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Discussion Starter · #1 · (Edited)
Has anyone changed the rear gear ratio? Almost all of my driving is on the freeway and I would love to have the car running at 2,000rpm on the freeway instead of 3,000 or 3,500rpm. That alone should improve the gas mileage and lengthen the life of the engine. Yes, I might have to downshift into 4th once in awhile but it would be worth it.
There are many rear gear ratios available for my Mustang but what about the smart?

I have 70 series tires on order for the back to help BUT that will not drop it to 2000 rpm. I live at 4500 ft elevation and drive 54 miles to work which is a sea level. I can drive the entire way at 1500 to 2000 rpm no problem. Going home I might have to drop into 4th gear to climb the 4,500ft but 1st gear is almost worthless. I shift out of 1st gear within one car length.
 

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Discussion Starter · #5 ·
I am going to 70 series tires. That will drop the revolutions per mile from "about" 900 to "about" 800 but I STILL would like to have a much lower gear ratio or overdrive. I drive 54 miles from 4,500ft elevation to sea level and I can do that at 1500 to 2000 rpm's no problem. YES, I might have to down shift to 4th at times to climb the hills but I have been climbing the hills for 62,000 miles now at 3,000 rpm so I would just down shift to 4th if needed.
 

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Discussion Starter · #6 ·
I have 70 series tires on order now so I will be going from 55 series to 70 series. It will help but don't think it will drop the rpm's from 3000 to 2000. I will post once I have the tires installed. I am getting 45mpg with now using Royal Purple oil and a K & N air filter but would like to improve the gas mileage if I can.
 

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Discussion Starter · #31 ·
Use taller tires, it would effectively raise the gear ratio w/o taking anything apart but will affect the speedometer.
I put taller tires on the car and either the ABS braking system or the electronic stabilization program shut the car down. After about a 1/4 mile the car would only do about 5 mph and I KNOW IT WAS NOT THE TIRES THEMSELVES DOING IT. It was some kind of electrically (computer) control issue.
 

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Discussion Starter · #37 ·
The car only has 71 hp but I can go up hill at 2500rpm all day long. I have to shift out of 1st gear after one car length so what good is it. I can drive on a flat road at 1200 to 1500 rpm so why sit at 3500 rpm? I have nine cars so if I want power I will drive the 67 Mustang or the older Chrysler with a REAL HEMI in it. It costs me $45 to drive the hemi to work so this smart is JUST about gas mileage period. Don't care what it looks like or sounds like. Just get me 50 plus miles per gallon.
 

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Discussion Starter · #38 ·
I left the original tires on the front and put 70 series on the back. That would have dropped the revolutions per mile by I believe 100. I think the low rider style 55 series goes around about 900 turns a mile and the 70 series about 800 turns a mile if I remember correctly. All I care about is gas mileage period. I am not road racing just straight line driving 110 miles a day.
 

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Discussion Starter · #39 ·
I use regular oil in my eight older cars and change it every 2,000 miles and they last forever. I run Royal Purple in the smart and change it every 5,000 miles so I hope the car lasts another 8 years until I retire. My Toyota pickup and Miata both went 300,000 miles and only used a half quart of oil between oil changes. I sold those and they still ran. One guy bought the Miata and drove it cross county from my house. I hope the smart lasts for 8 years. Then I can drive the 64 vw bug as the daily driver and the big finned gas hogs about once a month.
 

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Discussion Starter · #41 ·
I put 70 series tire on (same as an older VW bug). That set off all the electronic warnings. The ABS sensor light came on, the traction control software (yellow triangle) came on along with the engine check light. If that wasn't bad enough the software took over and the car would not go more than 5 miles per hour. I already drive the car like a 120 year old lady. I don't go over 65 miles per hour. Accelerate out sooooooooo slow. I coast up to lights and coast down hills. The real problem is the 4:52 rear gear. The car is doing 3,500rpm on the freeway when other cars next to you with overdrive will run as low as 1,800rpm. This engine will only have a "half life". I runs like a weedwacker on the freeway and will never make it to 150,000 miles. My last Toyota and Mazda made it to 300,000 but this car will not at this rate. If the people at smart are reading these posts PLEASE give us a 6 speed trans and a clutch. Get rid of half the electronics on the car and go back to SIMPLE.
 

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Discussion Starter · #46 ·
The can climb 99% of the hills in 5th gear at 2500rpm and run slower speeds in 5th at 1200 to 1500rpm so why not run 60 or 65mph in 5th with better gearing?
Yes, this transmission is always trying to think for you. I WISH they would have just put in a 6 or 7 speed trans with a clutch so the owner could drive like THEY WANT instead of the car trying to think for you. Once I retire I can drive my 1964 VW bug since I will not be driving 110 plus miles a day.
 

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Discussion Starter · #47 ·
I left the original tires on the front. I just want to see if the rpms would drop on the freeway since that is where I put on 99% of my miles in straight line driving. The car will drive fine at 2,000rpm at a lower speed in 5th gear and even as low as 1200rpm on flat ground. So why not drive the freeways at 2000rpm. It does NOT put strain on the engine. And YES I might have to down shift into 4th gear on major grades but so what.
 
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