Does upsizing tire affect acceleration in all gears?

[Infomercial]

here is a calculator to plug in your tire sizes and stock gear to get a final effective gear ratio:
https://tiresize.com/gear-ratio-calculator/




10% isn't much of a change. Your speedometer will only be off within the margin of error. You will actually gain mpg on highway miles. The horror stories about big wheels are exaggeration to fabrication. There are a few factors at play. For performance I would worry most about the rotational weight you are potentially adding.

 

[MRC01]

If you've got a recent manual trans car I think bumping up a size can be a good thing, top gear in all of them is too short for good mileage. Probably not a good idea with a modern automatic car as they are all geared for maximum mileage from the factory.
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That sounds like a good top gear in mazda. That's the first compact car I've heard of with a decent gear for mileage in here.

However, the Mazda may be the exception. I don't know whether your notion that the top gear of a manual is usually shorter than the top gear of an automatic is true, but it does makes sense. When driving on the freeway (top gear), if the automatic has to downshift to make it up a hill, the driver doesn't have to take any action and might not even notice. If the manual does, the car will bog, slow, and driver will have to downshift. We can assume that people who buy manuals like shifting gears, so they don't mind. They'll probably shift before it ever bogs or slows, and enjoy doing this. But manufacturers probably want to avoid that anyway.

 

[tblt44]

Yes

 

[IndyIan]

However, the Mazda may be the exception. I don't know whether your notion that the top gear of a manual is usually shorter than the top gear of an automatic is true, but it does makes sense. When driving on the freeway (top gear), if the automatic has to downshift to make it up a hill, the driver doesn't have to take any action and might not even notice. If the manual does, the car will bog, slow, and driver will have to downshift. We can assume that people who buy manuals like shifting gears, so they don't mind. They'll probably shift before it ever bogs or slows, and enjoy doing this. But manufacturers probably want to avoid that anyway.

It's my understanding there's some rule in the EPA mileage test that prohibits a manual trans from downshifting once on the highway... So usually the top gear of manuals is quite short, because of that. Or I've read that BMW used to put a higher ratio diff in the N.A. cars for more acceleration, but leave the all the ratios in the gearbox the same.

The only automatic cars that I've driven with quite high rpm in top gear at 60mph are 3spd automatics in my 81 Omega and 95 Neon. Neither one needed a downshift for a well planned pass, and every semi-modern automatic now seems to have the top gear at quite a low ratio for mileage. All manuals I have driven, had a 60mph rpm well above 2000. The most comical one was 2002 Nissan Pathfinder which rev'd much higher in 5th gear than my 2003 4cyl mtx Chevy Tracker.... Why? the 3.5VQ had over double the hp and torque at any rpm.... Sure the Pathfinder was a bit heavier, but not nearly twice as much, and there's no need to spin a 3.5VQ at nearly 3000rpm on the highway, unless you are towing a huge RV trailer...

 

[Silver]

Larger tires will reduce acceleration and increase power output needed to maintain speed, except during some odd examples such as going downhill at a speed in which the air resistance doesn't offset the increase in rpm's at the tire's tread, etc, or if you've got such small tires that your engine is somehow in a bizarre fashion operating mostly above its torque peak... etc.