tire size

Charlie60 · 04-13-2008, 10:12 AM

I have a 1999 ranger and I want to change the tire size to 15 inch. My question is will the increase in size have any effect on my transmsmission shift point? Thanks for your help

Charlie · 04-13-2008, 11:19 AM

Are you looking to put on taller tires? What size are you looking to put on? 15" would be your wheel size.

Charlie60 · 04-13-2008, 12:39 PM

I would be giong from a 14 Inch tire to a 225-70-15

Charlie · 04-13-2008, 12:42 PM

Assuming that the overall height of the wheel/tire doesn't change, it won't change anything. What is the size of the 14 inch wheel's tire?

Charlie60 · 04-13-2008, 01:02 PM

The 14's are P205-70-14

Charlie · 04-13-2008, 01:12 PM

Tire size calculator

That shows that the new tires are taller. This shouldn't have any effects on the shift points, just know that your speedometer will be a little off.

Charlie60 · 04-13-2008, 01:18 PM

Thanks for the info.

Charlie · 04-13-2008, 01:25 PM

Just out of curiosity, why are you looking to change up the tire size?

Charlie60 · 04-13-2008, 01:50 PM

I am just trying to get a little more ground clearance. We have newer Rangers at work and I like the ride hieght.

Mike J. · 04-13-2008, 11:20 PM

Charlie60,

The larger tires will only give you 1" more of ride height. Your speedometer will be off by 5 mph at 60 mph. Speedo will read 60 mph, actual speed will be 65 mph. Your odometer will also be incorrect by the same, so if you track your mpg, it will look like it's dropped.

If you just want more height, then a lift kit may be the way to go. Here's one site I found while typing this and the kit is only $215:

Ford Ranger & Explorer 3" Complete Lift Kit 1998-2008

What does your door sticker say your tire size should be? The 205/70R14 isn't a stock tire for the 1999 Ranger. From what I've found the following are possible tire sizes:

205/75R14 (2WD - Most likely your stock tire, which will give .4" more height)
225/70R14 (2WD - Will give .55" more height)
215/75R15 (4WD - Can be used on 2WD and is most likely an option in the ECM)
235/75R15 (4WD - Can be used on 2WD and is most likely an option in the ECM)

My 2001 came with oversized tires (235/75R15 instead of the stock 225/70R15.) The speedometer and odometer were incorrect as well. I like the tires because they fill the wheel well better. But the incorrect speedometer was a ticket waiting to happen. The incorrect odometer was eating up my extended warranty.

I took my Ranger to Ford and had them adjust the tire size in the ECM ($80). Fortunately, the larger tires were an option in the ECM. My speedometer and odometer are now correct. Here's what I've noticed about the larger tires.

1) The truck is sluggish off the line and when climbing hills. This is due to the larger tires requiring more torq to make them turn. The only way to improve this is to change the differential ratio as well.

2) It gets worse city mpg, but better highway mpg than it's rated. Remember #1. More torq to get them moving means more fuel is needed. But, once cruising on the highway, it runs at a lower RPM than before. Lower RPM means less fuel consumed.

3) Be carefull when hauling a load or towing. Remember #1. Less torq means less towing capacity because of the torq needed to get things moving. This is more a transmission issue than anything else. The heavy load can cause the tranny to overheat. That's bad juju, if you know what I mean.