Can you use 1.5" tubes in 1.25" tyre?

[ironstamp]

So I just ordered two 1.25" Schwalbe Marathon tyres off Amazon and they came with two free tubes. Problem is, the tubes are for 1.5" or higher. They look way too big to fit in the tyres and it is a battle to even get them in. I contacted the seller and they said that they *can* be used. I'm not so sure. Thoughts?

[meic]

Yes they "can" be used but they are not suitable.
You can prove this to yourself (and to argue your point) by pumping them up just enough to take shape without expanding at all. If this inner tube is then larger than the tyre it is supposed to fit in, it will be kinked and creased if put in the tyre and that is not how they should be.
It will however work OK for thousands of miles if needed.

[ironstamp]

Thanks for the confirmation. I thought maybe I just didn't know my stuff but I've managed to get them to accept a return. Surprised they made it so difficult.

[andrew_s]

Any tube you can get properly fitted in the tyre will work.
If the tube is too large, it's easy to get the tube pinched between tyre and bead, and there may be creases that will eventually rub through, at which point the tube will be scrap. I'd expect the wear to take more than a thousand miles though.
If the tube is too small, any tiny fragment of glass that reaches the inside of the tyre will cause an instant flat, even if the protrusion inside is less than the thickness of the inner tube rubber. In contrast, tubes on the large side can often give a "slow" puncture that may take a few days to need pumping.

My worst mismatch was a 650x18-23c tube in a 700x28c tyre (failed to check what was actually in the box).
The smaller diameter of the tube made fitting difficult, with the tube occupying the bottom of the rim well and making the 2nd bead difficult to get on. It got ditched when it punctured.

[Gearoidmuar]

The biggest tube what will fit has one advantage. You will need to pump it only occasionally.