BRZ - what does it use to determine vehicle speed? - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

Joesurf79 · 04-03-2017, 05:02 PM

Searched some but didn't find the answer. Does the BRZ use wheel speed to determine vehicle speed? I have a different final drive ratio now, and the speedo seems off compared to GPS displayed speed. But I can't reconcile why the final drive ratio would have affected it? Thanks for any info you might have - Joe V

Kodename47 · 04-03-2017, 05:23 PM

Rear wheel speeds. There is always a difference between GPS and displayed speed.

churchx · 04-03-2017, 06:20 PM

Speedo is off in all new cars even stock. By 4-10%. IIRC was ~8% slower in my gt86.

mav1178 · 04-03-2017, 06:40 PM

Perhaps you should also disclose what else is different on your car, aside from your final drive.

Turdinator · 04-03-2017, 11:49 PM

I believe the speed is determined by the ABS sensors so changing a final drive should have no effect on detected speed. Wheel, tyre size and even tyre wear will effect the detected speed however.

CSG Mike · 04-04-2017, 03:58 AM

Wheel speeds (specifically rear). FD doesn't affect speedo.

JoeC · 04-04-2017, 10:23 AM

Quote:

Originally Posted by CSG Mike

Wheel speeds (specifically rear). FD doesn't affect speedo.

so then is the speedometer not affected by changes to the rear end?

PandaSPUR · 04-04-2017, 10:27 AM

Quote:

Originally Posted by JoeC

so then is the speedometer not affected by changes to the rear end?

Speedo is affected if you change tire/wheel diameter.

Tcoat · 04-04-2017, 10:56 AM

Quote:

Originally Posted by CSG Mike

Wheel speeds (specifically rear). FD doesn't affect speedo.

Quote:

Originally Posted by JoeC

so then is the speedometer not affected by changes to the rear end?

How is that not a clear statement?

JoeC · 04-04-2017, 11:32 AM

Quote:

Originally Posted by Tcoat

How is that not a clear statement?

hahhah. it was totally clear. I guess I just hadn't had enough coffee yet because apparently I didn't even read the entire sentence. may bad

Tcoat · 04-04-2017, 11:33 AM

Quote:

Originally Posted by JoeC

hahhah. it was totally clear. I guess I just hadn't had enough coffee yet because apparently I didn't even read the entire sentence. may bad

LOL I thought I was missing something somehow!

04-03-2017, 05:02 PM	#1
Joesurf79 Senior Member Join Date: Mar 2016 Drives: 2016 White Pearl BRZ Premium Location: Houston, Texas Posts: 548 Thanks: 204 Thanked 252 Times in 147 Posts Mentioned: 6 Post(s) Tagged: 0 Thread(s)	BRZ - what does it use to determine vehicle speed? Searched some but didn't find the answer. Does the BRZ use wheel speed to determine vehicle speed? I have a different final drive ratio now, and the speedo seems off compared to GPS displayed speed. But I can't reconcile why the final drive ratio would have affected it? Thanks for any info you might have - Joe V

04-03-2017, 05:23 PM	#2
Kodename47 Senior Member Join Date: Oct 2012 Drives: UK GT86 Location: UK Posts: 3,040 Thanks: 185 Thanked 1,633 Times in 1,113 Posts Mentioned: 156 Post(s) Tagged: 1 Thread(s)	Rear wheel speeds. There is always a difference between GPS and displayed speed. __________________ .: Stealth 86 :. Abbey Motorsport/K47 Tuned Sprintex 210 Supercharger Kodename 47 DJ: Soundcloud / Instagram / Facebook

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04-03-2017, 06:20 PM	#3
churchx Senior Member Join Date: Mar 2015 Drives: 2014 GT86 Location: Latvia, Riga Posts: 4,334 Thanks: 698 Thanked 2,086 Times in 1,436 Posts Mentioned: 53 Post(s) Tagged: 1 Thread(s)	Speedo is off in all new cars even stock. By 4-10%. IIRC was ~8% slower in my gt86.

04-03-2017, 06:40 PM	#4
mav1178 Senior Member Join Date: Apr 2013 Drives: 2005 Toyota Camry Location: 91745 Posts: 6,562 Thanks: 493 Thanked 6,099 Times in 3,030 Posts Mentioned: 95 Post(s) Tagged: 3 Thread(s)	Perhaps you should also disclose what else is different on your car, aside from your final drive.

04-04-2017, 03:58 AM	#6
CSG Mike Join Date: Jul 2012 Drives: S2000 CR Location: Orange County Posts: 14,562 Thanks: 8,942 Thanked 14,211 Times in 6,854 Posts Mentioned: 970 Post(s) Tagged: 14 Thread(s)	Wheel speeds (specifically rear). FD doesn't affect speedo.

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