gas mileage decrease with 285s

[HadjiHunter]

I've searched for an answer but can't find it on this question. I will be putting on a toytec run-3dr 3'' lift with 285/75/16s in about 2 weeks but I keep hearing that tires that big really cut into gas mileage. Does anyone have 285s and how bad did it kill your mpgs?

 

[p nut]

You will be in the 15mpg range.

 

[techno]

Switching from 265/70's to 265/75's dropped my mileage about 1.5 mpg. (The deckplate mod returned it to normal tho!)
You might want to consider re-gearing to 4.56s or similar.

 

[HadjiHunter]

I was thinking about re-gearing but I don't want my highway performance to go down as I've heard with that.

 

[techno]

Re-gearing after increasing the tire diameter essentially keeps everything close to stock performance. Larger tires means the engine has to work harder to turn them, hence an increase in fuel consumption. But re-gearing by a similar percentage to what the tire size was increased by will let the engine work 'normally', and have similar fuel consumption.
If you just do bigger tires, yes, your highway performance will get a little better, but your acceleration and torque will suffer noticeably.
If your not sure, do the tires and see how it all feels then. If you're happy, then you wont have spent the $$s on gears that you didnt need, and if you're not happy, then get the gears.

 

[HadjiHunter]

Ok. Now i'm starting to see. Thanks for the info.

 

[p nut]

Re-gearing after increasing the tire diameter essentially keeps everything close to stock performance. Larger tires means the engine has to work harder to turn them, hence an increase in fuel consumption. But re-gearing by a similar percentage to what the tire size was increased by will let the engine work 'normally', and have similar fuel consumption.

I'm sorry, but regearing will NOT get you back up to stock MPG's. It will help a tiny bit, but your mileage will still suffer. This is why I haven't gone up to 33's. My friends who have 33's with the regear hardly saw any difference in MPG (they did see performance gains, though). Your engine is still turning a 33" tire.

 

[beallen21]

I when I lift mine and put 275/55/r20 (like a 32x11) on it i wanted to cry my gas mileage dropped so bad, if lifting one and putting big tires on it is something you wanna do MPG prolly shouldn't be a big deal to ya, i do good to get 14 or 15miles a gallon, it's sad

 

[techno]

Yeah, you are right, it wont get you back to stock mpg because a bigger tire is heavier, but it definately helps.
Doing the calculations is good. At 65 mph with a 1:1 transmission ratio:
31" tire, 4.11 diffs - 2896 rpm
33" tire, 4.11 diffs - 2720 rmp
33" tire, 4.27 diffs - 2826 rmp
33" tire, 4.56 diffs - 3018 rpm

That gives a basic idea of what to expect rpm-wise (power & torque), but the heavier tire will always take performance away. Keeping the rpms as close to original as possible is the best way to minimize the negative effects.

 

[swimminggerman]

I run 35's with 4.88's and get around 16 mpg. Planning on going up to 36-37's depending on which brand I buy next. Im used to trucks around that range. My Z can get 31. But due to an occasional twitch in my right foot it gets 22.

 

[toytech76]

remember also, it depends on what type of driving you do. Also, your speedo will be off and your mileage counter is also off so that will make a diff. A larger tire will make your speedo read slower so that means less miles therefor looking like worse mileage

 

[HadjiHunter]

toytech you'r rig is bad ass! Thanks for the info, also have you had any issues after you'r lift?

 

[toytech76]

toytech you'r rig is bad ass! Thanks for the info, also have you had any issues after you'r lift?

Thanks! I havent had any issues at all. I had another 97 before this one and had coilover adjustables in the front and cranked them up to at least 3.5" without any problems. I dont know why alot of people talk about cv joint buzz. I have never had any problems with my cv joints. Ive had boots split but thats no biggie

 

[HadjiHunter]

Ok cool. I've had people trying to scare me out of a 3in lift with the whole cv and u joint buzz. I ordered my Toytec run-3dr lift today! Can't wait to get it in! Should I upgrade shocks even though toytec says the lift will work with stock equipment?

 

[toytech76]

its up to you. I still have my stock ones in front. If you have the extra cash I say do it

 

[beallen21]

if you plan on replacing the shocks in the future you may as well do it while you have the thing took apart makes life a little easier

 

[HadjiHunter]

Ya I agree I just didn't want to spend the extra cash. I already blew my wad on the lift and the 285s. I think I'll just put the rear shocks for now. Not to jack my own thread but I was thinking about the bilstien 5125 ext. length shocks. Any other suggestions for good shocks and/or anybody with experience with these?

 

[beallen21]

i just used the Monroe heavy duties from the local parts store and they have treated me great thus far and I'm off the pavement prolly every other weekend, and I forgot that my mileage is really 1.08 what my odometer reads cause of my tires, so I can add like 2 or 3 mpg to my total, that's cool I guess

 

[PhdNPrerunners]

Bumping an old thread cause I don't feel like starting a new one. I am picking up a set of wheels that come with a set of 285 KM2s and I am having a hard time deciding whether or not I should run them. My 4runner has 4.30 gears but it is my daily driver so I know they will hurt the gas mileage. Also at the beginning of August I am moving back to Houston which is 1700 miles so I don't know if I would be better off to just put the new wheels on my 265/70 tires and sell the 285s or just say screw it and run the 285s. What do you guys think?

 

[SCRunner12]

Screw it, keep the 285's. I have 265/75's and will be moving up to 33's as soon as I can. Although you could sell the 285's and buy some 265/75 all terrains.