Brother if the new size i.e. 185/65/R15 is the same as the previous / stock ones, then rest assured; Irani Goldstone Tyre Company has got nothing to do it. Problem is something else. And if you have upsized your tyres, rims or both, then this is the main issue.
Also get wheel hubs, brakes, brakes shoes, handbrake, etc. Checked for any abnormality.
Brands can matter for drive pleasure, good road grip, low noise, comfort, etc. But not for this strange behavior.
After tires change, IMO; wheels balancing and alignment is a Must! Also get it done.
I hope this helps. Thank you.