Got a new 2009 RX350 about a month ago. Because the number of cars passing us on the freeway seems greater than we're accustomed to I suspected the speedometer is not accurate and checked it using 2 different GPS units. When we set the cruise control so the car speedometer is exactly on 70 mph, the actual speed according to the 2 GPS's is 67 mph.

We reported it to the dealer (Northshore in Milwaukee, WI) and they said that's the way all the Lexus's are and they cannot adjust it.

Anyone else notice this? (I don't see a "search" feature on this forum).

Until we bought this vehicle we have been life long GM customers, and the many new cars we have bought from them always had accurate speedometers. So it is annoying to discover that when we move up to a luxury brand like Lexus that all that advanced technology does not include an accurate speedometer.

 

Ok, now that I logged in to post I see the search button. Apparently if you're not logged in you don't get that?

 

Car and Driver magazine did an interesting article on the speedo issue several years ago. Lexus is not alone in this. BMW is the worst and Ford is the best in speedo accuracy.

Many drivers like to pass luxury cars to boost their egos. I have noticed that after I moved up to Lexus from a GM car as well. Lots of insecured people out there.

 

Boy,is that ever true!!
Ryan

 

never really noticed that, but now that i think about it i saw a bright red ferarri f430 on the street in the middle lane flowing with traffic not speeding, but also not holding up traffic either. people just kept speeding up to then cutting that f430 off, strange

 

Yeah right?

 

Same experience. On our 09 RX the speedo is almost 4-5 mph off at 70 mph. I am checking speed via hand held GPS unit which seems to be very accurate on everything else. I have not been to dealer but it sounds like there is NOT a fix.

Thanks, BB

 

My 08 IS250 i had before the RX had the same problem. I was able to calculate it was off 8 mph. I have also noticed the RX has the same problem but it has never bothered me. At least you know that if you are going 70-75 mph, the cops will see you going alot slower than that...

 

RX speed is calculated on rotation of the wheel and thus can never be accurate as the circumference changes with level of inflation/tire_wear, making turns etc.

Once you accept that there WIll be in-accuracy you can get into +-tolerance.

I vaguely recall that the speedo can be +-10% at 55mph. You can argue your way out of a speeding ticket.

German laws required that it can only err on the side that it displays faster than actual [thus allowing the law abiding driver to not cross the speed limit unintentionally].

Salim

 

I thought the industry accepted tolerance error was + or - 5% at 60 MPH, so being off by a few MPH at 70 doesn't seem like a major concern for me. Our State's car modification laws state we can alter our over all diameter of the rims/tires from stock by 7%. Now, a 7% change in tire over all diameter is getting fairly large, but that is within the margin of error according to our State laws. Each state is probably different, but I don't think a few MPH off is a big deal.

 

hawaii has some strict mod laws it seems......i always wondered if it was off whenever i fly by those signs that clock your speed my actual and what is clocked is always off.

 

Going a bit off topic here, but it is actually just Honolulu City on the main Island of Oahu that has very strict modding laws. In fact, modding technically is not allowed although everyone still does it. According to our city laws, you actually have to have all modifications inspected and submit for a reconstruction permit to legalize any modifications. Those mods that do not pass inspections or state laws are technically not allowed and you don't get a recon permit. If you don't have a recon permit, technically (Although many are still able to side step the laws) you can't obtain your annual safety inspection stickers and thus technically that vehicle would not be allowed to be driven legally.

 

I guess it amazes me that anyone would accept that in a brand that A) costs a lot, and B) touts its high quality as justification for A.

The speedometer is the most used item on the panel. In a car with this much technology, is it really too much to expect that the speedometer be accurate?

I recently bought a new Chev Cobalt for my teenage daughter to drive to school. It cost a third of the price of the RX350, but the speedometer is dead nuts. As is every other cheaper GM vehicle we have ever bought.

As for the claims that they intentionally overstate your speed to get you to drive slower... it's bad enough I live in a nanny state, I don't need a nanny company too. I think I'm capable of deciding for myself how fast I want to go. And that's generally 5 over the limit. Now I need to always be holding over by 3-4 mph which I find annoying.

I also found interesting the comment made by someone in a related thread I found on search, that if the speedometer is overstating speed by 5%, then the odometer is also overstating miles by 5%. This robs you of 5% of your warranty miles and saves Lexus 5% on warranty costs. And if miles is overstated by 5% that also affects the resale value. There was reference to Honda losing a class action suit over the same issue.

 

Our car is new, so tire wear is not an issue. As the tire wears the diameter will be smaller and it will turn faster for a given speed, thus the error (overstated speed) will become larger.

 

Do understand that I am simply explaining how it works. You will have to take your issue to Lexus Corp.

I am all for accuracy [with torque-wrenches and tension gauges etc], but at the same time I realize that there are allowable/acceptable range. Then there are rules and regulation on how those inaccuracies are to be handled. [Like you can not sell product by weight by using any weigh-scale, and why German vehicles would err on the side they do].

I respect your view and drive for accuracy, but for me I primarily use and enjoy the RX as a means of transportation.


Salim