Question about Wheel Diameter change ?

[Garageguy60]

Good morning everyone. I was wondering if I was to change my original 2004 Ford Ranger wheels which are 16 inch dia. to 15 inch dia. would that change my speedometer reading that much ? I would think bigger is slower and smaller is faster meaning more revolutions ? Reason im wondering is because i really like the aluminum slotted wheels (summit racing) and they dont make them in 16 inch . i remember on one of my Chevelles I used to have I changed wheel diameter and I changed the nylon gear that is on the end of the speedometer cable that screwed into the transmission. Just wondering how much from 16 inch dia. to 15 inch dia would throw me off at the speedometer ? Thanks for any help on this.

 

[Curious Hound]

Only if you don’t have tires on the wheels.

Overall outside diameter of the tire is what affects speedometer reading because that is what touches the road.

 

[Uncle Gump]

Not all 15 inch wheels will fit... depends how they're made. Ford went from an 11 inch rotor to a 12 inch I believe in 2004. 15 inch Alcoa wheels were used from the factory.

There may even be a tech article in the library...

 

[Blmpkn]

Your speedo doesn't read accurately until the truck has 30" tires on it as well, itll read a few mph slow until then.

 

[Garageguy60]

Allright, thanks everyone who replyed on this question so quickly. Appreciated all the info.

 

[19Walt93]

15's will fit over the brakes just fine, I bought one of our last 2011's and it had 15" wheels. My 04 had 16's and looked better but it was too late to order one when I bought the 11.

 

[Roert42]

15's will fit over the brakes just fine, I bought one of our last 2011's and it had 15" wheels. My 04 had 16's and looked better but it was too late to order one when I bought the 11.

Some 15's will fit. There is a notch/ bump on the inside of the wheel to clear the calipers on the factory wheels. there is a thread with pictures on here somewhere.

 

[pjtoledo]

15's will fit over the brakes just fine, I bought one of our last 2011's and it had 15" wheels. My 04 had 16's and looked better but it was too late to order one when I bought the 11.

2wd never went to 12" rotors., on Rangers. they did on Sport tracks.

Ford changed some 15" wheels in the later years to fit over 12" rotors on 4wd. the back half has a different taper to allow more clearance.
I posted pics of this a few years ago, they may have gone away due to photobucket issues.

 

[pjtoledo]

try this thread for the differences
post # 26

OEM Alcoa 15" wheels don't fit | Page 2 | The Ranger Station

 

[Garageguy60]

Thanks again everyone for the info.

 

[sgtsandman]

My 2011 came off the lot with 15" rims. So, 15" rims will fit in theory. The design of the back of the rim makes a difference. As far as tire size, the above comments are correct. 30" reads correctly. The factory 235/75R15 tires my truck came with (29") read 2 mph faster than what the truck is actually traveling. Since the question always seems to come up, 31" tires read about 3 mph slower than the track is actually traveling.

So, short answer, yes. With the right rim. Speedometer reading, it depends on the tire size you get.