New Tyres and Alignment

[HighlandPete]

Sorry if you have discussed this before, I've had a search but not found a discussion.

 

What's the opinion on having a re-alignment when fitting new tyres? Obviously if the old tyres have strange wear patterns, but if there is even wear, I personally leave alone. Many shops want to check and adjust toe at any opportunity, to me that is the last thing I want touched unless there is a valid and clearly understood reason to do so.

 

Also would you normally touch toe settings without a full alignment? For example if there was some nearside front outer scrub at the end of a tyre's useful life. To me, I want the rear given the all clear and running true, before the front is adjusted.

 

I do appreciate a lot will depend on the tyre history and whether the owner has been looking after the tyres, like regular and accurate pressure checks and observing wear over their life.

 

HighlandPete

[Tony]

The tyre condition cannot influence the Geometry figures because the Geometry positions the wheel via the chassis, the tyre cannot exert influence to the chassis to alter the readings. In fact there's more violation to the readings if the car is jacked in order to fit the tyres due to suspension droop and settling.

 

You are correct about how the alignment should be measured since the front wheels have no dead-A-head point of reference?..... The actual reference is the Thrust angle or in other terms the centre of the rear.