New Tyre Query

[Baldricks Pilot]

One of my front tyres punctured with a screw through the outer edge of the tread. As it was not that far off the wear indicator anyway and with the MOT and service coming up I decided on a new one. Decided on keeping matched front tyres so opted for a Michelin Primacy HP (ouch, the cost is not low!!!) The other tyre is part worn but still with plenty of tread left. Anyway the car pulled to the left (RH tyre was the new one) so checked the pressures which were slightly out but it made no difference when corrected. Changed the backs to the front, two different makes and one not far off the wera indicator and everything runs tickety boo. Seems that the new one must have different characterists to its stable mate when brand new which I was not expecting.

[Opensauce]

I was always told that tyres of equal tread depth should be used on drive axle or it would stress the diff. In your case in theory at least with the new rh tyre being of a slightly larger diameter than the worn lh tyre, rh would travel slightly further than lh for each revolution & cause a pull to left.

[evdama]

If the one tyre is 'dragging' is it therefore causing more fuel consumption than the other?
I have a set of old 'dog-ends ' I put on with some of the places I have to go and with my driving style I dont notice any adverse effects ,but I would imagine it would also affect the abs under emergency conditions.

[j90xxx]

If possible you should try and keep same make, same pressure, same tread pattern, same depth on the same axle.
If not you will get the problems you have experienced.