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Super Spikes? New Balance FuelCell Sigma SD-X Impressions

July 10th, 2021
Super Spikes? New Balance FuelCell Sigma SD-X Impressions

Last week, I got my hands on a pair of New Balance’s sprint spikes for 2021, the FuelCell Sigma SD-X. Although not as hyped as Nike’s Air Zoom MaxFly, New Balance’s sprint team has been running some ridiculous times in the SD-X: Trayvon Bromell is the fastest man in the world this year, and Sydney McLaughlin set the 400mh world record wearing New Balances.

Like other super spikes, the SD-X has an extremely stiff carbon fiber plate and a layer of foam in the midsole designed to maximize energy return on the track. The foam layer makes for a taller ride than most spikes—the stack height is comparable to trainers. That said, it’s definitely not a training spike: its spikes are non-removable.


  • These spikes definitely run big. I wear a 10.5 in most shoes and spikes, but sized down to a 10 for these.
  • The carbon fiber plate is as stiff as advertised—it’s significantly harder to bend than the Superfly Elite’s I’ve been running in.
  • Despite the stiffness, they’re surprisingly comfortable to run in. The springiness was obvious from my first stride in them—it really feels like the carbon fiber plate and foam are propelling my legs forward.
  • The springiness is enough to affect my technique—I don’t have any videos, but I felt like I was sitting back a little more than normal for the first few reps.
  • New Balance claims that the SD-X has a “strong lockdown feel”. Unfortunately, that doesn’t apply to the heels. Wearing socks is impossible with the amount of heel slippage. Heel lock lacing is a non-starter as well since the spike doesn’t have a tongue. Running barefoot mostly solves the problem, but I’ll have to keep experimenting to find a more secure fit.


Do super spikes make you faster? I’ve run two workouts since getting the SD-X—I alternated between using my old Superfly Elites and the SD-X to try and compare. Obviously, take the results with a huge grain of salt: it’s an unblinded, single subject test with many confounders, including fatigue, wind, and my own fallibility as a mediocre sprinter.

These workouts came in the middle of my last training block—I was pretty beat up. For context, my workout PRs are 2.87 for a 30m fly and 3.83 for a 30m block start.

Workout 1: 30m flys

Each fly had a ~35 meter run-in. I had full recovery between reps, and there was no wind to speak of. Times were measured by a Freelap.

Rep Shoe Time
1 Nike Superfly Elite 2.98
2 New Balance SD-X 2.96
3 New Balance SD-X 2.97
4 Nike Superfly Elite 3.05
5 Nike Superfly Elite 3.01
6 New Balance SD-X 2.96

And the times by shoe:

Shoe Rep 1 Rep 2 Rep 3 Average
Nike Superfly Elite 2.98 3.05 3.01 3.01
New Balance SD-X 2.96 2.97 2.96 2.96

My slowest SD-X rep was faster than my fastest Superfly Elite rep—and my average fly time was 0.05s, or ~1.5%, faster in the SD-X. If you were to extrapolate that across the ~50-60 meters of non-acceleration in a 100m, you’re looking at an advantage of a full tenth of a second.

Workout 2: 30m block starts

Block starts felt weird in the SD-X at first. I still had some problems with heel slippage—I think I have another couple hundredths to unlock once I figure that out.

I had Freelap gates at 10 and 30 meters, with another cone at 40 meters to signal the end of my transition phase. Again, I had full recovery between reps, and there was no wind.

Rep Shoe 0-10m 10-30m 0-30m
1 Nike Superfly Elite 1.80 2.22 4.02
2 New Balance SD-X ? ? 4.04
3 New Balance SD-X 1.85 2.19 4.03
4 Nike Superfly Elite 1.90 2.21 4.11
5 Nike Superfly Elite 1.82 2.19 4.01
6 New Balance SD-X 1.81 2.18 3.98

And by shoe:

Shoe 0-10m Average 10-30m Average 0-30m Average
Nike Superfly Elite 1.84 2.21 4.05
New Balance SD-X 1.83* 2.19* 4.02

*: My Freelap failed to record the 10m split for my first, slowest, SD-X rep, so the 0-10m and 10-30m splits are skewed downwards for that shoe.

Again, the SD-X seems slightly faster than the Superfly Elite. I think the results are somewhat skewed by my fourth rep—I’m not convinced that the SD-X is actually any faster out of the blocks right now. Maybe with a better heel lock I can squeeze a bit more out of them.


One of my goals for 2021 was to become 1% faster. A couple of workouts in these new shoes, and it looks like I might have hit that goal just by swapping spikes! I only have one competition left in the season, and I’ll definitely be wearing the SD-X for it.

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