TwinTurbo.NET: Nissan 300ZX forum - CA Smog: Car not testable because of tire size?
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Subject CA Smog: Car not testable because of tire size?
     
Posted by just4kinks on April 09, 2021 at 5:37 PM
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Message My first post here in 9 years! Great to see that some of the other old-timers are still around.

I live in California, and I tried to smog my Z yesterday. After a few tries, the guy said he couldn't test my car because he couldn't get it into the correct rpm range on the dyno. He said the RPMs were too low for whatever speed he had to test at.

Has anyone had this problem before?

The same thing happened last time. Different shop, but the guy had to try multiple times before he got it. He was blaming my aftermarket wheels/tires and at the time I just dismissed him, mechanics always find something to blame other than their own abilities. And I had never had a problem with smog testing before, including two or three previous tests on those same wheels and tires.

Anyways now that it has happened again, I'm wondering if my tire size is to blame after all. I'm running 285/35/18 in the rear, which is about 5% larger than stock in diameter. I need to buy tires anyways so I don't mind switching to another size just to pass the smog test. I'm thinking I'll get 285/30/18 in the rear and 245/35/18 in the front. But it's only a 5% difference, so it'll be a bit surprising if it solves the problem.

Is anyone here knowledgable about CA smog testing? Other than the tires, is there anything that could cause this?

My car's gearing is all stock.

     
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