Using Google Earth to check odometer...
Using info on this page:
http://www.metrompg.com/posts/odometer-verify-google-earth.htm
I found a 20 mile or so straight section of highway to test the odo on my four banger.
GE measured distance = 20.17 miles
ODO = 19.8 miles (195/60/14 Kumhos @ 44 PSI) = ( - 1.87 % )
Turns out that the odo is showing 1.87 % LESS miles than actually traveled....with tires that are supposed to be around 1% undersized.
So the ODO would be showing around .87 % LESS miles traveled with OEM sized tires on it.
* had it wrong....
Groups:
Comments
Using Google Earth to check odometer...
When I used Google Earth to check my test loop, I found that my 1-size over tires caused the odometer to under-report by 3%.
Using Google Earth to check odometer...
I have some 5% (?) oversized tires that I got 37 mpg with as compared to around 30 mpg with the current wheels/tires at 1% under.
Going to put these back on and try them again. Want to see how they affect the odo and what mpg I still get.
Might hit the big 40 with fuel heat.........
Using Google Earth to check odometer...
I think the reasoning behind larger tires is that it lowers the final drive ratio which in turn helps to lower engine rpm's.
Using Google Earth to check odometer...
[quote="diamondlarry"]I think the reasoning behind larger tires is that it lowers the final drive ratio which in turn helps to lower engine rpm's.[/quote]
OK, I'll play Devil's Advocate. Shouldn't you first go get your vehicle dyno'd to find out where the torque curve is so that you can match the final drive to keep you under the curve more max efficiency? You don't want lug the engine. Also if the RPMs are too low, you might not have enough oil pressure for the load you're putting on the engine for proper lubrication.
Using Google Earth to check odometer...
From what I've heard...."lugging" only happens under maybe 1000 rpm under heavy load when the oil pump isn't spinning fast enough to keep the oil pressure up....usually occuring in top gear when people fail to downshift at lower speeds.
No way will you be able to put large enough tires on most vehicles to get the rpms under 1K at cruise.
For my wagon I'd have to more than double the circumference of my tires. She'd look R E A L C O O L..but wouldn't go very far! :lol:
The tires/wheels I have are the original 13" with oversized 80 series on them...the 80s are a real pain since they have little side to side stability...make the handling much sloppier than the 60 series on 14" diameter wheels I have on there now.
There is an interesting difference in these tires. The oversized 13s are el cheapo types that are max rated at 35 psi...I was running them at 32 psi on a 2400 lb car...just to have some side to side stability. 37 mpg.
The 14s have a max rating of 44 psi and I run them at that...but they still will soak up the bumps some. 30 mpg.
So the difference in mpg is likely due to tire design as much as diameter.
So if you want to max out mpg...go with oversized and cheap 80s at higher pressures...just don't try to stop or go around corners a lot.
The Google Earth odo test takes the guess work out of finding distance traveled and mpg. Took me a while to get to it..but it works?
Using Google Earth to check odometer...
I use my GPS to verify that my last set of tires which were 10mm smaller, was infact throwing off my speedometer by 4%.