How many grams of carbs per hour you really need, why the dreaded bonk is completely avoidable, and how to prevent stomach trouble on long rides.
## Introduction Why am I suddenly completely empty after 60 km, when my legs were fine before? The honest answer: that's the bonk — your carbohydrate stores are empty and the body switches into emergency mode. The good news: it's 100 % avoidable if you eat early and regularly.
The key number: your gut can only absorb a limited amount of carbohydrate per hour. From pure glucose that's around 60 g per hour. Combine glucose and fructose (roughly 2:1) and absorption rises to up to 90 g per hour — about 50 % more energy, because the two sugars travel into the body through different doors. That's not a pro secret, it's simple gut physiology.
For long rides (from about 2.5 hours) these 90 g/h are the gold standard. This guide shows you how much, what and when to eat and drink — so you don't collapse on the climb but still have something left.
## What You Need - Carb sources for the road — bars, gels, bananas, dried fruit or a carbohydrate drink. - Two bottles — one with water, one with an electrolyte or carbohydrate mix. - Reachable pockets (jersey rear pockets) so you can eat while riding. - For long or hot rides: electrolytes (especially sodium) against cramps and fading performance. - A rough time-and-amount rule in your head: every 20 minutes a few bites or sips.
### 1. Fill the tank before the ride Eat a carb-rich meal 2–3 hours before a long ride (oats, bread, rice, pasta), easy to digest and not too fatty. That way you start with full stores. Just before the start a banana or a bar on top is enough. Avoid anything new and too much fibre in the morning before the ride — your stomach will thank you later.
### 2. Start early — don't wait until you're hungry The classic mistake: only eating when hunger hits. By then it's too late, the tank is already half empty. Start after 30–45 minutes and then eat every 20 minutes. Eating and drinking on the bike is a craft — plan it, don't rely on feel.
### 3. Match the amount to duration and intensity Short ride (under 90 minutes): water plus maybe a bar is usually enough. Long, hard rides: aim for 60–90 g of carbohydrate per hour. For reference: a typical energy bar holds around 25–40 g, a gel 20–30 g, a banana about 25 g — build your hourly ration from those.
### 4. Mix glucose and fructose — and don't forget to drink Use products or combinations with glucose and fructose to get past 60 g/h without your stomach revolting. Drink small amounts regularly alongside — thirst is already a late signal. In heat and on long rides electrolytes belong in the mix, or cramps and an early fade loom.
## Common Mistakes - Starting to eat too late. Fix: start after 30–45 minutes, then top up every 20 minutes. - Only water on a long ride. Fix: take in carbs; water alone doesn't refill empty stores. - Too much at once. Fix: small portions, often — the gut only absorbs so much. - Testing new products on race day. Fix: always try fuelling in training, never for the first time in a race.
## Safety Notes A bonk isn't just unpleasant, it's a safety risk: shaking, loss of concentration and dizziness at speed or on a descent are dangerous. At the first sign — sudden emptiness, a queasy feeling, irritability — eat fast carbs immediately and ease off the pace.
Conversely, don't overdo it with brand-new gels and amounts: too much or unfamiliar stuff at once causes gut trouble, one of the most common reasons long rides fall apart. Train your gut like your legs — get it used to higher amounts step by step, rather than trying everything at once on race day.
## Pro Tip Set an eating timer on your bike computer or phone: every 20 minutes a beep = a few bites or sips. On long rides you'll otherwise forget to eat in the rhythm of riding — until it's too late. The timer doesn't eat for you, but it reminds you before the bonk does. Pros deliberately "train the gut" and manage 100–120 g/h with practice — for you a clean 60–90 g is plenty.
### How many carbs do I need per hour on the bike? On long, intense rides 60–90 g per hour. Pure glucose only gets you around 60 g, a glucose-fructose mix up to about 90 g, because the two sugars are absorbed by different routes. Short, easy rides under 90 minutes usually need barely any extra carbs.
### What is a bonk and how do I prevent it? The bonk is the abrupt performance drop when your carbohydrate stores run empty — legs like lead, head blank. You prevent it by starting to eat early (after 30–45 minutes) and topping up every 20 minutes, instead of waiting for hunger.
### Is water enough or do I need sports drinks? For short rides water is fine. From about 90 minutes, in heat or at high intensity, carb and electrolyte drinks help: they supply energy and replace the sodium you sweat out. A drink with glucose and fructose is also an easy way to hit your 90 g/h.
### Why do I get stomach trouble eating on the bike? Usually because you take in too much at once, too concentrated, or unfamiliar products — the gut is sensitive under effort. Eat smaller portions more often, drink enough water with them and rehearse your race fuelling in training. The gut is trainable: step by step you get it used to higher amounts.
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