adidas Prime X 3 Strung
£250
UK RRP
Midsole to scale · mm · red dashes mark the 40mm road limit
- Weight
- 285 g
- men's US 9
- Stack
- 50 / 43 mm
- heel / forefoot · drawn above, against the 40mm line
- Drop
- 7 mm
- Plate
- carbon fibre
- Foam
- Lightstrike Pro
- Stability
- balanced
- Competitive life
- ~500 km
- before the foam stops giving it back
- Built for
- Marathon · Ultra
Verdict
Deliberately built past the rules. Enormous stack, huge cushioning, and superb for long training runs or any race that does not apply World Athletics regulations.
■ Caution
At 50mm this is 10mm over the road limit. Not legal for any World Athletics Applicable Competition. Fine for most local races and all training.
Straight answers
- Is the adidas Prime X 3 Strung legal for road racing?
- No — not for World Athletics Applicable Competitions. The adidas Prime X 3 Strung measures 50mm, 10.0mm over the 40mm road limit. It remains fine for training and for the many races that apply no shoe rule.
- How much does the adidas Prime X 3 Strung weigh?
- 285g in a men's US 9 (UK 8), by the manufacturer's stated figure. Weight moves roughly 3.5% per UK size step, so a UK 11 weighs materially more than the spec sheet says.
- What is the stack height and drop of the adidas Prime X 3 Strung?
- 50mm at the heel and 43mm at the forefoot — a 7mm drop. A carbon-fibre plate runs through Lightstrike Pro.
- How long does the adidas Prime X 3 Strung last?
- We estimate roughly 500km of competitive life — the point at which the foam has degraded enough that you are no longer getting the benefit you paid £250 for, not the point at which the shoe falls apart. Spread over race cycles, that is what the cost-per-race figure on this page is built from.
- Is the adidas Prime X 3 Strung good for a marathon?
- Yes — the marathon is one of the distances it is built for (marathon and ultra / 50k+). Deliberately built past the rules. Enormous stack, huge cushioning, and superb for long training runs or any race that does not apply World Athletics regulations.
Legality by event
Prime X 3 Strung at 50mm · every panel drawn to one scale
Road racing
40mm · 10.0 over
Track events
20mm · 30.0 over
Field events
20mm · 30.0 over
Cross country (spiked shoes)
20mm · 30.0 over
Cross country (non-spiked)
40mm · 10.0 over
Race walking
40mm · 10.0 over
Mountain and trail
no limit
Drawn from the manufacturer’s stated stack height, which is not the measurement World Athletics takes — the rule is measured on a men’s US 8.5 sample, and larger sizes may legally exceed it. An indication, not a ruling. Limits bind Applicable Competitions; most club and local races apply no shoe rule at all. What that means in practice.
Reading — what would the Prime X 3 Strung save you?
Time bought back
−2:32 – 3:53
Off 3:45:00, that lands you at 3:41:07 on the optimistic end.
- Per race
- £32
- ~7.9 races in the foam
- Per second
- £0.16
- whole-life basis
- Sticker
- £250
- UK recommended retail
Economy gain 3–4.2% v. a traditional flat, adjusted for pace and your current shoes. Full method.
Manufacturer-stated specs unless marked estimated · last reviewed 2026-09-04 · prices are UK RRP; check the retailer for the live figure.