18" tires and wheels

gofast

New Member
I have purchased a 2009 SS/TC as a donor car and hope to order a kit yet this year. I have a question related to tire/wheel sizes. I'm located in Wisconsin and cold temperatures are a concern. I've heard too many stories of "summer only" tires cracking when subjected to cold temperatures. C7 Corvettes were arriving at dealers with cracked tires just from being transported in cold weather. For that reason, I'm looking at Ultra High Performance All-Season tires, more specifically, Michelin Pilot Sport A/S 3+285/35ZR18. The tire diameter is almost identical to the stock tire. I have noticed almost no one else is running 18" tires on their Goblin. Is there a reason why I should not use 18" tires and wheels?
 

Ken R.

Member
If corners are taken too sharply, the wheel being forced over the curb may scrape/ chip, same goes for pot holes. More sidewall is used to absorb these impacts and road vibrations. If handling characteristics/looks are valued over physical injuries, reduce the sidewall to your hearts content.
 

Ross

Well-Known Member
Just asthetics. Lower profile tires don't absorb bumps (rocks/potholes/etc) as well, but have reduced sidewall roll in corners.
They also are more sensitive to correct tire pressure.
 

TravMac

Member
Another reason is those stock 18s are HEAVY wheels. A lot of people change to a much lighter setup and wrap it in a performance tire to maximize their performance driving. That being said, if you change to a set of 15's you can get all sorts of all season tires and shave a few lbs off each corner. Tires will be less expensive in general too - performance or otherwise.
 

Desert Sasqwatch

Well-Known Member
Wisconsin has potholes year around - been there, done that. I would advise going with nothing bigger than 17 inch rims, which gives a reasonable amount of sidewall but still has a low-profile look.

BTW, the 285/35-18 is about an inch taller than stock - 26 versus 25.
 
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Desert Sasqwatch

Well-Known Member
Think of it this way: a 26 inch tall tire on a 17 inch rim has roughly 4.5 inches of sidewall height. When you increase rim size, in order to keep the same tire diameter, the sidewall gets shorter. This is regardless of tire width.

Extreme example: my 33 inch tall tires on my Jeep, on 16 inch wheels, have roughly 8.5 inches of sidewall. Lots of 'give' to go over obstacles.
 

gofast

New Member
Wisconsin has potholes year around - been there, done that. I would advise going with nothing bigger than 17 inch rims, which gives a reasonable amount of sidewall but still has a low-profile look.

BTW, the 285/35-18 is about an inch taller than stock - 26 versus 25.
My SS has 225/45r18 tires, 25.9" outer diameter. Maybe I got ahead of myself. What outer tire diameter should I be targeting? I want my speedometer to be correct.
 

Karter2026

Well-Known Member
This is a great site to compare tire sizes. Tire size Comparison on the chart it will show speedometer difference if you put the OEM size in as tire #1. It also gives you a list of brands of tires in that size at the top of the page. I also found this place where I ordered my tire / wheel package from Performance Plus Tire It was the easiest place to order a staggered package from. I got wheels, BfGoodrich tires, lugnuts, mounted and balanced, filled with nitrogen and shipping all for just under $1000.00 If you search there are some coupons available to help keep costs down.
 

Ross

Well-Known Member
My SS has 225/45r18 tires, 25.9" outer diameter. Maybe I got ahead of myself. What outer tire diameter should I be targeting? I want my speedometer to be correct.
My stock tires were 215/45R18, 25.6" in diameter, so you are in the right ball park. HP Tuners can modify the speedometer for different size tires, so it reads correctly, at least it can for my 2006 LSJ.
 
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