Speedometer incorrect on 265/70/17 tires

[mckennar]

2016 trail, brand new stock size (265/70/17) Bridgestone Duelers.

With the bald stock Dunlop AT20s, my speedometer was off ~3 - 4 mph (speedometer read faster than the vehicle was actually moving), verified with multiple GPS apps on 4 different phones and by pacing with radar cruise on a 2016 E-Class. I figured this was due to the decreased diameter of the bald (3/32) tires.

Now with fresh rubber (265/70/17 duelers as mentioned above, OE on the SR5s I've seen), it is still off the exact same amount. At 75 mph on the speedometer, the GPS and other cars are indicating 71 mph.

After reading the 5th gen tire size guide ( http://www.toyota-4runner.org/5th-gen-t4rs/156378-going-bigger-5th-gen-tire-fitment-guide.html ), I'm thinking I can get somewhat close if I go to 285/70/17 once I get the 2" front/1" rear leveling kit installed?

Follow up: has anyone had any luck getting the dealer to correct this annoyance? Thinking about asking them to fix it when we're in for the next service appointment.

Thanks folks.

 

[el_kab0ng]

Weirdly enough, I have a similar problem. I've had two radar guns and one of those speed trap radars show me 2 mph under the actual speed limit. This might explain why @ 75mph on the Tollway I'm getting lapped by a Prius at a pretty good clip.

 

[JET4]

I run 275/70/17 tires and the speedometer is perfect. I checked it with GPS.Toyota speedometer is a little fast so you don't speed. Lol

 

[mckennar]

This might explain why @ 75mph on the Tollway I'm getting lapped by a Prius at a pretty good clip.

Same here, only with guys in brodozers. This is the wifemobile, and she was wondering why so many people were honking and flashing their high beams at her when she was going an indicated 75 (speed limit) in the passing lane... yes, while actually passing other cars.

What prompted our little experiments were the above info and the radar-speed signs (like you see when entering a construction zone) all displaying 3 - 4 mph slower than we were driving.

And, unfortunately, some pretty stellar fuel mileage numbers. Now that we know the speedo is wrong, our 21 - 22 mpg highway between fill ups is probably going to drop some once it is corrected.

 

[el_kab0ng]

I forgot to point out that I, too, have a 2016 TE with stock Dunlap tires (with less than 6500 miles on three of them and 50 miles on a replacement for the front left when I ran over a downed speed limit sign on an off ramp at 50 something miles per hour)

 

[Saxainpdx]

I have 285/65-R18's and my speedometer appears to be correct, checked against Waze, GPS Speed app, radar sign, and a Dodge Durango with adaptive cruise control behind me.

I know my Tacoma was always off by 2-3% on stock tires.. at least checked against a Garmin GPS and phones..

 

[Shawk00]

Both of my 5th Gen 4Runners have been the same... they read approx 2mph faster than actual according to GPS (@ around 70mph). My wife's Highlander is the same. I've never given any thought to having the dealer look at it... not a big deal to me either way since I keep a Garmin in every vehicle we have (whether they have a factory GPS or not). But it would be interesting to see what a tech would do or say.

 

[Storm Runner]

Same story with mine. Stock tires made my speedometer incorrect. Once I upgraded to my current 255/80/17 tires, my speed is now spot on according to all the radar signs I pass.

 

[FrontRange4Runner]

2016 trail, brand new stock size (265/70/17) Bridgestone Duelers.

With the bald stock Dunlop AT20s, my speedometer was off ~3 - 4 mph (speedometer read faster than the vehicle was actually moving), verified with multiple GPS apps on 4 different phones and by pacing with radar cruise on a 2016 E-Class. I figured this was due to the decreased diameter of the bald (3/32) tires.

Now with fresh rubber (265/70/17 duelers as mentioned above, OE on the SR5s I've seen), it is still off the exact same amount. At 75 mph on the speedometer, the GPS and other cars are indicating 71 mph.

After reading the 5th gen tire size guide ( http://www.toyota-4runner.org/5th-gen-t4rs/156378-going-bigger-5th-gen-tire-fitment-guide.html ), I'm thinking I can get somewhat close if I go to 285/70/17 once I get the 2" front/1" rear leveling kit installed?

Follow up: has anyone had any luck getting the dealer to correct this annoyance? Thinking about asking them to fix it when we're in for the next service appointment.

Thanks folks.

Its common for manufactures to have the speed read higher than a vehicle is actually going. It happens on many vehicles. I'm not sure why, my guess is that its a safety thing. I would say that the odds of getting a dealership to touch the speedo are very close to 0. They are just going to say that it is operating as it was designed to(and they are correct in this case).

 

[jwkilgore]

I have seen this occur in countless newer vehicles, including my 4Runner. I rent a lot of different type of cars and truck for work. The speed error doesn't occur in every vehicle, but it happens enough to be noticeable. I have never observed a speedometer that read slower than GPS-verified travel speed.

One theory is that it's intentional to reduce speed thereby saving gas for better fuel economy ratings. Also to get people out of speeding tickets and be safer in accidents.

If I believed in conspiracies, I would say it was intentional to sneak out of paying for warranty service. Using a 75/71 ratio, a part that failed at an odometer reading of 37,000 would technically have only traveled 35,027 miles.

 

[NZDZRT]

Speedo Error...

And in the meantime, we are all putting more (indicated) miles on our vehicles. I have noticed the same on my '15. I don't think it's a good situation at all. Technology should allow them to be damn near spot on. They are off too much, and we are paying the price!

NZDZRT

 

[Lindenwood]

The speedometer is not necessarily hard-connected to the Odometer.

With 285/70r17s, my speedo is now within a half MPH at 80mph, but the odomoter reads slower almost in direct proportion to the increase in tire circumference.

This was all GPS verified over hundreds of miles.

Basically, the speedo seems to read fast from the factory, but the ODO is actually set to spec. This is a big issue in the motorcycle world, especially on sport bikes, where speedos often read 10% fast or more. However, the odomoters are all usually as accurate as they should be. Lots of 600cc riders out there thinking their bikes will do 170 .

 

[mckennar]

Its common for manufactures to have the speed read higher than a vehicle is actually going. It happens on many vehicles. I'm not sure why, my guess is that its a safety thing. I would say that the odds of getting a dealership to touch the speedo are very close to 0. They are just going to say that it is operating as it was designed to(and they are correct in this case).

I understand. Over the past 20 years I've owned dozens of cars, and while I have come across this phenomenon before, it has always been on cars with modified tires and/or gearing.

Put another way, I've never had a stock, new vehicle be this far off. I understand why they do it, but I was hoping for a bit more precision... the kind of precision all of my 1st gens and 3rd gens have exhibited.

Looks like this will be reality on the highway (around town the speedo and GPS are identical) until the Duelers give up the ghost and I chuck a set of larger tires on there.

 

[mckennar]

The speedometer is not necessarily hard-connected to the Odometer.

Funny you mention that. On all of my older (pre-2000) vehicles, the odometer was tied directly to the speedometer. Post 2000, I noticed on one of my Volvos (2003 V70 T5) the speedometer stopped working, yet the odometer continued to function properly. My brain immediately dismissed that as an outlier, and I still (until you mentioned it) always assumed a direct connection between speedo and odo.

The wife and I drive a lot (~20,000 miles since July), so next highway trip I'll do a GPS vs. odometer and see how close it is.

Thanks for the reminder.

 

[gm350reratliff]

Add me to the list. My 5th gen is off a good 4 mph at 75 mph. I don't recall my 4th gen being off that much but I do know it was also off with the OEM tires. I'll be upgrading the tires on my 5th gen soon anyway.

 

[Saxainpdx]

If it bothers you too much, you can get a Speedohealer to correct the difference. [MENTION=66389]BlackWorksInc[/MENTION] has a thread on his install here(4th Gen, but I assume it will be similar)

 

[Lindenwood]

Funny you mention that. On all of my older (pre-2000) vehicles, the odometer was tied directly to the speedometer. Post 2000, I noticed on one of my Volvos (2003 V70 T5) the speedometer stopped working, yet the odometer continued to function properly. My brain immediately dismissed that as an outlier, and I still (until you mentioned it) always assumed a direct connection between speedo and odo.

In my experience, even modern speedos and odos often get their data from the same reference point. However, to be more specific, this doesn't mean the error comes from early wnough in the chain that it applies to both. So, the speedo could be deliberately or carelessly off, but the odometer could still be accurate.

I have heard anecdotes that manufacturers sometines make their speedos read fast for various reasons. A few have been mentioned, like driving slower nets greater fuel efficiency and resuces severitt of accidents. Another I have heard is to make their vehicles seem faster (i.e. all those 600s that wrap the dial to 170 plus but can't break 155 on a GPS).

 

[NZDZRT]

Thanks!

The speedometer is not necessarily hard-connected to the Odometer.

With 285/70r17s, my speedo is now within a half MPH at 80mph, but the odomoter reads slower almost in direct proportion to the increase in tire circumference.

This was all GPS verified over hundreds of miles.

Basically, the speedo seems to read fast from the factory, but the ODO is actually set to spec. This is a big issue in the motorcycle world, especially on sport bikes, where speedos often read 10% fast or more. However, the odomoters are all usually as accurate as they should be. Lots of 600cc riders out there thinking their bikes will do 170 .

Very interesting, I hadn't considered that. Sounds like some additional testing is in order! I just love the great input on this board. :cowboy::cowboy:

Best Regards,

NZDZRT

 

[BlackWorksInc]

4th Gen and newer 4Runners utilize the ABS Speed Sensors to determine an average vehicle speed that is sent to the instrument cluster.

There is a roughly 2mph allowance in accuracy for the speedometer (there's a more structured variance in the FSM that has a progressive tolerance as speed increases IIRC at like 70mph and higher it gets in the 3~4mph range of variance).

It does sound like you did a fairly good job of verifying the speed difference so that's good, usually I have people using those speed limit signs on the side of the road; which I have found to be very inaccurate. GPS apps and units may be accurate depending on the quality and model and software coding, I would say that the E-Class might be fairly accurate, but again they also allow a variance of about 2mph (it's sort of an industry thing, typically the variance is more that the speed is faster than the actual vehicle's speed.)

 

[NorthwoodsRunner]

2016 trail, brand new stock size (265/70/17) Bridgestone Duelers.
With the bald stock Dunlop AT20s, my speedometer was off ~3 - 4 mph (speedometer read faster than the vehicle was actually moving), verified with multiple GPS apps on 4 different phones and by pacing with radar cruise on a 2016 E-Class. I figured this was due to the decreased diameter of the bald (3/32) tires.
Now with fresh rubber (265/70/17 duelers as mentioned above, OE on the SR5s I've seen), it is still off the exact same amount. At 75 mph on the speedometer, the GPS and other cars are indicating 71 mph.
After reading the 5th gen tire size guide ( http://www.toyota-4runner.org/5th-gen-t4rs/156378-going-bigger-5th-gen-tire-fitment-guide.html ), I'm thinking I can get somewhat close if I go to 285/70/17 once I get the 2" front/1" rear leveling kit installed?
Follow up: has anyone had any luck getting the dealer to correct this annoyance? Thinking about asking them to fix it when we're in for the next service appointment.
Thanks folks.

I have had similar experiences on Toyotas (2007 Camry, 2014 Camry and 2016 T4R). The odometer seems correct but the speedometer is off by ~2mph at 70mph (the Toyota is traveling around 68mph based on GPS). My two Hondas are spot on with the GPS. Not sure if this is really fixable since it likely to be within the speed error specification. You can get slightly bigger tires but then your odometer would be slightly under reporting the mileage.