17" Wheels and speedometer issues

[Val Naso]

I am putting 17" wheels on my '05 ST. How off is my speedometer going to be and is there a quick fix to this problem? Any help would be greatly appreciated.

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The vehicle has 235/70/16's now.



I am putting 245/65/17's on it.

 

[TrainTrac]

What size are the OEM wheels/tires, and what size are the new 17's? If you're doing just the right combination of wheel/tire size, then there could be little, if any difference in the speedo. Use the tire size calculator linked below to check it out.



An XCal 3 with custom tunes can correct for the new tires so your speedo is accurate.

 

[Val Naso]

Excellent website, just did the calculations and there is 1.2 MPH difference. Not a big deal at all, thanks for the help.

 

[Brandon Poorman]

I'm running a 245/65/17 on my st with explorer wheels. I have never had any problems whatsoever. The speedometer on mine is about 2-3mph off my gps but not a big deal. My spedo reads faster than what i'm going

 

[Val Naso]

Wheels are on and they look great.

Minor rub on the front wheel when making a tight turn.

Minor rub on rear wheelhouse liner when I have people in the truck.

A little trimming will resolve this problem.

 

[Dan Long]

Val, it sounds like you put a set of 17" Explorer or Gen 2 ST wheels on your Gen 1. If so, the high offset of the wheels is what's causing the rubbing, not really the tire size. You've basically moved the wheels in towards the center of the truck more, which really isn't a good thing for handling and stability either. If anything, you want the wheels to be moved out a bit, this gives a wider "footprint" and makes it harder for the vehicle to roll.

 

[Brandon Poorman]

Did you put on wheel spacers?

 

[Val Naso]

I did not put spacers. They are wheels 17" from an Explorer.

 

[Brandon Poorman]

I have zero rubbing with my 17" explorer wheels. I'm also running spacers and a 245/65/17 soon to be 265/70/17 or a 31X10.50 with a little twist and turn here and there.