Most likely it's either a bent wheel, a faulty tire or someone didn't balance it right. Take it back to the tire shop.
That is typically a wheel balance problem.
Check the balance on your tires as well as the lug nuts. You'd be suprised.
Possibly a front tire out of balance or a bad front shock. You need to inspect front suspension or take it to an alignment shop.
Tires out of balance, out of round, or worn out ,front end out of align may have caused this
It may be from tires being worn unevenly and off balance or the front end is out of alignment.
Tire out of balance, bent wheel, loose or worn suspension or steering parts.
More than likely you have a tire out of balance. It can also be a bent wheel or suspension parts are worn. Have everything inspected.
Well if you have a bent rim then it will shake or if you have dirt inside your wheels or even a tire just off balance will result in shaking.
* Worn components. (shocks, struts, ball joints, tie rod ends) * Out of balance wheel/tire. * Bent wheel
Tires out of balance. WHEEL bent, The steering shock may be worn out.
Usually it's caused by an out of balance tire/wheel. If that's not it, you could have a defective tire or bent component.
I would check to make sure your tires are not terribly out of balance or that one of them a bad spot (bulge) or tread separating. Any of these conditions on the front tires could cause the shaking between 40 and 60 mph.