Piston Slap: Pounding the LaCrosse Super With Too Much Air?

Sajeev Mehta
by Sajeev Mehta

Jim writes:

I just got new wheels and tires on my 2008 Buick LaCrosse Super, 245/45R19s to replace the stock 18s. The tire dealer put in 40 lbs of air, and when I said “is that a little high?” they pointed to the sidewall and said “look, it can take up to 51 lbs.” I’ve never run more than 36 lbs in my tires, but I’ve never had a profile this low before. Am I just behind the times?

Sajeev answers:

Behind the times? You do own a Buick . . . but there’s an argument for displaced American muscle junkies (of all ages) needing a “Super” for their Yank-Tank fix with a new car warranty. If you believe in the latter, consider yourself off the hook. I agree with your conclusion, for two reasons. That wide of a tire with a 45-series sidewall is far from a rubber band donk-mobile, there’s enough cushion to merit conventional tire pressures.

Reason two: never, ever use the sidewall’s pressure for justification. That number is usually (always?) the maximum pressure allowed by the tire maker, with little relevance to the engineers who designed your car. If my knowledge of the LS4-powered Impala, Grand Prix and LaCrosse holds true, the staggered tire sizes and air pressures of the Pontiac and Buick came from extensive testing on how to put down massive power in a wrong-wheel drive application with less of the Impala’s drama. So don’t discount their calculations: it’s kind of a big deal.

Matter of fact, I suspect the Venn diagrams for tire maker/auto maker tire pressure ratings never overlap. Not that I’m gonna make one and find out, I’m just sayin’.

Sadly, I can’t find information on tire pressure changes for “+1”wheel and tire upgrades. This is what you really need. I’d recommend sticking with 1-2psi more than what the owner’s manual says, or follow GM’s recommendations as-is.

Bonus! A Piston Slap Nugget of Wisdom:

Automotive OCDs unite! If you measure air by “lbs” (pounds) and not “psi” (pounds per square inch), you’ll probably blow up the tire. Yeah, I know that “lbs” is in the American vernacular, but I didn’t ignore wild college parties and NCAA football for Mechanical Engineering homework for no reason. Believe that.

[Send your queries to mehta@ttac.com]

Sajeev Mehta
Sajeev Mehta

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  • Joeaverage Joeaverage on Nov 03, 2009

    So my little CUV calls for 26 psi cold. Unloaded. How much do I raise the tire pressures when it is fully loaded? Is there a sliding scale? Say max cargo weight means 32 psi. At half the max weight do I use 29 psi? FWIW I use about 2-3 psi more than the door jamb calls for. Rides a little better (tighter) and the fuel mileage is a little better. Tire wear is a little better because we aren't sawing the edges off of the tires from cornering.

  • Sajeev Mehta Sajeev Mehta on Nov 03, 2009
    joeaverage : FWIW I use about 2-3 psi more than the door jamb calls for. Rides a little better (tighter) and the fuel mileage is a little better. Tire wear is a little better because we aren’t sawing the edges off of the tires from cornering. Since 26psi is pretty low by modern standards and you are enjoying 29-30 psi, I'd keep it there. Check tire wear over the course of years, not days or months to know for sure.
  • ToolGuy This might be a good option for my spouse when it becomes available -- thought about reserving one but the $500 deposit is a little too serious. Oh sorry, that was the Volvo EX30, not the Mustang. Is Volvo part of Ford? Is the Mustang an EV? I'm so confused.
  • Mikey My late wife loved Mustangs ..We alway rented one while travelling . GM blood vetoed me purchasing one . 3 years after retirement bought an 08 rag top, followed by a 15 EB Hard top, In 18 i bought a low low mileage 05 GT rag with a stick.. The car had not been properly stored. That led to rodent issues !! Electrical nightmare. Lots of bucks !! The stick wasn't kind to my aging knees.. The 05 went to a long term dedicated Mustang guy. He loves it .. Today my garage tenant is a sweet 19 Camaro RS rag 6yl Auto. I just might take it out of hibernation this weekend. The Mustang will always hold a place in my heart.. Kudos to Ford for keeping it alive . I refuse to refer to the fake one by that storied name .
  • Ajla On the Mach-E, I still don't like it but my understanding is that it helps allow Ford to continue offering a V8 in the Mustang and F-150. Considering Dodge and Ram jumped off a cliff into 6-cylinder land there's probably some credibility to that story.
  • Ajla If I was Ford I would just troll Stellantis at all times.
  • Ronin It's one thing to stay tried and true to loyal past customers; you'll ensure a stream of revenue from your installed base- maybe every several years or so.It's another to attract net-new customers, who are dazzled by so many other attractive offerings that have more cargo capacity than that high-floored 4-Runner bed, and are not so scrunched in scrunchy front seats.Like with the FJ Cruiser: don't bother to update it, thereby saving money while explaining customers like it that way, all the way into oblivion. Not recognizing some customers like to actually have right rear visibility in their SUVs.
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