I have had to replace a front tyre on my 2011 ford kuga. The tread on one side is 4.5mm the new tyre is 8mm. can this cause any problems. The tyres are both the same make and size.

There's not a lot to go on here but there are several things that cause this. Usually this will be caused by a wheel or tyre problem and to confirm this I would swap the two front wheels over and see if the wobble transfers to the other side. If it does jack up the side with the wobble and spin the wheel to see if the wheel and tyre run true, by this I mean the wheel and tyre don't show signs of buckling. If tyre is distorted but not the wheel buy a new tyre. If the wheel is distorted buy a replacement wheel and probably a new tyre. If neither tyre nor wheel are distorted and the tyre has plenty of tread left, take the wheel to a tyre distributor and have it rebalanced. If when you swapped the wheels around the wobble remained on the same side then there is probably something wrong with the steering or suspension components. With the wheel off the ground and the ca? secured on axle stands have an assistant pull the wheel around while you look for play in the joints and the wheel bearing. Worn components need replacement. Out of all the problems I have highlighted here, the wheel balancing is the most likely cause of your issues.

yes check all the pressures first
if no better out of round/old tyres ..tread choice
noise also depends on modifications to suspension and exhaust

The legal answer here is to replace the tyres as decaying rubber is the first cause of blow out and accident
Putting tubes in tubeless tyres is creating a problem and causes overheating of the tyre case and tube as air is caught between the case and the tube and this causes friction as the tyre rotates on the road
Using an air leak preventative here is a waste of money because as you have stated there is no air leak

If the tyres are slicks on one side and new tyres on the other this is a possible consequence. Check that the tyres on either side are of identical profiles and sizes with approx. the same tread wear.

It is an alignment problem caused by you raising the vehicle 2" Have the toe in adjusted to positive and have the camber reset to positive as well. As you raise the vehicle you shorten the tie rod end making the tyres point out and the tyres will also lean more out at the top causing the tyres to scrub on the outsides. Unfortunately because you have run the tyres in this condition they will continue to wear in the same pattern after an alignment so you will be up for 2 new tyres. to fix the problem properly

take the car to a suspension specialist shop and have the rear wheels aligned first
have the suspension checked for worn mounts or bad springs
it is very important that the rear end is aligned before the front end
suspect that the suspension rubbers need replacing as it is over 6 years old
the tyre rotation is a myth perpetrated on drivers to sell tyres
when the tyre construction was cross-ply and not radials yes rotation then on cross-ply tyres could get the wear to even out but with radials once the wear is started then the tyre continually wears in that pattern regardless of which wheel it is on
even if you take that tyre of the car and put it on a trailer , it will still continue to wear in that pattern
tyres are no longer rotated but simply put front to back on the same side other wise the belts flex in a new direction in the tread and fail earlier that expected
besides that fact that tyre rotation will not allow you to monitor for suspension problems or wheel alignment problems and cost you 4 tyres at a time instead of two

hi there ,this is a tyre problem we in the business call an "out of round tyre" to find which tyre it is so you can replace it ,go to each wheel and feel around the tread part of each tyre with your bare hand laying flat on the tread and feel right around each tyre ,you will find the problem tyre quite fast using this method as you will feel a raised bit on the bad tyre thats making your steering wheel shake ,a reputable tyre shop could do this for you if you dont feel capable ,then have the tyre replaced and ask them to balance all your wheels in the processand THANK YOU for using FixYa !!!

replacing one is ok but replace two minimum to create even wear on the tires

If they are all terain or off road tyre's then it's normal if it has road tyre's then it would be best to get it checked wheel bearings and brakes.

Unless there is noise or play when cornering sharply at low speeds (parking), the CV joint / boot is still ok. The joint does need grease in there and the rubber boot fitted properly very soon.

As the suspension is set, the axle does little more than provide drive. It doesn't affect toe-in or camber angle.

Camber angle (vertical tilt inwards) is a product of the suspension design, and often cannot be altered.

Weak front springs can also throw this angle out, as the vehicle sits too low.

Toe-in (forward point angle) can and must be set accurately, or you will skid about in wet weather depending which tyre grips more.

What is most important to you, is the tyre design, tread width and outer radius. Also the tyre pressures MUST be mid limit when cold on the front - otherwise excess wear will result.

Having tyres with a large contact area that are too rigid on the front will increase wear to the insides.

Also, it is good practice to rotate the tyres to even-out wear. Usually front tyres move to rear axle, and rears swap sides to front axle. If wear is uneven, pop them off and turn around before refitting. Some tyres you cannot do this with.

If you choose a tyre with a harder tread compound, or ones with "C" at the end of the code, these will again last a lot longer.

Thanks for using Fixya!. If this provides an answer for you, please rate as such. Thanks.