On Cloudboom Echo 3 Marathon Review: Fast, Direct and Demanding

Introduction

The On Cloudboom Echo 3 is On’s latest carbon-plated super shoe, built around a new HF super foam midsole, a carbon plate, and a stripped-back, hugging race fit. On positions it for all-out racing over the marathon and shorter distances. To see whether it holds up when fatigue sets in, we took it through a full marathon-distance test on mixed terrain, including long paved stretches.

The Marathon Test

The test covered 18 miles on the Transpennine way, starting slow and building up to close-to-marathon-pace miles on a mix of pavement, stony sections, and compacted softer paths. It was not an all-out race effort, which is actually useful: it shows how the shoe behaves when legs and brain get tired, which is exactly the point where marathon racers need their shoes most.

How They Feel Early On

In the early miles, the Cloudboom Echo 3 does most things you want from a super shoe. There is enough protection, enough pop, and enough zip. The shoes feel light, agile, nimble and racy, and they sit comfortably alongside the fastest carbon shoes on the market. They are minimal, stripped back, direct, a touch firmer, and slightly stiff, in a way that reads as speed rather than harshness on fresh legs. Energy return is good when you are moving well.

Deep into the Miles

This is where the picture gets more complicated. Deeper into the run, on tired legs, firmness started to come up through the shoe. On long tarmac and pavement stretches from around mile 13 to 15, road feel increased noticeably and the ride felt too direct, without quite enough cushioning to soak up ragged form. On softer, groomed compacted paths, the shoe ran noticeably better and felt more forgiving.

The practical takeaway: if you are a four- or five-hour marathon runner, or you want more cushion protection deep into a marathon, this may not be the right shoe. If you can hold good form for a full 26.2 with a high turnover on your toes, there is arguably just enough comfort to chase fast times. For many runners, it will be better suited to half marathons, 10Ks, and interval sessions, where its directness becomes an asset rather than a liability.

A Word on Durability

One caution worth flagging: after around 75 total miles, including the marathon test and some slightly rougher paths, the heel rubber started coming loose. That is a genuine question mark over long-term durability and a factor to weigh before committing to these shoes for a full marathon build-up.

Buying Advice

Think of the Cloudboom Echo 3 as a bit Jekyll and Hyde. It performs brilliantly when you are moving well in fine form, and it is less forgiving on tired legs, a little like older-generation super shoes that almost demand you race well to get the most out of them. If cushioning is your priority, softer-riding alternatives will serve you better. If you are confident in your form and want a fast, direct, minimal carbon racer for shorter races or a strong marathon day, it remains a genuinely good carbon competitor.

Conclusion

The On Cloudboom Echo 3 is a light, nimble, and direct carbon racer with excellent energy when you are running well, but firmness on tired legs and an early durability concern are real trade-offs. Choose it for fast, shorter racing and confident marathon days; look elsewhere if you need deep-mile cushioning.