improvements a newer cyclist can make. However, individual physiology varies — some riders naturally perform better at higher or lower cadences, and this should be respected.
Rollout (also called "development" in European cycling) is the distance your bicycle travels per complete pedal revolution in a given gear. It is calculated as:rollout = gear_ratio × wheel_circumference
For example, a 50/17 gear on a 700c wheel has a rollout of approximately 6.1 metres. This means each time you push the pedals around once, you travel 6.1 metres forward. Rollout is useful for understanding absolute gearing — two different chainring/sprocket combinations with the same ratio have identical rollout and speed at the same cadence.
FTP (Functional Threshold Power) is the highest average power you can sustain for approximately 60 minutes. It is the cornerstone of power-based training and defines all 7 training zones.
The most common testing protocol is the 20-minute FTP test:
Shorter ramp tests (progressive 1-minute steps to exhaustion) are also popular and well-validated. Garmin, Wahoo, and TrainingPeaks all have built-in ramp test protocols.
W/kg (watts per kilogram) normalises power output for body weight, making it the key metric for climbing performance where you must propel your mass against gravity. Benchmarks for male cyclists (FTP-based):
Most coaches recommend retesting FTP every 6–8 weeks of structured training, or whenever you feel your zones no longer feel accurate (Zone 2 work feels too easy, Zone 4 intervals feel impossibly hard, etc.).
FTP can change significantly with training — a 10–15% improvement over a focused training block is achievable for newer riders. Conversely, FTP declines quickly without training stimulus (roughly 1% per week of complete inactivity).
Zone 2 (56–75% of FTP) corresponds to a conversational pace where you can speak in full sentences. At this intensity, the primary energy system is aerobic fat oxidation, driven by slow-twitch (Type I) muscle fibres and mitochondrial metabolism.
Zone 2 training has gained attention because research — particularly work by Dr. Iñigo San Millán and Dr. Peter Attia — shows it builds the aerobic base (mitochondrial density, fat oxidation capacity, lactate clearance) upon which all higher-intensity training depends. Elite endurance athletes spend approximately 80% of their training volume in Zone 2.
For most amateur cyclists who do too much "medium-hard" riding (Zone 3), shifting more volume to true Zone 2 and less to "junk miles" produces significant fitness improvements.
It depends heavily on riding position, weight, and conditions. For a 75 kg rider on flat road with no wind:
Use the Power vs Speed calculator with your exact weight, position, gradient and wind for a precise result. The model includes gravity, rolling resistance (Crr), aerodynamic drag (CdA), and 97.5% drivetrain efficiency.
Aerodynamic drag scales with the square of relative air speed — so a headwind has a disproportionately large effect. Riding at 30 km/h into a 20 km/h headwind means your body is effectively moving through air at 50 km/h, multiplying drag enormously.
A rider needing 160 W to hold 30 km/h in calm conditions may need 280–320 W into a 20 km/h headwind at the same speed. Enter a positive wind value (headwind) or negative (tailwind) in the Power vs Speed calculator to see the exact impact.
A clean, well-lubricated chain drivetrain loses about 2–4% of power to friction in the chain, derailleurs, and bearings. Our calculator applies a standard 97.5% efficiency factor — the power shown is what you must produce at the pedals before these losses. A dirty or poorly-maintained drivetrain can lose 5–8%, which is measurable over longer rides.
VAM (Velocità Ascensionale Media) — Italian for "average ascent speed" — is vertical metres climbed per hour. It was developed by Dr. Michele Ferrari as a gradient-independent way to compare climbing performances.
VAM benchmarks for cyclists:
Our Hill Climb calculator converts climb length, elevation gain and target time into VAM, estimated watts, and W/kg automatically.
The calculator uses a full physics model (gravity + rolling resistance + aerodynamic drag) and is typically accurate to ±5–10% for steady-pace road climbing. It assumes a consistent effort throughout the climb, standard road CdA (0.38 m²), and smooth tarmac.
Accuracy decreases if the climb has significant flat or descent sections mid-climb, or if you varied pace significantly. For best results use a consistent effort on a clean climb segment.
CdA is the product of the drag coefficient (Cd) and frontal area (A). At speeds above 30 km/h, aerodynamic drag accounts for more than 70% of total resistance on flat terrain — far exceeding rolling resistance.
Typical CdA values by position:
Reducing CdA by just 10–15% (e.g. moving from hoods to drops) saves roughly 30–40 seconds over a 40 km time trial at the same power output — more than most equipment upgrades.
Our Aerodynamics calculator estimates CdA from power meter data + GPS speed on flat terrain. For best results: choose a flat, sheltered road, ride a steady effort for 5+ minutes, then enter average power and average speed with your weight.
For higher precision, the Chung Method uses multiple laps of a loop and regression analysis to isolate CdA from Crr. GoldenCheetah (free software) can perform this from any .fit power file. Wind tunnels and velodromes provide the most accurate results but cost £200–1000+ per session.
Rough estimates for a 75 kg rider on flat road:
Our calculator uses MET values from the 2024 Compendium of Physical Activities — the gold standard academic reference for exercise energy expenditure, published by the American College of Sports Medicine. Individual results carry ±15–20% variation based on fitness level, temperature, and terrain variation.
General guidelines based on ride duration:
The most common fuelling mistake is waiting to feel hungry. By that point you're already in deficit and performance will be declining. Eat early, eat consistently. The Calories calculator includes a full pre/during/post ride fuelling plan tailored to your ride duration and terrain.
TSS (Training Stress Score) quantifies the total physiological load of a ride using power data. Developed by Andrew Coggan and Hunter Allen, it is the foundation of modern power-based periodisation.
Formula: TSS = (hours × NP × IF / FTP) × 100 — where NP is Normalised Power and IF is Intensity Factor (NP ÷ FTP). A 1-hour ride at exactly FTP produces 100 TSS.
Practical categories:
TSB (Training Stress Balance) = CTL − ATL, also called "Form". It represents the balance between fitness and fatigue:
Form guidelines:
A typical taper for an important event involves reducing ATL over 7–14 days while maintaining CTL, bringing TSB from −15 up to +15 to +25.
Accuracy varies by calculator. Gear ratio and speed calculations are mathematically exact — they use pure mechanical relationships with no estimates involved.
Tyre pressure recommendations are accurate to ±5–10 PSI for most riders, based on the Silca contact patch model. Real-world optimal pressure depends on additional factors not captured here: tyre casing construction, road surface temperature, rider position, and personal comfort preference.
Rolling resistance estimates carry ±20–30% uncertainty, especially on unpaved surfaces where conditions vary enormously. See our methodology page for full accuracy details.
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Absolutely — suggestions are welcome and many features in the current tool came from user feedback. Ideas currently being considered include a gradient speed estimator, a calorie burn calculator, and a training load (TSS) estimator.
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