When I type in your size here, it really shows the difference. You do have some slicers!!

https://tiresize.com/calculator/

 

Dave-

Is your photo with the 205/80's??

 

Yup! downside is the disco digs ruts way easier in my driveway

 

Yes thats them

 

Thank you numer9. Actually what you said makes sense but why on the VIN tag suggest to 205 or 235?

 

You're welcome.

VIN is for recommended size and load rating purposes. Size may affect handling and if too large you may have clearance problems.

When you put larger dia tires on a vehicle you be going a bit faster than the speedo reads and changes your "gearing" making it a little higher.
......

 

This is patently wrong. There are just too many other considerations to factor into make this sort of claim. Going "bigger" with tires has an impact on the vehicle ranging from increasing unsprung weight:

"Reducing unsprung weight is the key to improving handling. The lower the unsprung weight, the less work the shocks and springs have to do to keep the tires in contact with the road over bumpy surfaces. Lot of problems, if not all of them is caused by inertia. Bigger weight means higher inertia. Higher inertia means more workload for shocks and springs to keep tiers on the ground. If unsprung components have a high mass they are harder to accelerate/decelerate and thus it is more difficult for the suspension to maintain a consistent tire load."

Unsprung Weight

To messing with the way the vehicle performs based on the torque curve of the engine relative to its weight. Engineers used a specific tire size for optimizing the torque curve for the most efficient operation of the vehicle.

"Engines are generally most efficient when running at the RPM at which they produce peak torque, or the greatest amount of force per revolution. A car should be geared so that it stays as close to the peak torque RPM as possible for greatest efficiency. If you have too large of a tire, the engine will fall below its range of optimal efficiency, requiring more fuel to stay running at the same RPM. If the tire is too small, the engine will be spinning faster than necessary to maintain speed, thus wasting power and fuel."

Do larger tires improve gas mileage?

Changing the width or height of the wheel and tire combination have been shown to aversely impact fuel efficient AND overall performance.

Effects of Upsized Wheels and Tires Tested - Tech Dept. - Car and Driver

I remember way back in 1982 when I bought my first BMW, a 320i. It came with 175/75/13 tires on measely 13" rims. I went Plus 2 and used 195/55/15 tires on 15x7 BBS rims. I definitely remember seeing a good drop in my MPG. I also remember when, in the last years Rover imported the old Series III into the US they dropped the size of the wheels down from 16" to 15" and decreasing the height and width of the rubber all in an effort to increase that trucks horrible mileage. That was back in the early 1970's.

I'm sorry but "going big" will not increase your gas mileage.

 

I'm sorry you add links without reading them and they may contradict your knowing all attitude. Your experience may be different from mine and it doesn't make either of them wrong.

From your link:

 

The only way a larger tire (with the same or less aggressive tread than the tire it replaced) would result in higher fuel economy is if the vehicle spent the vast majority of the time cruising at 55 mph where optimal fuel economy typically is reached. Personally, I don't know many people driving 20 year old Land Rovers who use them daily for long highway commutes.

Show me scientific evidence that increasing the size of your tires increases your mileage in anything other than the specific incident I just mentioned and I'll be more than happy to believe you. And don't cite the "rolling resistance" argument because it is not really a factor in outfitting our Rovers with larger tires. More than likely, anyone going up a size in tires, either in width or aspect ratio, is doing to along with outfitting more aggressive rubber. I don't recall hearing stories about Rover guys ditching their A/T's so they could fit a nice pair of highway tires on their rig.

 

Is your way.
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