Has anyone seen any tests along these lines? If lifting a truck causes more aerodynamic drag, thus reducing milage, you'd think that the opposite would be true...

 

Most people that lift there truck put oversize tiers on it. That's were the gas mileage goes.
I don't think you'll get any noticeable difference in mileage by lowering it,,,lol.

 

Bigger tires do not automatically mean lower mpg, it's the drag that the lift causes. You can increase your highway mileage by putting on bigger tires, thus effectively making your overall gear ratio higher. (numerically lower) You just want to be sure your new tires/wheels don't weigh a lot more than the stockers, but since I have stock steel wheels and I'm going to aluminum wheels, I should lose weight there...

But since increased drag lowers mileage, I just figured that with the same stock tire size, but less frontal area, the truck would have to get better mileage, and it would also fill up my wheelwells, which look rediculously empty with the dinky stock tires. I'll have to do one of two things, either of which might increase mileage: put on the tallest possible tire, or lower the truck until the stock tires fit.

 

Sorry but I don't mean 1 or 2 inches bigger! MOST guys that lift a truck is to fit bigger tiers. And thous tiers are much heaver.
Something like this.

Now I love the look of a lowered truck but don't think your going to break any MPG record by doing it. But it will look great!
Lets face it,,,,,it's a truck. Not a NASCAR. You will probably do better with a bed cover.

 

You can increase mpg (very little, I might say) by lowering your truck. But no, I didn't do it, and not planning on doing it either.

 

Hmmmm.....I've never thought about that. I'm thinking the difference in MPGs would probably not be that big.

 

One thing you could do is use sheet metal or aluminum and cover the bottom of the truck to reduce drag from under carriage stuff

 

I had a conversion 4x4 3;55 rears had low profile tires and was lowered tire were same highth as 2357515 but wide.(2656015 I think) When I put Stock springs back on it and the right rear block I lost 1 MPG and still had same tires. Air drag Over 2 months I check every fill up.

But several guys have put on or removed sunvisors and lost or gained also . If you run on open road it might help but its still same weight truck only lower around town

 

Aerodynamic drag doesn't really become significant until you are at freeway speeds, so I'd expect you to see a little improvement on freeway trips, but certainly not around town, as was mentioned earlier. And, since the frontal area is somewhere in the area of 20 square feet, lowering it a couple of inches won't make a large difference on that area, hence not a big difference in drag or mileage.

 

Lowering helps cover up the wheels and undercarriage. This reduction in frontal area will reduce aero drag. I believe trucks might benefit from lowering even below 50 MPH, because drag is not only caused by frontal area but also how many times that air gets hit passing under the truck. Benefits increase down to about 3 or 4 inches off the ground. Below 3 inches there is no benefit because the proximity to the road surface unless you have a well designed splitter. Covering the bottom with a flat skin will help also. Ideally for a truck, it would good to able to raise the ride height for off road or bad weather. The shape of the front and rear is also very important. I haven't seen a truck yet that was designed for optimal mileage. The need is, to ask, what does nature say a truck should look like instead of, what have trucks always looked like. I see no major improvements in the aero drag of light trucks since my 59.

 

Well, many of the things that could improve mpg via reduction in aerodynamic drag would make the truck less usable as a truck. Yes, a ground clearance of a few inches would be good on a highway. but not so on a dirt road. And cargo capacity is a more important design factor for the tailgate and bed than mpg. IMHO, today's trucks are more curvy and aerodynamic than older ones.

 

I dont have the figures in front of me and there are other variables, such as powertrain improvements and increased curb weights, but the 97-04 F-150 at least looks a lot more aerodynamic than the -96 or 05- models before and after.

As far as lowering via tires, the problem is rolling resistance. A wide low-profile tire is generally less efficient than a tall, narrow one (still P and not LT, which are worse).

Jim

 

Perhaps the largest mileage gains in recent history occurred with the radial tire. And then the trend went towards wide and low profile with no way to shield the front of the tire from the wind, we lost part of our gains. And raising a truck exposes more of the upper half of the tire. Which is going 110 MPH wind speed. I was amazed to find out that Indy cars are limited in speed primarily because the top of the tire is going 460 Mph wind speed. And that's a slick.
The front surface of a truck could be raised or lowered based on the ground clearance requirements. A trucks cargo and passenger areas could change shape based on those requirements. I am talking conceptual here because as soon as I think in the box then, I am stuck in the same old mud puddle.

 

Well, after being referred to as a fool in another forum, here's what I have:
2006 Mark LT 4x2
Mods:
cat back exhaust
PCM programmer
Rear sway bar (self built since the hellwig is a POS IMHO)
WIX HP filter
Flush mount bed cover (self built)

MPG City: 15-16
MPG HWY: 20 (with AC 18.5)

Note: based on my calcs, if I lowere the truck 2" up front and 2" in the rear, that would in theory increase MPG by .5 mpg at HWY.

 

That seems quite a bit, but it's not an unbelievably high number. I have a 2.5" lift kit for my Bronco, so I guess the lack or presence of that much of a lift should yield a comparable mpg difference.