Spec analysis — not yet tested
What this page is. A podiatrist’s reading of the published specifications for the Brooks Glycerin 23 — Brooks’ own figures and an independent lab’s measurements, side by side. Nothing here has been measured, worn or scored by us. There is no score and no seal on purpose: under our standard, a number only appears once a pair has been on the bench and on the road. When we test this shoe, this page is replaced by the full review and the change is logged.
The Glycerin is Brooks’ softest neutral daily trainer, and the 23 makes one change that matters more clinically than the marketing suggests: the heel-to-toe drop has come down from 10 mm to 8 mm.
What Brooks says it is
Brooks positions the Glycerin 23 as a max-cushion daily trainer for neutral runners — easy miles, long runs, and in practice a great deal of standing and walking. It runs on Brooks’ nitrogen-infused DNA Tuned midsole and lists at $175, up from $165 for the 22.
The published specification
Every figure below is attributed to whoever published it. Where Brooks and the lab disagree, both numbers appear. No number on this page was measured by us.
| Specification | Figure | Source |
|---|---|---|
| Heel stack | 38 mm | Brooks |
| Heel stack | 37.2 mm | RunRepeat lab |
| Forefoot stack | 30 mm | Brooks |
| Forefoot stack | 29.0 mm | RunRepeat lab |
| Heel-to-toe drop | 8 mm | Brooks |
| Heel-to-toe drop | 8.2 mm | RunRepeat lab |
| Weight, men’s | 10.7 oz / 303 g | Brooks |
| Weight, men’s | 303 g | RunRepeat lab |
| Weight, women’s | 9.0 oz / 255 g | Brooks |
| Midsole softness | 29.2 AC (lab average 35.6) | RunRepeat lab |
| Toe-box width | 73.9 mm | RunRepeat lab |
| Toe-box height | 27.7 mm | RunRepeat lab |
| Torsional rigidity | 14.0 Nm | RunRepeat lab |
| Heel-counter stiffness | 4 / 5 | RunRepeat lab |
| Longitudinal stiffness | 15.2 N (lab average 15.5) | RunRepeat lab |
| Outsole thickness | 3.3 mm | RunRepeat lab |
| Insole thickness | 4.4 mm, removable | RunRepeat lab |
| Price | $175 | Brooks |
| Toe-Box Index, Depth Index, Orthotic Volume Rating, all nine scores | Not measured — we have not tested this shoe | Podiatrist Tested |
What the spec sheet suggests — and what only a test can answer
The drop change is the story. Going from 10 mm to 8 mm sounds trivial and is not. Drop decides how load is shared between the Achilles and the front of the foot: the lower the drop, the more dorsiflexion the ankle has to find and the more work the Achilles and calf do. If you chose the Glycerin 22 because a 10 mm drop settled an irritable Achilles, treat the 23 as a different shoe rather than a refresh.
Brooks publishes an honest sheet. Every Brooks figure here lands within about a millimetre of the lab’s measurement. That is worth saying out loud, because it is not universal — we have looked at shoes where the stated drop and the measured drop differ by more than 4 mm. You can plan around these numbers.
The toe box got taller, and nobody markets that. Lab height went from 23.6 mm on the 22 to 27.7 mm on the 23. Height, not width, is what a clawed or hammered second toe runs out of, and it is what decides whether the upper presses on a dorsal bunion. This is the change most likely to matter to a foot that was borderline in the 22.
The base got wider. Lab midsole width at the heel went from 89.7 mm to 98.6 mm. A wider platform is more stable under a heel strike without the shoe being sold as a stability model.
The insole comes out, and it is thinner. 4.4 mm against 5.0 mm on the 22 — so a custom device drops into slightly less freed volume than it did last year. Whether that matters depends on the device, which is exactly the kind of thing a spec sheet cannot settle.
What only a test can answer: whether that 4/5 heel counter actually resists a single-leg stance the way the number implies; whether the toe box is deep as well as tall; the real Orthotic Volume Rating with a device seated in it; and durability, which no published figure predicts.
Likely a fit
- Neutral runners who want the softest daily Brooks and do not need posted support.
- Heel strikers — the cushioning and the wider heel platform are aimed squarely at you.
- Anyone running a custom orthotic who needs the factory insole to come out cleanly.
- Toes that were crowded for height in the 22.
Wait for the test, or look elsewhere
- An irritable Achilles that was settled by the 22’s 10 mm drop — this is 2 mm lower.
- Anyone who needs genuine motion control; a wide base is not a medial post.
- Feet that need width rather than height — the toe box measured 73.9 mm, which is ordinary.
- Anyone who wants a score from us. There is not one yet, and we will not invent it.
What changed from the Glycerin 22
All comparisons below are the lab’s measurements of both shoes, not ours.
- Drop: 10.3 mm → 8.2 mm measured.
- Toe-box height: 23.6 mm → 27.7 mm.
- Midsole width at the heel: 89.7 mm → 98.6 mm.
- Insole thickness: 5.0 mm → 4.4 mm, still removable.
- Traction score: 0.44 → 0.66.
- Price: $165 → $175.
The Glycerin is not the only shoe whose published stack heights an independent lab has re-measured — see our Skechers Aero Burst spec analysis, where the published 6 mm drop measured 8.8 mm.
Where to buy
Disclosure: the links below are paid links. If you buy through them Amazon pays us a commission at no cost to you. Commissions never influence a score, a ranking or the seal, and this page carries no score because the shoe has not been tested — see our independence policy.
Amazon listings are colourway-specific; these point at one common colourway of each. Price checked 9 September 2026 at a $175 list.
Questions people ask about the Glycerin 23
Is the Brooks Glycerin 23 good for plantar fasciitis?
The features that tend to help are present: a lot of cushioning under the heel, a removable insole so an orthotic can go in, and a stiff-ish heel counter. Two honest caveats. Plantar fasciitis responds to load management, and a shoe supports that rather than replacing it. And the drop came down 2 mm, which very slightly increases the work the calf and Achilles do — relevant if your heel pain travels with a tight calf. We have not tested this shoe, so it carries no score for plantar fasciitis or anything else.
What is the drop on the Brooks Glycerin 23?
Brooks publishes 8 mm. RunRepeat’s lab measured 8.2 mm on a retail pair, so the published figure is trustworthy here. That is down from 10 mm on the Glycerin 22 — the single most consequential change in this update if you are choosing on drop.
Glycerin 23 or Glycerin 22 — is it worth upgrading?
If the 22 worked and you liked its 10 mm drop, the 23 is not a like-for-like replacement and the remaining 22 stock may suit you better. If your toes felt shallow in the 22, the 23 gained about 4 mm of toe-box height and is worth trying. Neither shoe has been through our measurement protocol.
Does the Glycerin 23 work with custom orthotics?
The factory insole is removable and measures 4.4 mm, so removing it frees that much volume for a device — marginally less than the 5.0 mm the 22 freed. Whether your specific orthotic seats well also depends on heel-cup depth and last shape, which published figures do not describe. That is what our Orthotic Volume Rating is for, and this shoe does not have one yet.
Do podiatrists recommend the Brooks Glycerin?
The Glycerin is Brooks’ softest neutral shoe, and it comes up in clinic for the straightforward reason that a painful heel on a hard floor wants cushioning. The 23 also has an unusually accurate spec sheet: heel stack, forefoot stack, drop and weight all land within about a millimetre of the independent lab figures on this page — 8.2 mm measured against 8 mm published. When a shoe is chosen for its drop, that kind of accuracy is what makes the advice hold. Two cautions. Its 8 mm drop is lower than the Glycerin 22’s 10 mm, so anyone whose Achilles had settled on the older version is being moved in the wrong direction. And soft is not the same as supportive — this shoe offers no motion control. Podiatrist Tested has not worn or measured this pair, so it carries no score and no seal.
What happens next
When we buy this pair, it goes on the bench: calipers on stack and toe box, scale at men’s 10, torsional twist, heel-counter squeeze, single-leg stance, then real logged miles. At that point this page is replaced by the full review with all nine scores and a seal decision. Until then it stays exactly what it says it is — a reading of other people’s numbers.