harder than third grade arithmetic to me
Wheel sizing help
Thread Starter
Pro
Joined: Jul 2008
Posts: 577
Likes: 0
From: Palm Harbor Florida
Wheel sizing help
My front tire size is P245/45zR17 and the rears are P275/40zR18...I measure the front rim from lip to lip with a tape measure and I get 18.5.
I measure the rears from lip to lip same way and get 19.5. I'm shopping for Z06 rims for my non-z06 C5 and see the 19/18 set for a good deal. I want to keep my new tires but I dont understand the fitment. I'm thrown off by what the tire size reads (17/18) compared to what I measure.Can anyone advise on this?
I measure the rears from lip to lip same way and get 19.5. I'm shopping for Z06 rims for my non-z06 C5 and see the 19/18 set for a good deal. I want to keep my new tires but I dont understand the fitment. I'm thrown off by what the tire size reads (17/18) compared to what I measure.Can anyone advise on this?
Team Owner
Joined: May 2001
Posts: 87,294
Likes: 1,579
From: Western NY
When you measure the rim, you measure the portion where the bead sits, not the OD of the rim at it's largest point. The same applies for measuring the width...It's the dimension between the beads, not the overall width, from outside to outside, of the rim.
Safety Car
Joined: May 2006
Posts: 3,799
Likes: 1
From: Northern Virginia
St. Jude Donor '08
If you read the tire size it will tell you the size of the rims.
My front tire size is P245/45zR17 and the rears are P275/40zR18.
FYI - the stock C5 rims are 17 front and 18 rear.
My front tire size is P245/45zR17 and the rears are P275/40zR18.
FYI - the stock C5 rims are 17 front and 18 rear.
Team Owner
Joined: May 2001
Posts: 87,294
Likes: 1,579
From: Western NY
Paully understands that, but he was initially having a little difficulty. If you lay a ruler across the wheels, and measure the extremes, the beads add 1" to the OD measurement (1/2"+1/2"). So, if you make that mistake, it appears that the wheels are 18 and 19, when they're actually 17 and 18.
The same when measuring width...If you measure from outside to outside, you get a number that's 1" wider that the actual rim width.
Safety Car
Joined: May 2006
Posts: 3,799
Likes: 1
From: Northern Virginia
St. Jude Donor '08
Paully understands that, but he was initially having a little difficulty. If you lay a ruler across the wheels, and measure the extremes, the beads add 1" to the OD measurement (1/2"+1/2"). So, if you make that mistake, it appears that the wheels are 18 and 19, when they're actually 17 and 18.
The same when measuring width...If you measure from outside to outside, you get a number that's 1" wider that the actual rim width.
The same when measuring width...If you measure from outside to outside, you get a number that's 1" wider that the actual rim width.
Given all the questions I see on rims and tires, they ought to create a sticky just for that.
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