TTAC Reader DeSoto writes:
Greetings, Sajeev — longtime reader, first time author, and I benefit from the content material your column provides to TTAC! (Woot! — SM)
I just lately acquired an all-wheel drive 2014 Cadillac CTS with about 15,000 miles on its manufacturing facility 255/35 R19 Pirelli P7 run-flat tires. Looking forward to an upcoming three,500 mile driving journey, I’ve concern for the sturdiness/drivability of the run-flats. The CTS isn’t outfitted with any wheel-changing instruments (jack, wrench, spare tire/wheel). A spare tire meeting (for the CT6) is out there on-line, however I imagine the usual compact spare is just too small in diameter to be suitable with the 19-inch wheels on the AWD drivetrain. I favor the liberty of having the choice of fixing a tire myself and persevering with on my means, quite than ready hours for help. I’m thus contemplating, so as of my present choice:
1) Buying (together with 4 alternative non-run-flats) an extra wheel and tire to hold as a spare (utilizing priceless trunk house, I do know, however it’s okay). With the AWD issues concerning uneven tire diameters inflicting drivetrain injury, will a 5 tire rotation scheme each 5,000 miles be acceptable to forestall drivetrain injury attributable to unequal tire diameters? Is there a “greatest” jack specification obtainable for buy? I’ve discovered diagrams indicating the lifting factors to be used with a lifting rack, and these look like accessible to be used with a single level jack.
2) Changing the 4 run-flats with non-run-flats, and carrying a can of fix-a-flat. Does using fix-a-flat require plugging a puncture on the time of use? Will fix-a-flat hurt the TPMS sensor?
three) Give up worrying a lot, getting with the 21st century already and buying alternative run-flats. Even when the Pirellis are awful tires, are there excessive performing run-flats (vs. non-run-flats) on the market, when it comes to dealing with, consolation, and sturdiness (pothole induced blowouts, speedy treadwear)?
Would you imagine there’s an internet site for purchasing spare tires, together with the jack? That’s a cottage trade I encourage on this age of rubber-band sidewalls, crumbling concrete infrastructure and run flat tires that also depart you stranded in case your TPMS is on the fritz. (Which occurs!)
That web site lists two tires, both means too brief on diameter (T125/60R-18, which is 2+inches shorter) or nonetheless brief sufficient to say “no”” on an AWD car (T155/60R-18, 7/10ths too brief). Ouch. Utilizing extra Google-fu, an official GM spare exists (with jack!), however it’s nonetheless kinda brief (T135/70R-18, 6/10ths too brief) in your software.
Learn your proprietor’s guide, however I reckon GM will insist on far lower than a half” diameter discrepancy between tires. And use this enjoyable device if the discrepancies are measured in circumference. A lot for that, however a minimum of we tried.
Concerning your three choices:
Off to you, Finest and Brightest!
[Image: General Motors]