4motion spare wheel size

[Tim Cole]

Hi
I have a 4motion with 18in Dakar wheels tyres are 235/50/r18 the spare is a steel 17 in 235/55/r17 they seem very close in overall size but can anyone confirm if it's safe to use the spare or will the miss match cause issues ?
Thanks
Tim

 

[Loz]

You should try and to keep within 2mm diameter across the axel and 3mm front to rear.

Have you worked out the rolling circumferences of them all?

 

[Tim Cole]

Hi
6mm difference in rolling circumference , 3mm static radius and 1mm rolling radius I think.

 

[Loz]

Hi
6mm difference in rolling circumference , 3mm static radius and 1mm rolling radius I think.

If the spare is just for temporary use then you can compensate by keeping the speed lower and the distance short.

 

[Tim Cole]

It's emergency only I may take a spray of tyre foam with me as well.
Thank you for the advice

 

[Loz]

It's emergency only I may take a spray of tyre foam with me as well.
Thank you for the advice

Forget foam, too messy, get yourself a tyre string kit. You can normally fix a puncture without removing the wheel.

 

[Tim Cole]

I have never heard of these but just googled them and looks like a good option.
Thanks again