Fiesta tyre question

[22rgt B Squadron]

One of my Fiesta vans (2002) has a set of pretty dire soon to be replaced anyway budgets and have been offered a couple of sets of Colway mud and snows in 175/70/14, Theyre not expensive but rather than try them and have to sell them on does anyone know if these will fit without issues over the std 185/55/14's? Vans only do a small mileage p/w so speed/handling/noise issues are not a priority.
Any help appreciated.

[McSam]

Not compatible sizes, I'm afraid, the rolling radius is very different - 6% greater on the 175/70R15s - which means it'll cause a corresponding speedo error, which will probably be exacerbated because the M&S tread pattern of the new tyres would be slightly taller still.

It would be irritating if you changed all four - speedo way out, gearing changed, etc - but a definite no if you only planned to change two.

To give you an idea, the correct aspect ratio for a 175-section tyre on that van would 60%, rather than 70%.