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Discussion Starter #1 (Edited)
According to the ford web site specification comparison section:

SE hatch
standard: P185/65R15
optional: P195/50R15

SES hatch
standard: P195/50R16

According to this web site tire size calculator
Tire Size Calculator - tire & wheel plus sizing

The optional P195/50R15 tires are 7.32% smaller diameter and will cause the speedometer to read 7.903% too fast. (64.7 mph at 60)

The standard P195/50R16 tires on the SES are 3.23% smaller and will cause the speedometer to read a 3.339% too fast. (62 mph at 60)

Does anyone know if the speedometer is adjusted at the factory in either of these situations? Can it be adjusted by the owner or at the dealer?

The Super Fuel Economy package lists P195/60R15 tires which are only 1.03% smaller so they are probably not a concern.

Thanks
 

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It depends on the vehicle. Some manufacturers will program it into the car's computer. Other times they don't. In some cases, those tire calculators online are just an estimate on the average diameter. Some tire manufacturers can deviate from that due to factors like a higher tread depth (which would make the tires "larger" than what people think).

Most of the time any sort of speedo changes can't readily be done by a simple reprogramming either by a dealer or the owner. In a lot of cases, if the wheels are going to differ by a large margin people start to install aftermarket speedometer/tachometer drivers (like this one from Ford Racing for a Mustang).

I can only assume Ford has adjusted the speedometer to the tire sizes. Only a Ford technician or Engineer could confirm this for us. Usually many people don't worry about tire sizes if they stick with what's offered OEM for their vehicles. It's when people start adding different sized rims and tires (non-OEM) and significantly modifying their cars that it becomes tricky.
 

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I can only assume Ford has adjusted the speedometer to the tire sizes. Only a Ford technician or Engineer could confirm this for us. Usually many people don't worry about tire sizes if they stick with what's offered OEM for their vehicles. It's when people start adding different sized rims and tires (non-OEM) and significantly modifying their cars that it becomes tricky.
Yes, this is standard across the industry....and is very easy due to the full computerization of the speedo and related accessories....

My GUESS is that the Ford Scan Tool will show this change in one of the pages...It would be interesting to know if it can be user customized....after all the dealer will sell the optional larger wheels to customers at retail so I can't believe that they couldn't simply "flash" the new spec into the information module. You'd think for legal reasons they would have to do it.

The nice thing about this is you could possibly use just about any wheel that would fit and still have a accurate speedo.

It would be important to keep the aspect ratio very close to spec though due to the ABS and ECT systems.
 

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According to the ford web site specification comparison section:

SE hatch
standard: P185/65R15
optional: P195/50R15

SES hatch
standard: P195/50R16

Thanks
I'm pretty sure that is a typo on the web site. the optional 15-inch tires are 195/60-15 not 195/50-15 based on the order guide and specification sheet that my dealer showed me.

TIRES AND WHEELS (TYPE, SIZE)
S sedan 15-in steel with 6-spoke cover, P185/65R15 BSW
SE 15-in 8-spoke aluminum alloy, P195/60R15 BSW
SEL sedan 16-in premium painted aluminum alloy, P195/50R16 BSW
SES
hatchback 16-in premium painted aluminum alloy, P195/50R16 BSW
 

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I can only assume Ford has adjusted the speedometer to the tire sizes. Only a Ford technician or Engineer could confirm this for us. Usually many people don't worry about tire sizes if they stick with what's offered OEM for their vehicles. It's when people start adding different sized rims and tires (non-OEM) and significantly modifying their cars that it becomes tricky.
I can't tell you for sure until I get my Fiesta but yes on some Ford,Lincoln and Mercury the Instrument cluster,PCM or ABS module can be programmed for tire size. This is usually on SUV's and trucks though and that is why I have to wait until I get the car in order to say for sure.
 

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I can't tell you for sure until I get my Fiesta but yes on some Ford,Lincoln and Mercury the Instrument cluster,PCM or ABS module can be programmed for tire size. This is usually on SUV's and trucks though and that is why I have to wait until I get the car in order to say for sure.
Thanks.

The way things can be locked down from the manufacturer these days, I know it's all speculation until techs actually get down and dirty into all the computers and tools any good Ford, Lincoln and Mercury technician has access to. ;)
 

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Don't forget 185/60 r15 tires with 15x6" wheels. That is currently what is on my Fiesta.
 

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Don't forget 185/60 r15 tires with 15x6" wheels. That is currently what is on my Fiesta.
Yes, with 15" wheels and without the SFE package, the tire size is 185/60/15. The tires are Kumho Solus KH25. There seemed to be some conflicting information about whether the size would be 185/60/15 or 185/65/15.

With the SFE package, the tire size is supposed to be 195/60/15, with Hankook something or other. This gives a slightly larger diameter (effectively higher gearing) than 185/60/15. It is basically the same diameter as 185/65/15, which does offer lots of tire options for hypermilers (185/65/15 is the OEM size for the 2004-generation Toyota Prius).
 

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I can't tell you for sure until I get my Fiesta but yes on some Ford,Lincoln and Mercury the Instrument cluster,PCM or ABS module can be programmed for tire size. This is usually on SUV's and trucks though and that is why I have to wait until I get the car in order to say for sure.
Mine reads 4mph slow at 60mph. The service manager said that was acceptable. Not to me. Please post if this can be reprogramed.

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Might be

Old VW GTI spec: +/- 5mph +/- 10% of the speed. At 50 this means +/- 10 mph. Could never get them to get it closer.

You might want to compare it to the read out of a GPS.
 

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The Ford web site has the tire sizes all messed up. they are wrong.
Edmunds has them right. 185/60x15 standard. on the SES/SEL 195/50x16.
The SFE package uses the 185/60x15 tire only it is a low rolling resistance tire so I am told.
The Tire Rack also has the sizes correct.
 
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