Alignment Specs for bigger tires

[Smoothie97]

I drive a GST. I got my car aligned with 17" tires. Firestone pulled up the GSX spec because it has 17" wheels standard. So, they aligned my GST (sporting after-market 17" wheels) with the stock GSX specs. A week later, I put some 18" wheels. I took advantage of my lifetime alignment and took it back to another Firestone to check the alignment. This time, they checked my car using a GST 16" wheel specs but I didn't even realize it until I got home and read the work order.

It turned out that none of my alignment readings changed at all going from 17" to 18" tire, which tells me that changing wheel sizes does not affect alignment significantly. However, I did notice that the Mitsubishi-released GST 16" specs vs. the GSX 17" specs were slightly different in all categories (i.e. camber, caster, toe, thrust angle). Firestone was able to get my 18" wheel into the spec based on a 16" wheel which really doesn't sound that was the proper thing to do. But keep in mind, they didn't adjust anything at all the second time...and thus, the alignment still stands as if it passed the 17" wheel spec.

My question is: For those of us running 18s, how accurate is our alignment when the mechanic can only rely on specs from a 17" or 16" wheel?

 

[14.5 drift]

I could be off, but it seems to me the tire size wouldn't have any affect on the geometries of the suspension, a 16 inch tire should sit the same on the ground as an 18

However the gs-t and gsx might have different specs according to the different weight biasses and handling characteristics to each car

 

[Ballin' GS]

Maybe give some thought to the fact the of the 't' and the 'x'. GSX is all wheel drive and from what i have seen they require a lesser camber in the rear as a stock spec. I've noticed alot of AWD guys putting their camber settings at -1 degree all around and saying that the sheet said it was all in spec. I know on the FWD eclipses the rear spec is around -1.88 degrees. Do you still have the sheets with you? Because if you do would you post of different specs for the FWD and the RWD so we can see the differences? I did a search but came up with nothing.

 

[cuttheduck]

I beleive the issue is not necessarily the rim diameter. Seems like a more important number is the rim's offset because it can change the toe settings. Anyone wanna back me up or am I wrong?

 

[Ballin' GS]

Maybe on the toe idea, but that wouldn't affect the camber settings. The camber settings has to be with the AWD drivetrain, thats the only reason i can think of.

 

[wret]

We discussed this before here: http://dsmtuners.com/forums/showthread.php?t=130770&highlight=wheels+alignment

Consensus was that the size of the wheels should not effect alignment. Perhaps the engineers were trying to anticipate different driving styles.

 

[92awddsm]

Rim diameter, with and offset will not affect alignment in any way. Toe, caster, and camber will stay the same regardless of the wheel because you only change the wheel size, not the suspension geometry. I would take it back and have it aligned to the gst specs because a gsx is awd drive and it has different toe and camber specs than the fwd.

 

[Smoothie97]

My car's most recent alignment was based on the GST with 16" wheel specs. It got into spec.