Does going to a wider tire change alignment specs?

If so, how does service dept know what specs to use for alignment?

The alignment specs are set by the manufacturer of the vehicle and are not dependent on tire size. Changing the tire width will in most cases change the size of the contact patch. Changing the tire height will do the same and also change your revolutions per mile making your speedo incorrect. But neither should affect your alignment unless you were making huge changes in sizes.

In lots of cases, running a really aggressive wheel and tire setup will cause you to have adjust your vehicles suspension outside of the factory specs to get the new setup to fit properly without rubbing.

If your shop is using decent alignment equipment the machine should have the factory specs built in and the tech will align it to those specs.

No, the desired specs shouldn't change just because you changed wheels/tires.

Now, if your goals for the car change, then you may want to tweak your alignment... Factory alignments are full of compromises.

Unless your doing a setup and lowering it, it should not require a alignment.

Now if you do for instance a 11.5 and 345 then yes it needs some adjustments and things across that line.

What type of adjustments are needed for 11.5 and 345's?

S550MG said:

Changing the tire width will in most cases change the size of the contact patch.

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It changes the shape, the relative size stays pretty constant.

awdtsi said:

What type of adjustments are needed for 11.5 and 345's?

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Normally in this case if lowered we do -2 degrees

You never got back to me by the way brotha.

Depends. I can see if the center of the tire has been shifted towards the outside of the car meaning there will be more leverage on the hubs causing the suspension to compress a little more, you might need an alignment.

Paul@PKAUTODESIGN said:

Normally in this case if lowered we do -2 degrees

You never got back to me by the way brotha.

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Yes, more camber can tuck the top of the tire in proving more fender clearance with wide tires or preventing the top of the tire from poking out.

Wider tires are probably also a bit more sensitive to alignment because a given amount of camber or toe moves the outside edges of a wider tire more.