Speedometer Reading

james · Post by **james** » Mon Sep 25, 2006 8:57 am

I always thought my speedo read a bit low given the amount of people hairing past me through the average speed restricted roadworks near Dundee a while back. My suspicions were confirmed when I had the chance to drive in convoy the other day with car to car mobile phone. The other car being a brand new family hatchback with a digital speedomoter al-la-nightrider

Apparently when my car ready 30 MPH, Im actually doing 24MPH. 70 is really 60 and I have to be showing 80 to be anywhere near a real 70MPH

Is this normal? This may explain the lack of speeding tickets.

PS as far as I know the wheels/tyres are standard.

roadboy · Post by **roadboy** » Mon Sep 25, 2006 9:01 am

I think the Elise speedo is usually a lot more accurate than most other cars.

Cars in general are calibrated to slightly overread.

HTH

Dan@JPS

MacK · Post by **MacK** » Mon Sep 25, 2006 9:21 am

Use a gps handheld to see how accurate the speedo is, the readings you give are similar to my Jeep/gps,i.e reading over, however the Elise is nearly spot-on with the gps.

Post by ed » Mon Sep 25, 2006 10:00 am

james wrote:I always thought my speedo read a bit low given the amount of people hairing past me through the average speed restricted roadworks near Dundee a while back. My suspicions were confirmed when I had the chance to drive in convoy the other day with car to car mobile phone. The other car being a brand new family hatchback with a digital speedomoter al-la-nightrider

Apparently when my car ready 30 MPH, Im actually doing 24MPH. 70 is really 60 and I have to be showing 80 to be anywhere near a real 70MPH

Is this normal? This may explain the lack of speeding tickets.

PS as far as I know the wheels/tyres are standard.

thats definintely not normal. I pretty much ignore my speedo and use my road angel. the reading varies from 3mph out at 30mph to 8mph out at 150mph.

edit: sp

alicrozier · Post by **alicrozier** » Mon Sep 25, 2006 10:50 am

Mine tends to overread most when coming back from the track...

Most accurate coming back from the tyre fitters...

james · Post by **james** » Mon Sep 25, 2006 11:20 am

So if/when I get stopped and the copper asks "do you know what speed you were doing?" I can confidently reply "No"

robin · Post by **robin** » Mon Sep 25, 2006 1:23 pm

james wrote:So if/when I get stopped and the copper asks "do you know what speed you were doing?" I can confidently reply "No"

No, never even jokingly say that! I know it was

but even so ... they can lack a sense of humour - you are required to know what speed you are travelling at (more-or-less).

So the correct conversation is:

"Are you aware what speed you were travelling, sir?"

"Yes"

"Would you mind telling me what speed that was?"

"Yes"

"Would you agree it was in excess of the speed limit?"

"No comment"

In short, you are meant to know, but you don't have to tell them - that's their job to prove ...

I echo the other comments - check it out with a GPS - assuming you have correct wheels/tyres fitted it should read pretty close to correct; if it doesn't you may have damaged the pickup on the rear wheel (very unlikely IMHO) or the sensor gap may be too large (ditto).

Cheers,
Robin

Post by **Shug** » Mon Sep 25, 2006 1:33 pm

I also hear rumour (not sure of the truthfulness) that the S1 was pretty accurate up to ~80, but they changed the S2 to over-read for the same reason most manufacturers have theirs over-read as standard. El's S3 is exactly 4mph out at all speeds (according to Road Angel)

I guess it's safer having the margin of error on the right side of the law in case some clever-dick tried to pass on a speeding conviction due to faulty calibration of the car's speedo (although it's legally your responsibility, etc etc....)

james · Post by **james** » Mon Sep 25, 2006 3:09 pm

robin wrote:
james wrote:So if/when I get stopped and the copper asks "do you know what speed you were doing?" I can confidently reply "No"
No, never even jokingly say that! I know it was but even so ... they can lack a sense of humour - you are required to know what speed you are travelling at (more-or-less).

So the correct conversation is:

"Are you aware what speed you were travelling, sir?"

"Yes"

"Would you mind telling me what speed that was?"

"Yes"

"Would you agree it was in excess of the speed limit?"

"No comment"

In short, you are meant to know, but you don't have to tell them - that's their job to prove ...

I echo the other comments - check it out with a GPS - assuming you have correct wheels/tyres fitted it should read pretty close to correct; if it doesn't you may have damaged the pickup on the rear wheel (very unlikely IMHO) or the sensor gap may be too large (ditto).

Cheers,
Robin

Its just too far out to be simply an over read. Anyway Im comparing it to another car which I would also presume over reads somewhat. An indicated 30mph really is only 24Mph is just TOO far out.

And I thought people were looking at the car as they passed. Got overtaken by a Punto 1.2 with baby on board today on the M8, I was doing "80Mph"

Andy G · Post by **Andy G** » Mon Sep 25, 2006 3:27 pm

my gps indicates that the speedo over-reads by about 8tuts at an indicated 100 tuts, 110 tuts is roughly 100 real tuts, if that makes sense

McKeanne's S1 is pretty accurate though speedo wise, compared to my 111r.

MacK · Post by **MacK** » Mon Sep 25, 2006 4:35 pm

james wrote: Got overtaken by a Punto 1.2 with baby on board today on the M8, I was doing "80Mph"

Sit behind a lorry at 55 mph or whatever they are limited too, and see what speed you're indicating..

Or drive through Wilkieston on the A71 towards Edinburgh, there is a sign there that flashes up your speed. In my Elise it is near enough what is indicated on my speedo, i.e. 29 mph

mckeann · Post by **mckeann** » Mon Sep 25, 2006 5:00 pm

Andy G wrote:my gps indicates that the speedo over-reads by about 8tuts at an indicated 100 tuts, 110 tuts is roughly 100 real tuts, if that makes sense

McKeanne's S1 is pretty accurate though speedo wise, compared to my 111r.

yeah, we only worked it out after andy was matching my speeds at the end of the straight at cadwell, even when i was pulling away. That also explains why he was able to keep up through thr high speed bend.

Andy G · Post by **Andy G** » Mon Sep 25, 2006 6:00 pm

mckeann wrote:
Andy G wrote:my gps indicates that the speedo over-reads by about 8tuts at an indicated 100 tuts, 110 tuts is roughly 100 real tuts, if that makes sense

McKeanne's S1 is pretty accurate though speedo wise, compared to my 111r.

yeah, we only worked it out after andy was matching my speeds at the end of the straight at cadwell, even when i was pulling away. That also explains why he was able to keep up through thr high speed bend.

that and the fact you thought we weren't being too bad on the motorways

The_Rossatron · Post by **The_Rossatron** » Mon Sep 25, 2006 6:12 pm

My speedo was about spot on +/- 1mph on GPS

james · Post by **james** » Wed Sep 27, 2006 4:53 pm

Ok, so either my car or the wifes is massively out.

Thinking about it, I measured the tyre pressures. They are 19.5psi front and 21 rear. Sounded ok to me at first until I checked with the old posts on tyre pressure and now it sounds like they are WAY under inflated. BTW this is how they came when I bought the car.

So which pressure is best for std bridgestones? Theres a lot of conflicting posts on this subject.

Sorry to be such as pain, but I guess this is another item under the "sorting niggles after initial purchase" heading.

Scottish Elises

Speedometer Reading

Speedometer Reading

Re: Speedometer Reading