Tight means two different boundaries, and only one is a measurement
The verdict says Tight and the bag still clears. Which is it?
A verdict of Tight reads like a warning about millimetres, and on most dimensions that is what it is. On one dimension it is not. The engine judges every clearance against a threshold, and the threshold is not the same number everywhere — so a gap can be wider than the band governing the rest of the bike and still come back Tight.
15 mmthe tyre gap the engine insists on, however well the frame was measured
Each dimension is held to the larger of two numbers: how well the frame was measured, and how much room that dimension needs in use. On all three reference frames the measurement tolerance is 8 mm, and for every dimension but one it is the larger of the two, so it is the one that decides. The tyre gap is the exception. It carries the margin above, which is larger, so that is what the tyre gap is held to instead.
Two seat packs on the same frame, one verdict apart
| Seat pack | Exposed seatpost | Tyre clearance | Verdict |
|---|---|---|---|
| 11000 ml | 20 mm, against 8 mm | 31 mm, against 15 mm | Fits |
| 14000 ml | 30 mm, against 8 mm | 12 mm, against 15 mm | Tight |
The pack that comes back Tight has more room at the seatpost than the one that fits. What it has less of is tyre clearance, and that is the only gap in the pair sitting inside the threshold applied to it — while still being wider than the band every other dimension on the bike is held to. Measured anywhere else, that gap would have cleared.
Everywhere else, Tight means what it looks like
| Bag | The dimension that decided it | Clearance | Judged against |
|---|---|---|---|
| Handlebar, 15000 ml | to the headlight bracket | 2 mm | 8 mm |
| Frame bag, 6500 ml | clearance at the down-tube boss | 3 mm | 8 mm |
| Frame bag, 7000 ml | thigh line | 4 mm | 8 mm |
| Fork or cargo, 3000 ml | of strap purchase on a rigid fork leg | 6 mm | 8 mm |
Where a verdict carries no millimetres at all
Some bags clear every dimension the ruleset measures, and the engine still names something as limiting: in-frame volume, with no clearance recorded behind it. The 5500 ml frame bag reads that way on all three reference frames, and on the large frame the 18000 ml seat pack and the 4000 ml fork bag do too. Those are verdicts of Fits with no margin to report, because nothing the sweep measured came near a threshold.
What this cannot tell you
Whether Tight will bother you. The threshold behind most of these verdicts is a measurement tolerance, which describes how well a frame was measured rather than how a bag will sit on it — so Tight on a carefully measured frame and Tight on a rough one are the same word about different situations. All three reference frames carry the same tolerance, so nothing above shows what a worse measurement would do to the verdicts. The refusals are absent on purpose: a blocking finding records no clearance, so a bag the engine rejects has no margin to appear here with, and which bags those are is a different sweep. A reference frame is also not your frame. And nothing here was ridden or loaded; every figure is a rule applied to a measurement.
Every claim above, and how it is known
- DERIVEDEach clearance is judged against the larger of two numbers: the frame's measurement tolerance, and the safe margin the dimension itself carries.
- DERIVEDOn all three reference frames the measurement tolerance is 8 mm.
- DERIVEDThe tyre gap is the only dimension carrying a safe margin larger than the measurement tolerance, at 15 mm.
- DERIVEDOn the medium reference frame (The Mule) the 11000 ml seat pack returns fits, with 20 mm of exposed seatpost and 31 mm of tyre clearance.
- DERIVEDOn the medium reference frame the 14000 ml seat pack returns tight, with 30 mm of exposed seatpost and 12 mm of tyre clearance.
- DERIVEDThat 12 mm of tyre clearance is wider than the 8 mm measurement tolerance and still returns tight, because the tyre gap is judged against 15 mm.
- DERIVEDThe 15000 ml handlebar bag returns tight on all three reference frames, with 2 mm to the headlight bracket.
- DERIVEDThe 6500 ml frame bag returns tight on the medium and large reference frames, with 3 mm of clearance at the down-tube boss.
- DERIVEDThe 7000 ml frame bag returns tight on the medium and large reference frames, with 4 mm at the thigh line.
- DERIVEDThe 3000 ml fork or cargo bag returns tight on all three reference frames, with 6 mm of strap purchase on a rigid fork leg.
- DERIVEDThe 5500 ml frame bag returns fits on all three reference frames with in-frame volume named as its limiting dimension and no clearance recorded against it.
- DERIVEDOn the large reference frame the 18000 ml seat pack and the 4000 ml fork or cargo bag also return fits with no measured clearance recorded.
Other notes worked the same way
- Two weeks asks for the same list a weekend does
Sweep the nights answer from one to ten: the list stays at twenty lines, one spec moves, and the food only grows once the shops are thin.
- A frame size is a name; these are the measurements that decide
Swap one measurement of a medium frame for another frame's value: the top and down tube edges move verdicts, and the triangle's volume moves none.
- Where the planner picks for you, and where it will not
Twelve of the twenty-six requirements offer a choice. The planner names one only when an answer makes another wrong, and in one it never does.
Every figure here came out of the same rules that answer the interview, so it moves when they do. Yours differ wherever your answers differ.