Tire size difference?
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Cadillac SRX First Generation Forum - 2004 - 2009 Discussion, Tire size difference? in Cadillac SRX Forums; After searching this forum I didn't see an answer to this specific question. Any help would be appreciated since I'm ...
  1. #1
    Djacobs64 is offline Cadillac Owners Member
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    Tire size difference?

    After searching this forum I didn't see an answer to this specific question. Any help would be appreciated since I'm shopping for new tires.

    I've got a 2004 SRX V6 AWD and currently have P235/65R-17 in the front and P255/60R-17 in the rear.

    With this setup you can't rotate the tires.

    I read a thread earlier where someone said they put the 235's on all 4 wheels with no problems.

    My question is will the rotational difference of the smaller tires in the rear affect the computer or the speedometer?

    Thanks!!!

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  3. #2
    Northern SRX's Avatar
    Northern SRX is offline Cadillac Owners Enthusiast
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    Re: Tire size difference?

    Quote Originally Posted by Djacobs64 View Post
    After searching this forum I didn't see an answer to this specific question. Any help would be appreciated since I'm shopping for new tires.

    I've got a 2004 SRX V6 AWD and currently have P235/65R-17 in the front and P255/60R-17 in the rear.

    With this setup you can't rotate the tires.

    I read a thread earlier where someone said they put the 235's on all 4 wheels with no problems.

    My question is will the rotational difference of the smaller tires in the rear affect the computer or the speedometer?

    Thanks!!!
    No impact - the outside circumference is almost identical from the 235s to the 255s and you won't see any impact.

  4. #3
    Djacobs64 is offline Cadillac Owners Member
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    Re: Tire size difference?

    Thanks for the info!!!

  5. #4
    Northern SRX's Avatar
    Northern SRX is offline Cadillac Owners Enthusiast
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    Re: Tire size difference?

    I should have said that there's a negligible difference, not that there was none - in any case, you won't notice anything.

  6. #5
    wraunch is offline Cadillac Owners Member
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    Re: Tire size difference?

    I have a good pair of 255/18 Nittos on the rear of mine but I need to buy fronts. should I get the 235/18 or just get the 255 so I can rotate them?

  7. #6
    Northern SRX's Avatar
    Northern SRX is offline Cadillac Owners Enthusiast
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    Re: Tire size difference?

    It depends on how worn those Nittos are. If you've had them for a while, you might have to replace them even though they're in good condition. At best, you can keep them where they are but I wouldn't normally recommend mixing worn tires into a rotation with new ones.

  8. #7
    wraunch is offline Cadillac Owners Member
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    Re: Tire size difference?

    Maybe 12,000 miles on the Nittos tops. I was asking more in regards to the size difference. Should I keep the staggered fitment or just do 255s all the way around? What kind of difference will it make?

  9. #8
    Tequila Mockingbird is offline Cadillac Owners Member
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    Re: Tire size difference?

    I'm getting conflicting info re tire sizes and rotation. Do I have to stay with the 2 different sizes because of the AWD or the warranty? I bought an 09 SRX4 last year with 10k miles on it. started noticing rear vibration and cupping (goodyear tires) around 18k and had balance and all-wheel alignment checked. everything checked out almost perfect only 1/2 degree off. now I have 27k on it and the vibration and cupping is becoming intolerable. 2 tire dealers, and the dealer say I'll just have to get used to replacing the tires every 25-35k since I can't rotate them! ouch!$! I like the car but I wish I had known about this issue before purchase. If I really can run same size front/rear I'll be much happier. Thanks.

  10. #9
    PJ1520 is offline Cadillac Owners Connoisseur
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    Re: Tire size difference?

    Quote Originally Posted by Tequila Mockingbird View Post
    I'm getting conflicting info re tire sizes and rotation. Do I have to stay with the 2 different sizes because of the AWD or the warranty? I bought an 09 SRX4 last year with 10k miles on it. started noticing rear vibration and cupping (goodyear tires) around 18k and had balance and all-wheel alignment checked. everything checked out almost perfect only 1/2 degree off. now I have 27k on it and the vibration and cupping is becoming intolerable. 2 tire dealers, and the dealer say I'll just have to get used to replacing the tires every 25-35k since I can't rotate them! ouch!$! I like the car but I wish I had known about this issue before purchase. If I really can run same size front/rear I'll be much happier. Thanks.
    The change to one common tire size for rotation, wear, and practicality purposes is being/has been thoroughly discuused on this forum as it pertains to AWD, the differential, the warranty, VDC, ABS, traction control, and the speedo error implications. You may want to do a search......all questions answered and good stuff to know.

    Summary: i don't believe there are any serious issues. Many run same size winter tires on all four corners. There could be a speedo error if the diameter of the replacement tires is different from what came on the car, though the tire dealer can match what you need and can provide you with the revolutions per mile ratings as well.

    I don't quite agree with your tire dealers or the car dealer. I walked away from NTB in frustration after using them exclusively for twenty years for all of my tire and alignment work....after Sears acquired them. The integrity of the ride you get depends on the equipment they use, the experience of the techs, and the condition/calibration of their equipment. One friend suggested an alternative wholesale tire chain shop to me in the Northeast US that uses Hunter tire balancers, said it was the "motorheads and gearheads" shop(s) of choice. One stop there and my long standing vibration issue (balancing precision) and my cupping issue (alignment) disappeared. Imagine that.

    Re the rear tire cupping and vibration issues, I believe cupping is related to a caster or toe in/toe out setting. When I have had problems in the past with other vehicles, I was advised to never accept "it's in spec." You pay for an alignment, demand you get it. The vehicle should be set precisely to dead center of the setting or specified range, no fudge. Most national tire chains supply you with the factory recommended settings, your before, and your after. And they will set to precision, not just the range, if you insist.

    Once cupping starts, the noise is with you for the life of the tire. My experience has been that tires with higher mileage on them make more and more racket, cupping or no, even when wearing evenly. I never had a tire that I was happy with much beyond the 35K mileage you mention, just went in and swapped them out.

    You bought the SRX used, maybe an outside chance something is slightly off in the rear suspension? Did the "dealers" measure or just pass you off? It doesn't take much of a variance.....

    Re selecting the correct replacement tire sizes for avoiding speedo error, try out this link:
    http://www.miata.net/garage/tirecalc.html

    The tire dealers have all of the tire specs too should you go to a common size.

    Hope this helps.

  11. #10
    cutterman is offline Cadillac Owners Fanatic
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    Re: Tire size difference?

    @Tequila

    To answer your question, my 09 AWD SRX came factory equipped with 20in (P255 50R20) all around. So having all the same tires will not cause problems with the drivetrain. In addition I have been driving the last 5 months on 18in snow tires (P235 60R18) all around with no problems. I have also heard the stock Goodyears wear poorly and are loud.

    I think the previous post should be heeded. When you are due for new tires, dont get Goodyear OEM's and take your car to another shop for an alignment.

  12. #11
    Tequila Mockingbird is offline Cadillac Owners Member
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    Re: Tire size difference?

    Thanks. I tried the search but didn't see any answer to the warranty question. The all-wheel alignment was done at a local independant shop that both Goodyear and the GM dealer use when they have a problem beyond thier capability. I'm in a small midwest town with limited choices and I've known the GM dealer and the independant alignment guy for years. The management at the Goodyear tire store keeps changing so I don't have the same confidence in them. I did get a sheet with before and after spec values and it was almost right on and the tech did tweak it anyway but he didn't think it was off enough to make any difference. Maybe new tires will fix it and gee wouldn't it be great if the problem didn't reappear.
    note: I have always had some lingering doubts about the drive train. They found the car for me thru a GM dealer-dealer trade network and it was listed as "front line" A1 or whatever with no damage and when I picked up the car it had obviously been wrecked and had a brand new front-end. The headlights were wacked way out of line and the drivers door had been removed and remounted. everything else looked factory and was checked out supposedly OK. the rear diff puked gear lube so then the dealer found it was supposed to have been under a service notice to change the vent and add a line to the front. it still vented gear lube out so now it has an extension and vents the rear axle up by the brake master cylinder.

  13. #12
    genet is offline Cadillac Owners Member
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    Re: Tire size difference?

    Next week I am replacing the original Bridgestone 18" tires on my 2005 SRX. I am going to Kumho Venture APT KL51's, and the 255/r55x18 on all four wheels, replacing the 235/r60x18 on the front. If you look at the specs on TireRack, they are the same diameter, so it shouldn't make any difference to the computer.
    I'm also installing Wagner ThermoQuiet Ceramic brake pads all around. the best price for them is at Summit or Rockauto, or have your local store match their prices of $40/pair. Also, there is a $15/axle rebate available until 5/31/10, which makes them only $25/pair.

  14. #13
    242swm is offline Cadillac Owners Member
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    Re: Tire size difference?

    255/45r/20 is what I have on my 05.... very quiet and responsive

  15. #14
    n7don_srx is offline Cadillac Owners Enthusiast
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    Re: Tire size difference?

    Out of curiosity those who have replaced the staggered sizes with the same size all around did you have any problems getting them installed. I haven't gotten too serious yet but have made a couple inquiries and got the "not sure we'd install something not factory recommended".
    My RWD's rear Michelin Pilots (OE)tires are nearly worn out at 32k. The fronts probably will make it to 40k.

  16. #15
    Cadyman77 is offline Cadillac Owners Member
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    Re: Tire size difference?

    ok just to throw my two cents in i have 2004 awd v8 summer tires are 255/55/20s all around winters 255/55/18s....... my wifes has 235/65/18 front and back too with the v6 awd
    no problems best way is to bring your rims in off the car no hassle....... just we all are clear 255 and 235 are wight not height they are puting a narrower tire on the fronts of these cars

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