Changing tire size using FORScan

[Benvolio]

Is it possible the factory TPS syncs with the cars computer and adjust the speedo accordingly? I'm still trying to figure how and why my Speedo and GPS speed never changed when I swapped out my premium wheels and tires (255/40-19) with a set of take off PP wheels and tires (275/40-19 rear).

I gotta say, you and I end up on a lot of the same threads lol. I just swapped my stock 255s with a set of 275/255 performance package takeoffs from Shelby American. My Speedo has been within 1 mph of my Uniden R7’s GPS speed, just like the 255s were. I don’t think the TPMS sensors are coded with wheel data though, so I’m unsure how this is possible.

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[goodlettjr]

@AZ_Ryan the TPMS sensors don't sync with anything other than the pressure. With that being said, I went from the stock GT PP tires on the back; Pirelli P Zero 275/40/19 to a Michelin Pilot Sport A/S 4 315/35/ZR20. Every GPS type device (draggy, phone, etc..) I have measure it right at the same speed ~1 mph like yours. It just might be it isn't that much of a difference. I expected it to be though, but I haven't bothered to change it in FORScan.

 

[AZ_Ryan]

@AZ_Ryan the TPMS sensors don't sync with anything other than the pressure. With that being said, I went from the stock GT PP tires on the back; Pirelli P Zero 275/40/19 to a Michelin Pilot Sport A/S 4 315/35/ZR20. Every GPS type device (draggy, phone, etc..) I have measure it right at the same speed ~1 mph like yours. It just might be it isn't that much of a difference. I expected it to be though, but I haven't bothered to change it in FORScan.

According to the math, we should be goimg faster than what the speedo says.

 

[goodlettjr]

According to the math, we should be goimg faster than what the speedo says.

Agree. Maybe I’ll break out my draggy. It is the most accurate speed detector I have.

 

[Aggie1999]

When I went from the stock 255/40R19s to my now 305/35R20s on the rear @ 35mph on my dash a cop friend if mine checked me at doing 37.5.

30 minutes of learning how and then 1 minute of making a change in Forscan and I'm now showing slightly faster than my actual speed. Which is fine by me when avoiding tickets.

 

[Fruitstang]

When I went from the stock 255/40R19s to my now 305/35R20s on the rear @ 35mph on my dash a cop friend if mine checked me at doing 37.5.

30 minutes of learning how and then 1 minute of making a change in Forscan and I'm now showing slightly faster than my actual speed. Which is fine by me when avoiding tickets.

So, and which parameters did you change with Forscan?

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