Seatpost parts for the Trek Domane AL 2 Gen 4

We have not verified this bike yet

12 of the 14 measurements are on file; 6 confirmed by two independent sources.

A documented replacement can be recommended even while unrelated bike measurements are missing.

Salsa Lip-Lock seat collar 30.0 mm
Seat clamp
unknown · confidence: single-source
- Seat clamp diameter : 30 mmCheck your installed setup or its technical sheet.
Why? The facts we compared (1 dimension compared)
- Seat clamp diameter: bike nothing on file · part 30 mm — not on file
Sources:
- Salsa Cycles — Lip-Lock seat collar (tier 1, read 2026-08-21)
View specifications
Salsa Lip-Lock seat collar 35.0 mm
Seat clamp
unknown · confidence: single-source
- Seat clamp diameter : 35 mmCheck your installed setup or its technical sheet.
Why? The facts we compared (1 dimension compared)
- Seat clamp diameter: bike nothing on file · part 35 mm — not on file
Sources:
- Salsa Cycles — Lip-Lock seat collar (tier 1, read 2026-08-21)
View specifications
Thomson Elite seatpost 27.2 mm
Seatpost
unknown · confidence: single-source
- Seatpost shape : RoundCheck your installed setup or its technical sheet.
Why? The facts we compared (2 dimensions compared)
- Seatpost diameter: bike 27.2 mm (single-source) · part 27.2 mm — match
- Seatpost shape: bike nothing on file · part Round — not on file
Sources:
- Trek Bicycle — Domane AL 2 Gen 4 · Canada archive SKU 5301345 · specification and size table (tier 1)
- Thomson — Elite Seatpost (tier 1, read 2026-08-21)
View specifications
Thomson Seatpost collar 28.6 mm
Seat clamp
unknown · confidence: single-source
- Seat clamp diameter : 28.6 mmCheck your installed setup or its technical sheet.
Why? The facts we compared (1 dimension compared)
- Seat clamp diameter: bike nothing on file · part 28.6 mm — not on file
Sources:
- Thomson — Seatpost Collar (tier 1, read 2026-08-21)
- Thomson — Seatpost collar dimension sketch 008, dated July 2011; linked from current product page (tier 1, read 2026-10-07)
View specifications
Thomson Seatpost collar 31.8 mm
Seat clamp
unknown · confidence: single-source
- Seat clamp diameter : 31.8 mmCheck your installed setup or its technical sheet.
Why? The facts we compared (1 dimension compared)
- Seat clamp diameter: bike nothing on file · part 31.8 mm — not on file
Sources:
- Thomson — Seatpost Collar (tier 1, read 2026-08-21)
- Thomson — Seatpost collar dimension sketch 008, dated July 2011; linked from current product page (tier 1, read 2026-10-07)
View specifications
Thomson Seatpost collar 34.9 mm
Seat clamp
unknown · confidence: single-source
- Seat clamp diameter : 34.9 mmCheck your installed setup or its technical sheet.
Why? The facts we compared (1 dimension compared)
- Seat clamp diameter: bike nothing on file · part 34.9 mm — not on file
Sources:
- Thomson — Seatpost Collar (tier 1, read 2026-08-21)
- Thomson — Seatpost collar dimension sketch 008, dated July 2011; linked from current product page (tier 1, read 2026-10-07)
View specifications
PNW Components Loam dropper post Gen 2, 30.9 mm × 150 mm
Dropper post
does not fit · confidence: inferred
- Seatpost diameter : 30.9 mmDoes not match the documented build.
- Seatpost shape : RoundCheck your installed setup or its technical sheet.
- Dropper-post routing : Internal (stealth) routingCheck your installed setup or its technical sheet.
Why? The facts we compared (3 dimensions compared)
- Seatpost diameter: bike 27.2 mm (single-source) · part 30.9 mm — mismatch
- Seatpost shape: bike nothing on file · part Round — not on file
- Dropper-post routing: bike nothing on file · part Internal (stealth) routing — not on file
Sources:
- Trek Bicycle — Domane AL 2 Gen 4 · Canada archive SKU 5301345 · specification and size table (tier 1)
- PNW Components — Loam Dropper Post Gen 2 (tier 1, read 2026-08-21)
View specifications
PNW Components Loam dropper post Gen 2, 31.6 mm × 150 mm
Dropper post
does not fit · confidence: inferred
- Seatpost diameter : 31.6 mmDoes not match the documented build.
- Seatpost shape : RoundCheck your installed setup or its technical sheet.
- Dropper-post routing : Internal (stealth) routingCheck your installed setup or its technical sheet.
Why? The facts we compared (3 dimensions compared)
- Seatpost diameter: bike 27.2 mm (single-source) · part 31.6 mm — mismatch
- Seatpost shape: bike nothing on file · part Round — not on file
- Dropper-post routing: bike nothing on file · part Internal (stealth) routing — not on file
Sources:
- Trek Bicycle — Domane AL 2 Gen 4 · Canada archive SKU 5301345 · specification and size table (tier 1)
- PNW Components — Loam Dropper Post Gen 2 (tier 1, read 2026-08-21)
View specifications
PNW Components Loam dropper post Gen 2, 34.9 mm × 150 mm
Dropper post
does not fit · confidence: inferred
- Seatpost diameter : 34.9 mmDoes not match the documented build.
- Seatpost shape : RoundCheck your installed setup or its technical sheet.
- Dropper-post routing : Internal (stealth) routingCheck your installed setup or its technical sheet.
Why? The facts we compared (3 dimensions compared)
- Seatpost diameter: bike 27.2 mm (single-source) · part 34.9 mm — mismatch
- Seatpost shape: bike nothing on file · part Round — not on file
- Dropper-post routing: bike nothing on file · part Internal (stealth) routing — not on file
Sources:
- Trek Bicycle — Domane AL 2 Gen 4 · Canada archive SKU 5301345 · specification and size table (tier 1)
- PNW Components — Loam Dropper Post Gen 2 (tier 1, read 2026-08-21)
View specifications
Thomson Elite seatpost 25.4 mm
Seatpost
does not fit · confidence: single-source
- Seatpost diameter : 25.4 mmDoes not match the documented build.
- Seatpost shape : RoundCheck your installed setup or its technical sheet.
Why? The facts we compared (2 dimensions compared)
- Seatpost diameter: bike 27.2 mm (single-source) · part 25.4 mm — mismatch
- Seatpost shape: bike nothing on file · part Round — not on file
Sources:
- Trek Bicycle — Domane AL 2 Gen 4 · Canada archive SKU 5301345 · specification and size table (tier 1)
- Thomson — Elite Seatpost (tier 1, read 2026-08-21)
View specifications
Thomson Elite seatpost 30.9 mm
Seatpost
does not fit · confidence: single-source
- Seatpost diameter : 30.9 mmDoes not match the documented build.
- Seatpost shape : RoundCheck your installed setup or its technical sheet.
Why? The facts we compared (2 dimensions compared)
- Seatpost diameter: bike 27.2 mm (single-source) · part 30.9 mm — mismatch
- Seatpost shape: bike nothing on file · part Round — not on file
Sources:
- Trek Bicycle — Domane AL 2 Gen 4 · Canada archive SKU 5301345 · specification and size table (tier 1)
- Thomson — Elite Seatpost (tier 1, read 2026-08-21)
View specifications
Thomson Elite seatpost 31.6 mm
Seatpost
does not fit · confidence: single-source
- Seatpost diameter : 31.6 mmDoes not match the documented build.
- Seatpost shape : RoundCheck your installed setup or its technical sheet.
Why? The facts we compared (2 dimensions compared)
- Seatpost diameter: bike 27.2 mm (single-source) · part 31.6 mm — mismatch
- Seatpost shape: bike nothing on file · part Round — not on file
Sources:
- Trek Bicycle — Domane AL 2 Gen 4 · Canada archive SKU 5301345 · specification and size table (tier 1)
- Thomson — Elite Seatpost (tier 1, read 2026-08-21)
View specifications

Slots in this region

Seatpost
Dropper post
Seat clamp

The seatpost of the Trek Domane AL 2 Gen 4: 3 slots — Seatpost, Dropper post and Seat clamp. 1 fit fact on file for this region. The parts menu below lists every catalogued part that belongs here with its computed verdict — fits, fits with adapter, does not fit or unknown — and why.

Seatpost diameter	27.2 mm (single-source)

What does "unknown" mean on this page?: That we do not have, on file, the bike measurement this part needs. It is not a quiet "yes": until the measurement is on file, we do not sell the part for this bike.

Sources

Trek Bicycle — Domane AL 2 Gen 4 · Canada archive SKU 5301345 · specification and size table (tier 1, read 2026-10-17)

Parts menu — 12 parts

Slots in this region

Sources