mdv

Was wondering if anyone has notice that there speed is off. I have a 450H and have noticed that the speed is about 2-2.5 off per radar speed signs and my Garmin gps

w4rjd

My RX350 is the same.

F800GS

Higher or lower ?

mdv

Reads 25 and I am only doing 22.5 -23 mph

wyau01

So, Is this a Lexus or a Garmin issue? Which one is giving out the wrong reading?

ziggy1

This is tricky. There are a lot of things that could contribute to the slight discrepency (tire pressure and size, instantaneous reading, etc.). Also, the radar has to be tuned correctly to give an accurate reading, and I suspect there's not a great deal of effort in that respect for those speed signs that get drogged around or can sit for days. I think that's why police give a few mph cushion before grabbing someone for speeding. Does your Garmin agree with the radar reading?

MEP7557

If I compare mine to the radar, I am actually going 1-1.5 mph slower than the radar says. I like the fact that it does that. I feel safer when I come up on photo radar.

Of course I have no idea how accurate the radar is. It's a permanent sign and they just replaced it with a new one, so I'm thinking pretty dead on.

mdv

Garmin and radar are pretty close. I think that the milage is close, will check that later. It is not a big deal was just wondering if others had noticed it.

sleepysurf

I've noticed it as well with my 2010 RX 450h. Speedometer is 1-2 mph lower than my Garmin GPS and the speed-radar signs. FYI, I have the 19" wheels, and thought it might be due to that. Not a big deal, but I wonder if the total odometer mileage is also effected.

RXSF

yep, my 2004 is the same thing. I am actually going faster than what the radars say. As in, if it says im going 35, im actually going 37 ish according to the speedo. I dont think car makers change the speedo in regards to tire size options

jtrue28

another question would be do the owners with 18" wheels have the same problem? then if not, compare the overall diameter of the 19" wheel & tires to that of the 18" wheels.

size of wheel doesn't really matter in this scenario as it's the combination of wheel and tire that determine the overall diameter.

1NEAT_SC

Hmmm.... I did notice it a couple weeks ago. I was traveling 75 and it showed up some place I was going 73. I checked it several times on a trip to and from Michigan (from Indy) and noticed it both directions. Now I set the cruise to 77 when I want to go 75. I have the 19" tires as well and did process that too.

lar

wyau01

I heard similar stories from BMW owners. Radar is higher than the car. Maybe it's a hint to slow down.

MEP7557

OK after re-reading that post I need to clarify. The car says I am doing 35 mph, the radar says I'm going 33-34 mph. 19" tires

My head hurts after that one.

integlikew

Yes this is normal for all cars google it. This has been done to keep you under the speed limit. The cars always tell you you going faster then you really are, this way if the cop radars you over the speed limit you can't say my speedo must be off. The tolerances are not close enough and there is to many variables (to make the speedo 100% exact) so the car manufactures just makes sure it reads a few % faster so they are covered from any border line lawsuits.