Tyre sizes

[P6cat]

Hi has anyone tried a bigger tyre size
I read the specs for India are
215/55-17 which would fill the arches
Better and seem cheaper than the
215/50-15s that are standard
Obviously the Speedo would be out
But if it’s a option may it could be reset?

 

[Gomev]

A quick search on this forum came up with this

Bigger wheels, wider tyres, boy racer 4 life ?

Hi all, Thought I could share a couple of photos of my (wife's) MG ZS EV, which has been lightly modified (initially by @shikoku14 ) with tints all round, and now by myself with the addition of some new wheels and tyres. The original wheel specifications from MG are 17" X 7", ET41, with...

www.mgevs.com

 

[Kithmo]

215/55/17 would only read 3.1% out on the speedometer. You would be doing 72.2 mph when the speedo reads 70 mph.
Would the 0.5" bigger sidewall, make much difference to filling the arches ?
The only thing that confuses me about changing tyre sizes is how do you know what pressures to put in on the new size.
Tyre size calculator

 

[pjmuk]

Car speedometers can legally read up to 10% over the actual speed, but are illegal if they under read. I.e at a true 70mph, a Speedo can legally display 70 - 77, BUT cannot display 69!

 

[Kithmo]

Car speedometers can legally read up to 10% over the actual speed, but are illegal if they under read. I.e at a true 70mph, a Speedo can legally display 70 - 77, BUT cannot display 69!

Not technically illegal, but not meeting the vehicle construction and use regulations.
But who's going to know if it's reading under ?