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Old 05-29-2006, 03:02 PM   #21
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GeoMetry, if you still have your calculations of what you accomplished with your wheel/tire upgrade (e.g. wheel revolutions per mile, or engine RPM at a given road speed), do you mind sharing them here? Or start a new thread? It's good to have that kind of thing worked out for everyone to see.
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Old 05-29-2006, 03:19 PM   #22
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Pretty interesting. So there are no major gear ratio changes (besided FD) until you hit the 1.6L Swifts. At that point you'd be looking at a huge torque difference between the 1.0L and the 1.6L so that probably wouldn't be a wise move at all.

Plus it does nothing for you since you already have the "free" transmission. It's a lot of work for an "experiment" isn't it?
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Old 05-29-2006, 04:12 PM   #23
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Larger diameter tires would be the same as changing the final drive, just looking at the numbers. But a larger diameter tire also has a bigger contact patch and that means more rolling resistance. I don't know how much it would affect things, but if nothing else your car should handle better.
On second thought maybe not. A taller tire will raise your center of gravity and your might loose handling. Another factor with the taller tire and the car sitting taller is more air going under the car with more aero drag.
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Old 05-29-2006, 04:36 PM   #24
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I do not claim to actually know anything about camshafts. I will point you to http://www.teamswift.net/3tech/ They sell several different camshafts for the 3 cylinder Geo Metro including an economy camshaft that is very similar to an XFi camshaft. So close in fact that when I inquired about their economy camshaft they advised me not to purchase it since I already had an XFi camshaft. There are links to reviews of many of their products. I have never actually purchased anything from them but they seem to be highly regarded.

Using the tire circumference calculator at http://www.5speedtransmission.com/calculators.html it appears to me that switching from the standard 145/80 R12 tires that are specified for my 1994 Geo Metro to 155/80 R13 tires would produce almost exactly the same result as swapping the standard 4.105 final drive transmission for an XFI 3.789 final drive transmission.

Cross multiply and divide.

66.3 71.6 Tire circumference
3.789 4.105 Final drive ratio

(4.105 * 66.3) / 71.6 = 3.801

You would have to drive well over 300 miles for the difference to add up to one mile. Since both 4.105 transmissions and 155/80 R13 tires are easier to find I am using the 4.105 transmission and the larger wheels/tires. There are implications to the brake system as well, the larger wheels will make the brakes less effective. I have read a few posts talking about rotational weight and how important it is to keep that to a minimum. What is that all about and how much effect will what I am doing have in that respect?
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Old 05-29-2006, 05:02 PM   #25
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The more weight you have the more gas you use to get it to move. I forgot about the brakes. Most people go to larger diameter brakes and that's just more weight. You need to keep the same size rotors and go with better calipers that have more clamping power.
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Old 05-29-2006, 06:56 PM   #26
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Quote:
Originally Posted by 95metro
Plus it does nothing for you since you already have the "free" transmission. It's a lot of work for an "experiment" isn't it?
Well, there's no doubting it would help my overall mileage. The only experimental question is whether it would hurt the car's driveablility so much that I wouldn't like it.
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Old 05-30-2006, 01:31 AM   #27
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In my case we are talking about going from 12" to 13" in your case it would be from 13" to 14". I have an XFi transmission sitting in my garage but it has a bad syncro. The advantage to me of using the XFi transmission would be that my speedometer would read correctly. The disadvantage would be the difficulty of finding 12" tires next time I need them. The way I drive these days my tires will probably last forever. I accelerate slowly, I rarely use the brakes. About the only thing I do that stresses the tire is occasionally take a corner a bit fast.
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Old 05-30-2006, 02:35 AM   #28
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My car has the best gearing for fuel economy, if you upgrade to that transmission you'll hate it. I have no power whatsoever in 4th till about 55mph.

I'd love to switch to the 2000-2001 manual tranny, not only will I have manual but it will lower my 1/4 mile time more than a full second. From 16.9 to 15.7 or maybe lower. I would still gain mpg because of the fact that I could do engine off coasting and could coast anytime I want in the top gear.
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Old 05-30-2006, 04:25 AM   #29
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I wouldn't call your gearing the best for fuel economy, since mine is better...

Besides, I don't think any gearing that is attached to a torque converter can rightly be called the best, at least not until auto transmission surpass driver abilility.

Anyway, I also do not think darin is terribly concerned with his speed, I know that my car is much slower now and I don't care, though to be honest I'm prolly way low in the rpms, but I dunno since my tach isn't working...
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Old 05-30-2006, 05:13 AM   #30
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you're right, I wish I could put in a 2000-2001 gearing or even get a manual car.
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