I got 4 new Kumho road venture tires about a month ago and I've noticed that my mileage has gone down since then

I used to average 430-450 on a fill up and now im barely getting 375.

I had bfgoodrich a/t tires on there before getting the hire mileage.

I also have noticed a couple of other issues:

1. I seem to have wander in the steering wheel going to the street tires and sometimes it makes it look im a drunk driver.

Could the camber adjustment have anything to do with that or do i need a new steering stabilizer?

2. There is a horrible shake in the truck between 50-60

It goes away over 60 and doesnt happen until 50

It is so smooth and quiet at 60+ it puts a smile on my face and it makes me want to drive that fast so i dont have to feel the shake in the truck

I've had the tires re-balanced and rotated and it's not as bad as it was before, but it definitely is a noticeable shake.

Could it be a bad tire or something mechanical?

 

Were both sets of tires the exact same size?
Were both sets of tires set to the exact same pressure? Lower pressures will net lower MPGs and can induce a wander into the ride.
Have you actually calculated the fuel mileage with either set of tires? Hand calculated miles driven by gallons burned.
For the vibration, find a shop that can do a high speed balance with the tires on the truck.
Have you made a camber adjustment prior to this new wander?

 

they did the camber adjustment and its within spec

Same size yes, but the bfgoodrich with all terrain tires

i don't know where the previous pressure was set at, but I know that the new ones are at spec

I know based on what the mileage read when it was empty with the previous tires and the new ones and it's a big difference.

I got the tires at kauffman and they do road force balancing.

they did it once after i got the tires on and that took out some of the vibration, but it seems to just show up at that speed

I've got a new fuel pump installed 2 months ago but I have noticed that since it got installed, i smell gas all the time.

im assuming its the filler neck and needs to get replaced, but could that have anything to do with reduced milage

 

What spec? On the Door in the Owners Manual?

Try 65 PSI on all four.



So you are just guesstimating based on a tank of fuel? Not really an accurate method of determining MPG. Miles/Gal=MPG over the course of a minimum three tanks.



If after adjusting tire pressures you may want to consider shock absorbers.



You drive around smelling gasoline and don't consider that a problem? Smelling evaporating fuel will definitely affect MPG.


Uh, yes, big time.

 

Should be filled to tire specifications, but ill check when i get a chance

Im basing it on the 4 fill ups ie done this past month and how its gone down each time i have to fill up.

I was getting 430-450 prior to changing the tires to 375-400 with the new tires

I have new front shocks and springs and need to get new rear shocks and springs.

This vibration/shaking wasn't happening with the a/t tires that were on before the switch

The filler neck has moved up to the top of the list to get done, but since i just started a new business, my finances and time has been spread thin

 

Gas is very volatile and typically if you can smell it (especially if you can smell it inside the cab!) there is enough of it out in the open (where it shouldn't be) to support combustion if it finds a source of ignition. I wouldn't drive it in this condition until the fuel leak is repaired, that's only my opinion but it's based on 30 years as both a firefighter and oil refinery worker.

Mark is spot on about the fuel mileage calculations, guesstimating based on the gas gauge is less than accurate.

It is possible that there is an issue with a tire, move the fronts to rear and rears up front to see if the vibration changes.

I agree on trying 65PSI on all tires if they are load range E.

 

65?! Dear God y'all are crazy. 55/50 is where my last two sets have worn evenly and thankfully also rode the best, minus towing. Towing the tears get pegged to 65.

I agree with Tom and Mark, if you can smell gasoline it's not your tires that are the problem with fuel consumption. That's like getting shot and not bandaging the wound yet complaining about low blood pressure.

 

65 PSI is the starting point then deflate (like Tom Brady) 5 PSI at a time to your desired ride/comfort level.


BTW, when shot your blood pressure will increase. HEHE.

 

Haters gonna hate !!!

 

60 psi!!!! Jeez, no wonder so many people complain about the wander in the X. I keep mine at 75frt and 80rear 100% of the time. Probably why I can get near 15 mpg out of my V-10/4.30 equipped X! And it still rides comfortable!

 

Why do you bother with the 5PSI difference ??

 

I've been a Pats fan since Drew Bledsoe, no hatin' here just a "current-events-sub-reference."

 

It`s for towing and has been proven to make a difference in how the X handles a long heavy trailer!

 

New tires will reduce fuel mileage somewhat, believe it or not, compared to a well worn set. That's what the tire manufacturers say anyway.

The balance thing I dunno. Did any of the tires take an unusual amount of weight?

Interestingly there's balanced - within minimum specs - and then, there's _balanced_. The latter is a PITA, because the mechanic have to mount and dismount the tire itself a couple times and find the best orientation of tire and rim together before they ever start adding any weight. Nobody does this. Good balance makes tires and other components last longer, too.

 

Remember also, you can balance an egg but that doesn't mean it's round.

Meaning you may have a high spot in the tire even though it's "balanced."