Tyre vs rim size.

[Willam]

Anyone know if 1.25 inch tyres are safe to fit to 25mm internal rims?

 

[geocycle]

Schwalbe and WTB both have online calculators. By my reading 25 rim and 32 mm looks an acceptable combination.

 

[Punkawallah]

Sheldon Brown has the needful, along with how to measure the rim:
https://www.sheldonbrown.com/tire-sizing.html

 

[Willam]

That’s the thing I keep getting different answers depending where I look, Schwalbe say 29-34mm and Sheldon says 44-57mm?

I must be misreading the charts, as those are totally different answers.

 

[presta]

Schwalbe say 29-34mm

Schwalbe say 42-62mm.

 

[Dogtrousers]

Sheldon Brown has the needful, along with how to measure the rim:
https://www.sheldonbrown.com/tire-sizing.html

Beat me to it. I think I've posted that Sheldon link more than any other.

 

[Ajax Bay]

Anyone know if 1.25 inch tyres are safe to fit to 25mm internal rims?

Not advised. The minimum width I'd fit on such wide rims (1" internal) is 11/2" (37mm).

 

[Willam]

Schwalbe say 42-62mm.

View attachment 748318

Which is still much different to other charts.

 

[Ala133]

Hey!Yeah, 1.25 inch tyres should be safe on 25mm rims, but it's pushing it a bit, Just check the fit, make sure there’s no cracks when mounting, It might be harder to balance, so be careful, Definitely keep an eye on the pressure – don’t overinflate.Check after a few miles if everything’s holding up fine!

 

[presta]

Which is still much different to other charts.

Sheldon Brown says "Note: This chart may err a bit on the side of caution. Many cyclists use slightly wider tires with no problem."

 

[Ajax Bay]

make sure there’s no cracks when mounting, It might be harder to balance, so be careful

What do you mean by "cracks" please? Why will it be harder to balance (with narrower tyres)?

 

[Willam]

Sheldon Brown says "Note: This chart may err a bit on the side of caution. Many cyclists use slightly wider tires with no problem."

44 is the minimum sheldon recommended, 33mm is a long way from 44mm and the note says many people use wider tires with no problem but in my case the tire would be a lot narrower not wider.

Don’t think I’ll risk it.