Fuel, gears, and tires ?

The Gas and Diesel Engines - VQ40De, VK56DE, YD25DDTi, V9X, Transmission, Transfer Case, Oil, Differentials, Axles, Exhaust...

Moderator: volvite

amr40509
Posts: 210
Joined: Tue Jun 27, 2006 3:35 pm

Fuel, gears, and tires ?

Postby amr40509 » Sat Nov 11, 2006 1:15 pm

I wonder about other people's experiences.

To the best of my knowledge, and correct me if I'm wrong:

The Pathfinder S/XE comes with 245/75/16 General Grabber tires. These are what I have on my '06. The pretty much suck from a traction standpoint (especially in the rain). They should be 30.5" tall.

From what I understand other models come with 265/70/16, which is 30.6" except the off-road which is 31.6"

I haven't seen anything to indicate that the off road has any different gearing then the other models.


So my question is, what is the ideal tire size for the Pathfinder with stock gearing? Has anyone out there driven different tire sizes back to back?

I know blink32 should be able to give some feedback, as he has gone all the way up to 32.7" tall tires.

Last weekend I drove a bit under 400 miles of Kentucky/Indiana interstate, so some hills but nothing too steep, at 70-80mph with the cruise on and ended up w/ 21.8mpg. Temp was about 40-45. Tires at 37psi cold. This was a round trip and I used 87oct on the way there, then topped off the 1/2 a tank I needed before the return trip w/ 93oct. Did not see any change in mileage w/ fuel grade.

The reason I wonder about tire size is in playing w/ the trip computer I have noticed that at 60mph I get 24+ mpg, then when I up to 75 it goes down to 21-22mpg.

I figure that the bigger tires should give an effective numerically lower gear ratio, so I would think that would give somewhat better gas mileage at higher speeds, but also that it takes more to get the truck moving, so that should hurt city mileage. Just looking for some real world numbers.


Also have any of you that have gone up on tire size done any towing before/after? I tow a boat every weekend in the summer and don't want to give up too much towing performance.


User avatar
blink32
Sponsored Member
Posts: 866
Joined: Wed Sep 13, 2006 6:38 am
Location: World Traveler

Re: Fuel, gears, and tires ?

Postby blink32 » Sat Nov 11, 2006 4:04 pm

I can't vouch for any other model, but the LE's come stock with 265/65R17 General Grabbers. And according to the owners manual there are two additional sizes, 265/75R16 and 235/75R15, besides the two you listed for a total of 5 apparently available.

Besides that bit of info I may be able to give some impressions tomorrow but as of now I've put about 1/4 of a mile on my 285/70R17's. I have no idea if the onboard computer will even be able to self-compensate for the change in tire size. I'll need to find a measured mile and clock myself travling it. Unfortunately too many regular life issues are getting in the way of having fun with vehicles.......

amr40509
Posts: 210
Joined: Tue Jun 27, 2006 3:35 pm

Postby amr40509 » Sun Nov 12, 2006 6:24 am

I would be amazed if it could self-compensate for the tire size change.

Your old 265/65/17 would have been 30.6" tall, making 660 revs per mile.

Your new 285/70/17 would be 32.7" tall, making 617 revs per mile.

SO I guess if your speedo is showing the same rpm at 60 mph as it used to, or the same as a stock 265/65/17, then your truck will be off. It should be showing at 100-110 rpms lower at 60 mph.


at 60 mph indicated you will actually be going 63.5 mph.

marked001
Posts: 38
Joined: Mon Aug 21, 2006 8:23 am

Postby marked001 » Sun Nov 12, 2006 8:03 am

I've got about 32.7's on my pathy... and my gas mileage has gone way down...like 16-17 instead of 20-21... I really dont see how the computer can self compensate...but my speedo is dead on when i'm going down the highway and they have the radar's in the construction zones...

User avatar
blink32
Sponsored Member
Posts: 866
Joined: Wed Sep 13, 2006 6:38 am
Location: World Traveler

Postby blink32 » Sun Nov 12, 2006 9:03 am

Marked, do you happen to have NAV? I hadn't thought about it before but *maybe* the pathy's with nav integrate with the comp somehow and the computer can reset its-self. Now I've never heard of this before but I didn't design the vehicle so who knows. Just hypothesizing.

amr, I use the heck out of http://www.miata.net/garage/tirecalc.html to compare sizes, speeds, etc.

marked001
Posts: 38
Joined: Mon Aug 21, 2006 8:23 am

Postby marked001 » Mon Nov 13, 2006 6:54 am

no blink..i have the lowly S model (long story) haha.. I have no idea how it could adjust itself, but it really seems to be right on.

also, wanted to say that my poor mileage may not be necessarily b/c of tire size.. but b/c my tires have a pretty aggressive tread..

boogyman
Posts: 519
Joined: Tue Jul 04, 2006 6:04 am
Location: Jersey

Postby boogyman » Wed Nov 15, 2006 6:20 am

I have found that pretty much all car companies set the speedo on the conservative side. So putting bigger tires on, probably did bring it in sinc. I know my saab is about 2 or 3 miles an hour off.

SHAWNATGERBROCK
Posts: 209
Joined: Fri Sep 01, 2006 4:11 pm
Location: Portland OR

Postby SHAWNATGERBROCK » Wed Nov 22, 2006 10:01 am

I love my 275-60-HR17's Falkens ..... they came out to 29.8 .... actualy feels quicker and handles way better ....and NO loss in mileage ...


Return to “R51 Engine, Driveline and Powertrain”

cron