Speedo accuracy

[Anonymous]

I'm new, please be nice....

I was wondering if anyone has an indication of the accuracy of the speedometer on their 2 at high speeds. Also what speeds have people seen on the clock (at track days and airfields of course). I'm presuming those with lots of performance mods will have clocks with a much higher limit than my standard paltry 140mph!

My 2 is standard and I've had 128 showing before having to brake at the end of the "runway". I know roadsters aren't really about top speed, but you have to see what it'll do don't you?!   s:D s:D

[GSB]

90mph on the speedo equates to about 86-87mph on the GPS.

[kanujunkie]

yep same here 90mph on dial 85 on GPS

[SimonC_Here]

A very old thread! MPH has the record I think!

http://www.mr2roc.org/phpBB2/viewtopic.php?t=1676&highlight=autobahn+adam

Simon

[Slacey]

At anything over 30mph mine over-reads by 5mph.

[Anonymous]

100 on the speedo is 92 on the road angel

[proeliator2001]

With standard tyres this is by far the most accurate car I have ever had - 90 on the speedo equals around 87 on the GPS.

[MikeB]

Hi, I have just put our UK model MR-2 back on the road after 2 & 1/2 years off the road & I have found the speedometer over reads by about 20%. When it says 30 we are actually doing about 23mph on a GPS. With GPS showing 30mph car shows about 36/7mph. Car is a 5 speed 2000 model year and has new standard size wheels & tyres on it. No warning lights on and no faults showing in engine management system. I know accuracy of speedometers is usually anything up to 10% margin of error but 20% seems a bit high.

Has anyone had any similar issues or identified a cause?

[Chilli Girl]

Both my 2's read abt 10%. Needle reads 30mph but actually car is moving at 27mph. I tend to p#ss alot of people off in 30mph limits. Sorry, cant help you with yours. Sure someone will come along soon & help.

[MikeB]

Thanks for your reply, I realised there was an issue when cars kept coming so close behind and trying to push me along when I thought I was already going over the limit, realise now I was well under. I will see what response I get and ask around if settings can be changed, some posts seem to think the settings for tyre size may have been changed in the past if the car has had different wheels on at some time.

I'd be surprised if it has lost configuration by having had no power to it for 2 years as even the trip counter kept both Trip A Trip B settings in that time.

[Ardent]

Hi, I have just put our UK model MR-2 back on the road after 2 & 1/2 years off the road & I have found the speedometer over reads by about 20%. When it says 30 we are actually doing about 23mph on a GPS. With GPS showing 30mph car shows about 36/7mph. Car is a 5 speed 2000 model year and has new standard size wheels & tyres on it. No warning lights on and no faults showing in engine management system. I know accuracy of speedometers is usually anything up to 10% margin of error but 20% seems a bit high.

Has anyone had any similar issues or identified a cause?

Tis a bit excessively out.
Definitely wheels n tyres match the sticker in the glove box?

[m1tch]

Its usually a 10% overreed, was careful to chose the same OEM sized tyres to make sure it wasn't messed up, think the speed is taken from the front left ABS sensor.

[MikeB]

Wheels have been refurbished and new tyres which are standard size matching the ones that came off it. When we bought the car in September 2017 I only drove it about 80 miles before deciding to take it off the road to refurbish it so not sure if the speedometer was like that before or not? I might try and get in touch with the previous owner to see if they had any issues with it.
Although I have had all the suspension out I have not changed any hubs, bearings or wheel speed sensors and the ABS light stays off so cant see it being an issue with any of the wheel speed signals.
Next step is going to be follow it down the road and compare speeds through the ranges and check if it is a set % out compared to another car.

I'll keep you updated of my findings.

[Topdownman]

If you had only just bought it then maybe the error was there before buy you only just noticed it.

If you take the speedo needle off for any reason, it is very hard to get it back in the right place as the natural resting place of the needle is a minus speed but it is held at zero by the stop pin. If you put the needle back on normal side of the stop pin, then it will read fast as it starts at the wrong place. This could easily be 20 mph fast at speed.

It is easy to get to the needles by pulling the instrument cowl forward and then doing the same to the perspex cover. The needle will come off by pulling or using a fork or trim removal tools (take care not to scratch the fascia). Getting it back in the correct place is hard though as you need to put it on something like 3-4 cms from memory the wrong side of the stop pin and then very, very gently, easing it over the stop pin. Check the result against a sat nav to see how you have done (try to see how far in distance you are out then use that  distance beyond the pin as a guide).

I have heard a suggestion to take it off, drive at a steady 30mph (sat nav)  and put it back on at the 30 position. I am not sure how safe that is, but sounds easier if you can find somewhere safe you are happy to do it!

[Ardent]

Talk about everyday being a school day.

[carolineasb]

You said that you swapped the tyres for matching ones that came off but can you confirm what wheels and tyres you have and what age of car you have i.e. PFL or FL?

[Joesson]

@Topdownman
Simon, your post sounds like the voice of experience speaking. I guess you removed the needle when fitting replacement/ snazzy fascia to the dial.
If the OP has snazzy dials that would likely confirm that. If not, why else would the needle have been removed?

[Topdownman]

@Topdownman
Simon, your post sounds like the voice of experience speaking. I guess you removed the needle when fitting replacement/ snazzy fascia to the dial.
If the OP has snazzy dials that would likely confirm that. If not, why else would the needle have been removed?

Yes, I put a new fascia on mine with the small hole option which requires removing all the needles.



This is where the needle naturally comes to rest and you can see the mark I made for reference when refitting it. If you have an aftermarket fascia then this would likely be the culprit. The other not so good reason I can think of is that it could have been removed to fit a lower mileage cluster but I hope its not that!

[Joesson]

Hang on there chaps and chap chapesses, the OP / @Anonymous whose details I reproduce below, said " I'm new, please be nice". But first registered in 2008.
Many have " been nice" , but one brief  response from the OP , but then observe the " Post count"!
That counter is surely overspeeding!!


Posts: 88,275 (20.159 per day)Age:N/A
Date registered: June 9, 2008, 22:01Local Time:June 6, 2020, 11:03

[SV-3]

Hang on there chaps and chap chapesses, the OP / @Anonymous whose details I reproduce below, said " I'm new, please be nice". But first registered in 2008.
Many have " been nice" , but one brief  response from the OP , but then observe the " Post count"!
That counter is surely overspeeding!!


Posts: 88,275 (20.159 per day)Age:N/A
Date registered: June 9, 2008, 22:01Local Time:June 6, 2020, 11:03

In a similar vein, I've been puzzled by the Most Online Ever figure:
687 (Jan 22, 2020, 23:53)

[MikeB]

Isn't it amazing, no matter how many times you check things some basics still get missed!

The car is an early pre-face lift model, built January 2000 & registered March 2000 so should have 185-55-15 on the front (which it has) and 205-50-15 on the rear. I have just checked again and I now see that the rears are actually a 55 profile (205-55-15) I'm not convinced that 5% variation would give me a total of 20% inaccuracy on the speedometer though! Just checked the images I took of the old tyres prior to sending the wheels for refurbishment and new tyres (which I said like for like to supplier!) and the rear ones were originally wrong too so my schoolboy error not checking specification against fitted item. If I had ordered tyres elsewhere or had a quote first I would possibly have ended up with the right ones & not had this problem?

Still going to do some comparison checks with another car later today after my shift working.

Will keep you updated.

[Joesson]

@SV-3
I'd not noticed that, it does seem a very high number to be "on line" at one time.
For certain there are not that many posters/ activists, not to mention non voters!
I did say "not to mention non voters"

Amended / corrected to be NON voters rather than voters .

[Joesson]

Isn't it amazing, no matter how many times you check things some basics still get missed!

The car is an early pre-face lift model, built January 2000 & registered March 2000 so should have 185-55-15 on the front (which it has) and 205-50-15 on the rear. I have just checked again and I now see that the rears are actually a 55 profile (205-55-15) I'm not convinced that 5% variation would give me a total of 20% inaccuracy on the speedometer though! Just checked the images I took of the old tyres prior to sending the wheels for refurbishment and new tyres (which I said like for like to supplier!) and the rear ones were originally wrong too so my schoolboy error not checking specification against fitted item. If I had ordered tyres elsewhere or had a quote first I would possibly have ended up with the right ones & not had this problem?

Still going to do some comparison checks with another car later today after my shift working.

Will keep you updated.

If @m1tch is correct in thinking that the speed sensor is front left then your rear tyre effective diameter should not be affecting the speedo. The plot thickens.

[MikeB]

According to; http://www.autopartuk.com/tyre-calculator/

with that tyre size change this should be the result; Your speedometer will be 3.5% too slow.
When your speedo reads 60 mph, your actual speed will be 62.1 mph

My speedometer reads too fast but then again it is working off combined calculation from all ABS wheel speed signals???

[MikeB]

So,

I managed to check the speed through a variety of speed ranges and the error does seem to be a reasonably consistent variation rather than a % of error.

Having checked with another car following it seems to be somewhere between 7 & 9 MPH high on the MR-2 compared to the other car.
Taking the car on a longer drive and getting it up to higher speeds whilst checking on a GPS speed check, even with the car at 80 MPH on the speedometer the GPS is showing 71 / 72 MPH when held at a constant speed.

Beginning to think that those who suggested needle removal and refitting on the road may be the best fix for this but still considering getting a second hand instrument cluster just to compare it.

Thanks for all your input.