I plan to upgrade from the stock 205/75/15 tires to 235/70/15. I have been getting ~25 mpg with the 205's. Would my gas mileage suffer after the change of tires? If so, how much? I tried a search to answer the question, but couldn't find another thread about it, so if anyone remembers where there is another thread that answers my question, point me in the right direction. thanks

 

It will suffer. The 235 are wider so ther is more ground contact. More resistance. Plus the speedo and OD wil be off. A dealership can rescan the PCM to correct the speedo and OD to your tire size.

I think the ride will be better than the pizza cutters you have on there now. I would get 235/75/15 installed. Then the recalibration done.


Do you hand calculate your gas mileage BTW?

 

yea. I would fill it up and reset the odometer. when I went to the station this morning to get gas I filled it up with a little more than 14 gallons and went 346.2 miles. So I rounded up to ~25. This is all highway, no stop lights or stop signs, going 60-70 the 120-something mile roundtrip. I can't decide whether to get 235/70's or 235/75's. How much would the speedometer be off comparing the two?

 

go to www.1010tires.com it has a tire size calculator thier

 

well that calculator says that if I upgrade to 235/70 then i am at risk of brake failure. it says anything over 3% is and 235/70 is 3.05% but i don't think .05% will matter.

 

man your doing the same calculations im trying to do....my 17 inch rims dont have enough tire right now and i want a big beefy set of like bf goodrich or something but i dont know what size would a) fit and b) my truck would be able to handle...braking etc.

 

i went from a 205 to a 235 and i havent had brake failure yet

 

I think I'm just going to go with 235, but I don't know whether or not 75 or 70. I guess I'll just get whatever size they have in stock of the style tire I want. I have friends that have put 20's and 22's on their vehicles with no braking problems, so I don't think I'll have a problem. I hate doing math before school starts[:@]

 

I just checked out that tire size calculator too. It's a good tool. Just over 3% should be fine on a truck. I think the calculator just gives that big warning for liability reasons. If you're worried, just beef up the suspension and brakes while you're at it.

 

I went from 235/75R15 to 30x9.5" tires and just replaced the original rear disc brakes. I have 132,000 miles on the rear brakes, 100,000 of that on the 30" tires. The dealer replaced the front brakes when the truck had 27,000 miles, it now has 132,000 miles and I still have plenty of pad left. I drive 70%highwy 30% around town.
Its all in how you drive.

Your fuel mileage isnt changing that much, its the numbers you use to calculate it that are changing. Tire size, odometer readings. Tehy will not be correct unless you get them adjusted for the larger tires.