So I've been thinking hard about increasing my R&P ratio from the stock 4.62:1 to either 4:88.1 or 5.12:1 to gain back some power loss from running my "monster tires".  OK... they are only about 28.+" diameter... but I can still feel a little loss of "GO" in 5th gear and when I'm on trails and in heavy snow.   Even when in 4-L I can feel the loss of tractor power.   I'm leaning towards throwing in a set of 4.88:1 R&Ps (from an auto tranny Tracker).  I'm concerned 5.12 gears would cause my engine RPMs to increase significantly, where as 4.88s would be lesser but get me back closer to my stock gearing +.  I'm a 99% daily road driver so RPMs are important cause it relates to increased fuel consumption and engine wear.  So I checked out a link to compare the loss-n-gains in power and I came up with the following:

New tire size:         27      28      29      28       29      30     31
Old tire size:           27      27      27      28       28      28     28
Current gears:       4.62    4.62   4.62    4.88    4.88   4.88   4.88
Effect gear ratio:   4.62    4.46   4.30    4.88    4:71   4.55   4.41

So... if I throw in a set of 4.88 gears, with my current 28+" tires I should be pulling a final effective gearing of right at 4.88?

If, in the future, I opt to go with a slightly taller tire, like a 29+" tire, I will still be pulling a final effective ratio of about 4:71, which would still be slightly higher than the stock 4.62 gears that came factory in my truck?

Finally, if I opted to go with a 30" tire, my final effective ratio would be about 4.55, which is still slightly higher than the 4.46 ratio that my stock gears provide me now (4.62s) on 28+ inch tires?

Are my thoughts and figures (above) correct... or am I missing something here?  This stuff hurts my head.

The loss in power is in yor head. You have less than a 29" tall tire, and definitely not an LT tire. So you've added a few pounds in weight and slightly taller tire. There is no way you feel any difference. I mean there is just no way.

I went from stock 215/75-15's on my Tracker to 235/75-15's without worrying about gears, and there there is no discerneable difference in on-road performance. And as far as fuel economy, who gives a shite. Look, if you want fuel economy measured in those kinds of minute details, buy a Prius and stare at the video display all day long, getting a hard-on whenever the electric motor kicks in.

Look. If you're going to swap gears, for for the 5.125's out of a previous generation Tracker or Sidekick. The vehicle will have a big increase in "off the line" performance and if you decide to go with taller tires, you will be glad you didn't take that baby step in between 4.62-4.88-4.125. Go big or go home.

Oh yeah, and call hawks suzuki. Those guys have everything!

Yeah, I do feel a loss of power as I stated... and when I'm pulling my trailer too.   Might be in my head, but it's my head, and that's where I live.   Don't want a Prius or I would have had one already.  I don't even get chubbies from the thought of a Prius.   But now if a Prius looked and handled like Lonnie Anderson, that would be fund to drive and I probably would have already bought one.  Probably even would have wrecked a few already because I was spending too much time staring at all the guages.   

I totally agree going with 5.12 gear set would be the most gear power gain.  But.... I found a set of carriers in 4.88 for $170 bucks.  They are about 30 miles from me.   The price for these is almost as good as suddenly finding a set of them in the corner of my over-stuffed garage.   I'm not going to be buying new (larger) tires until I wear the hell out of the ones I have, and with the miles I drive... and the way these are wearing that will probably be about two years from now.  I expect that thanks to our government, gas prices will be back up bumping $4.00+ per gallon again by then (to help repay the HUGE freakin debt from their great idea on "economic assistance" spending) so the less I have to buy, the further I can go.   I also agree with you on Hawks Suzuki.  They have squared me away on some parts in the past.   If they could square me away with a set of 5.12 carriers now for about $200 bucks, I might be tempted to go that route.   But you can add another $100 plus for shipping costs cross country.

So how about the figures on the ratios I asked about....   am I tracking or should I have used the 27 inch tire all the way across because that is what the entire drive train in the truck came set-up with?   

Seriously, thanks for your thoughts, I understand your point.  You'd go with the biggest gear.

i had posted up a gear calculator a while back, not sure where it is but if you google izook gear calculator you might find what your looking for

For a 28-30 inch tire I think the 4.88 gears would be real nice and they'd bring everything back to a stock feel.  For $170 I'd say go for it.

I have 215/75/15 BFG AT's (27.8") and there was a noticeable power loss from the 205/75/15's (27.1") that came stock.

Here is a spreadsheet that I use for a variety of gear and speed calculations. 

Don't remember where I got it but it is not protected so you can modify it as you see fit. 

The engine rpm is currently set at 3000 rpm which is where the 2.0 makes maximum torque so you can see what happens with a tire or gear change and how far the engine falls off the curve.

Again, you can change it at will, add a gear, subtract a gear, whatever.

I just noticed one error on the Gear and speed calculator.  The 10mph speed is actually 5mph if you look at the formula at B11 and B27.  The text at A11 and A27 needs to be changed to 5 from 10.

Here is the ammended spreadsheet.