[Simuse]

I've been trying to figure out tires and have been struggling a bit with getting a sense of when you cross over from "that's cool and should work for that wheel" to "you're an idiot, if you use that tire on that wheel your car will blow up".



This has just gotten a bit more serious for me as I find myself with some new 18" wheels / tires and am worried about the rear tires - more on that later. So...am just thinking that this thread could help tell us for those who have 18" wheel what tire size is working for them. Here are a couple of helpful links I have found here:





968 Engineering Wheel Calculator



DML Tire and Wheel Calculator



Note that below the calculator shows the difference in millimeters from OEM 16". The front to rear OEM difference is (0.09%).



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First off this is Anchorman's setup, and from what I can see seems to work great, and looks great too (pic below on right):



F: 8x18 / 57 offset, R: 10x18 / 58 offset.



Tires: Goodyear Eagle F1 GS-D3



F: 235/40ZR18

R: 265/35ZR18



Calculator (from 16" OEM):



F Diameter: 13.3

F Inboard Clearance: 17

F Outboard Clearance: 13

R Diameter: 11.3

R Inboard Clearance: 26

R Outboard Clearance: 14



Front to Rear Differance: (0.39%)



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Here is what I am looking at (pic below on left) - am worried about the rear tires...should I be? What will the 3.6% difference do to me?



F: 8x18 / 57 offset, R: 10x18 / 58 offset.



Tires: Continental SportContact 2



F: 235/40ZR18

R: 265/40ZR18



Calculator (from 16" OEM):



F Diameter: 13.3

F Inboard Clearance: 17

F Outboard Clearance: 13

R Diameter: 37.8

R Inboard Clearance: 26

R Outboard Clearance: 14



Front to Rear Differance: 3.59%



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Brian's setup:



F: 7.5x18 / 50 offset, R: 10x18 / 65 offset.



Tires: Dunlop FM-901



F: 225/40ZR18

R: 265/35ZR18



Calculator (from 16" OEM):



F Diameter: 5.3

F Inboard Clearance: 5

F Outboard Clearance: 15

R Diameter: 11.3

R Inboard Clearance: 33

R Outboard Clearance: 7



Front to Rear Differance: 0.86%



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[SILVY968]

I am running Porsche 993 18" Turbo Twist wheels and tires. Wheels are 18"x7.5(ET-50) front with 225-40ZR18 and 18"x10(ET-65) rear with 265-35ZR18. Tires are Dunlop FM-901's. Great tread for dry, not that good for wet.

   



Tough on the butt and the suspension with low pro tires. Also not too great for the car with 18's instead of 16". More weight out there is not good for long lived suspension, but it sure looks pretty.



Brian

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[Simuse]

Do you think I am going to have a problem with the 265/40ZR18 on the rear? It seems like everyone has either 30s or 35s for rear tires...?

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[flash]

what the heck units are the diameter numbers in? are the clearance numbers millimeters?

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[Simuse]

[quote name='flash' post='48589' date='Mar 2 2008, 03:34 PM']what the heck units are the diameter numbers in? are the clearance numbers millimeters?[/quote]



Yes - mm.......those are the differences from from stock according to the spreadsheet...I made an edit above to hopefully make it more clear...do you think the 4% difference is a problem? The 265/40ZR18 rear tires seem to be making that difference...

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