Stack and reach
How high and how far forward the top of the head tube is, from the bottom bracket. They are the two numbers that decide whether a frame can be set up like yours.
BB, or bottom bracket
The axle your cranks turn on, in the middle of the frame. Every number on this site is measured from it, because it is the one point that sits in the same place on every bike.
Headset cover
The little cap on top of the head tube, under your spacers. Most makers do not publish it, so I assume 15 mm and add 6 mm to the band, which on its own is enough to hold an answer at "probably" rather than "fits".
Stem clamp, and its centre
The collar on the steerer that your stem bolts to. I need the middle of it. Where a maker gives only the height, I assume halfway up and say so on the answer.
Steerer
The tube coming up out of the fork. The cover, the spacers and the stem all sit on it, and it is the thing a mechanic cuts to length.
Bar reach
How far forward the hoods sit from the middle of the bar. Two bars on the same stem can put your hands 20 mm apart, which is why I ask.
Setback
How far your saddle sits behind the bottom bracket.
Drop
How much lower your bar is than your saddle.
Rails, and the rail centre
The two rods under your saddle, and the middle of the straight part of them. That midpoint is the point I use, because it is the one you can find with a tape.
The band
How far out I could be, in millimetres, and why. It is a straight sum of everything I had to assume rather than a clever average, so it errs wide on purpose.
wb, stand, trail
Wheelbase, standover and trail: how long the bike is, how high the top tube is where you straddle it, and how steady the steering feels. I show them against your bike, and I leave them out when the maker does not publish them.
est.
Estimated: a number I worked out rather than read off the maker's table. Anything marked this way can move if the maker publishes the real one.
Close Escape closes it. The measuring guide has the pictures. Open the measuring guide
Specialized Aethos 2
Road · 6 sizes
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- Bike
- Specialized Aethos 2 · Road · 6 sizes
- Geometry
- specialized.com, fetched 29 Aug 2026, re-checked, no differences
- Cockpit
- Generic stem and bar, assumed
- Solved with
- cover 15 mm (assumed), max spacers 40 mm (assumed), stem clamp centre 20 mm (assumed), so every verdict carries ±10 mm at the bar
- Sheet
- 6 September 2026 · 210 bikes, 43 makes, 1,262 sizes in the catalogue
Geometry, every size, from the maker's table
The tinted row is the size drawn beside it. Press a size to draw it.| Size | Stack (mm) | Reach (mm) | Head angle (deg) | Seat angle (deg) | Head tube (mm) | Chainstay (mm) | Wheelbase (mm) | Standover (mm) |
|---|---|---|---|---|---|---|---|---|
| 49 | 522 | 373 | 71.4 | 75.5 | 114 | 410 | 978 | 719 |
| 52 | 538 | 377 | 72.1 | 74.5 | 128 | 410 | 981 | 737 |
| 54 | 559 | 384 | 72.5 | 74 | 150 | 410 | 992 | 759 |
| 56 | 580 | 391 | 73 | 74 | 169 | 410 | 998 | 779 |
| 58 | 606 | 398 | 73 | 74 | 198 | 410 | 1013 | 805 |
| 61 | 627 | 404 | 73.5 | 74 | 218 | 410 | 1020 | 834 |
The table runs on to the right: 6 more columns after Reach. Scroll it sideways to read them.
The 56 drawn to scale from the table, with no build on it. Stack and reach run from the bottom bracket to the top of the head tube; every size is solved from those two. One square is 100 mm.
The maker's cockpit
No stock cockpit I can name, so every size is solved on a generic stem and bar unless you choose one on the sheet.Generic stem and barAssumedNo bar is listed for this frame.
In the maker's words
Kept whole, as I read it off specialized.com.Aethos 2 Frameset: frame, fork, Roval Alpinist carbon seatpost and alloy 30 mm seat binder; complete bikes use a two-piece Roval Alpinist bar and stem (sizes per build).
Cockpit and seatpost, in the maker's words · 46 words
Aethos 2 Frameset: frame, fork, Roval Alpinist carbon seatpost and alloy 30 mm seat binder; complete bikes use a two-piece Roval Alpinist bar and stem (sizes per build). Seatpost length row 300 mm (49-52) / 360 mm (54-61). Spacer and top-cover heights not on the page.
OFFICIAL SOURCE: Specialized GB page for the Aethos 2 Frameset (code 4221561), six sizes 49-61, the second-generation Aethos (2026 Design and Innovation Award on the page). Source: html table (official Specialized GB product page, "Geometry" accordion, HTML table; fetched 2026-08-29
How I read the maker's table
the first-generation Aethos is in specialized-aethos.json. BB drop printed to a half millimetre (76.5 / 75 / 73.5) and BB height 265.5-268.5 mm as printed. Values are printed with mm and degree suffixes, stripped by script. Stack/reach are to the head tube top per Specialized's geometry drawing. Model year is not printed on the page (null); the page is the current GB listing on the fetch date.
Source: html table (official Specialized GB product page, "Geometry" accordion, HTML table; fetched 2026-08-29, HTTP 200)