robbieracer

I have a 97 Tacoma 4x4 V6, I currently have the stock 31" Goodyear RTS tires on and was wondering if I went to a 30" tire, if this would improve my gas mileage. I know my RPM would run a little higher, and feel a little more power due to the smaller diameter wheel. The Goodyears new, are 30.4" tall and I was thinking of going with the Bridgestone Revo's in a 30" tire. The 31" tires are 30.5" tall and the 30" tires are 29.6" tall. This is mostly driven on the street so I don't mind the smaller tire. It's pretty flat in the Sacramento valley where I live unless I drive into the mountains. Has anyone tried this? Do you think my mileage would improve or go down?

keisur

with me I think the opposite of what everybody says happened. I went from 31" tires to 33" tires and my mileage got worse. it makes sense to me but I thought it was supposed to go the other way. judging from my experience I would say that your engine will not have to work as hard, eventhough more rpm's, so you will burn less gas since your are going to smaller tires. I would say go smaller, better gas mileage, go bigger worse gas mileage (unless you regear to a lower gear which is what I am going to do, I'll be going to 4.88's)

robbieracer

It worked on my 86 toyota. I had 31' tires and was getting about 16-17 mpg, then I switched back to the stock 235 and was getting 20-21 mpg. That's why I was thinking one size smaller would help, less weight, less rolling resistance = better gas mileage...

keisur

i think it has more to do with the fact that you need more power from the engine for more torque on the drive shaft to turn the bigger wheels which burns more gas.

Mohamed

Ah finally feeling the effects of $2.00 a gallon gasoline robbieracer? It seems that's the norm around town.

It's pitful isn't it, you know it's damn expensive when gas here at McClellan and Costco start selling it at $1.85 a gallon.

Del

That's what's supposed to happen. Bigger tires = your engine working harder. He's talking about if going smaller will improve the milage, which it will. Although I don't know how much of a difference you will see only going one inch smaller.

robbieracer

Yep, the cost of gas is really starting to climb...:mad: I'm due for a new set of tires and thought going to 30" tires might help with the fuel economy a little. I have a borla exhaust and K&N filter and removed the snorkle on the air box, that helped with the power and I'm sure with the fuel economy too...

What do you do at McClellan?

rowan

yeah, you should get mileage.

im going the opposite way though and getting bigger tires... not quite yet though it'll be a few months.

maybe if we bomb some mid-eastern countries, gas prices will go down. that'd be a good way to get support of the american public. hahahaha

keisur

I know, I explained this in my post above. I just say "I think" because I don't want some yeahoo jumping up and telling me I'm wrong, this way it looks like I'm wishywashy on the subject but have the right idea. I guess it is psychological side effects from some of the other, more touchy, discussion boards.

Churnd

If your truck was geared for 31's, that's the best gas mileage you'll see with those gears, IMO. If you drop your tire size, you'll over-rev your engine. But since it's only an inch, I doubt it'll affect it that much. You just might not be able to get going that fast on the interstate.

Victor

I would like to go from a 31x10.50r15 to a 265/75r16. Most 31's are atually 30.7 inches and the 265 should be 31.6 inches. The small gain in ground clearance will be nice and my gearing shouldn't be too far from stock. With a 3.0 that is very important since I don't have a supercharge 3.4 to make up for bad gearing. I hope the small drop in highway RPM's will keep my mileage equal or perhaps slightly better - especially considering both tires are rated at 10.5 inches wide.

gwhayduke

If you can give me specifics, such as:

Highway speed you want to drive at.
Current rear end ratio
Diameter of 31" tire
Diameter of 30" tire

Then we can calculate what rpm your engine will be running at at that highway speed. Then you also get a torque curve for your engine and see where that rpm falls on the torque curve. If there is a big change (positive change) in the torque curve between the two diameters then do it. If there is only a small change or a negative change, then don't.

Generally most engines and cams have a "sweet spot" where the components of the engine seem to match up and the torque and horsepower jump and gas mileage will generally be better. The torque curve will help you find that point.

Don't guess...gather the data and make an informed decision.

Then tell the rest of us where the hell it is.

robbieracer

My differential ratio is 4.10
The stock Goodyears are 30.4" tall new
The new tires I want to buy are 31" = 30.5 and the 30" = 29.6
I drive between 70-75, I try to keep it at 70, but you know how that goes.......


Thanks for the help!!!!!!!

Victor

There is a link on the front page of Yotatech for a tire calculator. You have to use Corey's portal to see it tho: https://www.yotatech.com/~corey/portal/portal.htm

From the info you provide you will:

1.Lose 0.4" ground clearance
2. Your effective axle ratio will be 4.21
3. I entered 2300 RPM for your RPM at 55 - the new reading would be 2362 RPM at 55. (Obviously you can correct for that one - I turn 2300 RPM at 55 so I went with what I know)
4. Your speedometer will read 2 MPH slow at 55 from actual speed
5. To return to stock performance if your not happy you would need a 3.99 gear which I'm sure doesn't exist - your 4.10 would be the closest available.

Mohamed

Part of AFRPA...I'm a project manager.

robbieracer

I was in the Air Force 13 years ago and we had some equipment on the base that I worked on, I was stationed at Beale. I wasn't sure what was left at McClellan, I thought SureWest bought some data equipment there.

Mohamed

Ah yes Beale, very hidden away, I remember going there once, I still don't remember how to get there since you have to go through various small towns. Surewest has a big office, they took over Base Logistics building (right across the way from the museum) and gave the building a nice face lift. There's also cute women that enter and leave that building everytime I drive by .

gwhayduke

Rob...
At 70 mph, with 31" (30.5") tires, I calculate a engine rpm of 3,163. Check and see if that sounds about right.

Same speed with 30" (29.6") tires, comes out to 3,258 rpm's.

Check your torque curve now and see where these fall.

Los Gatos?

Wow I'm usually turning about 5-6k RPM on the highway...oh is this BEFORE the cop realizes the car is stolen?

1Runner

I dont know fellas..... I seriously doubt anyone would see an increase in gas mileage that would justify the cost of a set of 4 new tires mounted and balanced. Your un-corrected speedo will SAY youre going further on a tank, but really, you'll just be putting more miles on the speedo than youve actually travelled. I'm not saying you wont get some small gain..... but would it be worth it price wise? Whats a good set of 4 new tires mounted and balanced??? $400.00, $450.00?