3.4 5spd MPG 31's vs 32's

[huhwhye]

I have seen many MPG figures from 3.4/auto rigs. I want to know how the 5speed does with different tire and gear combos. I am considering a few things and what to know what the effect will be on economy.

I don't want any numbers from automatics.

Because of the different overdrive ratio with the 5speed I run about 500 rpm higher than an auto. Comparing my 00 to my friend Taco with an auto. This puts me at 3000 rpm at 80mph.

Auto ratios (these may be off)
2.804 1st
.705 OD

Manual ratios
3.83 1st
.838 OD

If I go to a 32" vs stock 31" tire what will be the effect? This is the biggest tire I want to run on this vehicle. I know autos can take a big hit with stock gears. How to the manual trucks do?

What about a gear change? from stock 4.10 to 4.30 or even 4.56 with 32" tire. What will be the effect of that?

5speed guys tout their excellent mileage, and I want to keep mine. But I like the tire choices of a 75 series better.

 

[RonMAIDEN]

I figure the 5 speed will notice little or no change and don't go over a D load rating since E adds even more weight and the ride will be stiff,definetly overkill on a 3rd gen.

I get 2 MPG less than my mom sees with her '99 Limited on stock tires vs my D load rated 32" Nittos and part of that is due to me having a bit of a leadfoot. My truck is an auto too.

 

[huhwhye]

I was considering the Toyo Open County in Load Range C.

 

[RonMAIDEN]

Good choice,similar to the Nittos but in a lighter load range so I doubt you'll notice much of any diff.

 

[GatorGreg]

I had 265/75-16's on my old '00 w/5spd and I don't think it really effected the mileage that much. Don't forget that by adding the slightly bigger tires your speedo will read a few % too slow, and therefore your odometer will also be a few % low, thus making it difficult to calculate your real MPG with the new bigger tires. I'm not a mathematician, but I think for example if your circumference is say 3% bigger, then if you drove 100 miles according to the odo you'd have to adjust it to 103 miles for the mpg calculation in order for it to be accurate.

Since the circumference of tire is a bit bigger, I would think your highway mpg would be either the same or even slighly better since your using slightly fewer rpm to cruise at the same speed. But I would think it would be a slight detriment to the city mpg due to the extra weight and oomph needed to get you moving from a stop.

 

[RonMAIDEN]

+1 size is about 3% bigger (like greg stated) than stock and getting say 250ish a tank I add 7-8 miles to my calculation;it's not as big a diff as you'd think.

 

[huhwhye]

I think I'll give it a try. I'm planning a gear swap when I get lockers but that's a few months off due to funds and I need tires this month.

I know 32's can really hurt an automatic.

My friend with an auto lost 2mpg with lighter 75 series Revo's vs the heavier 70 series BFG AT's. BFG's are a lot heavier.

 

[RonMAIDEN]

I still get 16-17 city consistently and 21hwy.

 

[huhwhye]

That's not bad. Thanks for your advice.

 

[greentoy]

I switched from 31" to 32" BFG's on my 99Tacoma manual tranny, noticed no diff in MPG, 33" + tires you may need to alter gear ratios.

 

[02SE]

I was considering the Toyo Open County in Load Range C.

I've been running LT265/75R16 C (32") tires on my '97 4Runner, since it was 1 month old.

I have a 4x4, 5VZFE, 5-speed manual, 4.10 gears, rear E-locker, it came with the optional P265/70R16 (31") tires stock.

I noticed no real sense of a loss in power, due to the larger and heavier tires.

Gas mileage didn't seem to change either. As previously stated, your speedometer/odometer will be slightly off due to the larger diameter tires.

My last two sets of tires have been the Toyo Open Country AT's. They're a great tire for the road, rain, snow, moderate off-roading, IMO.