Question Speedometer accuracy

[pull my lure]

Hi All,

2004 Sequoia, and my Speedo doesn't read true. It is actually displaying roughly 5% lower than my speed when compared with GPS speed.

If you calculate miles driven per the odometer (seems to be linked to Speedo), it's lower than displayed by the trip computer.

If you multiply trip miles * 1.05, then you get the same # as the trip computer.

I wonder if I'm the only one with this issue. I discovered it when someone in a Lexus and I were on a trip and decided to both set cruise at 55 (I was going closer to 60 on her speedo). I've compared with 2 GPS units, a corvette, a couple Lexuses (Lexi?), and I've also ridden in those cars with the GPS in-hand. It's most dead-on in the Corvette believe it or not.

Anyway, post here if you need more info/have experienced this yourself. Pls include year & tire size.

TIRE SIZE: 265/70/17

[czechm8]

Mine is just the opposite. My actual speed is lower than the speedo reads.
It's all about the tires. The stock 265/65/17's mine came with read faster than actual speed. When I switch over to my winter tires.......265/70/17's the speedo is pretty much right on. The 265/70/17's are about 31.5 inches while the stock tires are about 30.4 inches. I have a GPS nav unit so I can track my actual speeds.

[pull my lure]

Interesting - I guess your '05 has a different tranny (5 spd, right?) so .. perhaps it's the sending gear on the 4 speeds? Anyone else have any ideas?

[AnywhereAT]

My speedo reads faster than actual speed, measured against a couple different GPS units. 2004 Sequoia with 265/65/17 tires.

[mikgrail3]

It all depends on what the stock tire size on your truck was and what the speedo and odo was calibrated to. I think the stock size (on the door panel sticker) is 265/70/16. That means your tire 265/70/17 is larger, making your actual speed higher than the readout....see below:

Stock Tire - 265/70R16********
Section Width: 10.43 in 265 mm
Rim Diameter: 16 in 406.4 mm
Rim Width Range: 7 - 9 in
Overall Diameter: 30.60 in 777.24 mm
Sidewall Height: 7.30 in 185.42 mm
Radius: 15.30 in 388.62 mm
Circumference: 96.13 in 2441.7 mm
Revs per Mile: 679.7
Actual Speed: 60 mph 100 km/h
Speedometer Difference: -
Diameter Difference: -%


New Tire 1 - 265/70R17********
Section Width: 10.43 in 265 mm
Rim Diameter: 17 in 431.8 mm
Rim Width Range: 7 - 9 in
Overall Diameter: 31.60 in 802.64 mm
Sidewall Height: 7.30 in 185.42 mm
Radius: 15.80 in 401.32 mm
Circumference: 99.27 in 2521.4 mm
Revs per Mile: 658.2
Speedometer1: 58.1 mph 96.8 km/h
Speedometer Difference: 3.266% too slow
Diameter Difference: 3.17%

taken from: Tire Size Calculator - tire & wheel plus sizing

My 4Runner has 315/75/16 tires on it but geared lower for 265/75/16 tires. My speedo reads 10% lower than my actual speed. So my guess is that your tire size is the reason for the discrepancy. Just be aware if it and you'll be fine, no harm.

[kat-toy]

My 2003 SR5 with 265/65/17 tires is off by about 3 mph. Didn't discover this until traveling with others who kept asking why we were driving so fast. Funny thing is -- the car had 90K+ miles on it at that point and it had never caused a problem.

[pull my lure]

Well, I got a ticket Monday.

My speedo showed 70 on the dot (it was on cruise) and apparently the road I was on throttled back to 55mph (it was 65) so I didn't slow down when I saw the FL State Trooper... he said I was going 75MPH. Bummer. I know my speedo is off, and I should adjust accordingly, but I find it difficult to always do so.... haha.... part of me wishes it was off in the opposite direction like my last vehicle was!!

As an aside, you're off by 3mph at what speed? My guess is that it's not a 3mph "lump" in your speedo but it would grow as your speed increases..

[Greggcellent]

Here is a cool tool .

Tire size calculator.

[Padron]

Can the dealer re-flash the computer to the corrected speed for the larger tire size? I know a previous vehicle I had I could do it myself with an Edge programmer.

I am thinking about some larger tires for my recently purchased 2006 Limited 4x4