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

[farna@xxxxxxx]

Thanks, but I'm not looking to compare directly with the 205/70. What I was thinking about was to keep what I have now. So go to a higher gear (3.31) so I can run a smaller diameter tire. That wasn't real clear in the original post though. I should probably go with a slightly wider tire anyway. I'm sure 215/60 would fit, but 225 would be pushing it in the 63 Classic wheel wells. 

On May 14, 2005 Ken Ames wrote:

> 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
> > >
> > > =============================================================
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> > >
> > >
> > >
> > >
> > >
> > > .
> >
> >
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> >
> >
> >
> >
> 
> 
> 
> 
> 
> 
> .


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