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40Race Shoe FinderEst. 2023 · London

Head to head

adidas Prime X 3 Strungvs
Nike Zoom Fly 6

Prime X 3 Strung

£149

Typical street price · £250 RRP

■ 50mm — over limit
Zoom Fly 6

£110

Typical street price · £165 RRP

40mm — on the limit

Choose the Prime X 3 Strung if…

  • You want the bigger return: 3–4.2% economy gain against 1.5–2.6%, and that gap widens the longer you are out there.
  • You want more shoe underneath you late on: 50mm against 40mm, which is protection over a long race rather than speed over a short one.
  • You race off a strong, repeatable stride and want the more aggressive ride rather than the safer one.
  • You are racing Ultra / 50K+ — built for it, where the Zoom Fly 6 is not.

Choose the Zoom Fly 6 if…

  • Your race is run under World Athletics rules — this one is legal at 40mm and the Prime X 3 Strung is not.
  • You want the lighter shoe: 248g against 275g, a 27g difference you will feel late in a race.
  • You want something more forgiving. This is the steadier platform — useful if your form goes late, or if you are on your feet longer.
  • Money matters: it is selling around £110 against £149, and the time difference between them is smaller than the price difference suggests.
  • You want more races out of one pair: about 600km of competitive life against 500km.
  • You are racing Half marathon — built for it, where the Prime X 3 Strung is not.

What does this
mean for you?

Every figure below is recalculated from your race and your current time. The gap between two shoes is not fixed — it grows with how long you are on your feet.

Over marathon from 3:45:00

Time back
Prime X 3 Strung: 152s–233sZoom Fly 6: 49s–124s
Cost per second saved
Prime X 3 Strung: £0.10Zoom Fly 6: £0.13

Ranges, not promises. Both figures are against a standard trainer, and the honest answer for most runners is that the difference between two shoes of this class is smaller than the difference a month of decent training makes.

Every number.

010203040505044
Prime X 3 Strung
010203040504032
Zoom Fly 6

What you pay

Street price
Prime X 3 Strung£149
Zoom Fly 6£110■

What the shoe is actually selling for across the shops we read, not its RRP.

RRP
Prime X 3 Strung£250
Zoom Fly 6£165

List price. Almost nobody pays it for a race shoe.

Cost per race
Prime X 3 Strung£19
Zoom Fly 6£12■

Street price divided by the races the foam stays fast for.

Cost per second saved
Prime X 3 Strung£0.10■
Zoom Fly 6£0.13

The whole-life question: what each second of race time costs you.

What it does

Estimated saving
Prime X 3 Strung152s–233s■
Zoom Fly 649s–124s

Against a standard trainer, over the distance and time set above.

Economy gain
Prime X 3 Strung3–4.2%■
Zoom Fly 61.5–2.6%
Built for
Prime X 3 StrungMarathon · Ultra
Zoom Fly 6Half · Marathon
Best use case
Prime X 3 StrungDeliberately built past the rules. Enormous stack, huge cushioning, and superb for long training runs or any race that does not apply World Athletics regulations.
Zoom Fly 6The sensible answer for a first marathon. Carbon plate, durable foam, a third of the cost per race of an Alphafly because it lasts more than twice as long.

How it is built

Weight
Prime X 3 Strung275 g
Zoom Fly 6248 g■

Manufacturer figure at men's US 9.

Stack (heel)
Prime X 3 Strung50 mm
Zoom Fly 640 mm
Stack (forefoot)
Prime X 3 Strung44 mm
Zoom Fly 632 mm
Drop
Prime X 3 Strung6 mm
Zoom Fly 68 mm
Foam
Prime X 3 StrungLightstrike Pro
Zoom Fly 6ZoomX over SR-02
Plate
Prime X 3 Strungcarbon fibre
Zoom Fly 6carbon fibre

Rules and fit

Road legal
Prime X 3 StrungNo (50 mm)
Zoom Fly 6Yes (40 mm)■

World Athletics caps road racing shoes at 40 mm of stack.

Fit
Prime X 3 Strungstandard
Zoom Fly 6standard
Stability
Prime X 3 Strungbalanced
Zoom Fly 6stable

Neither is better in the abstract — it depends on your stride.

Race life
Prime X 3 Strung~500 km
Zoom Fly 6~600 km■

How long the foam stays fast, not how long the shoe survives.

Data confidence
Prime X 3 Strungverified
Zoom Fly 6verified

■ marks the better figure where one is genuinely better. Fit, foam, drop and stability carry no mark — they depend on your foot and your stride, not on which shoe is superior.

In your size.

Where to buy

Your UK size

Best price today — some sizes£145at Runningbear — £105 under RRP

9 retailer checks failed on the last run, so their prices are missing rather than wrong.

Prices are captured when the site is built and stamped with the time of that check. We never rank a retailer by what it pays us; where a link earns a commission it is marked sponsored and the price you pay is unchanged.

Where to buy

Your UK size

Best price today — some sizes£109.99at Run North West — £55 under RRP

9 retailer checks failed on the last run, so their prices are missing rather than wrong.

Prices are captured when the site is built and stamped with the time of that check. We never rank a retailer by what it pays us; where a link earns a commission it is marked sponsored and the price you pay is unchanged.