Do I need bolts on my fork to carry a bag there?
Only for the bolt-on fork bag; the strap-on one comes out Tight
Most of what the fit check says about a bag is a margin: millimetres of room against a threshold, on a frame that was measured. A few bags are asked something else. They bolt to a boss on the frame or fork, and the check asks only whether that boss is there.
2 of 13bags in the catalogue that bolt on rather than strap on
What each reference frame carries
| Frame | Bottle | Rear rack | Three-pack | Thru-axle |
|---|---|---|---|---|
| Small · 47 cm | 2 | none | none | none |
| Medium · The Mule | 2 | 1 | none | none |
| Large · 58 cm, three-pack fork | 3 | 1 | 2 | 1 |
The two bags that bolt on
| Bag | Needs | Small · 47 cm | Medium · The Mule | Large · 58 cm |
|---|---|---|---|---|
| Fork or cargo, 4000 ml | 1 three-pack mount | No fit: three-pack mounts | No fit: three-pack mounts | Fits |
| Seat pack, 18000 ml | 1 thru-axle mount | No fit: thru-axle mounts | No fit: thru-axle mounts | Fits |
For this fork bag the answer is yes. Without a three-pack boss it is refused, on the small frame and the medium one alike, and how much room the fork has never enters into it. The refusal names the missing mount and no margin, because a boss is present or it is not. The seat pack is the same argument at the other end of the bike: it asks for a thru-axle mount, which only the large frame offers. The rear rack mounts on the medium and large frames are asked for by no bag in the catalogue.
The bags whose verdict never moves
| Bag | Needs a mount | Verdict on every frame | Named as limiting |
|---|---|---|---|
| Frame bag, 5500 ml | No | Fits | in-frame volume |
| Handlebar, 9000 ml | No | Fits | to the cables at full lock |
| Handlebar, 15000 ml | No | Tight | to the headlight bracket |
| Fork or cargo, 3000 ml | No | Tight | of strap purchase on a rigid fork leg |
The reference frames run from small to large so that a verdict which reads the frame will move between them. These do not, and none of them needs a mount, so a bolt is not what holds them still. The last row is the other half of the fork question. The strap-on fork bag needs no boss at all and comes out Tight on every frame, limited by how much purchase a strap gets on a rigid fork leg. A fork without bolts can carry it, and the check will say so as Tight rather than as a clean fit.
What this cannot tell you
The check reads the mounts a frame is declared to have, not the ones on the bike. A boss left out of the inventory is refused exactly as one missing from the fork, so a mount list entered wrong gives a confident wrong answer with no margin to make it look doubtful. It counts bosses and knows nothing else about them: whether a thread is stripped, whether a fork leg is built to take a loaded cage, and what a bag weighs once it is full are not things the planner holds. And the catalogue is only the bags that were measured; a fork bag outside it may ask for mounts these two do not.
Every claim above, and how it is known
- DERIVEDOf the 13 bags in the catalogue, 2 declare a mount they have to bolt to.
- DERIVEDThe small reference frame, 47 cm, carries 2 bottle mounts and no other mount.
- DERIVEDThe medium reference frame carries 2 bottle mounts and 1 rear rack mount.
- DERIVEDThe large reference frame, 58 cm, carries 3 bottle mounts, 1 rear rack mount, 2 three-pack mounts and 1 thru-axle mount.
- DERIVEDThe 4000 ml fork or cargo bag needs 1 three-pack mount, is refused on the small and medium frames for want of it, and fits the large frame.
- DERIVEDThe 18000 ml seat pack needs 1 thru-axle mount, is refused on the small and medium frames for want of it, and fits the large frame.
- DERIVEDThe 5500 ml frame bag needs no mount and fits all three frames, with in-frame volume named as limiting.
- DERIVEDThe 9000 ml handlebar bag needs no mount and fits all three frames, limited to the cables at full lock.
- DERIVEDThe 15000 ml handlebar bag needs no mount and is Tight on all three frames, limited to the headlight bracket.
- DERIVEDThe 3000 ml fork or cargo bag needs no mount and is Tight on all three frames, limited by strap purchase on a rigid fork leg.
Other notes worked the same way
- I have bags for a weekend. Do I need more for two weeks?
Two weeks asks for the same list a weekend does
- My bike is a size M. Will this bag fit?
A frame size is a name; these are the measurements that decide
- Tent or tarp, down or synthetic — does the planner pick, or do I?
Where the planner picks for you, and where it will not
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.