Gps

thefatfj, Jan 18, 5:56pm
i have a 1963 ej holden, 192 supra 5 speed 3.08 diff gears, on the m/w i cruise at about 55 mph my speedos in mph,i got a speeding ticket for 113 ks i no i was doin about 55mph,i dont speed as a rule,however,cant find correct speedo corerction info, someone suggestd the best op would be a gps, i no nothing about them, i would only want one that i could use for basically a more accurate speedo , can anyone help with info on wat i would need,dont want to spend heaps so a good secondhand one will do, cheers n thanks,
mrfxit, Jan 18, 6:14pm
There are several apps for smart ph's that display your road speed in real time via GPS
Mine shows a std analog speedo + a digital readout.

Straight road & clear day is best for consistent readings plus a passenger to read the screen.

Presuming it is out by that percentage, You also NEED to get the speedo corrected by an instrument shop because this will be a wof fail if noticed by the inspector & a possible insurance fail on an accident claim if they notice because of suspected excess speed.

Best to get it corrected asap
cjdnzl, Jan 18, 10:50pm
55 miles per hour equates to 88 kilometers per hour, so nowhere near 115 k's. Suspect your speedo reading low - but indicated 88 actually being 115 is an error of 30.6%, most probably unlikely. A gps or smartphone will give you an accurate speed indication on a straight and level road.
But if your speedo is that far out I would get it repaired.
mrfxit, Jan 18, 11:02pm
Might be able to fix most of the speedo error with a different speedo drive in the gearbox.
cjdnzl, Jan 18, 11:27pm
That'll stuff up the odometer.
loose.unit8, Jan 18, 11:31pm
Assuming the odo isn't as stuffed up as the speedo?
smac, Jan 18, 11:37pm
An old car will have both speedo and odo running from same cable, so if speedo is out so is odo. First drop is get error verified - 30% is entirely possible with mismatched parts. My mini used to read 80mph at 100kph. Kinda cool watching the speedo climb so fast ;)
gmphil, Jan 19, 12:08am
yup I believe u find when this conversion was done a cable was made to work. and was not calibrated . could possibly be as easy as change the cog in box most make have variety of different colours witch represent different amount of teeth .if u look at a speedo with both kms and miles u will see 100kmh is 60 miles hour roughly, get a felt and drawn on dail help u remember
sr2, Jan 19, 1:05am
Yes the speedo needs recalibrating (I use Auckland Speedometer Services) but I'm interested in your case history re the insurance issues!
mrfxit, Jan 19, 1:05am
100kph = 62mph
mrfxit, Jan 19, 1:09am
No case historys but simply presumption based on the fact that insurance will take anything they can to get out of a claim & if thats a case of proven that you were exceeding that specific speed limit which contributed or caused the crash AND they could prove you knew about it, then yea . buggers (recent speeding tickets would be 1 way to prove you knew about the error)
mrfxit, Jan 19, 1:10am
Won't matter on a petrol motor
smac, Jan 19, 1:12am
Well no, it just says you were speeding. Can't quite follow the dot joining here.
mrfxit, Jan 19, 1:14am
Deliberate excess speed causing an accident.

Eg:. >
But the driver said the speedo only read 100kph BUT it was proven he knew the road speed was 120kph which was what caused the car to crash.
sr2, Jan 19, 3:18am
A bit of a stretch of the imagination to me but we both agree on the need to get the speedo recalibrated.
daryl14, Jan 19, 4:04am
You can get wee speedo cable adaptors that change the ratio. I seen one in my mates shed. you just need the right ratio. But yeah, instrument shop is easiest bet.
smac, Jan 19, 4:11am
Still don't follow you.

If you go too fast for conditions and your speed causes a crash, that's one thing. But it's got nothing to do with whether or not you claim you thought your speedo was accurate, because the reading on your speedo has nothing to do with the safe speed to travel at any point in time. There's no such offence as "went over the speed limit and caused an accident". All offences relating to careless/dangerous driving very deliberately have no mention of the speed limit in the regs.
bwg11, Jan 19, 4:43am
Gosh, that takes me back, as well as ratio changers, there were also splitters, one cable to OE speedo and another to rally computer. Think they were made by Halda, but haven't seen one for years. Recalibration would be a better option. Parrot Instruments in Christchurch are good.

OP, it is not surprising your speedo is miles out, the 5 speeder will have an overdriven 5th (about 0.85:1) and the 3.08 diff is a much higher than the original would have been.
mrfxit, Jan 19, 4:51am
I didn't say it was a legal offence, I said it could be a way for insurance to deny your claim. (Eg: knowingly drove to fast for the conditions)
bwg11, Jan 19, 4:57am
Or conversely, a slow speedo could be a defense. Just watching Prime news a few minutes ago a car which wound up in a bedroom was deemed to be doing 100 kph, because that is where the speedo was stuck.
mrfxit, Jan 19, 5:03am
LOL yep it's always possible.
I nearly got stuck with a ticket many years ago for doing 70kph on the Auckland motorway on the middle lane.
Got off it by getting a dyno speedo test done that proved the speedo was screwed
smac, Jan 19, 5:35am
You're still linking the reading on the speedo with a safe speed for the conditions - they're not related.
lookoutas, Aug 3, 4:16am
Digression kicks in as usual.
All the answers have been given.

Recalibration.
Changing drive gears at gearbox. (if available) Look for one with less teeth than your one.
Phone app. (there's a few available)
GPS Nav system.
GPS radar detector. (find a mate who has either one, if you don't want to buy one)

I use the last option on both my USA cars. In fact, I wouldn't have a clue where 100KPH reads at what MPH. It's OK to know that and remember or mark where it is, but what about 70, 80, 60? We have to continually deal with those speeds too.
I never go on a trip in any car without it - even in my Subaru.
It's an old unit, so doesn't pick up camera's. But that's not a problem, as it keeps me within the limits by knowing exactly what my speed is.
Always good to pick up plod way down the road - just for the hell of it.

Trouble is - the cruise controller/optional airbag can see the speed too!
Which is not a bad thing either - just consistently annoying.