CTS-V Tire change (labrat)
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2004-2007 Cadillac CTS-V General Discussion Discussion, CTS-V Tire change (labrat) in Cadillac CTS-V Series Forum - 2004 - 2007; Hello all! I'm pulling the trigger today! Dropping the runflats for some ContiSportContact2s: http://www.tirerack.com/tires/tires....omCompare1=yes Not my first choice but I'm ...
  1. #1
    WhiteLightning is offline Cadillac Owners Member
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    CTS-V Tire change (labrat)

    Hello all!

    I'm pulling the trigger today! Dropping the runflats for some ContiSportContact2s:

    http://www.tirerack.com/tires/tires....omCompare1=yes

    Not my first choice but I'm ok with them over the runflats. The shop tells me (and I have trouble believing due to the rarity of these cars) that 255/45R18s won't fit, they've tried. That I can only do the stock 245/45R18s. The rolling diameter difference is small (less then 1.5% change):

    Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
    245/45-18 4.3in 13.3in 26.7in 83.8in 756 0.0%
    255/45-18 4.5in 13.5in 27.0in 84.9in 746 1.3%
    255/40-18 4.0in 13.0in 26.0in 81.8in 775 -2.4%

    So, two thoughts:
    ONE - I'll give you the news later tonight on hop etc.
    TWO - Should I force them to try the 255s?

    WL

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  3. #2
    lasstss's Avatar
    lasstss is offline Cadillac Owners Connoisseur
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    Re: CTS-V Tire change (labrat)

    Thats nonsense. They will fit fine . I had 285's on a 9" wheel. Worked and wore fine. Speedo might be a tad off.

  4. #3
    WhiteLightning is offline Cadillac Owners Member
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    Re: CTS-V Tire change (labrat)

    Ok- I'll blame you


    WL

    Quote Originally Posted by lasstss
    Thats nonsense. They will fit fine . I had 285's on a 9" wheel. Worked and wore fine. Speedo might be a tad off.

  5. #4
    CTSV OWNER is offline Cadillac Owners Fanatic
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    Re: CTS-V Tire change (labrat)

    Does to GM Tech 2 scan tool have the tire size 255/45R-18 in the calibration sizes? If yes then speedo error is not a issue

  6. #5
    miscreant's Avatar
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    Re: CTS-V Tire change (labrat)

    Quote Originally Posted by WhiteLightning
    Hello all!

    I'm pulling the trigger today! Dropping the runflats for some ContiSportContact2s:

    http://www.tirerack.com/tires/tires....omCompare1=yes

    Not my first choice but I'm ok with them over the runflats. The shop tells me (and I have trouble believing due to the rarity of these cars) that 255/45R18s won't fit, they've tried. That I can only do the stock 245/45R18s. The rolling diameter difference is small (less then 1.5% change):

    Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
    245/45-18 4.3in 13.3in 26.7in 83.8in 756 0.0%
    255/45-18 4.5in 13.5in 27.0in 84.9in 746 1.3%
    255/40-18 4.0in 13.0in 26.0in 81.8in 775 -2.4%

    So, two thoughts:
    ONE - I'll give you the news later tonight on hop etc.
    TWO - Should I force them to try the 255s?

    WL
    Well...I'll chime in on the opposing side.
    Speaking front's here only...And speaking about CTS Sports, not V's, BUT Suspension geometry is virtually identical, but with much less body roll, so you decide...
    We've had several 255/45R18s that DID NOT work on Sport Package CTS's here. Had to refit them with 40 series rubber. In fact, none of them did. Cost us alot of mulla. Either they would scape the upper arm pivot joint, or scrape the front of the facia on hard turns...

    In fact, we just put 245/45R18's (Nitto's which run *big*) on a Sport CTS and the customer ended up bringing them back in a couple days with a big chunk taken out of the sidewall from the facia...

    NOW, this is completely dependent on offsets, but remember, too steep and you'll hit the upper arm pivot joint, and too shallow and you'll scrape the fender...

    NOW, additionally, keep in mind that the F1 Supercar tires are SMALLER than just about any other tires in the same size. The 245/45R18 F1's are about 26.4" tall, and about 9.2" in section diameter. The Nittos we had were about 26.8" tall and almost 9.8" in section diameter (nitto's own specs are not right on most of their tires).

    I'm inclined to believe that 255/45R18 tires, unless selected correctly, will be too large for the fronts. Reach inside your wheel well and locate the upper pivot joint - it's like a fraction of an inch from your tire now.

    I've just recently got back from the CTS-V driving school at Texas Motor speedway. They had three custom V's there, and ALL of them sported a staggered front to rear pattern (245/45 front and 275/40 rears). I'm further inclined to think this is probably the way to go...
    2004 Cadillac CTS (**SOLD** ): http://www.ctsowners.com
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  7. #6
    JEM
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    Re: CTS-V Tire change (labrat)

    Missing a critical point here:

    The spec rim size for the 245/45-18 is 8in. The spec rim size for the 255/45-18 is 8.5in. A tire's section width changes 0.2in for every 0.5in in rim size variation. Make sure you're comparing apples to apples in width. The Tire Rack site doesn't give tread widths for these tires.

    Also, curiously enough, the 255/45-18 ContiSportContact 2 is a reinforced (XL) tire. For SUV use, or for some particularly heavy vehicles (Benz S600s)? Their 245/45-18 is available in both standard-load and reinforced.

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    Clintonwmills is offline Cadillac Owners Fanatic
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    Re: CTS-V Tire change (labrat)

    Is there anyway to keep the rims and just get new tires, still fixing the wheel hope problem? I would love to keep the rims, they look nice!) I don't mind leaving the 245 in front and changeing to a 275 in the back. Miscreant, how was the driving school? That seems awesome!

  9. #8
    WhiteLightning is offline Cadillac Owners Member
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    Re: CTS-V Tire change (labrat)

    All-

    Ok. I'm back. It didn't go 100% as planned.

    ONE: Didn't do the conti's. Did P-Zeros.
    TWO: They nicked 3 of the four rims and scratched the fourth.
    THREE: 255/45R18 PZERO Asimmetrico hasn't hit/rubbed anything yet.
    FOUR: Shop (not brilliant, nice guys but ugh) says the rim measures more like a 9".
    FIVE: (and the big big big deal....) Still hops. Not as bad, I can launch harder, but no burnouts.

    WL

    Quote Originally Posted by Clintonwmills
    Is there anyway to keep the rims and just get new tires, still fixing the wheel hope problem? I would love to keep the rims, they look nice!) I don't mind leaving the 245 in front and changeing to a 275 in the back. Miscreant, how was the driving school? That seems awesome!

  10. #9
    nandanrp is offline Cadillac Owners Member
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    Re: CTS-V Tire change (labrat)

    Sorry to hear they scratched your rims :madtalkin

    Those new tires should have saved you some weight too, since they aren't run flats.

  11. #10
    miscreant's Avatar
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    Re: CTS-V Tire change (labrat)

    Quote Originally Posted by WhiteLightning
    All-

    Ok. I'm back. It didn't go 100% as planned.

    ONE: Didn't do the conti's. Did P-Zeros.
    TWO: They nicked 3 of the four rims and scratched the fourth.
    THREE: 255/45R18 PZERO Asimmetrico hasn't hit/rubbed anything yet.
    FOUR: Shop (not brilliant, nice guys but ugh) says the rim measures more like a 9".
    FIVE: (and the big big big deal....) Still hops. Not as bad, I can launch harder, but no burnouts.

    WL
    Wow. That's encouraging. Zero's tend to run pretty big. That's good news.
    2004 Cadillac CTS (**SOLD** ): http://www.ctsowners.com
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  12. #11
    JEM
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    Re: CTS-V Tire change (labrat)

    Quote Originally Posted by Clintonwmills
    Is there anyway to keep the rims and just get new tires, still fixing the wheel hope problem? I would love to keep the rims, they look nice!) I don't mind leaving the 245 in front and changeing to a 275 in the back. Miscreant, how was the driving school? That seems awesome!
    The problem there is that sidewall support for a 275/40 tire will be really marginal on an 8.5in wheel, particularly if you're still running the much-better-supported 245/45s in front. So on turn-in the rear is going to be squirrelly.

  13. #12
    lasstss's Avatar
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    Re: CTS-V Tire change (labrat)

    The P-O's are a good tire, a lot less road noise also . I had the 285's on my impala, trick little P-O in yellow. I think your headed in the right direction. A shock with a bit more damping or inflatable air bags will probably get rid of the wheel hop problem IMO. I will be doing the stock rim offset up front with the 275's on the rear. Rear clearance is good . An 18" wheel can go about 1/2" more negative. A 19 " can probably go 1.0".

  14. #13
    JEM
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    Re: CTS-V Tire change (labrat)

    The PZero Asimmetrico is a very good tire, good ride, very good grip though the asymmetrical design is more important for Macstrut cars with a poor camber curve. They don't last all that long, though.

    Note that the 'PZero' name actually encompasses a bunch of different tires, the old Asimmetrico/Directionale and the new Nero are the serious-grip items, the Rosso is a softer/less serious tire.

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