Speedometer Off A Couple MPH's?

[DressedInBlack]

I noticed in my '08 Base model that the speedo was off about +2mph. I timed the miles traveled having the cruise set to 60 and the timing was slow. i also found the same difference with 2 separate GPS units (phone and Garmin), my sister in her car with cruise set to a certain speed, and those silly "you are going too fast" radar detectors that display your speed in an attempt to get drivers to slow down. in each of my highly scientific tests, the result was around the same...+2 on the speedo. it didn't bother me much, i just found it curious.its a different story with my '09 GT. my GPS said i was doing 70 but my speedometer said 74. same result with my phone's GPS feature. and a close result with the aforementioned speed display sign (it had the difference at +3 for my speedo). i wasn't able to do the distance/time test because i didn't have mile markers to go by. has anyone else noticed this anomaly or do you guys think I'm just plain nuts?my main concern is if my speedometer is indeed reading "fast", i will be racking up more miles than the actual which means my warranty will expire prematurely.

[morbay]

Quote, originally posted by DressedInBlack »has anyone else noticed this anomaly or do you guys think I'm just plain nuts? My 09 is off by 2 mph, I think others may have the same issue too. So I don't think it's just you.

[ponta2147]

I think they're off on purpose... I've heard of a lot of cars "overestimating" slightly on higher speeds for safety reasons (to make you think you're going faster than you are).Mine is also off by 2mph

[areles]

My '09 is off by +4 mph throughout it range.

[bodhi_tree777]

My 03 GT has me going about 4-5 mph faster than I actually am. I've read it can be due to wheel size. I have 16's on now, but I wonder if I went up to 17's (which I think the GT came with stock, I could be wrong there) it would be more accurate?

[ou.grizzly]

Quote, originally posted by bodhi_tree777 »My 03 GT has me going about 4-5 mph faster than I actually am. I've read it can be due to wheel size. I have 16's on now, but I wonder if I went up to 17's (which I think the GT came with stock, I could be wrong there) it would be more accurate?17" wheels were an option for GT, never standard. 16" Alum were standard. In 2003, you were unable to get the 17" rims and sunroof together.

[09vGT]

My '09 GT is around 4-5 MPH.. Compared with GPS and once had someones else read off their speedo compared to mine.. Glad others have this problem..

[SlammedNiss]

Quote, originally posted by areles »My '09 is off by +4 mph throughout it range.I somehow doubt that. If that were true, when you were barely moving it would show 4MPH. If it were off by +4MPH at 60MPH, then the slower you go the less off it will be. Just like the faster you go the more it will be off. The cars are calibrated at the factory and all that can change when you get new wheels/tires. The smaller the diameter of your wheel/tire combo from factory will throw off the speedo by showing you going faster, because the tires are rotating more times to get the same distance. Even hen your tires have lost 1/4" tread from everyday driving, that will eventually throw the speedo off a little.

[dayday]

I noticed the same thing with mine the other day while using my GPS. From past experience in my Grand Prix's and using tuning/scanning hardware, the problem comes when the digital/sensor signal is displayed by the analog/needle instrument. So in those cases my scanner was reading correctly while the needle was over by a couple mph. If this is the case the odometer is accurate since it gets it's info from the correct digital signal.

[03VibeOttawa]

With my 17s on, my speedo is low by 4% throughout the entire range. I'm going to try and remember to check what it's like with my stock steelies this and snows on this winter.

[GMJAP]

My 05 is about 2 MPH high, as is our 04 Camry. I'm sure speedo accuracy is only so good from the factory and may "settle" 1-2 MPH one way or the other after it leaves the assembly line. It's likely they don't want it ever to show slower than actual speed (could lead to lawsuits in case of tickets or accidents) so they set it a bit high, the idea being "worst case" after settling it'll never be lower than the actual speed.In fact I think there is an EU law that a speedometer can never read lower than the actual speed.

[DressedInBlack]

well im glad to know im not the only one seeing this. on the flip side, im not to happy knowing im not the only one seeing this...lol. our cars dont have as many miles on them as we think. i suppose it wouldnt matter so much if we had our cars for a short while...but after 5, 7, or 10 years, those false miles would have added up big time.at first, i didn't trust the GPS's readings. after seeing the same on my phone's GPS program, it got me suspicious. thats when i did all of the other tests. i could live with +1 or +2 but a 4 is too much for me.the whole situation seems kinda bunk. id like to have mine adjusted just because im a stickler for things like that. anyone know how to make such adjustments?

[dayday]

The odometer reads the computer signal, which is most likely correct, not the MPH shown by the needle. Your odometer is most likely the correct miles driven.

[DressedInBlack]

im not saying you are wrong, but, i dont think that is accurate either. going by the mile markers on the highway, my odometer was off as well. a few 10ths after a few miles.

[moonstonemike]

Mine is off by the same amount at 100km it reads 102. But when i have my snow tires on which are 205/60/16 it reads right on. When my summers are done, i will probably by a tire as close to the height of my snows as possible

[star_deceiver]

The speedo says 120km/h while the GPS says 118.

[VforVIBE]

Quote, originally posted by 09vGT »My '09 GT is around 4-5 MPH.. Same here.

[j42.snyder]

Funny how our Canadian spec cars seem to be more accurate. Mine is also only out by about 2km/h - which is just over 1mph. GPS says 100 when the speedo is reading 102.I've heard that legally they can't be allowed to read "low" - so some inaccuracy is probably designed in to allow for variances in tire sizes. More than 2mph seems a little excessive to me though.

[star_deceiver]

Quote, originally posted by j42.snyder »Funny how our Canadian spec cars seem to be more accurate. Mine is also only out by about 2km/h - which is just over 1mph. GPS says 100 when the speedo is reading 102.My RS-A's are almost at the wear bars (snow can't come soon enough so I can get rid of these damned things) so I'm sure that makes a small difference at speed. It could just be the placement of the needle on the speedo!

[lowincash]

My 09 GT is off by about 4mph but after getting some wider tires it's only off by 3mph now.

[djkeev]

Shy of having your speedometer based off of a constant GPS, there is NO WAY your speedometer will always be correct. It is based ultimately upon tire rotation and counting the rotation and converting it to MPH. As mentioned, a new tire which is larger due to new rubber will spin fewer times than a worn tire will running the same distance. Know what your's is off and drive accordingly. I would hazard a guess that every non GPS speedo made is off a little bit and that amount off will vary with tire wear and even tire inflation.My 95 Toyota Pickup is off almost 5 mph. I like it, I know I'm not speeding yet my speedo tells me that I am! Psychological games I know but it works for me!! Not really to different than setting you clock a few minutes fast to make it out of the house on time. Dave

[futureviber]

My husband always thinks I am driving so slow when he's following me. he actually "yelled" at me one time when he followed me cause he thought I drove 50 the whole way. The place was about an hour away and I had to drop my car off there for something. But while my car said 60mph - 65mph his was saying 50-55mph. He said I either drive slow or my speedo is off.I followed a friend home from work about a week later and asked her how fast she was going She told me 60 and my car showed 60 - comparing my car speedo to my gps it does show that I'm going slightly slower than my speedo says. My hubbys car is off too I just havn't had the gps in the car with me to show him.

[jake75]

What I find interesting, is that my 09 Vibe, like most other cars.over reads mph. So when my speedo says 70 mph I am actually at about 68 mph. Yet, the speedo under reports miles. By the highway mile markers I have actually traveled about 102 miles for every 100 miles shown on the odometer.

[ou.grizzly]

Quote, originally posted by djkeev »Shy of having your speedometer based off of a constant GPS, there is NO WAY your speedometer will always be correct. It is based ultimately upon tire rotation and counting the rotation and converting it to MPH. As mentioned, a new tire which is larger due to new rubber will spin fewer times than a worn tire will running the same distance. Know what your's is off and drive accordingly. I would hazard a guess that every non GPS speedo made is off a little bit and that amount off will vary with tire wear and even tire inflation.My 95 Toyota Pickup is off almost 5 mph. I like it, I know I'm not speeding yet my speedo tells me that I am! Psychological games I know but it works for me!! Not really to different than setting you clock a few minutes fast to make it out of the house on time. DaveWhat Toyo Truck? 22.RE, 3.0, or 3.4? Different size tires than stock?

[vibenvy]

I have noticed when passing speed signs, that the speedometer on my '09 GT is off by a couple miles per hour. I thought it was odd, but never really paid too much attention to it.

[djkeev]

Quote, originally posted by ou.grizzly »What Toyo Truck? 22.RE, 3.0, or 3.4? Different size tires than stock? 3.0, 4x4, 5 spd, extended cab, 225/75R 15 stock sized tires on stock alloy rims.BTW this unit only has 65,000 miles on it! That is 4, 318 miles per year!! This is actual mileage, no games. It gets used every day but only for a few miles at a time, rarely a long trip out of town or out of the county.Dave

[Kincaid]

I recently checked the speedometer on my '09 with 17" wheels against a friend's GPS - at an indicated 60 mph we were actually going 57 mph.

[Old Tele man]

...the week after we bought our 2009 Vibe 1.8L/auto, took it down and had the speedometer checked at the shop that also "calibrates" the AZ Highway Patrol vehicles....they said, it was "...low by a consistent 2 mph..." from 30 mph all the way up to 80 mph....and the MPH readings on our ScanGauge-II seem to corroborate their statement--consistently 2 mph low.

[jgvibe]

MY 03 AWD Vibe is off too. Before getting a gps, whenever I got zapped by one of those radar units which show you how fast your going, I always got zapped doing 2 under what my speedometer said. After getting a GPS it would say my speed way 2 MPH slower than what my speedometer said doing 55 and 4 under doing 70.I have used my GPS in a 2000 grand marquise and a 2005 town and country. In those cars the GPS reads same as speedometer, so Vibe is off!

[houseofbugs]

Yeah mine is off by 2 MPH too. I thought it was from when I changed the LED's on my Cluster. Glad to hear its not just me.

[jake75]

Way back in this thread is my observation that the speedo undereads by about 2 mph, and odometer on my '09 also undereads by about that same amount. I only rack up 100 miles for every 102 miles I travel. At one time I thought that was inconsistent - perhaps it is not.Anyway, for those who will diver more than 36,000 miles in 3 years that gives you a 2% leeway. You can take your Vibe in for warranty repair at 35,999 miles whereas the actual mileage is really 36,719. The other thing is that any mpg that you calculate is 2% less than the real mpg.

[wingman7000]

The speedo in my 03 GT was about 1-1.5 mph too slow. My gps showed I was doing 61-62 when the speedo showed 60. This was on 215/50/17 tires. I just changed the tires and got a 225/50/17 and now my speedo is about 3+ mph too slow. Hope it doesn't screw anything up.

[Vinlandr]

Radius or diameter of wheel affects the speedometer.Its important to respect the original radius when changing wheel by choosing the right sidewall/wheel radius size for tire.I read on some other thread that someone changed his tires and got higher sidewall on is 17 inches instead of lowering the car to hide the gap between wheel and well... not suggested even if more comfortable. This way one get lower reading of speedometer and must always think to speed down a bit.I got a friend who's mother's car was on overall smaller radius wheel and she was having faster speedometer reading but also a faster warranty end too...

[Kincaid]

The reason may simply be in cost savings during mfg of the vehicle. If NUMMI didn't stock more than one part or didn't recalibrate for optional wheels, the speedos will be off on some vehicles - there is quite a difference in overall diameter from model to model.The stock wheel/tire combo for the Vibe is 205/55-16 according to this tire calculator:http://www.1010tires.com/TireS...ubmitThe optional tire/wheel for the base Vibe is 215/45-17 and the GT has the 215/45-18.So, respectively, the 205/55-16, the 215/45-17 and the 215/45-18 would have:Overall diameters of 631.69 mm, 625.09 mm and 650.49 mm.Overall diameter differences from stock would be 1.05% for the optional wheel and 2.89% for the GT.If the optional wheel was put onto a base Vibe the speedo would read 60.6 mph at an indicated 60 mph and if the GT wheel was put onto a base Vibe the speedo would read 58.2 mph at an indicated 60 mph.

[MotoAce51]

My 04 is off by about 2mph as well. It annoys the hell out of me...

[LarryKingsShoes]

I've been curious about the accuracy of my speedometer since I bought the car a couple of weeks ago. It never felt like I was actually going as fast as the speedometer said. It didn't even occur to me to use my GPS to compare speed readouts. I'm charging my TomTom right now so I can do some tests tomorrow and see what the difference is between the two.It seems that a discrepancy of about 2 MPH is pretty common. Hopefully mine is only off by that amount instead of something much larger. I guess I'll find out in the morning!

[star_deceiver]

With my 205-50-17 summer tires, the speed sign yesterday read 111km/h while the speeometer read 109km/h.My winter tires were dead on with the same speed sign.

[MotoAce51]

Wouldn't the spedo reading 2mph higher make your ODO spin quicker as well? So your overall mileage is off....

[LarryKingsShoes]

Earlier in the thread dayday mentioned that his needle was off in one of his other cars but the scanner he was using would match the GPS speed readout. It seems that the computer has an accurate idea of what speed you're traveling at but the problem is with the needle representation. In that case, one can hope that the odometer is rolling with the more accurate computer signal. I'm not certain about this claim but it does seem to make sense. I haven't used a scanner to actually compare the two.Then again, another user mentioned that his odometer was slightly off when going down the highway and watching the mile markers. Maybe someone else can shed more light on the subject. I'd also be interested in hearing more about this issue.

[musicmanmu]

Yep, mine's slow by 2-3 MPH as well, according to my GPS.

[808 Vibes]

MusicMan! I was just thinking the other day we haven't seen that sexay BLUE Pontiac Performance Magazine feature car in awhile.