Speedometer Accuracy?

[tjm73]

I just picked up a used 2022 Big Bend with about 33K miles on it. Been great so far. Actually really happy with it. I am amazed by the 1.5L I3 engine. I didn't have much of an expectation, but it has impressed me a lot. It feels much bigger than a 1.5L probably should.

Anyway, the truck came with Landspider Wildtrax A/T tires on the OEM 17" wheels. They are up sized to 245/65R17 from the OE 225/65R17. Driving home today I started wondering about the accuracy of the speedometer with the bigger tire. So I opened this GPS speedometer app I keep on my phone.

I had my cruise set at 72 mph. I was on flat level ground. The GPS speedometer read 72 mph. Later in the evening I was driving and checked it again. This time I put the cruise on at 50 mph. Turn the GPS app on. Wait for it to acquire a signal and BAM...50 mph. So I'm like....how?!

For this bigger tire to be correct (exactly correct no less), the smaller factory tire would have read fast right off the showroom floor. I'm looking to upgrade my tires to something more road friendly. This is my daily driver commuter vehicle. Smooth and quiet is my jam.

I'm looking to get setup with a 3 season setup and a winter setup. I'll run the Landspider A/T's for the winter. They look like they might be decent in the snow. But I'm confused about the current tire size versus the replacement.

If I spec them out to be as close as possible to the OE tire diameter and revs/mile, I think the speedometer will be off a lot. I'm perplexed. I think I may need to jack this thing up and run a tape measure around the tire and then drop it and measure the installed tire height and select my tire accordingly.

This speedometer thing and the way the engine runs has lead me to wonder if this truck has been tuned. It's much more responsive and powerful feeling than the other three new 1.5L's I had driven recently before. And not by a just a bit. Are tuners able to compensate for tire diameter changes? A tune would explain the speedometer accuracy with taller tires and also how powerful it seems.

Is there a way to tell if one of these has been tuned?

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[BLUEOVALRACER]

It could also have an aftermarket Throttle Controller on it like a JMS Pedal Max or Banks Pedal Monster or a Pedal Commander. I have the JMS Pedal Max on my BB BS with the 1.5 Eco Boost and it made a huge improvement in Throttle Response compared to how it was stock. It made it much more enjoyable to drive.

 

[Glamdring70]

225 and 245 are the width profile of the tire. They're effectively the same diameter at 65R17.

 

[Dude]

Perhaps the prior owner used FORScan to set the tire diameter

https://www.broncosportforum.com/forum/threads/bronco-forscan-thread.844/post-171691

Example ECU settings for:
22565R17: 2202
24565R17: 2232
Bandlands, Falken Wildtrak AT3W (245/65/17) tire circumference: 2354mm (original value 2202)

 

[tjm73]

225 and 245 are the width profile of the tire. They're effectively the same diameter at 65R17.

The difference between 225/65 and 245/65 tires is a full inch. That is pretty significant.

 

[tjm73]

It could also have an aftermarket Throttle Controller on it like a JMS Pedal Max or Banks Pedal Monster or a Pedal Commander. I have the JMS Pedal Max on my BB BS with the 1.5 Eco Boost and it made a huge improvement in Throttle Response compared to how it was stock. It made it much more enjoyable to drive.

I'll get down there and check it out. Should be easy to see if anything is plugged in.

 

[B-Dog15]

As mentioned above there is about an inch difference in tire size which may not significantly throw off the speedo but my concern was the long term difference it would cause the odometer.
When I added BFG KO2’s in 245/65/17 I had my speedo recalibrated to make sure it was reading properly to avoid losing track of the actual mileage of the car.

 

[TNFurb]

Are the wheels the OEM wheels or are they custom? Could the prior owner have gone with a smaller wheel to accommodate a higher sidewall thereby making total diameter roughly the same as the OEM tires?

 

[tjm73]

Are the wheels the OEM wheels or are they custom? Could the prior owner have gone with a smaller wheel to accommodate a higher sidewall thereby making total diameter roughly the same as the OEM tires?

Factory wheels

 

[kshaw]

You can adjust for tire size in ForScan and this should correct any errors in MPH.

 

[tjm73]

Looks OEM to me.

 

[Mark S.]

The difference between 225/65 and 245/65 tires is a full inch. That is pretty significant.

It's 3.5%.

 

[RSH]

The difference in tire diameter from 225 65R 17 to 245 65R 17 tires in speed works out to 1 mph at 25 mph and 3 mph at 90 mph. I've had 245 65R 17"s for over 30k miles, for me, its not a problem to be concerned about.

 

[BLUEOVALRACER]

Looks OEM to me.

Maybe it's tuned but not sure how you could find out.

 

[ScareCrow]

Maybe it's tuned but not sure how you could find out.

Looks like this........

https://thebronconation.com/general-bronco-sport-discussion-n.140/sprint-booster-security-and-performance-is-now-available-for-ford-bronco-sport-owners-wont-void-warranty-t.9397/

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