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2009 CTS 3.6L DI rebuilt to FE3 J55 G80 3.42:1
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According to Lifespeed the spare size is 135/80R18 .
That is what I bought from Modernspare.com. It works great, and barely fits in the spare well diameter. OEM can't be any larger if it fits in the well.
 

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2009 CTS 3.6L DI rebuilt to FE3 J55 G80 3.42:1
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1,368 Posts
That has a 2236 mm circumference vs the stock 18s with OE spec at 2173 mm. That is not a huge difference (~3%) and shouldn't cause fits with the ABS/traction control. What is the tire size on the spare??
The ratio is between the standard tire and the spare, not between two different-sized tires. The spare is already smaller.
 

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2013 CTS Premium, 2009 3.6 DI AWD Performance Package, 2003 Seville STS
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156 Posts
Discussion Starter #25
That is what I bought from Modernspare.com. It works great, and barely fits in the spare well diameter. OEM can't be any larger if it fits in the well.
I stand corrected, the oem size is 135/70/18.
 

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2014 XTS Vsport Platinum White Diamond Tricoat
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33 Posts
I once got two flat tires during one trip from NYC to Long Island, thus needing a final tow home. NYC potholes are killers.
 

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'14 CTS-V LongRoof; '16 ATS-V Sedan,' 04 Trailblazer 4x4; '10 CTS LongRoof gone but never forgotten
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I got roadside towing for my tire issues. Who needs a spare:cool:
Yeah, and wait until you are in the middle of BuFu and have an issue.
 

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2013 Cadillac CTS Premium, 3.6L LFX, AWD
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421 Posts
594758

It's not a 19" , but overall size is what's really important. You don't want 2 different diameter tires on the same drive axle. It would be fine for my 20s that stand at 27.6". OEM 235/50R18 was 27.3".
You want to be at less than 1% difference in height for an AWD
 

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2009 CTS 3.6L DI rebuilt to FE3 J55 G80 3.42:1
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1,368 Posts
The modern spare is the same width but 80 series so a little taller, but still fits in the wheel well. Might be a better choice.
 

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2013 Cadillac CTS Premium, 3.6L LFX, AWD
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421 Posts
View attachment 594758
It's not a 19" , but overall size is what's really important. You don't want 2 different diameter tires on the same drive axle. It would be fine for my 20s that stand at 27.6". OEM 235/50R18 was 27.3".
You want to be at less than 1% difference in height for an AWD
That is the wrong attachment. My fault. That is only a 25" tire. I apologize
 

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2013 CTS Premium, 2009 3.6 DI AWD Performance Package, 2003 Seville STS
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156 Posts
Discussion Starter #33 (Edited)
My spare
That is the wrong attachment. My fault. That is only a 25" tire. I apologize
My spare stands at 25.4" and my tires stand at 28". After talking to my tire guy I've come to realize that I have no choices other then carrying a full size tire in my trunk. The spare tire compartment doesn't have room for anything taller then the original spare. To use a spare tire I'd need an extra 2.6", not gonna happen. I'll settle for AAA and will eventually buy another 19" wheel which I will just leave at home.

594761
 

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2009 CTS 3.6L DI rebuilt to FE3 J55 G80 3.42:1
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My spare stands at 25.4" and my tires stand at 28". After talking to my tire guy I've come to realize that I have no choices other then carrying a full size tire in my trunk. The spare tire compartment doesn't have room for anything taller then the original spare. To use a spare tire I'd need an extra 2.6", not gonna happen. I'll settle for AAA and will eventually buy another 19" wheel which I will just leave at home.
You've got one size wider relative to the OEM 245/45-19, which I think makes it 4.5mm taller due to the 45% aspect ratio. If you were local I'd let you try my slightly-larger-than-OEM 135/80-18 spare, might be enough to not trigger stability control.

I'm about to uprade wheels and tires to 245/45-19 and am expecting the spare to work with the factory tire size and Modern Spare.
 

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2013 CTS Premium, 2009 3.6 DI AWD Performance Package, 2003 Seville STS
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156 Posts
Discussion Starter #35
You've got one size wider relative to the OEM 245/45-19, which I think makes it 4.5mm taller due to the 45% aspect ratio. If you were local I'd let you try my slightly-larger-than-OEM 135/80-18 spare, might be enough to not trigger stability control.

I'm about to uprade wheels and tires to 245/45-19 and am expecting the spare to work with the factory tire size and Modern Spare.
Taller is definitely better but even with your taller spare there is a 1.54" difference. I think that is still too much of a difference to make the car drivable. SMH
 

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2011 CTS Coupe FE3, 2003 Thunderbird, Gone 2013 ATS, 02 Deville
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2,129 Posts
Purchased my Coupe in April 2017, the next day I bought a flat tire repair kit, a backup 12V air compressor to the OEM already in the trunk, two BIG cans of "fix a flat tire". I was already a AAA premium road-side member.
Two months later I had two punctures, in both front tires. They had picked up screws while on Interstate 15 at the Arizona strip. BuFu Arizona.

It was 115 degrees in the shade, but there was no shade. So I fixed both tires with the tire repair kit, used a can of fix-a-flat on each tire, and aired them up to 35 lBS. and drove home. It took two days to get two new front 19" tires and my patch tires held air for that time.
 

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2011 CTS Coupe Premium
Orlando - We take orphans
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3,467 Posts
Interesting, is pretty much what I have in the "inflater space" but wanted a compact spare also. Being a Floridian also have several umbrellas (shade).

Just fitted and turns out I need about a 1" wheel spacer with studs to clear that 8&%6&^&^ front brake caliper.
 

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2011 CTS Coupe FE3, 2003 Thunderbird, Gone 2013 ATS, 02 Deville
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2,129 Posts
also have several umbrellas (shade).
It's difficult to hold an umbrella and fix a tire. I always have a wide brim hat.
 
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