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Discussion Starter #1 (Edited)
I recently found a nice set of SRT-4 wheels, 17 inches, that came with 40 series tires installed. I was planning to install some 55 series tires on them to correct the speedometer reading, but I am loving the way the van handles and accelerates with the short tires. They make the final-drive ratio 9% lower and the van now does a 6% mountain grade without downshifting. The engine also has more horsepower when it is turning faster.

If any of you guys still have 14" wheels, get yourself some 16 or 17 from a PT Cruiser or SRT-4. It is a huge improvement in safety as well as looks and performance.

58466
 

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You should also say your fuel economy is suffering. Your engine will not last as long as it should either.
 

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Discussion Starter #3 (Edited)
Why should I tell a lie? I just got 26mpg at 70-75mph including 6% grades up mountains. If anything, my fuel economy went UP from operating more efficiently and the improved aerodynamics of a lower ride height. And that is without overdrive. I am looking into what parts I need for a 5-speed swap.
 

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Not saying you lied, but if engine is running at higher rpm's, then fuel deficiency will suffer, engine will not last as long as it should either.
 

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Discussion Starter #5
Why would the engine wear out more if it is doing less downshifting, so now it isn't doing silly RPM to go up mountains? And I use full synthetic oil, so it really isn't an issue anyway. And it's more aerodynamic.
 

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There is no way to tell based upon the "series" of your tires what the overall diameter is; believe it or not, there are LOTS of 40-series tires which have larger diameters than 55-series tires. What is the actual tire size you switched from and to?

As for being more aerodynamic, Hmmm, highly questionable; maybe .003%. Then there is the fuel economy thing; yes, you may be a tad more fuel efficient climbing a grade, but you will be less efficient at all other times; at best I'm thinking a push when it comes to your MPGs.
 

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Discussion Starter #8
believe it or not, there are LOTS of 40-series tires which have larger diameters than 55-series tires.
LOL, no. Not with the same width, there aren't. The series is a percentage of the width. 40% is never larger than 55%.

Well I live in mountains, so I am always going up or down, almost never flat. So if I get more mpg going up, and I coast going down, it makes sense to get more mpg.
 

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LOL, no. Not with the same width, there aren't. The series is a percentage of the width. 40% is never larger than 55%.

Well I live in mountains, so I am always going up or down, almost never flat. So if I get more mpg going up, and I coast going down, it makes sense to get more mpg.
I was trying to get you to tell us which tire sizes which you switched from and to, once again the width percentage is irrelevant without the rest of the info.

As for getting better MPG up and down, once again, I seriously doubt you are getting better economy; a push at best.
 

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Discussion Starter #10 (Edited)
Sounds to me as if you are implying that my eyeballs can't tell a shorter tire from a taller tire. The wheels on it are OEM from a Dodge SRT-4. The recommended tire size when mounted on the minivan is the same as a Subaru Outback, 55 series.

58465
 

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I never meant to imply anything, I just want to know the tire sizes involved here so I can run the math; so far you're doing everything to not answer my question.
 
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