Space Saver Spare O.K. With Different Tires Than Original?

Discussion in 'General Motoring' started by Jim, Nov 18, 2005.

  1. Jim

    Jim Guest

    Read in automotive column today something that made me wonder. The
    writer was contemplating getting "plus" size tires due to clearance
    problems with his Legacy. The answer included a caution to get 5 new
    tires because running the "plus" size with a the space saver spare on
    one wheel could cause "major drivetrain damage".

    My question is this: Last year I replaced the standard 215x70x15
    tires with Goodyear Triple Treds in size 195x60x15 (replaced the
    wheels as well). I don't know if these are "plus" size tires; in fact
    I don't know what that means. Since no adjustment in the speedometer
    was required, the distance travelled per tire revolution must be the
    same and thus it would seem there should be no more problem using the
    space saver spare on these tires then on the OEM sized tires. Correct,
    or incorrect?

    Jim, Nov 18, 2005
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  2. Hi,

    Not sure I understand how a 195-60 and a 215-70 in the same wheel size
    can have the same diameter or rolling radius. Did you actually mean your
    195-60s are on 16" wheels?

    My understanding is "plus" sizing, properly done, results in a larger
    wheel size than stock, with a correspondingly "shorter" tire so the
    overall diameter and RR remain as close to identical as possible. Many
    manufacturers now show "revs per mile" for their different tires so you
    can compare. So, for example, you have a stock 15" tire that gives, say,
    812 rev/mi, and you replace with a 16" that gives 810 or a 17" that
    gives 809 (all numbers made up for comparison only), you're about
    "perfect" in your "plus" sizing. This assumes, of course, you don't
    create other fit problems, such as going so wide on your "plus" wheels
    that you experience chassis interference and such. If you achieve that,
    your compact "donut" spare should be fine (with the usual considerations
    for using a "donut.")

    Rick Courtright, Nov 19, 2005
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  3. Plus 1 conversions usually refer to increasing the wheel diameter
    by an inch and sizing tires to be the same effective diameter.

    The numbers give the effective diameter for the 215s as 26.9 inches
    and the 195s as 24.2 inches. That is a whopping 10% difference.
    The diameter of the new tires is quite a bit smaller than the
    previous ones. It lowers your ground clearance by 1.5 inches.

    The distance travelled per tire revolution is only 90% compared to
    the previous tire. I would NOT use the spare.

    Did you give the incorrect wheel diameter for one of the numbers?
    Here and There, Nov 19, 2005
  4. Jim

    Jim Guest

    Sorry I read the Owner's manual wrong. On my Brighton the stock tires
    were 185x70x14. The new ones are 195x60x15. So it appears there
    should be no problem if I ever need the donut for a few miles. Have
    not had a flat in 8 years (knock on wood).

    Jim, Nov 19, 2005
  5. Jim

    Jim Guest

    Yea, misread the manual. The original on my Brighton was a 70X14"
    tire, the new is 60x15. According to the previous post, I should be

    Jim, Nov 19, 2005
  6. Jim

    Bonehenge Guest

    Is the car an automatic or stick shift? It matters for the correct
    Bonehenge, Nov 19, 2005
  7. Jim

    Jim Guest

    Jim, Nov 19, 2005
  8. Jim

    B a r r y Guest

    Most Subaru automatics are capable of 2WD (Front wheel drive) with the
    insertion of a fuse. Check your manual.

    If your car has this capability, you have no worries using the stock spare.
    B a r r y, Nov 21, 2005
  9. Jim

    S Guest

    Hi Jim, All!

    Barry is correct. If you must run the space saver, or a significantly
    different sized tire on one corner, put it on the _back_ (I know . . .
    this is a pain if you have a flat on the front, nevertheless . . .),
    and disable the AWD. Keep speeds below 50MPH, and replace ASAP.
    This is acceptable for cars with LSD rears (WRX, some older Legacys,
    ???) as well, but realize that you are abusing the LSD by doing so.
    The space saver spare is only designed to get you to the nearest
    service station in any event; usage beyond that is contraindicated.

    ByeBye! S.

    Steve Jernigan KG0MB
    Laboratory Manager
    Microelectronics Research
    University of Colorado
    (719) 262-3101
    S, Nov 22, 2005
  10. Jim

    k. ote Guest

    I just wanted to point out that the WRX is *NOT* capable of being put into
    2WD by moving the fuse. Absolutely not.
    k. ote, Nov 25, 2005
  11. I know the auto is an option on the 'limited' WRX but i have no idea
    what the owner's book recommends. maybe the lsd rear diff prevents use
    of a FWD fuse? I dunno

    Carl 1 Lucky Texan, Nov 25, 2005
  12. Jim

    Bonehenge Guest

    Hence the "check your manual" statement.

    There are at least THREE distinct Subie drive trains. Since most
    Subarus with automatic trannys aren't WRX's...

    Wait... You have an AUTOMATIC WRX? Why? That's like an automatic
    TR6! <G>

    Bonehenge, Nov 25, 2005
  13. Jim

    k. ote Guest

    Wrong: The automatic WRX is *not* capable of being put into 2WD by moving
    the fuse! Only those vehicles that have the fuse mentioned explicitly in
    their manuals can be put into 2WD like that.
    k. ote, Nov 28, 2005
  14. Jim

    k. ote Guest

    I drive a 2004 STi. I did have a 2002 WRX; however, the only reason I know
    for sure that the auto *can't* be put into 2wd mode is because this was
    already hashed out about a year or more ago in this very newsgroup, and I
    called up the local Subaru Master Mechanic to ask about it, whereupon he
    told me very specifically that the fuse slot does absolutely nothing in an
    auto WRX.
    k. ote, Nov 28, 2005
  15. Jim

    B a r r y Guest

    Nobody's debating that.

    The real question is WHY buy an automatic sports car? <G>
    B a r r y, Nov 28, 2005
  16. Jim

    k. ote Guest

    Oh. I dunno: maybe they drive in the city and don't want to screw around
    with the clutch all day long? Or--maybe they don't want to learn to drive a
    standard on a car like a WRX? :)
    k. ote, Nov 28, 2005
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