Piston Slap: Si or No to 'Minus 1' Tire Sizing?

Sajeev Mehta
by Sajeev Mehta
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piston slap si or no to minus 1 tire sizing

TTAC Commentator 70Cougar writes:


I am probably the first owner of a Civic Si to ever want to downsize his rims, so I’m looking to the expert on -1 matters: you. (Woot! –SM)

I have a 2007 Honda Civic Si sedan with the factory 17-inch wheels. I’ve always preferred the same generation EX’s 16-inch five spoke rims, and I wouldn’t mind a smoother ride and cheaper replacement tires if I still get decent handling performance out of the 16s.

Would the 16-inch rims fit around the brakes on the Si and otherwise safely function on my car? Would there be a significant decline in handling performance?

Sajeev answers:

I should be the reason why bangin’ big-ass wheels are dumped for smaller ones!

The first determination is front rotor size. Rears are almost always smaller, therefore irrelevant. Snooping around RockAuto, the Si has a much larger front rotor compared to its more plebian counterparts. Oh dear:

The caliper part numbers are also different and, if this thread is correct, increased surface area implies the Si calipers are larger. But are they taller or wider … or both?

It’s possible an 11.8-inch rotor and caliper clears a 16-inch rim. Googling up snow tires, this thread says 16-inch steelies fit, so test fit your preferred 16-inch cast-aluminum wheel. If Corvette ZR1 peeps can -2 down to an aftermarket 18-inch wheel wrapped around their fancy ceramic stoppers, isn’t anything possible?

Your last question is indirectly referenced in the ZR1 hyperlink. If the aluminum 16-inch wheel fits (less unsprung weight than a steelie) and if you buy a high quality, high performance 16-inch tire (plenty of grippy summer tires on TireRack) you won’t lose a drop in performance.

I betcha new 16-inch wheels with those aforementioned summer tires will spank the stock 17-inch Michelin Pilot All-Seasons around a road course. Perhaps you can run 16-inch summer tires and “ruin” your factory Si wheels with winter tires? That’d be something!

[Image: Shutterstock user PPstock]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

Sajeev Mehta
Sajeev Mehta

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6 of 140 comments
  • Ajla Ajla on Jan 05, 2016

    Where do you all find good tires in the 14 or 15 inch sizes? It seems like my options these days are either classic car tires (big $$) or bottom-spec no-name stuff.

    • See 3 previous
    • La834 La834 on Jan 06, 2016

      @gtem Many cars with 155/80R13s had 175/70R13s (often on the same width wheels) on the more deluxe models, and they remain more readily available.

  • Corollaman Corollaman on Jan 05, 2016

    I could not find ANY summer tires for the Corolla 14 in rim.I live in So Fla I don't need no stinking all season tire.

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