cruzdreamer

My husband seems to think my speedometer is way off. We were doing 90 mph and people were flying past us on the tollway? Could they all be doing over 90mph? Do these types tend to have problems? I am not sure.....the car is so smooth that way. I have different tires on ......little smaller...but wouldn't that only affect it my 1 or 2 mph? What do you think? I mean he thought it was at least 10-20 mph off!

RX8FanMan

wierd, the other day i was goin 50 in a 25 and i didnt even notice it til my radar detector went off.

Aratinga

There was another thread recently where speedo accuracy was discussed. Those of us with GPS pretty much agree that the 8's speedo is about 3% optimistic; i.e., when my speedo says I'm doing 70mph, the GPS says I'm doing 68.

If your winter wheel/tire diameter is slightly smaller than the summer set, that will introduce some additional error; so let's guess your speedo is about 5% optimistic. That means that if it's reading 90mph, your actual speed is still 85.5mph.

Not nearly the 10mph error your hubby's thinking. Just tell him to keep driving 90mph and some kind officer will certainly offer him a radar-calibrated speed measurement soon enough. Please let us know the result!

zoom44

did you accidentally switch the speedo to metric?

bon911

I think your speedo is set for metric.
The very first day I had that thing metric and was freaking out.

Texas 8

I switched it the other day to mess with my wife :D She leaned over and looked at the speed. 130'ish (km of course). Shoulder is healing nicely, thank you very much

G8rboy

Well, if you're sure you were in MPH mode, than it is worth noting your speedo is likely 7-9% off with the winter tires (4% for the tires, 3-5% for the fact that our speedos run quite a bit faster than you're really going. That would equate to an average fast reading of 7mph- enough to be noticeable, but on that big of a scale.

A few weeks ago I was playing around with the hidden menu in the NAV system that displayed GPS tracked speed (in KmHr) and was surprised that the speedo ran that much faster. If it helps keep the tickets down, then all the better : )

-Sean

cruzdreamer

I will check my speedo.......I am not sure how to switch it(metric/english)....guess that's what the manual is for! Maybe with it being a little off with the tires and all is enough to notice. Also, maybe we have some big time speeders on the tollway....but when some cheesy cars were passing us and we were doing 90mph I wondered about the speedo. Thanks gang for your input. I have a state trooper as a neighbor.....maybe I can have him point the radar gun at me for a test!!

AF-RX8

LOL . . . that's a good one . . . :D

glide

Where on the gps menue can you display ground speed?

G8rboy

It's the black push-button post on the left side of your gauge cluster (on the other side of the one that resets your trip-meter). I wigged out my mother in law on the way to O'Hare- was doing an indicated 155Km/hr briefly

If the tollway you're talking about it is I90, I have noticed that in non-rush hour that left lane really moves, like 90mph avg. I have trouble staying in that lane for fear of a ticket. Definitely ask your neighbor to gun you- that would be a fun test : )

-Sean

Mat

To check your speed:

- Go on the highway (preferably when it's non crowded)
- Put the cruise control at 60 flat
- Using the "current trip", calculate the number of seconds it took to make exactly 1 mile.

Of course it should be 60 seconds. If you got more than 60 seconds, then your speedo is fast (meaning you're going at less than 60), and if you get less than 60 seconds, your speedo is slow (watch out for troopers).

With this technique, you cannot figure out if you're in mph or kph though. But running at 60km/h on a state highway... well... you'll certainly KNOW it (you'll be passing absolutely no one, and people will keep high beaming you.)

dag

I love speeding on I-90. I used to visit the Chicago area sporadically and I would get a rental to beat on. Best one was an Eclipse Spyder - nice to have the top down.

Only Interstate that I have seen that I can speed on better was I-95 through MD.

dag

Boozehound

So where's the hidden nav menu? I'm itchin' to see what I can get at... (now only if I had my car back)

cruzdreamer

Ok Mat I will have to try that. Sean....yes, it was I90 as a matter fact...was heading out to the auto show. BTW, I loved the Acura TL, The Mazda 6 (hatchback version not wagon) and the 2005 Ford Mustang....the rest were just ok. GTO exterior is very bland...it's a shame! Looks like a Grand Am. The Pontiac Solstice was nice. RX 8 still ruled the whole bunch!! Will talk to my State Trooper neighbor tomorrow night......he's coming over for our monthly neighbor game night!!

G8rboy

Here's how to get to the main hidden menu- the screen that I found with GPS calculated speed is buried as a sub-screen off of one of those main hidden screens. Keep in mind that there's another screen that looks like it has speed, but it never updates (always indicates 0)... the one I'm talking about is different and does work. I'll play with it later and document how to find it again...

1. Open the menu
2. Choose "setup menu"
3. Choose "system information"
4. Choose "version"
5. Push the joystick forward 3 times
6. Push the joystick rearward 3 times
7. Push the joystick forward 2 times
8. Hidden Menu appears

Disclaimer- there are things in this menu that might screw your NAV system up, and so play around at your own risk : )

zoom44

that's a little too much time spent alone in the car playing with the joystick if you ask me!

f1michel

90 KPH is WAY WAY slower then 90 MPH so i'm sure you weren't mistakinly(sp) in metric. easy way to figure it out is 100kph equals 60mph (just about) . Oh and to swith from kph to mph and vice versa just push and hold the thing on the left of the dash.

Boozehound

Thanks for the info! As soon as I get my car back, I'll be all over those menus.

BTW - How did you find out about those menus?

G8rboy

I've been married for over 12 years- I'm allowed to spend time alone in my car playing with my joystick, thank you very much!


BTW- this info is available in several threads on the forum- one of them is titled 'Nav system FAQ' or something along those lines.