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40Race Shoe FinderEst. 2023 · London

Head to head

adidas Prime X 3 Strungvs
ASICS Magic Speed 5

Prime X 3 Strung

£149

Typical street price · £250 RRP

■ 50mm — over limit
Magic Speed 5

£130

Typical street price · £150 RRP

38mm — road legal

Choose the Prime X 3 Strung if…

  • You want the bigger return: 3–4.2% economy gain against 2–3.1%, and that gap widens the longer you are out there.
  • You want more shoe underneath you late on: 50mm against 38mm, 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 Magic Speed 5 is not.
  • You would rather buy on measured numbers: this shoe's specs are manufacturer-confirmed, the Magic Speed 5's are estimated.

Choose the Magic Speed 5 if…

  • Your race is run under World Athletics rules — this one is legal at 38mm and the Prime X 3 Strung is not.
  • You want the lighter shoe: 218g against 275g, a 57g 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.
  • You are racing 10K or 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–233sMagic Speed 5: 83s–158s
Cost per second saved
Prime X 3 Strung: £0.10Magic Speed 5: £0.14

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
010203040503831
Magic Speed 5

What you pay

Street price
Prime X 3 Strung£149
Magic Speed 5£130■

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

RRP
Prime X 3 Strung£250
Magic Speed 5£150

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

Cost per race
Prime X 3 Strung£19
Magic Speed 5£16■

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

Cost per second saved
Prime X 3 Strung£0.10■
Magic Speed 5£0.14

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

What it does

Estimated saving
Prime X 3 Strung152s–233s■
Magic Speed 583s–158s

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

Economy gain
Prime X 3 Strung3–4.2%■
Magic Speed 52–3.1%
Built for
Prime X 3 StrungMarathon · Ultra
Magic Speed 510K · Half · 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.
Magic Speed 5The best entry point to carbon. Real plate, real super foam, durable enough to train in, and about half the price of the flagships.

How it is built

Weight
Prime X 3 Strung275 g
Magic Speed 5218 g■

Manufacturer figure at men's US 9.

Stack (heel)
Prime X 3 Strung50 mm
Magic Speed 538 mm
Stack (forefoot)
Prime X 3 Strung44 mm
Magic Speed 531 mm
Drop
Prime X 3 Strung6 mm
Magic Speed 57 mm
Foam
Prime X 3 StrungLightstrike Pro
Magic Speed 5FF Blast Turbo
Plate
Prime X 3 Strungcarbon fibre
Magic Speed 5carbon fibre

Rules and fit

Road legal
Prime X 3 StrungNo (50 mm)
Magic Speed 5Yes (38 mm)■

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

Fit
Prime X 3 Strungstandard
Magic Speed 5standard
Stability
Prime X 3 Strungbalanced
Magic Speed 5stable

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

Race life
Prime X 3 Strung~500 km
Magic Speed 5~500 km

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

Data confidence
Prime X 3 Strungverified■
Magic Speed 5estimated

■ 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£119at Startfitness — £31 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.