LGT 5EAT speedo reading high..?

[Ed_T]

Hmm, just got sedan with 5k miles from dealer, totally bone stock.

 

Drove through one of those unmanned police radar units which flashed I was doing 35 steady. When I checked the speedo it was registering a solid 38 mph.

 

Anyone else seeing this anomaly with theirs? Assuming the radar was correct - this would be quite a discrepancy!

[jim1969]

And I went by one doing 45 and it read 39 on the radar. That radar probably isn't very accurate. They probably don't calibrate it as well as their car units.

[Sneezy]

My wifes Van & my Firehawk are both dead on. My Saab always read 4 high. I have yet to run through one with my Legacy.

[charlierh2]

i think that spec is with in 5% so if they have you at 3 or 4% high then your within spec but out of warrenty faster;)

[IwannaSportSedan]

Is the legacy speedo a cable and gear setup, or a hall-effect setup (electro-magnetic sensor?)

 

There is some sort of a company that makes a little yellow box that plugs inline to the speedo sender, and can adjust the signal plus or minus a few percent, to truly calibrate the speedo. I'd have to search again to find the exact details, but I have come across it a couple of times.

 

I never thought about the fact that it would run your warranty out faster (because my used cars haven't had warranties.)

[eamiller]

Vehicle speed is sent over the CAN bus from the ABS controller (wheelspeed sensors) which calculates speed by filtering the inputs from the wheelspeed sensors. From there, the engine ECU, Instrument Cluster, etc. can use the speed for whatever reason they need it for.

[rustler753]

All the speedos read a little high. I have my GPS sytem in my other cars and all the speedos are a bit off. Maybe its an anti speeding measure??

[XT6Wagon]

Subaru programs the cluster to read high intentionaly.

 

Which is nice... since I run larger tires it reads just about right.

[Prod]

From the radars I've seen it's about dead on. On my 01 Outback before the Legacy, it was about 3-4mph higher than what the radar said.

[doogdog]

My SM3 will confirm what you say, it says that I'm going 3-4 mph slower than the speedometer reads, this is plugged right into the OBDII port.

Rick

[chucktoo]

Has anyone figured out how to reprogram the ABS or Dash display [ instrument cluster] to fix speedo ? I know it is a digital signal from ABS to speedo over CAN bus . SInce Legacy and Outback have different rolling radius tires it must be programable somewhere ?

[IwannaSportSedan]

There has got to be a multiplier in there somewhere. Supposedly a dealer can set it for 18" wheels and tires of who knows what size, probably the same size as JDM GT Spec B 18x7s and their stock tire size.

 

(as well as turn on the tire pressure sensor receiver, and a few other things...)

 

With the ABS feeding the info to the CAN bus, the yellow-box thing probably won't work. I would definitely not want to mess with ABS wheel-speed measurements. It would be nice to be able to configure the chassis computer, or ECU to show the correct speed, though. Maybe a fraction taller tire is the way to go...