Should I lift my 4x4 truck a little?

[xshanex]

Originally Posted by madeouttaglass

I'm also sticking with the factory 265/70-16 inch tires which seemed quite large for such a small truck that sits somewhat low

when you go to replace the tires at some point the 265/70-16 can be replaced with 265/75-16 and fit well stock and obviously fine with a lift......they're a little cheaper too at most places and allow for a larger selection too

I was dumb when I bought my BFG AT's and got the 70's which are much much less common and cost like $25-30 more per tire. When I got a cut in one of my tires it took a couple of months before I could find a half-worn matching tire. I crawled all over used tire places and found tons of the 75's but never one of the 70's

[Bueller]

Originally Posted by Range Motorsport

Tacoma's are IFS so the drag added by lifting it is virtually zero.

Bigger tires will reduce engine RPM at the same speed as smaller tires increasing fuel mileage.

Most small lift kits will stiffen the suspension and improve road handling too.

The only part of this that is correct is the third sentence. Lifting increases drag, regardless of suspension type. That is one of a couple of reasons why the recommendation nowadays is to lift a vehicle only as much as is necessary to clear whatever size tire the owner wishes to use.

Reducing engine RPM is not the issue with regard to fuel mileage. Rolling resistance is the issue, and it requires more throttle to overcome the increased rolling resistance of larger/wider tires.

[scootertrash]

I just bought a 2008 Access Cab 4x4 Tacoma and moved my Durashell camper over to it from my 2004 2wd Tacoma. It sat right on the bumpstops with the weak springs bowing the wrong way. Toyota has a TSB on this, but my truck is out of warranty.



Notice the low rider stance above.

I then took it to 4WP in Westminster, CO and had the following done: 265/75/16 ProComp AT tires on 16" M/T black Classic Lock rims, SAA19 SuperSprings, 2" leveling kit and an add a leaf on the rear. Totally good to go and I love the stance.







BTW, the build thread for my adventure camper is here.

http://www.cheaprvlivingforum.com/po...73334?trail=15

[straightrod]

^ That Durashell looks good on your Tacoma. The hardware on the back looks stout.

[leakypetcock]

Originally Posted by xshanex

when you go to replace the tires at some point the 265/70-16 can be replaced with 265/75-16 and fit well stock and obviously fine with a lift......they're a little cheaper too at most places and allow for a larger selection too

I was dumb when I bought my BFG AT's and got the 70's which are much much less common and cost like $25-30 more per tire. When I got a cut in one of my tires it took a couple of months before I could find a half-worn matching tire. I crawled all over used tire places and found tons of the 75's but never one of the 70's

I wanted the BFG AT/KO's on my Titan but they don't make them in a 265-70/18. I upgraded to a 275 and got exactly what I wanted. No ordering, no waiting and exactly what I wanted. Sears didn't want to do it, Costco refused to put anything but the stock size on. Discount tire hooked me up. In and out in an hour.

[Range Motorsport]

Originally Posted by Bueller

The only part of this that is correct is the third sentence. Lifting increases drag, regardless of suspension type. That is one of a couple of reasons why the recommendation nowadays is to lift a vehicle only as much as is necessary to clear whatever size tire the owner wishes to use.

Reducing engine RPM is not the issue with regard to fuel mileage. Rolling resistance is the issue, and it requires more throttle to overcome the increased rolling resistance of larger/wider tires.

So you think that a vehicle that sits 8" off the ground from the factory is going to have a huge negative effect on the aerodynamics when it sits 10" off the ground? So using the same logic an airplane is better off staying on the ground and never taking off. No the problem with a lot of lifts is you increase the frontal area of the vehicle, thus increasing wind resistance. So again with IFS and a small lift there is virtually no increase in frontal area.

It's not the size of the tire that matters its the rotational mass, the tire tread, and the wind resistance. A small heavy tire like my rally tires get worse mileage than my lighter, wider, taller tires I normally run. There is a sweet spot that you must find when choosing tires. Sure a set of really big swampers are going to kill your mileage, but the same size tire in an AT tire won't. You just have to be reasonable with your tire selection and don't out size your gearing. From there pick a reasonable tread design, and proper load rating inflated to the right pressure and it's very easy to see mileage gains or in the least the same mileage as stock.

[Bueller]

Originally Posted by Range Motorsport

So you think that a vehicle that sits 8" off the ground from the factory is going to have a huge negative effect on the aerodynamics when it sits 10" off the ground? So using the same logic an airplane is better off staying on the ground and never taking off. No the problem with a lot of lifts is you increase the frontal area of the vehicle, thus increasing wind resistance. So again with IFS and a small lift there is virtually no increase in frontal area.

Yes, more lift equals more drag. But don't take my word for it.

http://www.ehow.com/how_7469758_impr...up-trucks.html

The average pickup truck, by its very nature, is a less fuel-efficient vehicle than most cars on the road. This is simply because a truck utilizes a heavier frame, heavy-duty suspension and a body design that's upright and less aerodynamic. Of course, some truck owners wish to adapt or accessorize their vehicles by way of a body or suspension lift. This lifting is often done for aesthetic purposes or to gain greater ground clearance for off-roading. One of the consequences of jacking up the height of the truck, however, is a further decline in gas mileage.

http://www.truckinweb.com/tech/body/...s/viewall.html

Wind tunnel testing has proved that the lower the vehicle the better its coefficient drag becomes, due to the fact that less air is able to flow underneath the chassis create drag. Elevated trucks and SUV's we see cruising the boulevards or prowling rugged terrain are a mess when it comes to creating a coefficient aero package. The greater the truck or SUV's ride height,the more drag and turbulence it's creating underneath the chassis. Other contributors are the massive wheels/tires that are part of the rugged off-road image. As these redundant rolling spools of aluminum RPMs increase, more turbulence is developed causing incredible drag load. Less air travels underneath causing turbulence.

Additionally, you can't draw a logical conclusion to an airplane because of a variety of reasons, not the least of which being an airplane becomes more aerodynamically efficient when it gets out of "ground effect" (approximately 15 feet of elevation AGL and below). You can't lift a truck up high enough to get out of ground effect because it's always on the ground!

Originally Posted by Range Motorsport

It's not the size of the tire that matters its the rotational mass, the tire tread, and the wind resistance. A small heavy tire like my rally tires get worse mileage than my lighter, wider, taller tires I normally run. There is a sweet spot that you must find when choosing tires. Sure a set of really big swampers are going to kill your mileage, but the same size tire in an AT tire won't. You just have to be reasonable with your tire selection and don't out size your gearing. From there pick a reasonable tread design, and proper load rating inflated to the right pressure and it's very easy to see mileage gains or in the least the same mileage as stock.

Weight is only one factor. When dealing with truck tires, taller tires usually weigh more than smaller diameter tires (unless you want to make a ridiculous comparison like a 3 ply carcass to a 10 ply carcass). Additionally, as diameter increases so generally does width, which means more rubber on the road, a wider frontal area creating more wind drag, and more rolling resistance.

When referring to out sizing your gearing, you also have to take into account the peak efficiency RPM of your engine, which is usually at or near the point of maximum VE (Volumetric Efficiency, which happens to be the point at which your engine makes maximum torque). The farther down the torque curve you go away from this sweet spot, the less efficient the engine generally becomes. So there is a trade off to lowering RPM to achieve less combustion events per minute, versus less efficiency in each combustion event combined with the requirement to add more fuel to each combustion event to make up for less efficiency and inertia.

Generally speaking what all of this means is if you lift your truck and put on bigger tires mileage goes down. It doesn't start all of the sudden at 6 inches of lift. It occurs progressively as you lift the vehicle away from the asphalt. So to answer your question, no, 2 inches isn't a "huge" difference in drag. But it does create more drag. With tires the equation is a little different, and you can indeed find a highway speed fuel mileage sweet spot in some vehicles by slightly lowering cruising RPM with a slightly larger tire. But this is limited to very small changes in tire size, and may have negative effects on fuel mileage under other driving conditions such as stop & go. By the time you've gone from, for example, a 33" to a 35" tire (1" taller) you are diminishing fuel mileage across the board.

[scootertrash]

Originally Posted by straightrod

^ That Durashell looks good on your Tacoma. The hardware on the back looks stout.

Thanks straightrod, it's built in Canada, all stainless hardware. Very nautical build quality. Supposed to weight 300lbs empty.

[_cy_]

Originally Posted by scootertrash

Thanks straightrod, it's built in Canada, all stainless hardware. Very nautical build quality. Supposed to weight 300lbs empty.

nice build... looks like you've got a ton of $$$ invested.
too bad they don't offer a small diesel like overseas toyota models.

running a 96 Cummins 12v, 4x4, extra cab, stick, that don't lifting. factory dodge 4x4 2500 has highest stock lift that I'm aware of.
one can run 35in wheels without mods ...

just took off my 20in 8 lug wheels in favor of 2012 factory takeoffs. Michelin 265x75Rx17 with factory aluminum 8 lug rims. picked up 3-4 mpg over 20in wheels. both with road biased tread, both same 265 width. main difference was height, 35in vs 33in with 17in

[Bueller]

Originally Posted by _cy_

just took off my 20in 8 lug wheels in favor of 2012 factory takeoffs. Michelin 265x75Rx17 with factory aluminum 8 lug rims. picked up 3-4 mpg over 20in wheels. both with road biased tread, both same 265 width. main difference was height, 35in vs 33in with 17in

^ ^ ^

Correct. Both the increased diameter and the probable extra weight of the 35's/20 inch wheels was eating some extra fuel. The fact that your engine revs slightly higher now than it did then is inconsequential.

As a side note, your brakes and some suspension components may wear a little less too.

[Clint Taurus]

If you hang one of those UN-naturally large scrotum's off the trailer hitch people will think you have a lift kit on it.

[1greenmachine]

I've got a 06 chevy 1500 with the z71 package and i hate how it sits with the front end lower. i wanna do a leveling kit so it sits flat and has that better stance. I understand the whole aero/mileage thing but its a truck and the majority of what i use it for is not condusive to good fuel mileage anyways

[Range Motorsport]

Originally Posted by Bueller

Yes, more lift equals more drag. But don't take my word for it.

http://www.ehow.com/how_7469758_impr...up-trucks.html

The average pickup truck, by its very nature, is a less fuel-efficient vehicle than most cars on the road. This is simply because a truck utilizes a heavier frame, heavy-duty suspension and a body design that's upright and less aerodynamic. Of course, some truck owners wish to adapt or accessorize their vehicles by way of a body or suspension lift. This lifting is often done for aesthetic purposes or to gain greater ground clearance for off-roading. One of the consequences of jacking up the height of the truck, however, is a further decline in gas mileage.

http://www.truckinweb.com/tech/body/...s/viewall.html

Wind tunnel testing has proved that the lower the vehicle the better its coefficient drag becomes, due to the fact that less air is able to flow underneath the chassis create drag. Elevated trucks and SUV's we see cruising the boulevards or prowling rugged terrain are a mess when it comes to creating a coefficient aero package. The greater the truck or SUV's ride height,the more drag and turbulence it's creating underneath the chassis. Other contributors are the massive wheels/tires that are part of the rugged off-road image. As these redundant rolling spools of aluminum RPMs increase, more turbulence is developed causing incredible drag load. Less air travels underneath causing turbulence.

Additionally, you can't draw a logical conclusion to an airplane because of a variety of reasons, not the least of which being an airplane becomes more aerodynamically efficient when it gets out of "ground effect" (approximately 15 feet of elevation AGL and below). You can't lift a truck up high enough to get out of ground effect because it's always on the ground!



Weight is only one factor. When dealing with truck tires, taller tires usually weigh more than smaller diameter tires (unless you want to make a ridiculous comparison like a 3 ply carcass to a 10 ply carcass). Additionally, as diameter increases so generally does width, which means more rubber on the road, a wider frontal area creating more wind drag, and more rolling resistance.

When referring to out sizing your gearing, you also have to take into account the peak efficiency RPM of your engine, which is usually at or near the point of maximum VE (Volumetric Efficiency, which happens to be the point at which your engine makes maximum torque). The farther down the torque curve you go away from this sweet spot, the less efficient the engine generally becomes. So there is a trade off to lowering RPM to achieve less combustion events per minute, versus less efficiency in each combustion event combined with the requirement to add more fuel to each combustion event to make up for less efficiency and inertia.

Generally speaking what all of this means is if you lift your truck and put on bigger tires mileage goes down. It doesn't start all of the sudden at 6 inches of lift. It occurs progressively as you lift the vehicle away from the asphalt. So to answer your question, no, 2 inches isn't a "huge" difference in drag. But it does create more drag. With tires the equation is a little different, and you can indeed find a highway speed fuel mileage sweet spot in some vehicles by slightly lowering cruising RPM with a slightly larger tire. But this is limited to very small changes in tire size, and may have negative effects on fuel mileage under other driving conditions such as stop & go. By the time you've gone from, for example, a 33" to a 35" tire (1" taller) you are diminishing fuel mileage across the board.

(Road Vehicle Aerodynamics) page 51:

"The effects of ground clearance would be different for very rough or smooth undersides. Some researchers suggest that a very rough underside and a large clearance, as in trucks and lorries, actually causes an increase of drag by creating conditiions of greater freedom for the formation of eddies in the underside flow[34]. On the other hand, a general increase in ground clearance leads to a more unobstructed airflow which by bleeding air from the other flow regions produces, in effect, a decrease in the aerodynamic force."

He then shows a diagram that indicates that for a rough underbelly, the Cd increases with increasing ground clearance, while for a smooth underbelly, Cd decreases with increasing ground clearance.

He then goes on to say "These diagrams were produced for cars with an average underside roughness and show that vehicles with bad aerodynamic styling, characterised by large total drag coefficients, display a slight increase in drag while those of good aerodynamic shape display a rapid decrease in drag with increasing ground clearance."

[Mleaky]

Originally Posted by rawdog

I have the same truck and I lifted it slightly. Now I think it is perfect. I used Bilstein 5100 adjustable shocks in the front (lowest lift setting) and 1" blocks in the rear. That was all it took. With stock BFG A/T's 265/75/R16, I think the truck looks the way it should. Those tires are big for a mid-size truck, now it looks right with the mild lift. I bought the parts from wheelersoffroad.com - they have very good service.

It's dark out, so I can't get a pic.

This is what I did also. Bilstein 5100's front and rear, except my rear lift came from Firestone Ride Rite air bags instead of blocks.

ETA - I went with the mid setting. According to my mechanic I am at the alignment maximum. If you go with anything 3"+ you will need UCA's that allow more alignment adjustment.

[Bueller]

Originally Posted by Range Motorsport

(Road Vehicle Aerodynamics) page 51:

"The effects of ground clearance would be different for very rough or smooth undersides. Some researchers suggest that a very rough underside and a large clearance, as in trucks and lorries, actually causes an increase of drag by creating conditiions of greater freedom for the formation of eddies in the underside flow[34]. On the other hand, a general increase in ground clearance leads to a more unobstructed airflow which by bleeding air from the other flow regions produces, in effect, a decrease in the aerodynamic force."

He then shows a diagram that indicates that for a rough underbelly, the Cd increases with increasing ground clearance, while for a smooth underbelly, Cd decreases with increasing ground clearance.

He then goes on to say "These diagrams were produced for cars with an average underside roughness and show that vehicles with bad aerodynamic styling, characterised by large total drag coefficients, display a slight increase in drag while those of good aerodynamic shape display a rapid decrease in drag with increasing ground clearance."

And what production truck or SUV that generally gets lifted for extra tire clearance has a good aerodynamic profile?

Answer = none. Therefore, lifting is almost guaranteed to have a negative effect on fuel mileage, a fact that is already very well substantiated in the real world.