Speedometer buffer?

[CatahoulaManiac]

After putting 275/70/17 BFG KO2s on my 4runner my speed is reading equal to GPS, before it was off about 2 mph.

Most vehicles aren't 100% accurate

 

[CatahoulaManiac]

1. You rack up miles faster on your vehicle so you feel like need to get a new car sooner

2. Bumps your vehicle out of the manufacturer warranties sooner

Those are my theories

How exactly would erring under on the speedometer reading lead to racking up miles faster?

 

[sandcrawler]

What I don't think I mentioned was he offered up that he used to drive a BMW and now a Lexus. The Lexus he claims was about two miles off, where the BMW he said was four to five miles off. Obviously, most are thinking he's just FOS.

Mine is consistently two miles off. That's unscientific testing watching speed displays and using a number of apps off the Android. In comparison, using similar speed displays and my smartphone apps, my 2005 4R was pretty close to dead on far as the speedometer. I dunno, it's not a big deal, just like to understand it a bit better is all.

my 4Runner speedo was ~+3 mph on 265s; now ~-1 on 285s. have a BMW that is consistently ~+4/5 mph. this is normal.

 

[sandcrawler]

I think I remember a lawsuit about this (Honda?) Their speedometer were calibrated to run faster so you used up the warranty faster and used up lease mileage quicker

1. You rack up miles faster on your vehicle so you feel like need to get a new car sooner

2. Bumps your vehicle out of the manufacturer warranties sooner

Those are my theories

How exactly would erring under on the speedometer reading lead to racking up miles faster?

whatever the minor inaccuracy of the speedometer may be, it should have no bearing whatsoever on the odometer.

 

[Airmapper]

There was a thread a while back on ExPo, some dude was convinced Toyota needed to buy back his Tacoma because of this.

Found it: http://forum.expeditionportal.com/t...-Heads-up?highlight=speedometer+tacoma+toyota

 

[CatahoulaManiac]

whatever the minor inaccuracy of the speedometer may be, it should have no bearing whatsoever on the odometer.

I really want to see the explanation the guy that made that claim has. I bet it's entertaining.

 

[Sifrk]

Good to know perhaps a tire change in the future will level the MPH a bit.

whatever the minor inaccuracy of the speedometer may be, it should have no bearing whatsoever on the odometer.

Could you expand on this statement? I would have thought the odometer would be impacted by the MPH (speedo), but it is an assumption on my part.

 

[1jzgte]

How exactly would erring under on the speedometer reading lead to racking up miles faster?

whats your theory on how mileage is recorded on the odometer?

 

[MossJenks]

whatever the minor inaccuracy of the speedometer may be, it should have no bearing whatsoever on the odometer.

Huh? How does that work? It's a single shared drive off the transmission. One is the same as the other. Maybe the needle is set slightly differently or the printing of the numbers on the speedo is cocked a little but the same inherent accuracy limitations apply. Please re-read my post:

In 30 years of driving I've never owned a car that had a speedometer that was perfectly accurate at highway speeds. You're really worried about TWO MPH? Heck, my Alfa Romeo is like 8 MPH optimistic. There's got to be more than a 2 MPH difference between a brand new off-road tire and a worn-out one at 75 MPH. And different brands and models often have slightly different diameters when new. How in the world would you expect Toyota to engineer a speedometer that's perfectly accurate with all of those variables? And just what would you expect the service manager to do, start replacing speedos and cables and transmissions in the long-shot hope that some combo would be perfect? Please.

Oh, and Sifrk - apologies for the "tone" of my first post, I was reacting with annoyance more to this topic in general and people's misunderstanding of the basic mechanics of it than anything you said.

 

[engineeer]

Here's a data point:

I have 275s on, which means I'm going ~1.7% faster than what my speedometer reads out.

I've checked my speed compared to GPS multiple times and I'm going 1.4% faster than what my speedometer reads now, so originally my speedometer was only off by ~0.3%.

Edit: I just woke up, so hopefully I didn't mess up that simple math.

 

[1jzgte]

Here's a data point:

I have 275s on, which means I'm going ~1.7% faster than what my speedometer reads out.

I've checked my speed compared to GPS multiple times and I'm going 1.4% faster than what my speedometer reads now, so originally my speedometer was only off by ~0.3%.

Edit: I just woke up, so hopefully I didn't mess up that simple math.

I find the 4runners odo to be very close to GPS speed readings vs my camry which is consistently 2mph faster on the odo.

 

[sandcrawler]

I really want to see the explanation the guy that made that claim has. I bet it's entertaining.

Good to know perhaps a tire change in the future will level the MPH a bit.



Could you expand on this statement? I would have thought the odometer would be impacted by the MPH (speedo), but it is an assumption on my part.

Huh? How does that work? It's a single shared drive off the transmission. One is the same as the other. Maybe the needle is set slightly differently or the printing of the numbers on the speedo is cocked a little but the same inherent accuracy limitations apply. Please re-read my post:



Oh, and Sifrk - apologies for the "tone" of my first post, I was reacting with annoyance more to this topic in general and people's misunderstanding of the basic mechanics of it than anything you said.

on older vehicles, both the speedo & odd may have reported off the same shared input, but today's vehicles are way more sophisticated (and complicated). multiple sensors, inputs, and ECUs contribute to the values reported and monitored in multiple systems. hook up Techstream live and look at the firehose-stream of data populated in real-time.

i'm not a Toyota engineer (@Quentin?), and while i know that not every vehicle does it the same way, i doubt it's a "single shared drive" off the 4Runner's trans. consider VSC and TRAC and where they get their data... (not the same thing precisely, but still...)

a click-through in the article linked above points this out as it differentiates between speedo and odo inaccuracies: "What about my odometer? That’s held to a tighter standard and is for a different discussion"

 

[Sifrk]

Oh, and Sifrk - apologies for the "tone" of my first post, I was reacting with annoyance more to this topic in general and people's misunderstanding of the basic mechanics of it than anything you said.

No worries! I'm sure we all appreciate it when the more knowledgeable guys set us straight.

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