Re: 304/290/200R4 - now V8 Fuel Mileage

[Ken Ames <ameskg@xxxxxxxxx>]

215 or 225/60 is what you're looking for for 60s to compare with the 205/70s.
math indicates  220.77/60.

Ken Ames

Quoting farna@xxxxxxx:

> A good site for gear/tire calculations: http://www.4lo.com/
> That's why I don't have 60 or 65 series tires on my Classic. I think they
> would look better, but would knock me out of the cruising rpm range I want to
> be in. I could drop to 3.31 gears (instead of 3.55) and stay in the same
> range with a 60 series tire instead of a 70 series. That's one reason I
> wanted 3.31 gears -- could use the 65 seriess and gain a few mph at my target
> cruising rpm and look a bit better! 
> 
> My tire size: 205/70, 15". Diameter (avg.) is 26.3"
>               205/65 15 is 25.5" (avg.)
> 
> w/3.55 gears and 205/70 tires I'm running ~63 mph @ 2000 rpm.
> Drop to 205/65 tires and speed drops to 61.1 mph @ 2000 rpm. 
> I'd need a 3.44 axle to maintain the same speed, or a 24.5" diameter tire
> w/3.31 gears (205/60-15 is ~24.7", and would be 63.5 mph @ 2000 rpm).
> 
> On the 4Lo site don't forget to enter 1 for the transfer case ratio (1:1) and
> enter your high gear ratio. I used 0.70 for the OD gear in the AW4. High gear
> in all three speed autos and most three/four speed manuals is of course 1:1.
> You can figure speed in any gear if you know the ratio. I used "average"
> (avg.) and "approximate" (tilde [~] means approximately) for tire sizes as
> there is a little variation among manufacturers. Should be +/- about 0.125"
> though. 
> 
> 
> On May 12, 2005 Jim Boone wrote:
> 
> > On May 12, 2005 Jim B wrote:
> > 
> > > A: You also have to take into account for the size of tires on your
> vehicle
> > > when calculating gear ratios. Too many offroaders wonder where their
> power
> > > went when they slap oversize tires on. I know my own power dropped a lot
> > > when I put 33" on (from 26") but going to 3.73 helped that. When I switch
> to
> > > AW4, I'll probably have to drop down to 4.10 to keep adequate power.
> > 
> > Great point;  I did figure in for 25" tires when I posted a day or two ago.
>  I think that the Jeepers have more to gain/lose than we do as going from 26"
> to 33" or more is quite a difference.  With a passenger car, and esp an older
> AMC that you're going to use 14" or 15" wheels, it's more of a fine tuning
> tool.
> > 
> > I think the rear end we're talking about in this instance (with an OD trans
> aka 200R4) is right at 3.54; however, if you wanted/needed to go a little off
> of that, you could change the size of the tires.
> > 
> > Jim Boone
> > Mims, FL
> > 
> > =============================================================
> > Posted by wixList Archiver -- http://www.amxfiles.com/wixlist
> > 
> > 
> > 
> > 
> > 
> > .
> 
> 
> =============================================================
> Posted by wixList Archiver -- http://www.amxfiles.com/wixlist
> 
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