Weight vs MPG

[Atrus]

Ok, so I know there's about 60,000 other variables (width, tread, diameter, etc) than this, but...

What would a change in tire weight translate to in MPG? Say, 5lb?

See, stock 225's are 27lbs. My OEM 235's are 32 lbs.

I want TKO's or AT2's....for the AT2's:

245-70 - 40.7 lbs
245-75 - 48.5 lbs
255-70 - 35.1 lbs
235-85 - 51.0 lbs

 

[Marlon_JB2]

Well you also have to think about rolling resistance.

With that said:

I did not notice any MPG drop when I put 245/70 A/Ts on my (red) 2004 KJ.

 

[Atrus]

What kind of A/T's were you running?

 

[Marlon_JB2]

Toyo Open Country A/T

Here's the original pics I posted back in 2005.

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[J-Thompson]

weight being the only factor we are talking about
then the loss in mpg will be very very little
so little that you will not notice ,from weight alone
same OD as the OE tire but just 10# more and it will still make almost no
noticeable diff.
now when you factor in a jump in OD then you see some loss in MPG but still
not much because people forget that while the loose MPG with bigger tires
the also cover more ground with the same number of tire RPM
I know that our KJ is 6-10% off ,it seems to vary
best case it is 10% off so when I look at the little computer thingy and it
shows 21.2 MPG @65 mph I can add 10% to both
I am really going 65 + 6.5 (10%) = 71.5 MPH
and getting 21.2 + 2.12 (10%) = 23.3 MPG
these are not real numbers but my best case
I have also gotten numbers in the 5% range but still not to bad
almost stock

 

[Atrus]

Hmmmm, thanks. so, I think I am worrying about something (weight) that I really shouldn't.

I do 50% highway, 50% surface roads. This morning the EVIC with the stock 235's showed 17mpg...not too bad when you consider it's 27*F here right now, so it's using more gas than warmer temps.

 

[JeepJeepster]

You will notice a drop in mpg with weight.

Something called "moment of inertia" will tell you this. Physics is mean sometimes.

 

[Atrus]

That's what I am thinking. I know there will be some effect (for every action...), I am just wondering if it's negligible or not. i.e., .5mpg drop or less, or would we be talking 2-3?

I'd assume as I do 50% highway (with little traffic, usually just cruising), it may be a little less for me than for some. I'd tend to think the real drain is the acceleration and increased inertia there. Once moving, I'd tend to think the extra weight would be offset completely or mostly by the increased diameter.

 

[JeepJeepster]

With more mass is takes more force to make it move but it also takes more force to keep it moving.

I noticed at least a 1-2 mpg loss when I had the 255/70/16 Grabbers. They had a higher amount of rolling resistance so its hard to tell what was doing what.

You would notice a major decrease in performance with a 51lb tire.

 

[Atrus]

From what I have in my little excel spreadsheet that I made up, 255/70/16 Grabbers should be 35 lbs. That seems kind of light. My stockers are 32 (235/70). I'll re-check that, maybe I recorded it wrong. 245/70 grabbers seem to be 40.7 and 245/75 are 48.5

Agreed on the extra force to keep it moving - the question in my mind was/is how material is it (.5mpg, 2mpg)? Thanks for the MPG figures, that helps. Gives me something to think about. I am kind of debating going to a more "street" A/T as 99% of my driving is on the pavement.

As you said, rolling resistance changes as well, that's what I meant in my first post re: the 60k variables. These decisions are always so hard for me, I research too much sometimes!

 

[Dave]

If you went from a street tire to an A/T in the same size I would think that the weight of the tire would be a little more due to it being a heavier lug and perhaps sidewall but the tread of the A/T would give a little more rolling resistance so it would be hard to tell if weight alone made much difference. Too many factors at play as you said.

Just put on whatever tire you like. The difference would be neglegable, unless you went to a bigger size yet and even more aggressive tread like an mtr or mt or such.

An A/T is a compromise. It's not a street only tire nor is it an off road only tire. When I switched from my pos goodyear hp's to the terra trac a/t's I did not notice a real measurable difference and I'm sure they weigh more in addition to having a more aggressive tread. They are sure better in the snow and off road. Most of my driving is on pavement though (as you said yours was) and they are fine.

Just get any A/T you like and don't worry about it.

Just my opinion.

Dave

 

[JeepJeepster]

These decisions are always so hard for me, I research too much sometimes!

No you dont. The problem is 99% of todays population does not research enough before buying things.

Just think of all the GM vehicles you see on the road. None of those people did research before buying.

 

[Marlon_JB2]

Just think of all the GM vehicles you see on the road. None of those people did research before buying.

x2 (Except Saab... those are fun.)

 

[J-Thompson]

Man you guys think about this stuff way to hard
I know that we lost only 2-3 highway MPG
going from BONE STOCK to lifted and 245/75 MTR's
now if you add up all the factors we changed besides the weight of the tires
then you can see why we lost MPG
Lift changes wind resistance
taller tires change effective gearing
more aggressive tires change rolling resistance
add all that up and we lost only 2-3 MPG
the biggest factor was changing the effective gearing
yes the weight will change it but if you compare the exact same size tire
1 being a C load range and the other being an E load range then the E will
be heavier by say 10# the MPG loss will be so small that it would be
>1 mpg and not enough to care

 

[Atrus]

No you dont. The problem is 99% of todays population does not research enough before buying things.

Just think of all the GM vehicles you see on the road. None of those people did research before buying.

Say all you want about GM, but this was a fun and great car. I understand everyone jokes about the "other" manufacturer, but 130k HARD miles on it, and it was still running like a ***** ape. I miss it:

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[Marlon_JB2]

Say all you want about GM, but this was a fun and great car. I understand everyone jokes about the "other" manufacturer, but 130k HARD miles on it, and it was still running like a ***** ape. I miss it:

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lol3.gif lol3.gif lol3.gif

ANYWAY, I think J-Thompson is right... too much thinking going on here.

Again, A/Ts don't really kill MPG as much as you'd think. Now M/Ts on the other hand.... that requires a thread, lol.

 

[Atrus]

Good deal. I am thinking General Grabber AT's are in my future.

Now, 245/70 or 245/75....hmmmm.... ;-) (Yes, I know 75 will require "adjustments")

 

[Dave]

Just think of all the GM vehicles you see on the road. None of those people did research before buying.

Blake, I have had several GM vehicles that went over 200,000 miles without problems. I have a v6 a/t Cutlass now with 145,000 on it and it runs fine and gets 28-30 mpg. I do all the basic maintenance myself and it's fine. It's all in how you take care of them.

Dave

 

[immadmacs]

OK, so the tire I'm looking at (Nokian Vatiiva) doesn't have an LT tire in the larger tires, the stock size is E rated and heavier than the other sizes I'm considering. I'm leaning toward the 235/75/16 for the extra clearance and a width compromise. Most of my driving is my 80 miles of commuting, but I will be using the Jeep to fish (mostly beach) and hunt. Is the P rated tire going to hold up to weekend off-roading. Will the E rated tire ride rough on the road? Which will affect mpg more, a heavier/narrow tire, or a taller/wider tire? What if I want a 1-1/2" CRD lift later (Daystar KJ09123BK), tread depth, speed rating, what about rubbing....... Over thinking this, not me!


Size Load Weight Diameter Width Tread depth Speed rating
LT225/75/R16 E rated 40.6 lb. 29.5" 8.8" 17/32" Q
235/75/R16 P rated 33.0 lb. 29.8" 9.3" 14/32" S
245/70/R16 P rated 35.0 lb. 29.5" 9.8" 14/32" S