Engine load after a lift and up-size of the tires

[Sifrk]

Hey fellas,

I know there's a bunch of threads out there, and I have read quite a few of them. I just wanted to ask as I don't know if my situation is any different.

I just got a lift with King 2.5s front and rear, TC UCAs, and Icon rear springs. Within a day, I threw on 275 /70 / 17 BFG KO2s onto the stock TRD wheels. The suspension went in last weekend, then the tires on that following Monday. I was told not to do any wheeling till I got at least 400 miles on the suspension. Then go back and have everything retorqued. That happened yesterday. I was ready to get dirty.

I'm in SoCal and often go up to the Cajon Pass to run those trails. I wanted to try out the upgrades so I naturally decided to hit the Cajon Pass. So a couple of things hit me as I was driving up there. First, the 4R was working much harder than I remember it ever having to do. In the week I was to throw on the 400 miles, my MPG dropped from 18.8 to about 17. On the drive up to the Cajon Pass today, it dropped to 15.9. Second thing, the drive does add elevation (although I couldn't tell you how much) and as I heavy-foot the throttle a bit more to keep the speed constant, I see the RPM go to about 3K and stay there, and it never drops below 2K even on the flats.

I'm curious if that's sounds about right to you all. It probably sounds like OCD about my MPG, and maybe some of it is. I knew I was going to lose some mileage but wasn't expecting what had happened today.

Thanks guys for any feedback you all might have.

 

[gainman]

Bigger tires take more effort to turn. Yes you will lose mpg

 

[fourwd1]

The larger tires put your engine out of the optimum RPM range, so power and MPG suffer . To get it back you would need to regear.
Also they throw the tach and odometer off, so your MPG calculations will be off.

 

[Sifrk]

Bigger tires take more effort to turn. Yes you will lose mpg

LOL ... I understand this. Probably didn't phrase my question clearly?

The larger tires put your engine out of the optimum RPM range, so power and MPG suffer . To get it back you would need to regear.
Also they throw the tach and odometer off, so your MPG calculations will be off.

Guess I gotta read up on regearing. The tach discrepancy I'm not quite understanding. I assume the higher load in rotating these large and more weighty tires would result in higher RPMs, is that not true? Would you explain further please?

Regarding the odometer, and I'll group the speedometer in as I assume they are tied to the same source of information. Anyway, I used to be 2 miles off on my speedometer faster than multiple sources I used to compare the speedo value (e.g., Waze and those speed meters you see on the streets). With the increased tire size, these sources are, if I was to hazard a guess, within .25 MPH. I'm making a big assumption that the speedometer is tied to the same mechanism which drives the odometer.

 

[bsa70]

Going higher and larger tires moves the whole drive train out of the engineering specs. So it has a negative effect on everything. Will also accelerate wear on all parts...

 

[Sifrk]

Going higher and larger tires moves the whole drive train out of the engineering specs. So it has a negative effect on everything. Will also accelerate wear on all parts...

I definitely am planning to keep the rig long-term. Although I've had a 4Runner in the past, this is the first one I've actually put any significant mods into. It's all going to be a learning process for me. Any suggestions you got to help minimize the impact over the long-term, please do share. The drive train impact I'm learning about now

 

[Dillusion]

As long as you don't drive like a complete ass hole I'd just drive and not worry. Regular maintenance is all you can do.

Its meant to be driven. (I shouldn't really talk mine is a garage queen and sees the road maybe once a week)

 

[YellowSnow]

Going higher and larger tires moves the whole drive train out of the engineering specs. So it has a negative effect on everything. Will also accelerate wear on all parts...

Interesting...i haven’t noticed a shortage of modded Yota’s everywhere running 100% reliable. What empirical data do you have to support your opinion?

 

[nimby]

If you want a larger tire, but are still concerned about mpg's, the best thing you can do is to shop for a lighter tire. This can come as a P or C load rated tire and/or a skinnier tire like a 255/75/17.

Do you know the load rating on your BFG's?

 

[Sifrk]

As long as you don't drive like a complete ass hole I'd just drive and not worry. Regular maintenance is all you can do.

Its meant to be driven. (I shouldn't really talk mine is a garage queen and sees the road maybe once a week)

That's the plan brother. I was hoping against hope that I might lose 2 MPG but it's at 3 now, and I haven't driven up to the mountains but one time...Ha! More than that, I'm hoping I'm not significantly reducing the life of the engine having it run under heavier load.

If you want a larger tire, but are still concerned about mpg's, the best thing you can do is to shop for a lighter tire. This can come as a P or C load rated tire and/or a skinnier tire like a 255/75/17.

Do you know the load rating on your BFG's?

The BFG's are E rated. I was told the 275s don't come available in any other rating than E. At 265, you have the C and E to choose from. Quite honestly, the 275s kinda suits the lift, if I had to for some reason go back to 265s (or skinny tires), I'd prefer to just put it back to stock height. Yep!

 

[fourwd1]

Guess I gotta read up on regearing. The tach discrepancy I'm not quite understanding. I assume the higher load in rotating these large and more weighty tires would result in higher RPMs, is that not true? Would you explain further please?

A typo, I meant speedo and odometer

Regarding the odometer, and I'll group the speedometer in as I assume they are tied to the same source of information. Anyway, I used to be 2 miles off on my speedometer faster than multiple sources I used to compare the speedo value (e.g., Waze and those speed meters you see on the streets). With the increased tire size, these sources are, if I was to hazard a guess, within .25 MPH. I'm making a big assumption that the speedometer is tied to the same mechanism which drives the odometer.

 

[Bumbo]

Interesting...i haven’t noticed a shortage of modded Yota’s everywhere running 100% reliable. What empirical data do you have to support your opinion?

Empirical data is not required, just common sense.

Nothing is 100% reliable, and the only guarantee is there is no guarantee.

It’s physics and engineering… no such thing as a free lunch. Every modification has it’s costs and savings / pros and cons.

People say spacers are fine too, but you are still increasing the amount of leverage there on the hub, which could case accelerated wear of wheel bearings, but the rate in which it would degrade is still dependent of plenty of other factors. That is the cost of a track increase. The savings are increased stability.

With bigger tires and factory spec gearing you just end up lugging the motor a bit more, and it could promote negative effects long terms, but most of us would probably REALLY feel the need to re-gear before getting to that extreme. Going that far "out of spec" is wildly annoying to the user. It's like peddling a bike in the wrong gear.

 

[nimby]

That's the plan brother. I was hoping against hope that I might lose 2 MPG but it's at 3 now, and I haven't driven up to the mountains but one time...Ha! More than that, I'm hoping I'm not significantly reducing the life of the engine having it run under heavier load.



The BFG's are E rated. I was told the 275s don't come available in any other rating than E. At 265, you have the C and E to choose from. Quite honestly, the 275s kinda suits the lift, if I had to for some reason go back to 265s (or skinny tires), I'd prefer to just put it back to stock height. Yep!

There are other 275 AT's that are not E rated. Firestone Destinations come in P and C ratings. 265's come in P rating as well. The Firestones are quite a bit lighter than the BFG's. You could probably regain some mpgs with a C or P rated tire.

 

[YellowSnow]

Empirical data is not required, just common sense.

Nothing is 100% reliable, and the only guarantee is there is no guarantee.

It’s physics and engineering… no such thing as a free lunch. Every modification has it’s costs and savings / pros and cons.

People say spacers are fine too, but you are still increasing the amount of leverage there on the hub, which could case accelerated wear of wheel bearings, but the rate in which it would degrade is still dependent of plenty of other factors. That is the cost of a track increase. The savings are increased stability.

With bigger tires and factory spec gearing you just end up lugging the motor a bit more, and it could promote negative effects long terms, but most of us would probably REALLY feel the need to re-gear before getting to that extreme. Going that far "out of spec" is wildly annoying to the user. It's like peddling a bike in the wrong gear.

So the answer is no....you don’t have supporting data other than the old tried and true “common sense” rebuttal.

 

[karmatp]

Load rage E is to much for our light 4runners. I would and did go for load range C after doing lots of research and talking with buddies who made the mistake of going with load range E on their Tacoma’s and 4runners.

 

[Sifrk]

There are other 275 AT's that are not E rated. Firestone Destinations come in P and C ratings. 265's come in P rating as well. The Firestones are quite a bit lighter than the BFG's. You could probably regain some mpgs with a C or P rated tire.

Load rage E is to much for our light 4runners. I would and did go for load range C after doing lots of research and talking with buddies who made the mistake of going with load range E on their Tacoma’s and 4runners.

[MENTION=173641]nimby[/MENTION] I had my heart set on KO2s, but to [MENTION=140586]karmatp[/MENTION] 's point, I didn't do my research and ended up going with the popular vote while not fully understanding the implications. That being said, these KO2s are just fantastic, on and off road. Bear in mind, I only have experience with the Grapplers and the KO2s. What other brands come close to matching the KO2s far as road noise and off-road performance?

So someone at work is interested in the TRDP wheels. He said he might take the tires also if I can give him a deal. Not quite sold on idea yet as I was thinking to keep the wheels and bring it back to stock if I were to sell down the road. I've been salivating over some Method wheels because I have spacers now mainly to improve the asthetics.

 

[YellowSnow]

Load rage E is to much for our light 4runners. I would and did go for load range C after doing lots of research and talking with buddies who made the mistake of going with load range E on their Tacoma’s and 4runners.

100% false...

 

[Bumbo]

Load rage E is to much for our light 4runners. I would and did go for load range C after doing lots of research and talking with buddies who made the mistake of going with load range E on their Tacoma’s and 4runners.

Have to agree with this... E load range tires provided the least desirable drive on and off-road for me.

These days it’s C load or D load for off-road tires. BFG mud terrains what I currently use, and P load range for anything that spends most of its time on-road.

I still have multiple sets of rims and tires, but the only thing I struck from inventory was E load.

 

[mteolus]

MPH was 1.5 mph lower than the digital display on stock 265 Duratracs. With 285 KO2s it is 1 mph faster than the display. I would imagine the 275s would be just about right.

Interesting that the MPG on the display was almost spot on with GPS tracking MPGs even though the speedometer was off by 1.5 mph. I haven't checked the MPG via GPS on the new tires yet. Just got them weekend after last.

On a trip to Colorado from Texas going uphill against the wind I got 15.9 mpg with the old 265s (I have a 3 inch lift, aluminum skid plates, and sliders). On the way back I got 20.2 mpg. Haven't tested this yet with the new tires. I know now why Toyota puts on the highway p-rated 265s, puts on very flimsy skid plates, and has low ground clearance (8.0 on a KDSS equiped TRD Off-road). Bigger tires, beefier skid plates, sliders, and a lift all affect gas mileage which would qualify them for a higher gas guzzler tax. At a certain point though, too much weight will start affecting 4x4 performance. I don't plan on putting steel bumpers or a winch at this time.

 

[nimby]

[MENTION=173641]nimby[/MENTION] I had my heart set on KO2s, but to [MENTION=140586]karmatp[/MENTION] 's point, I didn't do my research and ended up going with the popular vote while not fully understanding the implications. That being said, these KO2s are just fantastic, on and off road. Bear in mind, I only have experience with the Grapplers and the KO2s. What other brands come close to matching the KO2s far as road noise and off-road performance?

I completely understand that. You like what you like, but in this case you'll have to make the choice on what you want more, BFG's or MPG's.

As far as AT's go, all I can give is my personal experience with a couple different brands. I've had Bridgestone Dueler AT's......didn't like them because they rode really stiff and Goodyear Wrangler AT's......didn't last very long. I'll be trying the Firestone Destination AT's next. They seem to have a lot of really good reviews.

Plenty of other posters here will be able to give you comparisons on other tires.