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 Most makers do not publish it, so I assume 10 mm and add 6 mm to the band beside every answer.
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 hands sit than your saddle. On a riser bar I count the bar's rise, so the drop is that much less than it is to the clamp.
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
Trek Domane AL Gen 3
Endurance road · 7 sizes
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This is the bike I ride
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- Bike
- Trek Domane AL Gen 3 · Endurance road · 7 sizes
- Geometry
- api.trekbikes.com, fetched 20 Oct 2026, re-checked, no differences
- Seat angle convention
- Calculated from Trek's table
- Cockpit
- Generic stem and bar, assumed
- Solved with
- cover 10 mm (assumed), max spacers 40 mm (assumed), stem clamp centre 20 mm (assumed), so every verdict carries ±10 mm at the bar
- Sheet
- 22 October 2026 · 879 bikes, 79 makes, 4,979 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) |
|---|---|---|---|---|---|---|---|---|
| 44cm | 510 | 360 | 70.3 | 74.6 | 95 | 420 | 983 | 657 |
| 49cm | 540 | 368 | 70.8 | 74.6 | 123 | 425 | 1001 | 717 |
| 52cm | 561 | 371 | 71.3 | 74.2 | 145 | 420 | 1003 | 735 |
| 54cm | 575 | 374 | 71.3 | 73.7 | 160 | 420 | 1010 | 754 |
| 56cm | 591 | 377 | 71.9 | 73.3 | 175 | 420 | 1018 | 776 |
| 58cm | 611 | 380 | 72 | 73 | 195 | 425 | 1022 | 796 |
| 61cm | 646 | 385 | 72.1 | 72.7 | 235 | 425 | 1038 | 842 |
The table runs on to the right: 6 more columns after Reach. Scroll it sideways to read them.
The 54cm 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.
Frame facts
not read off the maker's page yet: api.trekbikes.com- Tyre clearance
- not recorded yet
- Bottom bracket
- not recorded yet
- Axles and brakes
- not recorded yet
- UDH
- not recorded yet
- Seatpost
- not recorded yet
- Frame weight
- not recorded yet
In the maker's words
Kept whole, as I read it off api.trekbikes.com.Trek's sizing feed carries no bar or stem rows; no cockpit was read for this file.
Cockpit and seatpost, in the maker's words · 16 words
Trek's sizing feed carries no bar or stem rows; no cockpit was read for this file.
OFFICIAL SOURCE: Trek OCC sizing feed for code 33085, the Domane AL 4 Disc (named by Bike Insights' citation of Trek's US page, which Bike Insights files as 2022), geometry asset Geometry_Lines_2050x1500_Road_DomaneSLR9, seven numeric sizes 44, 49, 52, 54, 56, 58, 61 cm. Source: html table (official Trek OCC JSON that renders the "Sizing and fit" geometry table of the trekbikes.com product page
How I read the maker's table
Trek's feed states no model year (null). FOR CARL: every cell equals trek-domane-al-gen-4.json except the 44 cm top tube, 501 here against 507 there; this file's 501 is the one its own stack, reach and seat angle close on (360 + 510 / tan 74.6 = 500.5), so the Gen 4 file's 507 may be a slip in Trek's Gen 4 feed (that file was not edited). UNITS: Trek publishes the table in centimetres to one decimal and angles in degrees; every length was multiplied by 10 to give millimetres (Decimal arithmetic, exact, no rounding). Column mapping from Trek's geometryDataHeaders: geometrySeattube -> seat_tube_length, geometryAngleSeattube -> seat_tube_angle, geometryLengthHeadtube -> head_tube_length, geometryAngleHead -> head_tube_angle, geometryEffToptube -> top_tube_effective, geometryBBDrop -> bb_drop, geometryLengthChainstay -> chainstay, geometryOffset -> fork_offset, geometryTrail -> trail, geometryWheelbase -> wheelbase, geometryStandover -> standover, geometryFrameReach -> reach, geometryFrameStack -> stack (Trek's frame stack and reach, so stack_datum head tube top). Front centre and saddle rail heights are not in this feed (front centre null). Bike Insights' 2022 Domane AL entry (citing Trek's US page for the same code) prints 507 for the 44 cm top tube and 1008 for the 56 cm wheelbase, where Trek's GB feed today prints 501 and 1018.
Source: html table (official Trek OCC JSON that renders the "Sizing and fit" geometry table of the trekbikes.com product page, https://api.trekbikes.com/occ/v2/gb/products/33085/sizing, Domane AL 4 Disc; fetched 2026-10-20, HTTP 200)