| Author | Message | ||
| Jim E (Jimpo1)
Intermediate Member Username: Jimpo1 Post Number: 1476 Registered: 7-2001 |
My car has a 'peg' at 10mph, so it isn't even possible for it to go below that. | ||
| Chris F. (Chrisfromri)
New member Username: Chrisfromri Post Number: 19 Registered: 1-2003 |
Borrow a handheld GPS and take it with you for a ride on a straight section of unused road. Just set it to read out speed, and then prop it up on top of the dashboard so you can read it, and its antenna can receive GPS signals through the windshield. I found that my 308 QV speedometer (whose needle never goes below about 15 MPH) was very accurate from 20 MPH to 100 MPH. The GPS read that I was actually going 1 MPH less at every 10 MPH increment on the speedometer (e.g.: GPS said 99 MPH when the speedometer said 100 MPH = 1 percent safe side error). IMO, this is very accurate. Kind Regards, Chris | ||
| Mr. Doody (Doody)
Member Username: Doody Post Number: 895 Registered: 11-2001 |
my 355 does this as well. i asked my mechanic about it and he said it's normal and futzing wtih things to try to get 0=0 is asking for trouble. doody. | ||
| EFWUN (Efwun)
Junior Member Username: Efwun Post Number: 250 Registered: 2-2003 |
Very true, Dennis and Ken. Hence the 360 pic with the speedo at 195mph, or the 208mph reading on a topped out 550 at Fort Stockton. | ||
| Dennis (Bighead)
Junior Member Username: Bighead Post Number: 56 Registered: 2-2003 |
I agree with Ken. All the Ferraris I've driven have significant speedometer error (actually, most *cars* have it). For Ferrari, I use a 8-10% error rule. And the faster I go, the greater the error. You can check error using a GPS, radar signs, or mile markers and a stopwatch. Funny enough, the only really accurate speedos I've seen have been the crappy GM digital speedos -- they are almost always dead on. Car & Driver had an article on this, I vaguely recall, where they pointed out that having a speedo that reads LOW is very, very bad, from a regulatory point of view, but having one that's high doesn't break any Federal laws. vty, --Dennis | ||
| John_Miles (John_miles)
New member Username: John_miles Post Number: 45 Registered: 7-2001 |
Ken, are you running undersized (lower-profile than stock) tires by any chance? 10% at 70 MPH is way too much error. Mine is within 1% at 70 MPH -- or at least the odometer is, as determined by the 'speedometer check' signs located up and down I-5. There are also numerous "your speed is xx" signs in the mountain passes that always seem to indicate within 2-3 MPH of my displayed speed, so I don't get the impression I'm off too much. | ||
| John Delvac (Johndelvac)
Member Username: Johndelvac Post Number: 277 Registered: 11-2001 |
So you can show a parking-cop that the car is only going 10MPH standing still instead of the 85mph it appears to be doing. HA! | ||
| ken rentiers (Rentiers)
Junior Member Username: Rentiers Post Number: 185 Registered: 2-2003 |
>*Not that it does all that well at other speeds anyway...... No kidding. it's useful to take your GPS and determine speedo error. Putting tiny white marks on the face for (eg) 70 mph you may find you can go quite a bit faster without worrying about the speed limits than you thought. My 328 reads 10% over. At an indicated 70 I'm really only doing 63. If the speed limit is 70, and the cops allow you 10 over, then travelling 79 mph is an indicated 87. Put a mark on the speedo at 87 - anything over is PAY ATTENTION territory.  | ||
| Mitch Alsup (Mitch_alsup)
Member Username: Mitch_alsup Post Number: 408 Registered: 4-2002 |
Ok--here's why. The spedometer is a damped oscilator that gets kicked every so often by magnets rotating with the input shaft. Above a certain speed, the number of magnet kicks per second is greater than the lowest frequency at which the damping works well. Under this speed, the needle will bounce up with the magnet and fall down to zero between kicks. That speed is around 10 MPH. So, in effect, the speedometer does not produce accurate and reliable* indication of speed under the lowest damped frequency. *Not that it does all that well at other speeds anyway...... | ||
| Taek-Ho Kwon (Stickanddice)
Junior Member Username: Stickanddice Post Number: 209 Registered: 11-2002 |
The Lamborghini 350 GT is the same way. Well...they all do look fast even when standing still...  | ||
| Mike Procopio (Pupz308)
Junior Member Username: Pupz308 Post Number: 186 Registered: 10-2002 |
I agree that it is the case--same behavior on my 78 308. I definitely don't think that it's a quality issue--I believe it's definitely by design, or accidently by design and came to be a preference or distinguishing characteristic. It's also probably more of a gauge manufacturer thing than a Ferrari thing. Somewhere, at Veglia, some engineer knows that it reads 10mph with no signal, and knows why it does and the justification (from Veglia's perspective, anyway) of keeping it that way. I can't really speculate as to what could be the technical basis and reasoning for this--anybody? | ||
| Ghostrider (Threefivefive)
Junior Member Username: Threefivefive Post Number: 95 Registered: 8-2002 |
Hey guys, Did some searching yesterday to figure out why the majority of F-Car speedometers (and often tach gauges) stay at 10mph (ie, above zero) when the car is at a standstill. Found a lot of threads where people agree that they do, and also that the speedometer and odometer are housed in the same box, but not connected... But no clear explanations as to WHY the speedometer stays at 10mph and not 0mph at a standstill. Is this just a quality issue? Does Ferrari do this on purpose? Keen on hearing people's thoughts and settling this issue once and for all. Regards. |