Need help selecting another tire size, will going bigger kill my gas m

[buckhousebuck]

Hello everyone.. I have a 2wd 2001 silverado that has the v6 in it and it currently has 235/75/r16 tires on it and they are in need of being replaced. The tires on it, was on the truck when i bought it, and they look really small on it. there is a lot of open space between the tires and the fender walls and i dont like the looks of that. From what I have researched 255/70/16 is the biggest stock tire I can go with..I have also seen that a 265/75/16 will fit also without doing any adjusting. My main question here is....

 

will going from a 235/75 to a 265/75 kill my gas milage ? This truck is all ready kinda hard on gas and seems to be geared low as well.

 

Also can someone explain what is the difference between 265/75 and 265/70 ?

[xXZ-71Xx]

The mileage shouldn't really be too noticeable. What gears do you have in your truck? 265 is the width of the tire, 75 is the height and is measured as a percentage of the width. In other words a 265/75/16 is 265 mm wide and 75% of that width tall or 199 mm tall sidewall if my math is right. A 265/70 is approximately 14 mm or about a half an inch shorter (once again if my math is correct) than a 265/75 and that is the only difference.

[buckhousebuck]

The mileage shouldn't really be too noticeable. What gears do you have in your truck? 265 is the width of the tire, 75 is the height and is measured as a percentage of the width. In other words a 265/75/16 is 265 mm wide and 75% of that width tall or 199 mm tall sidewall if my math is right. A 265/70 is approximately 14 mm or about a half an inch shorter (once again if my math is correct) than a 265/75 and that is the only difference.

Thanks for the reply... As for the gears on the truck i'm not sure.. Will it tell it on the door sticker or under the hood ? If so i can check tomorrow. Do you think the truck would do better with stock like a 255 or would it be about the same with a 265 ? And last do you think the 265 wil fit okay without adjusting anything ? I seen reports it would on most of these trucks but just want to make sure before I have some tires sent to me.

[xXZ-71Xx]

Check your glove box for one of these codes

 

GU4 : AXLE REAR, 3.08 RATIO

GU5 : AXLE REAR, 3.23 RATIO
GU6 : AXLE REAR, 3.42 RATIO
GT4 : AXLE REAR, 3.73 RATIO
GT5 : AXLE REAR, 4.10 RATIO

 

The 255 will get better gas mileage and won't affect your acceleration as much as the 265 because it is 21mm (.82 in) shorter. I can't say if the 265 will even fit or not, On my 4x4's I fit 275/65/18 (Same as 275/75/16) but could not go any bigger without rubbing and I would think the 2x4's sit lower but I'm not sure. If you want to be safe then go with the 255's or go to a tire shop that is willing to test fit a 265 if you promise to buy from them.

 

EDIT - I searched and did come across quite a few people saying that the 265's will fit but I personally can't verify if they will, Are you running stock or aftermarket rims?

[buckhousebuck]

There is a bunch of number sets and in those numbers thre is a GU6 at the end of one of the sets. If i'm reading this sticker right my truck has 3.42 ratio. Is that considered low geared ? I know the truck feels geared low when pulling out. Would there be any benifits to a larger tire like a 255 or a 265 over a 235 ?

[xXZ-71Xx]

There is a bunch of number sets and in those numbers thre is a GU6 at the end of one of the sets. If i'm reading this sticker right my truck has 3.42 ratio. Is that considered low geared ? I know the truck feels geared low when pulling out. Would there be any benifits to a larger tire like a 255 or a 265 over a 235 ?

The benefits of a larger tire are more ground clearance, a bigger contact patch and looks, The disadvantages will be acceleration and gas mileage. Those disadvantages can be fixed with proper gearing though. Maybe someone that knows more about gearing has a better idea but IMO I wouldn't go higher than the 255's with those gears. You might be able to find a whole axle for your truck that has 3.77 gears (probably cost less than a re-gear), I know they are pretty common and would be a direct swap.

[buckhousebuck]

I think i'm going to go with the 255 tires. Not sure what brands yet though. How much taller will the tire be over the 235 ? I was thinking about 1 inch but after researching some more, I don't think that's even close is it ?

[Jsdirt]

Here ya go: http://www.tacomaworld.com/forum/tirecalc.php

 

3.42 gears are towards the fuel economy side of things. 3.08's are super tall & 4.88's are super low given stock tire size. Bigger tires are like lowering the number. Since you have 3.42's, a larger tire would put it closer to a 3.23 - you'll lose off-the-line acceleration, but will have a reduction in engine RPM at any given speed.

[buckhousebuck]

Here ya go: http://www.tacomaworld.com/forum/tirecalc.php

 

3.42 gears are towards the fuel economy side of things. 3.08's are super tall & 4.88's are super low given stock tire size. Bigger tires are like lowering the number. Since you have 3.42's, a larger tire would put it closer to a 3.23 - you'll lose off-the-line acceleration, but will have a reduction in engine RPM at any given speed.

Hey thank you for the reply. Do you think the truck would perform better on a 255/70 or would it do better if i stuck with the smaller 235/75 tire or would it be about the same either way ? I hate to make it get less gas milage because its kinda hard on gas all ready.

 

Looking at the chart below, the diameter inches would be the height wouldnt it ? If i'm correct then there is very little to all most no difference in height correct ?

 

235/75-16 255/70-16

Difference Diameter inches (mm) 29.88 (758.9) 30.06 (763.4) 0.18 (4.5) 0.6%

[Jsdirt]

Yeah, the diameter is the distance around the outside of the tire - in other words, height when looking at it from the side.

 

That info says it's six tenths of a percent larger, which would make a slight difference in acceleration - may or may not be noticable. That's a pretty small change - less than 1%. You probably wouldn't notice the performance deficit at all.

 

A taller tire might add some MPG's at highway speed ... or not, if it's already geared too tall (wind resistance will make that worse).

 

All speculation - what happens to one truck might not happen to another identical model. So many factors play into MPG - fuel quality is a big one. Up here in MA we typically have more than the advertised 10% ethanol in our fuel (up to and over 20% sometimes!), which kills your mileage and performance. For example, I filled up on a road trip 2 weeks ago in NY with ethanol free gas. I gained 1.5 MPG towing a 2k lb. trailer! Was close to a 3 mpg gain unloaded.

 

Air pressure will affect it dramatically if underinflated. Engine tune is another big one - engine wear, ignition condition, air filter - they all play into it as well.

[buckhousebuck]

Thank you everyone for the replys.

 

i now see the 255 is about 3/16s taller then the 235 which isn't very much.

I since got to thinking about a 245/75 which is about a half inch taller then 235. How do you guys think the 245/75 will perform fuel wise ? It's not as wide as what a 255 would be but is a little taller. Do you guys think I would see a noticeable difference in performance ?

[buckhousebuck]

Thank you everyone for the replys.

 

i now see the 255 is about 3/16s taller then the 235 which isn't very much.

 

I since got to thinking about a 245/75 which is about a half inch taller then 235. How do you guys think the 245/75 will perform fuel wise ? It's not as wide as what a 255 would be but is a little taller. Do you guys think I would see a noticeable difference in performance ?

Want to give this a bump and see if anyone else will drop in for I decide on a set.. How do you guys think the 245/75 will perform fuel wise ? It's not as wide as what a 255 would be but is a little taller. Do you guys think I would see a noticeable difference in performance ?

[kstruckcountry]

I would just go to a 265... I went from a 255 to 13 pound heavier 265 and mileage stayed the same.

[buckhousebuck]

I would just go to a 265... I went from a 255 to 13 pound heavier 265 and mileage stayed the same.

what size engine was you running ? You think a V6 can handle a 265 without pulling it down to much ? I do about 50/50 highway and city mix driving.

[DwayneJ]

If worried about mileage and don't have a lot of snow or ice to deal with buy a LRR Low Rolling Resistance tire when going to the larger size. Tread compound and design can have a 10% impact on even car fuel economy where they don't get as extreme in variation with the tread as trucks.

 

Taller tire will hurt gearing and the only slight chance it might have of improving mileage from that perspective would be dead leave dead even speed, and modest speed conditions.

Most people assume lugging an engine is good for mileage, it isn't.