TNUCKL

Please be kind...newbie here.
95 Laredo I6 all stock except 16" wheels from a 98 Laredo and P235/75R16 Michelin LTX M/S...along with the correct speedo gear installed. The Laredo came with the stock wheels and Tires and the stock speedo.

I read on another thread about wheel size and gearing. The computer on my Laredo when I purchased it said 19.5 MPG for the last 600 or so miles. I've reset the computer and put on about 2000 miles since I got it at Thanksgiving and have gotten about 14.5 MPG since. Granted driving style and usage can play a huge part in ones MPG average, but I'm not an aggressive driver. My ride before I hit a deer was a 2002 Yukon with a 5.3 litre and I got a consistant 15 MPG for 3 years.

My question is about the tire and wheel 16" size along with the stock gearing setup for 15's. According to the receipts and notes I recieved with the purchase...the 16's have been on for about 2 years. And I don't doubt the honesty/integrity of the seller. How was he getting an average of 19.5 and I'm getting 14.5. It feels like there is no power and it downshifts a lot when climbing a little better than a slight grade at 30 or 40 or at freeway speeds. Is the gearing so wrong with these wheels and tires that I'm losing power and mileage?

wiggles

Gearing isnt for wheel diameter its for tire diameter. The wheel size has no real effect on mpg. While you own it it dropped? Are your o2 sensors all in good working order?

TNUCKL

The original tire size is 225/75r/15 and I now have 235/75r/16. Two different charts I've found show the 16 tire being about an 1.5 wider in diameter than the 15 tire. With the 16 being just slightly under 30 inches. And according to a chart on this site I can't find now...the axles on this 95 Laredo are meant for up to 30" diameter, but don't quote me on it. I also don't think axles have been changed and are all original. What axle would have come on my 95 Laredo?

And to your O2 sensor question...I have not gotten to checking on systems yet. Wanted to verify wheels and tires and their affect on my mileage with my stock axles.

dave1123

I'd like to add, the VDC lies all the time. The only way to know what your mileage actually is, is to fill it, record the mileage, drive it, fill it again, and do the math. This assumes your odometer is accurate due the tire size changes. You can be more accurate for distance with a GPS, but you still have to fill it twice to know how much you're really using.

TNUCKL

I'd agree with the computer being off. I did 2 300+ mile trips over the holidays and both trips had almost exactly the same odometer reading as the mileage indicated on mapquest and google maps. And MPG's are being calculated by hand based on odometer reading. I don't own a GPS. Is my stock gearing OK and compatible with the 16's I have on now?

dave1123

From your info, it sounds dead on.

TNUCKL

Just found original window sticker and it came with the luxury group listing a 3.73 rear axle ratio with p225/75R15 tires.
BTW- Laredo Package, Luxury group and added leather seats...$28,882
2013 Top of Line Prius...$29,000

dave1123

Here's a little bit of info. I drive a 2000 WJ 4.0 with factory optional 245/70R16s on it. Notice that they are 70s, not 75s. They are 29.5" in dia. I also have 3.55 gearing.

According to my local police stationary radar, My speedo says 38 when the radar says 35.

All these little inaccuracies, it becomes near impossible for a guy to correctly calculate his fuel usage. So, you know what I do? Watch the gas guage. When it gets low, I fill it up. I also keep it serviced on time.

TNUCKL

Agreed!!!
Just found two tire size vs. gear ratio charts and both describe my situation as being set up for more fuel economy and no power. Do these look correct to you?

http://www.southwestpowersports.com/GEARCHANGE.HTML

http://auto.howstuffworks.com/auto-p...size-chart.htm