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finally decided on 20's i was told by everyone on here that 245/35/20 is the correct size with no rubing but eveytime i call for rims and tire packages or search online they tell me i should get 245/30/20???
 

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Black the Darkside
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FreshWhiteWhip said:
finally decided on 20's i was told by everyone on here that 245/35/20 is the correct size with no rubing but eveytime i call for rims and tire packages or search online they tell me i should get 245/30/20???
You should be able to over ride that. Yes the 245x35x20 is what most of the 20" guys are using.
 

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Black the Darkside
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onephatguy said:
I have the 245/35/20's, but on my next set, I'll go with 255's (maybe) but definately down to 30 series. There is enough rub to annoy me with the 35's.
Have you lowered your car? 35 series usually don't rub if not lowered.
 

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2005 & 2008 CTS
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They are probably telling you 30 series tires b/c it's closer to the stock tire overall diameter.GO 35's
 

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03 CTS
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Hey Kael awesome find with that link, makes things easy..
So w/20" rims and a 35 series tire your speedo will be higher by approx 1.5, so when ur speedo reads 40 mph ur actually doing 41.5, not bad really. Only off by a few.
 

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The Mighty Kael, 2004 Black CTS, Every Option
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yeah i have tonnes of that sort of stuff, I have been doing car clubs for years and there are some questions that keep coming up over and over, one of the guys in my old extended club (national affiliation, not local) wrote that page up. damned useful
 

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I love how it gives u a good idea on the side wall difference/thickness so u can kinda judge what kinda ride quality you get. Going with 20's & a 30 series tire u cut out about half or a bit more of the side wall compared to a stock 16", that makes for a much rougher ride.
 

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2003 CTS Manual Trans., '93 STS
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What I found on my car is that after going with 245/45/R18's, my GPS (Nav) reports that my speed is actually 1 mph SLOWER than the speedo. This tells me that the CTS speedo is calibrated for the bigger tires to begin with, just like the V. This implies that keeping the stock size tires likely makes the car read 3% too FAST, from the factory, and you're putting 3% more miles on the odometer than you're actually travelling.

If anyone with factory tires and a Nav can confirm this . . . . I don't want to have to remount my stock tires to verify. I've only checked with the bigger tires.
 

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FreshWhiteWhip said:
finally decided on 20's i was told by everyone on here that 245/35/20 is the correct size with no rubing but eveytime i call for rims and tire packages or search online they tell me i should get 245/30/20???
I'd stick with the 35....All I know is my car came with 245/35/20s from the dealer....I'm not saying that dealers are are always correct, but if they are selling their wheel/tire option packages with 35 series tires for their 20" applications, that is a good indication of what you should go with.
 
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