Rx And Is Speedo Errors

[JB Not happy]

I purchased a RX350 from Melbourne City Lexus 12 month ago. The

car is very good and has in all but one respect lived up to its

reputation. Prior to buying it, I noted the RX350 has won many awards

including winner best luxury 4WD 2003, 04, 05 (& 6). “The RX350 not

only won its class, it won it for the fourth year in a row, proving that a

successful formula will stand the test of time, even when it has a

couple of dozen worthy challengers snapping at its high-class heels.” 1

Almost as soon as I purchased the car I noted that the speed display

appeared to showing the car was traveling at a higher speed than it

really was. This was noticeable because people were often tailgating

me while I was driving at what the rx350 showed me to be the

prescribe speed limit while I was the in the left hand lane of the

freeways and flashing lights and tooting horns before overtaking me

on single lane roads. I often drive to destinations several hours away

and was unpleasantly surprised to take over an hour longer as soon as

I took the trip in my new Lexus RX350.

LEXUS is aware of the problem and has yet to fix it ( three years Plus) You can test your car by using a hand held GPS. Then demand your car is fixed. IS250 models in Australia have even worse errors depending on the option rims sizes.

[Booyah]

SaY Whaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaat!

My speedo is rock solid with my GPS 60CSX!! dont know what your smokin bro

[Rx330driver]

over an hour long means that you would have to be driving 50% slower than what "think" to be the actual speed. So either your a flamer who is hear to bash lexus, or your what booyah said, smoking.

Your the only one in this forum to have mentioned this problem.

[Stango]

My new '08 RX350 speedo is off by 4 mph at 60 mph..... based on my GPS. I wonder if the 18" wheels/tires are a different diameter. Anyone else have an issue or dealer resolution ? What I dont like is it also racks up more miles than actually traveled (falsly making MPG look better than it is but hurting my miles on future resale)

[idoc]

My new '08 RX350 speedo is off by 4 mph at 60 mph..... based on my GPS. I wonder if the 18" wheels/tires are a different diameter. Anyone else have an issue or dealer resolution ? What I dont like is it also racks up more miles than actually traveled (falsly making MPG look better than it is but hurting my miles on future resale)

I agree. Our 2007 Rx 350 is about 3 to 4 miles slower than what is registered on the Lexus speedometer. We have varified this whenever we pass those speed display detectors on the freeway, following my wife in my MB while on the phone with her to confirm our speed, as well as with our portable GPS.

[Lexus88]

My new '08 RX350 speedo is off by 4 mph at 60 mph..... based on my GPS. I wonder if the 18" wheels/tires are a different diameter. Anyone else have an issue or dealer resolution ? What I dont like is it also racks up more miles than actually traveled (falsly making MPG look better than it is but hurting my miles on future resale)

I agree. Our 2007 Rx 350 is about 3 to 4 miles slower than what is registered on the Lexus speedometer. We have varified this whenever we pass those speed display detectors on the freeway, following my wife in my MB while on the phone with her to confirm our speed, as well as with our portable GPS.

I'm going to test mine too against my PDA GPS. But I have a question. As far as MPG is concerned, isn't it possible that your odometer is correct even though you speedometer might be off? Shouldn't one test the odometer before determining that the MPG calculation is erroneous?

[lenore]

My new '08 RX350 speedo is off by 4 mph at 60 mph..... based on my GPS. I wonder if the 18" wheels/tires are a different diameter. Anyone else have an issue or dealer resolution ? What I dont like is it also racks up more miles than actually traveled (falsly making MPG look better than it is but hurting my miles on future resale)

Also excellerating your time to finish your warranty....

[lenore]

My new '08 RX350 speedo is off by 4 mph at 60 mph..... based on my GPS. I wonder if the 18" wheels/tires are a different diameter. Anyone else have an issue or dealer resolution ? What I dont like is it also racks up more miles than actually traveled (falsly making MPG look better than it is but hurting my miles on future resale)

I agree. Our 2007 Rx 350 is about 3 to 4 miles slower than what is registered on the Lexus speedometer. We have varified this whenever we pass those speed display detectors on the freeway, following my wife in my MB while on the phone with her to confirm our speed, as well as with our portable GPS.

I'm going to test mine too against my PDA GPS. But I have a question. As far as MPG is concerned, isn't it possible that your odometer is correct even though you speedometer might be off? Shouldn't one test the odometer before determining that the MPG calculation is erroneous?

That is correct on the old analog speedometers, as they were gear driven many years ago...

[lenore]

If your car is running at a slower speed than what is indicated, it is probably getting better fuel economy, maybe that is why auto manufacturors are doing so.. I have checked my speedometer on My RX300 (99) and it is only 1 to 2 miles per hour faster than GPS indicates. My 2005 Ford F150 is about 4 mph faster than gps indication. The speed sensor on the drive shaft should be quite accurate if properly counted in the Computer on our cars. Yes Tire pressure and tire size could effect this, relating to revolutions per mile by the tire. All aside, I drive with the flow of traffic and yes it is generally faster than the posted speed limit.

[Stango]

If your car is running at a slower speed than what is indicated, it is probably getting better fuel economy, maybe that is why auto manufacturors are doing so.. I have checked my speedometer on My RX300 (99) and it is only 1 to 2 miles per hour faster than GPS indicates. My 2005 Ford F150 is about 4 mph faster than gps indication. The speed sensor on the drive shaft should be quite accurate if properly counted in the Computer on our cars. Yes Tire pressure and tire size could effect this, relating to revolutions per mile by the tire. All aside, I drive with the flow of traffic and yes it is generally faster than the posted speed limit.

The impact is miles accumulate faster, warranty expires sooner, MPG is exaggerated, etc. I suspect but dont know for sure, that the 18 inch wheels may be the reason..... not sure but I am not happy. and yes I did check the Odometer vs the highway posts and the Odo ir ticking off miles faster than it should be.

Yep it does make the mfg MPG look better than reality and I confirmed this with tank to tank fill ups.

[Lexus88]

My new '08 RX350 speedo is off by 4 mph at 60 mph..... based on my GPS. I wonder if the 18" wheels/tires are a different diameter. Anyone else have an issue or dealer resolution ? What I dont like is it also racks up more miles than actually traveled (falsly making MPG look better than it is but hurting my miles on future resale)

I have a 2008 RX350 with 18" wheels. My PDA GPS indicated 60 mph on the speedometer, but the GPS unit indicated 58 mph for an error of 3.4%. However, I also had another gps unit that tracks distance and that unit indicated 16.39 miles when the odometer showed 16.3 miles, so even if the vehicle odometer ticked over to 16.4 in .01 of an additional mile it indicates the odometer is right on the money or possibly even slightly pessimistic! Based on this data, at least for my vehicle, my odometer miles are not accumulating faster than they should consequently shortening my warranty period.

[Stango]

My new '08 RX350 speedo is off by 4 mph at 60 mph..... based on my GPS. I wonder if the 18" wheels/tires are a different diameter. Anyone else have an issue or dealer resolution ? What I dont like is it also racks up more miles than actually traveled (falsly making MPG look better than it is but hurting my miles on future resale)

I have a 2008 RX350 with 18" wheels. My PDA GPS indicated 60 mph on the speedometer, but the GPS unit indicated 58 mph for an error of 3.4%. However, I also had another gps unit that tracks distance and that unit indicated 16.39 miles when the odometer showed 16.3 miles, so even if the vehicle odometer ticked over to 16.4 in .01 of an additional mile it indicates the odometer is right on the money or possibly even slightly pessimistic! Based on this data, at least for my vehicle, my odometer miles are not accumulating faster than they should consequently shortening my warranty period.

Mine is opposite...... my GPS says 60 and the Speedometer says 65.... and at that rate I do tick off faster..... my speedo is under reality and your speedo is over..... maybe it isnt related to the 18" wheels (I have Goodyear tires btw)

[Lexus88]

My new '08 RX350 speedo is off by 4 mph at 60 mph..... based on my GPS. I wonder if the 18" wheels/tires are a different diameter. Anyone else have an issue or dealer resolution ? What I dont like is it also racks up more miles than actually traveled (falsly making MPG look better than it is but hurting my miles on future resale)

I have a 2008 RX350 with 18" wheels. My PDA GPS indicated 60 mph on the speedometer, but the GPS unit indicated 58 mph for an error of 3.4%. However, I also had another gps unit that tracks distance and that unit indicated 16.39 miles when the odometer showed 16.3 miles, so even if the vehicle odometer ticked over to 16.4 in .01 of an additional mile it indicates the odometer is right on the money or possibly even slightly pessimistic! Based on this data, at least for my vehicle, my odometer miles are not accumulating faster than they should consequently shortening my warranty period.

Mine is opposite...... my GPS says 60 and the Speedometer says 65.... and at that rate I do tick off faster..... my speedo is under reality and your speedo is over..... maybe it isnt related to the 18" wheels (I have Goodyear tires btw)

Actually what I meant is the speedometer read 60 mph and the GPS 58 mph, so I'm off the same direction as you are only not as much. Or another way of putting it is my GPS at 58 and speedometer at 60!

[JB Not happy]

over an hour long means that you would have to be driving 50% slower than what "think" to be the actual speed. So either your a flamer who is hear to bash lexus, or your what booyah said, smoking.

Your the only one in this forum to have mentioned this problem.

Your maths ability is astonding- Professor??? A 700 Km trip at 10% slower speed than the leagal speed limit. (100KM per hour) and you THE PROFESSOR worked out a 50% speed reduction. Gosh I thought at 50% it would take twice as long not just an hour. Thanks Professor :whistles:

[JB Not happy]

SaY Whaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaat!

My speedo is rock solid with my GPS 60CSX!! dont know what your smokin bro

Smoken Joe?? Or was it a few to many tablets you take for that twitch? Lexus tested my car and found the error. They just dont know how to fix it. Perhaps you think they are smoken??? Glad your car is Rock solid. Helpful as you brain may be a little wobbley

[SW03ES]

over an hour long means that you would have to be driving 50% slower than what "think" to be the actual speed. So either your a flamer who is hear to bash lexus, or your what booyah said, smoking.

Your the only one in this forum to have mentioned this problem.

Your maths ability is astonding- Professor??? A 700 Km trip at 10% slower speed than the leagal speed limit. (100KM per hour) and you THE PROFESSOR worked out a 50% speed reduction. Gosh I thought at 50% it would take twice as long not just an hour. Thanks Professor :whistles:

You wanna not be a prick? We don't tolerate rudeness here, come back and try again in a month.

[desertdave]

LEXUS is aware of the problem and has yet to fix it ( three years Plus) You can test your car by using a hand held GPS. Then demand your car is fixed. IS250 models in Australia have even worse errors depending on the option rims sizes.

So how do I calculate speed using a hand held Magellan?

[DArustik]

I believe it has to do with putting aftermarket wheels/changing the wheels etc. I had the same problem on my GS but was corrected when I reinstalled the factory wheels for the winter.

[LXPearl]

You need to check the specs to determine if the readout is acceptable or not. I checked the specs on one of my Toyotas once and the acceptable readout when traveling 60 MPH was a display of 58 to 66 MPH. It sounds like all the readouts mentioned above fall within this range, and therefore would be within specs.

When you check tire specs, you will find different tire lines and mfgs may have different revolution figures for the same size.

I suspect the above specs serve a double purpose - the variation is such that you should not get a speeding ticket if observing the speedometer readout; plus you may run through your warranty quicker. However, I found the odometer more accurate than the speedometer on my questionable Toyota, so I suspect the two are not as directly related as they used to be in the 60s and 70s (gear drive) - the CPU must be doing some calculations and displaying each readout separately.

I have noticed that the loaner RX350s I have driven tend to indicate about 4-5 MPH faster than actual.