abysmal mileage!

[127.0.0.1]

did the effective diameter of the wheels change...did you calibrate your odo to compensate ?

[enobmort42]

Originally Posted by 127.0.0.1

did the effective diameter of the wheels change...did you calibrate your odo to compensate ?

hmm. if i remember correctly, the stock 15's were 185/65/15 and my current ones are 215/45/17. i think the overall diameter changed. is that what you meant? and no, i haven't calibrated my odo... how do i do that? and how would that effect my calculations?

Originally Posted by MadMax

Instead, I would advise checking your speedometer against a GPS. My wheels were put on at the dealership, so I don't know it the speedometer was recalibrated or not; but with my 17" rims my speedo is spot-on.

On my Jeep I found putting on 2" larger tires actually made my speedo more accurate. It was optimistic beforehand, as are most...

the best GPS i have is my phone, and i don't trust that, at all. plus, i've never found it to be truly accurate. then again, i've always considered my speedo to be "the standard" for my speed. would the dealership be able to calibrate it for me? i'll give the gps thing a try, first, though.

Originally Posted by why?

Another thing to try is to just unhook your battery for a night. Strange things can happen, and who knows what the fuel cleanser might've made your ecu think it saw. But you've had those wheels on for a while, and while heavier wheels will hurt fuel economy, it would be constant.

Have you changed anything else in your car recently? The fuel cleaner might have done something, but I would hope not that. Maybe something else could be wrong. What
did you have to hook the cruise to? The accelerator, or something else?

Also I remember your car got soaked recently, was it bad enough to have gotten into anything electrical?

yes, my interior got soaked beyond belief lol, but the extent of the damage was to both front seats and the carpet on the far left of the driver's area. the only electrical components that may have been affected were insulated wires running under the driver's side door sill panel thing. they were covered and insulated properly. i'll give the taking off the battery thing a try...

i haven't tried anything other than the diy-cruise, which i had pre-mpg drop, the wheels, which was pre-mpg drop, and the fuel cleanser, post-mpg drop.

[docB]

Big wheels and tires are personal choice. If you like the look, let the mileage go. The heavier wheel and tire is not the only issue here. It is the larger distance from the center of rotation that is the big problem. It is easy to imagine a figure skater doing a spin. When arms and a leg are close to the body spin speed goes up. As the arms are put out away from the body, the skater slows. Same skater and weight, but slow spin when mass moves away from the spin axis. This is why a high wire walker carries a long pole. Performance can benefit from shorter side walls but only to a point. A larger overall diameter will make acceleration suffer. Less movement usually has the driver push on the gas more...less fuel economy. I'm looking to use 14" BBS wheels with a 185/70/14 tire for next summer. I 'll report milage at that time. Currently I have less than 4300 miles. I have averaged just over 40mpg with a one time high over 44 mpg.
I think the gps is way more accurate than an odometer. I just got a newer model and it recalculates much faster, aquires sats much faster and has better featuers than one I got for the wiffe two years ago.\
Madmax, an Altima I had '05 was off 2-3% on the odometer. I think it hurts the lease holder as the clock reads more miles than you drive.
doc