Hi, I am new to the forum. I have had my GX 550 Premium + 3 months and I’m impressed with the quality, my 1st Lexus. I apologize in advance if this had been discussed before. Yesterday I was driving and had my cruise sent at 64 mph. I had Waze open simultaneously in Apple Car Play and as you know Waze also displays your speed, it showed I was traveling at 68 mph, a 4 mph n discrepancy. My question is does Lexus compensate for different tire and wheel sizes? Some GX’s come with 18”, some with 20” and some with 22” wheels. Is this common and acceptable to have this much variance between Lexus and Waze?
Speedometer Accuracy
- Thread starter nbavo
- Start date
GPS speed measurement in apps like that is notoriously inaccurate. You'll see it be +4 mph then -2 mph from the speedo.
the tire size of the premium is 1” smaller than. The OT and Lux stock wheels. When I changed my premium 20’s to 33” (.5” larger then the OT tires) my Speedo became almost dead on to the GPS readings. Take that info however you want, but I think the premium wheels certainly make your Speedo rack up miles faster.
My longer theory
www.lexusgxforum.com
My longer theory
GX550 Real World MPG
19.1 after 500 miles. 40/60 city highway. I'm happy. Was expecting the worst.
www.lexusgxforum.com
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the tire size of the premium is 1” smaller than. The OT and Lux stock wheels. When I changed my premium 20’s to 33” (.5” larger then the OT tires) my Speedo became almost dead on to the GPS readings. Take that info however you want, but I think the premium wheels certainly make your Speedo rack up miles faster.
My longer theory
GX550 Real World MPG
19.1 after 500 miles. 40/60 city highway. I'm happy. Was expecting the worst.
Still can't understand why this isn't a calibration setting that the dealer can adjust. Most vehicles I've owned enabled this.
I have a speedo app and it's all over the road
I primarily use Waze for navigation, but the speed difference between what it showed my speedometer is very inconsistent. Pulled my Garmin GPS from my motorcycle and tossed it onto the dash and learned my GX is spot on across multiple speeds and multiple drives.
Waze should be spot on, it’s not.
Waze should be spot on, it’s not.
On a recent road trip with my new GX550, I noticed that if I set cruise at a certain speed (e.g. 70 mph), the speedometer would display one mph slower (e.g. 69 mph). This occurred often, but not always. Always 1 mph slower, never faster. I realize that the point at which I press SET on cruise may be a half mph different from actual speed. That could be why.
I use both Google Maps and Waze. Both display speed using GPS. Maps always matches my cruise setting. Waze tended to display a several mph higher speed for several seconds before the GPS caught up.
My dash camera also uses GPS and always matches my cruise setting.
I feel like the speed sensor is just a tad less accurate, because with at least two other systems agreeing, the speedometer was the only system disagreeing and always by 1 mph low.
My GX550 Luxury has 22” wheels. Other iterations come with smaller wheels and taller tires. Could Lexus be lax in calibrating the varied wheel/tire combinations? ¿Quién sabe?
I use both Google Maps and Waze. Both display speed using GPS. Maps always matches my cruise setting. Waze tended to display a several mph higher speed for several seconds before the GPS caught up.
My dash camera also uses GPS and always matches my cruise setting.
I feel like the speed sensor is just a tad less accurate, because with at least two other systems agreeing, the speedometer was the only system disagreeing and always by 1 mph low.
My GX550 Luxury has 22” wheels. Other iterations come with smaller wheels and taller tires. Could Lexus be lax in calibrating the varied wheel/tire combinations? ¿Quién sabe?
Yes, the Premium and Premium Plus with the OEM wheel and tires under reads speed by 2-4% especially when you are driving over 55-65 mph. What is worse is that it will inflate your odometer. I am pretty sure class action suits will come at some point as owners will argue that this causes the warranty to expire earlier and maintenance services to occur faster plus a whole host of other reasons.
I use Waze, Apple Maps, Google maps on other vehicles including few current generation 2025 Lexus loaners, the other vehicles are all much more accurate with GPS maps and speed readout. I think the calibration for the GX550 is set to to the (almost 33" OD) Overtrail or 22" Lux wheel+tire combo. I have a set of 18" 275 60 winter wheels on our Premium + and it still under reads the speedometer.
I don't need Waze to be accurate to confirm but I can tell when say, I set cruise control to cruise at 75mph on a 65 mph road on a frequent used road with Waze, Google maps etc. reporting 71-73mph on Carplay and other cars behind you start getting closer. I have to set cruise control to 78-79mph to actually cruise at 74-75mph.
I use Waze, Apple Maps, Google maps on other vehicles including few current generation 2025 Lexus loaners, the other vehicles are all much more accurate with GPS maps and speed readout. I think the calibration for the GX550 is set to to the (almost 33" OD) Overtrail or 22" Lux wheel+tire combo. I have a set of 18" 275 60 winter wheels on our Premium + and it still under reads the speedometer.
I don't need Waze to be accurate to confirm but I can tell when say, I set cruise control to cruise at 75mph on a 65 mph road on a frequent used road with Waze, Google maps etc. reporting 71-73mph on Carplay and other cars behind you start getting closer. I have to set cruise control to 78-79mph to actually cruise at 74-75mph.
The 1 mph below what you set it at is just a quirk of Toyota/Lexus Cruise control. It was like this when I had stock tires and it's still like this when I went with bigger tires.
Great feedback. I can live with quirks (although in this age of “analog is dead” and hyper accurate capabilities, it makes no sense that today’s programming code writers don’t do better work). I’m old enough to remember when used car dealers would run odometers backwards. Now people are spinning them forward to get you to in for maintenance more frequently? Hooey…
I found this thread because I'm having the opposite problem. I have a '25 Luxury+ and my speedometer reads lower than my actual GPS speed according to Waze. For example, when my speedometer reads 70 mph, Waze shows 73 mph +/- 1 mph. Some are saying that navigation apps like Waze and Google Maps are inconsistent, however, in my other vehcile the speedometer and GPS speed always match within 1 mph.
Most big map apps can have a 2-5% speedometer variance due to elevation, polling time and satellite coverage. Lots of articles on speedometer variances within the past 10 years, usually reading faster than you’re traveling. As long as your odometer accurately measures a mile, you should be fine.
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