Explorer: Replace with smaller tires

[venky]

I have a 1998 Explorer sport that came with 255/70/R16 109S tires. Its time to replace and I would like to get the standard 225/70/R15 since they are a lot cheaper.
My question is can the tires be replaced by smaller ones and will it affect the ride. Also will I get a better gas mileage.

Thanks

 

[Turdle]

You do know a 15 inch tire won't fit on a 16 inch rim.

I assume you have a correct set of 15" wheels to use? If not-buying new wheels will be a cost factor-

 

[venky]

You do know a 15 inch tire won't fit on a 16 inch rim.
I assume you have a correct set of 15" wheels to use? If not-buying new wheels will be a cost factor-

I don't have the 15" rims. So that will not be cost effective.

Can i get cheaper ones but with the same radius (16 inches). something like 225/70/16.

Thanks

 

[Turdle]

What you are asking, I assume, is if the smaller tire will actually save $$$

In my opinion no-here's why

the first set of numbers are the section width-measured right above the tread area-it is the tire width for lack of better terms-
the second number is the height of rubber between the wheel and road-proportional to the tire width--the 70 means the height is 70 percent of the width
so-if you decrease the width-and keep the proportion the same-you decrease the diameter-
this will INCREASE engine RPM's at highway speed, causing a decrease in economy.

doing quick math--

255mm = 10" (approx) width 255/25.4=10.03
70% would be 7" between wheel and road. When figuring tire diameter, this doubled-

so-add 16 (wheel diameter) + 14 (7"x2) and you have a 30" tire (approximate)
the 225-70-16 is a 28.4" tire---which is a 5% smaller tire. your speedo will be 5% high, and economy will drop 5% (roughly)


what if you went to a 235 -"75" -16?
235/25.4=9.25"

width 9.25" x.75=6.9" Proportional height.
16+13.8

this will give you a 29.8" tire-which in all actuality should not throw your speedo off much, and give better economy due to the thinner wind barrier of the tread--

JMHO

 

[hunterdan]

Depending on your gear ratio, your fuel mileage may actually decrease, especially if you have the 4.10s, but even with the 3.73's your mileage may decrease. Reason being, the engine has to spin faster to cover the same ground because of the reduced circumference of the tires. With my OHV Sport and 3.73's and 31" tires, I was getting about 25 mpg on the highway. Now I haven't seen those numbers in quite a while, but I was getting them. Now if your gear ratio is 3.55:1, then I would say go for it. But if your Explorer came with the 255/70/16s, then I would say you either have the 3.73s or even the 4.10's.

Dan

 

[Donner]

Sorry, I just need to ask a quick question of you jtsmith... I'm getting ready to run to the tire shop next door to have the lugs check/tightened... I would like to ask if the gear ratios are correct because I have a larger tire and I keep hearing ratios and tire size mentioned... what should the correct ratios be? I have 265/70/r17... I don't know what the current ratio is, but I just want to know if it does matter (p.s.: I don't know what their response will be, and I don't want to just agree with what they say) Thanks!

 

[Turdle]

Sorry, I just need to ask a quick question of you jtsmith... I'm getting ready to run to the tire shop next door to have the lugs check/tightened... I would like to ask if the gear ratios are correct because I have a larger tire and I keep hearing ratios and tire size mentioned... what should the correct ratios be? I have 265/70/r17... I don't know what the current ratio is, but I just want to know if it does matter (p.s.: I don't know what their response will be, and I don't want to just agree with what they say) Thanks!

That is a 31.6" tire-I would think a 3.73 ratio should be fine, although you are on the borderline for a gear change to 4.10.

Others are better to answer though. I'm not really experienced with larger diameter tires--

 

[sjr033]

The best way to tell what gear ratio you have is look at the door tag. It is in the drivers side door jam. It will have an axle code like d4

 

[Donner]

Got it! Thanks all.. but it sounds like it should be a 4.10 if it currently isn't? If I tell them that, and they say no problem, what does it entail? Costs, parts? or is it a computerized adjustment?

 

[techieman33]

Gears are a pretty big investment, you could easily be looking at hundreds of dollars to change gear ratio's. And if your 4wd double it. Unless your going with a much larger/smaller tire you would probably be better off just leaving them alone.

 

[Donner]

Sounds good to me...

Gears are a pretty big investment, you could easily be looking at hundreds of dollars to change gear ratio's. And if your 4wd double it. Unless your going with a much larger/smaller tire you would probably be better off just leaving them alone.

Okay, thank you... I guess it should be, if they recommend changing gears, I should say we're within range, so it's not necessary. Wow, I thought it was along the lines of balancing or rotating tires. Alright then, I'll stick with the current ratio. Thank you all very much

 

[ThePhoenix]

how come my stock 01 explorer sport tires are 235/75/15? smaller than previous years?

 

[Turdle]

how come my stock 01 explorer sport tires are 235/75/15? smaller than previous years?

that is a 29" tire-