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Don Ridley

Tire size settings in Forscan

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Forscan has several options for tire size and circumference. I did not change any settings to see if they worked. I have 215/50R-17 this and the 16 inch wheel settings should work.

Changing the setting should affect the speedometer, transmission and maybe other systems.

 

Here are the settings:

 

tire options.JPG

tire options2.JPG

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Very good information Thanks.

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There are 4 choices there in both menus, but none of them are very far from the stock  sizes.  Some models came from the factory with either 16 or 17 inch wheels, so it stands to reason there would be an adjustment there to make things 'right' for either size.  It looks like if you wanted to go very far from a stock size you're still out of luck though

 

Don

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I had looked at that awhile back to adjust for my 215/65R16's, but when I saw the available choices, I decided to just leave it as-is so I wouldn't have to recalculate the speedometer error between the options there and my actual tires. I know for a fact that my current setup is 5.9% higher, so 70MPH on the gauge is 74-75MPH on the road and 100 miles odometer is actually 105.9 miles traveled (for rare times when I check my MPG). 

 

I was really hoping for better/more choices, but I understand that Forscan is only interpreting what's in the factory computer and it's not as powerful as an aftermarket programmer - AFAIK, none exist for TC's. Which leaves me to wonder if anyone has tried a Focus programmer on a TC, since they're mostly the same under the skin, haha.

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Thanks for posting the answer to a question I've been wondering about!  And I agree with JRM, it's too bad there's not a "custom size" option amongst the canned choices offered.

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The factory setting are limited because too large a change will mess with the emission calculations. Ford Motor does not want to get into that.

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The F150s and US cars have different programming than the Euro models. The BCM in the TC doesn't have a lot of data that can be edited like a F150. We are stuck with the tire size options in the Forscan menu.

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5 minutes ago, Don Ridley said:

The F150s and US cars have different programming than the Euro models. The BCM in the TC doesn't have a lot of data that can be edited like a F150. We are stuck with the tire size options in the Forscan menu.

Bummer, but I’m glad to know. Thanks for the quick reply. The thing that bugs me the most is the odometer inaccuracy. 

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On 5/24/2019 at 11:00 AM, Harvey said:

Bummer, but I’m glad to know. Thanks for the quick reply. The thing that bugs me the most is the odometer inaccuracy. 

 

I just took mental note of the main speed differences, lol. Like 66 MPH on the dash is actually 70 MPH road speed (posted speed limit between my house & work is 70MPH). Since it's a percent change, you can't really say "Oh, it's off by 4 MPH" - at 66/70, yes. But at 40 MPH indicated, I'm doing like 42-43 MPH road speed. One thing I did early on was drive a designated route where my GPS said how long the trip was and then I compared that to the trip odometer to figure out the difference in ratio. Online calculators show something close to 7% difference in tire size, but my actual test trip showed my speedometer to be off by 5.9%, so 100 miles on the trip odometer is really 105.9 miles. 

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I run three different size setups on the front (rear doesn't count), none of them stock. 245/50/16, 225/55/16 & 225/60/16 for 1.2%, 1.6% & 5.1% respectively. The only one that concerns me much is 5.1% cause if I push the envelope too far I'm in "ticket range". The error gets progressively less as speed reduces so mostly its only at highway speeds that it matters much.

That said, since retiring recently I find that there is never a need to get in any hurry to get anywhere. 

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OLDSCHOOLFOOL, congrats on retirement.  Now welcome to the busy life!  I have a GPS app on my phone that is a speedometer.  I use it to check the accuracy of speedometers on all my vehicles when I get them.  Volt, TC and Honda CBR600RR were almost perfect  Kawasaki ZX6R 636 was very optimistic.  90 indicated was about 81 real, all the folks bragging about doing 140 weren't going that fast :-) My BMW motorcycle is 4 or 5 off at an indicated 80.  Stock TC is nice as I don't have to continually do a calculation in my head to figure out how fast Im really going.  

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