Onami

I don’t think it matters, but thought I better ask first…I’m going to put new 18 inch wheels and tires on my car which has 17’s now. I’m going to get an alignment done and would like to leave the 17’s on for this and then put the new wheels and tires on after they are done so I can make sure they don’t scratch some expensive wheels. Any problem doing it thus way?

Magdaddy

I would hope for better more knowledgeable comments…but, width and ET change might effect the “scrub radius”. I thought I felt a change between wheelsets, when I had the Tramonts built up, 0.5” wider up front, and a few mm difference in ET. Don’t believe the additional weight of the wheels compared to the hollow spoke 996TTS wheels was the reason.

I am no suspension/ alignment expert, and I didn’t stay at a holiday Inn express last night…so I could simply be full of $hit.

Happy you are getting the new ride to your liking.

Onami

Thanks Magdaddy! It’s still down in Texas, but I am gathering things for it. 2 trips and 4 hours today grabbing these 18 inch twists in 2 different locations. Off to be restored on Friday. I’ve got another set of wheels coming on Tuesday so I can change things up from time to time.

P-daddy

Mark- no issues doing like that at all. You don’t need to realign when swapping from 17s to 18s

Onami

Thanks Nam!

geolab

+1
if you like your alignment setup today, don't re-allign, just think it is not an improvement if your alignment is good already

Kein_Ersatz

Makes sense to this back yard mechanic... No real difference, the tools mount to the surface of the rim or hang off the suspension.

Factory alignment specs do not mention various wheel options for the 993, but the spec's also have ranges which will provide different outcomes.

Especially assuming between 17 & 18 factory rims, the proper mounted tire compensates for the rim size, trying to keep similar rolling radius, width, and offsets the same. Otherwise ride height will then vary and surface distance to pivot point could vary. Balance and speedo could also be off if tire dimensions vary significantly. Which could effect the feel of a given alignment, changing how you feel the car is handling and possibly slight tire wear difference. But apples oranges.

But I would also expect that a good alignment shop would own any scratches / scuffs to the rims and have the proper skills to not damage the rims with an alignment, so maybe reconsider the shop if you can't trust them with the new rims. I would align for the rim/tire I plan to use mainly. In the end, alignment is about safety, performance, tire wear, and "feel". That will avery between tires and to some extent the rims. Align to the rims/tires you plan to use the most.

Onami

Thanks for the input guys. The PPI found that the alignment was out slightly and they recommended I get it addressed at the next tire change.

It's not that I don't trust the shop, it's that I don't trust any shop when it comes to little accidents - they happen. One of the sets of wheels that I am getting was expensive and difficult to find, so I'd rather install them myself after all of the work is done to the car.

pp000830

Seeing that the alignment specifications for all factory wheels/tire combinations are the same. I think you are good to go if the upgrade is to a factory wheel or one with the same offset/wheel width/diameter/tire size combination as a factory combination.
Andy