Conference terri::cars_uk

    Just to resurrect a very old note...
    
    does anyone know the current law regarding speedo accuracy? My
    new Cavalier 2.0i LS over-reads by approx. 13%; a new speedo
    installed by the garage also over-reads by 13%.
    
    The garage is saying that "Vauxhalls are always a little generous
    on their speedo's", and Vauxhall are saying the car is within
    tolerances of +10% + 3mph, so at 70 mph it is OK for the speedo 
    to read 80.
    
    So, is the legal toleance 10%, or is it "10% + 3mph"?
    
    Peter.
    

    My understanding was that it was 10% + 2� mph plus, zero minus.  I
    thought optimistic speedos were more the province of Ford...
    
    Richard

My understanding (which is probably very out of date) is that the speedo must
read plus or minus 10% at 30 mph (no other speed was mentioned at the time).

This makes yours legal (but rather poor on a new instrument)

Dave

Peter,
	My Cavalier suffers from the same problem ( Vauxhalls 2 Ford 1 ). I
was told the same as you, and as mine was within these limits.

If you drive to the speedo, then all Deccies will have to allow a bit more
time for customer visits, I bet they never took this into account with the
changes in car scheme ;-)

    This is a typical example of regress  or backwards progress.
    
    On a recent run my dad rode his 1924 Raleigh motorbike with a Smiths
    speedometer. He went up the A5 to Holyhead, calibrated the odometer at a 
    milestone, and 63 miles later, at a milestone in Anglesey, it was spot
    on.
    
    I have yet to find a modern car speedo that could match the accuracy of
    the vintage ones.   
    
    Huw.

    
    How do you know your speedo's inaccurate?
    
    Mark

    re .7;
    
    s'funny that, but the mileometer is spot on. It's just the 
    speedo that seems to live on another planet.
    
    Or maybe it's designed that way, so that when I'm cruising at
    an indicated 75 mph, I think I'm getting good ecomony - especially as
    I'm only doing 65 mph at the time.
    
    So - does anyone *know* the answer as the legal tolerance of a speedo?
    
    Peter.
    

    RE: .8
    
    Here in Yurrup, we have marker posts at the side of the road, every
    100metres. With the aid of a stopwatch and a co-operative passenger,
    it's easy to check the speedo by timing oneself across the measured
    distances.
    
    Laurie.

Mark,
	You just know when you speedo is out, i.e when you are clocking 70 and 
everyone is overtaking you on the M4. Clocking 90 and you are just keeping up
with the flow. I also got the garage to check it out, and they gave me the
speedo reading for 50,60,70 & 80

    Making a speedo that is deadly accurate at all speeds is not
    impossible.  The exaggeration is deliberate.  I noticed a quite marked
    difference some years ago, when I "moved up" from a Golf to a Ford
    Escort....
    
    Richard
    

    < Note 634.12 by PEKING::SMITHRW "Off-duty Rab C Nesbit stunt double" >
    
    >Making a speedo that is deadly accurate at all speeds is not 
    >impossible.  The exaggeration is deliberate.  I noticed a quite marked
    >difference some years ago, when I "moved up" from a Golf to a Ford
    >Escort....
    
    I read an article on the Jag XJ220 a few months back when they were
    doing speed trials with Martin Brundle at the wheel. Tests showed using
    a telemetry device that when the speedo indicate 200 MPH they were
    doing a true speed of just over 199 mph.
    
    Pretty accurate I'd say.
    
    POL. (who has had over 145 MPH showing on his speedo when the max
    listed speed is 137)

Well if the speedo can be consistently 10% out, then it
can't be that difficult to make it accurate. I agree
that the inaccuracy is most likely deliberate.

Both my R5GTT's and my Clio are just about spot on speed wise.

All Cavaliers I've seen read about 85 for a real 70mph.

Mark.

    
    Tested it with Citroen ZX. When reading 100 km/h, really driving
    98 km/h. Tyres are 14" 175 65 Michelin MXT.
    
    
    Hannu

	Re .8

	On motorways and dual-carriage ways there are measured miles
	marked out with yellow and red disks.

	all yellow     -  start
	� red � yellow -  � mile
	� red � yellow -  � mile
	� red � yellow -  � mile
	all red        -  1 mile

	Measuring the time over this mile at 60 mph makes the maths
	easy but would make you a mobile chicane, as you're real speed
	is likely to be < 60. :-)

	Graham

	P.S. for the Reading locals there are meassured miles on both
	     carriage ways of the M4 between J11 and J12, and also on
	     the dual-carriage way section of the A33 south of M4 J11.

    re: .17
    
    Yes, but would I block up the traffic if I did a standing start?  And
    would the braking 'chute confuse the HGV drivers?
    
    Richard

	Whilst travelling at an indicated 80mph on the motorway, I reset the 
average speed on the trip computer. The results weren't too surprising,
the computer came back with 75mph. I tried it again over various speeds and up
to 35mph its spot on and gradually gets worse to a peak of 7mph fast.

	Dont know how accurate the computer is, my guess is probably more 
accurate than the speedo. Incidently, I checked the tyre pressures before the 
journey.

	I'll try the marker posts, the trip computer has a stop watch - I'm just 
a bit dubious about the accuracy of my starting/stopping the stop watch...

Andy

After several discussions with Vauxhall, and having the cavalier put onto
a certified rolling road, I have now given up.

Vauxhall is not prepared to do anything; their view is that the car complies
with legislation. The rolling road confirmed the speedo overreads by between
10% and 14%, but it is within the legal limit of +10% +4kmh.

Digital is not prepared to do anything either. 

So, I have accepted that Vauxhall deliberatly calibrate their speedo's to
over-read by about 10%. Please bear this in mind when planning long journeys,
and calculating economy figures.

Maybe this sums up the modern Digital, which perfers to do monopoly supplier
deals with companies who deliberatly act in border line illegal ways
(e.g. British Airways, Vauxhall.)

Peter.

Its also one way of providing a feeling of 'quality' in a car.

"See how quiet my new Vauxhall is at 80mph!"

Mark.

    
    
    It's much cheaper to tune the speedo than the engine!!  8*))
    
    Richard
    
    P.s. We'll all have tuned speedo's soon then!
    

    
    
     
    
    Surely it is to our advantage that the speedo reads low, if when
    doing the national speed limit of 70 mph we are only doing 60 mph
    we should be praising Digital and Vauxhall for making our roads
    a safer place.
    
    
    Martin
    
    

    You assume that driving at 60mph is "safer" than driving at 70mph. In
    my opinion, that assumption is wrong.
    
    Laurie.

    
>     You assume that driving at 60mph is "safer" than driving at 70mph. In
>     my opinion, that assumption is wrong.
    
    Are you saying that if as an individual you drive at 60mph (while
    everyone else does 80), it is not safer ?
    
    Or are you saying that if everyone drove at 60mph it is not safer ?
    
    Trevor

    Take your pick.
    
    Laurie.

	I drove/ raced for 2 yrs 1K rpm slower than I 
needed!!!!!!!!!!!!

    The Ford Escort 1.4LX proves that driving slowly can be downright b%$$dy
    dangerous...
    
    Scenario 1:  Just come off a roundabout onto a dual carriageway in the
    right hand lane; on the nearside is a Lada Riva. Unless I'm prepared to
    ram the gearstick into 3rd from 4th gear (considering the stodgy gearbox,
     'ram' is the correct word to use) and floor the car I'm in danger of 
    being left stranded in the right hand lane whilst I wait for the Transit 
    van behind the Lada to undertake me as well.
    
    Scenario 2: Travelling along the middle lane of the M3, doing about
    75mph about to overtake a Land Rover and Nissan Micra travelling in
    convoy; the Micra pulls into my lane; there's nowhere for me to go (as
    I'm being overtaken by vehicles in the right hand lane) so I brake.
    
    The Micra overtakes the Land Rover and pulls back into the nearside
    lane and I'm left floundering in the middle lane; at one point my
    passenger says: "Oh just get a move on never mind harrassing the
    bloke!"... because there's no sudden burst of speed my pasenger thinks
    I'm trying to pull abreast of the Nissan driver so that I can wave
    nicely to him... At this point my right foot is actually trying to
    force the accelerator through the firewall.
    
    None of these two scenarios actually illustrate the dangerous bit, but
    I could think of some hypothetical situations where the 'lack of speed
    bit' is, as I said... downright b%$$dy dangerous.
    
    Reargards,
    
    Stephen
    
    PS: The Escort was rented and is now back with AVIS.
                             
      

	... that there was nothing wrong with the car, just with your
	attitude?  Sounds like you're more used to a faster car (not
	difficult with the 1.4 escort).  A different mind-set and 
	you wouldn't have put the car in those positions...

	Dave

    
>>     Or are you saying that if everyone drove at 60mph it is not safer ?

> Take your pick

I certainly disagree with you on that point. Of course it is safer if
*everyone* drives at 60mph, as when accidents occur, there is less kinetic
energy to be dissipated, and thus less damage occurs to vehicles and their
occupants in absorbing this energy.


Trevor

RE:          <<< Note 634.31 by KRAKAR::WARWICK "Can't you just... ?" >>>

� >>     Or are you saying that if everyone drove at 60mph it is not safer ?
� 
� > Take your pick
� 
� I certainly disagree with you on that point. Of course it is safer if
� *everyone* drives at 60mph, as when accidents occur, there is less kinetic
� energy to be dissipated, and thus less damage occurs to vehicles and their
� occupants in absorbing this energy.

    Of course? You're assuming that the number of accidents per mph is
    constant. You're equating lower speed with fewer accidents. When you
    say "safer" do you mean "if an accident occurs then the likely
    damage/risk of injury is less because of the lower speed"? If you do,
    than that's not "safer" at all.
    
    Incidentally, back on the subject, I checked my speedo over a measured
    kilometre this weekend, and it was spot on at 140 kph (87.5mph). Car's
    a Pug 405 GLDT Estate.
    
    Laurie.

    I too recently had a Escort 1.4 LX from AVIS for a day and also found
    it VERY sluggish when it came to accelerating at ANY speed, also it
    drank petrol like it was going out of fashion, and before you say I had
    my foot on the floor all the way, I was trying to maitain a steady
    70mph going from REO to BBP via M4, A34, M40/42. Just so you know how
    much fuel was used 240 miles = �19 of unleaded!
    
    Neil

    
>     constant. You're equating lower speed with fewer accidents. When you
>     say "safer" do you mean "if an accident occurs then the likely
>     damage/risk of injury is less because of the lower speed"? If you do,
>     than that's not "safer" at all.
    
    Yes, that's what I meant by "safer" - I would argue that it is "safer",
    but it seems that we agree on the effect, if not the word used to
    describe it.
    
    It also seems logical that you would get fewer accidents at lower
    speeds, due to increased time available for reactions (assuming the
    same amount of traffic). Just how slow you have to make the limit so
    that this becomes significant, I don't know.
    
    Trevor

>    I too recently had a Escort 1.4 LX from AVIS for a day and also found
>    it VERY sluggish when it came to accelerating at ANY speed

I had the same type of car on hire for a while last year, and noticed the
same performance problem.  The car had almost acceptable acceleration if
the engine speed was > 4,500 revs, but this only made the already dire
fuel consumption even worse...  the CVH engine was a wonderful invention,
wasn't it?!

Chris.

I've timed my Cavalier 3 times and at 80mph indicated, I'm really doing 75mph!

Dave.

    My now-ancient 1600 CVH Escort has never been sluggish, nor is the fuel
    consumption too bad. It's done 96500miles now, and still coughing
    along.
    
    Laurie.

    I've got a 1300 91 Escort and can get a good 380-390 miles out of 20
    quid (and thats about 300 motorway miles doing anything between 70-95).
    I've got a mate who works for fords and he reckons the 1300 Escort
    engine is a lot pokier than the 1400.
    
    Trev

RE .34
    It also seems logical that you would get fewer accidents at lower
    speeds, due to increased time available for reactions (assuming the
    same amount of traffic). Just how slow you have to make the limit so
    that this becomes significant, I don't know.

Not necessarilly: The lower speed can lull people into a false sense of 
security, while also having the effect of slowing down their metabolism 
and thinking rate. Thus you can find that people driving at say 50 (like 
in the US) can have WORSE accidents, as they can't react properly when 
called to do so.

I'm not exonerating ton up jobs, nor even 40 in towns. But where it's safe 
(qualified by open, clear, visible, conditions, car, driver) then I 
believe it is no less *safe* than driving the same place at say 40.

Richard

    There's far too many variables to say that speed as an absolute is safe
    or dangerous.  How safe do you want to be?  An experienced driver could
    be a lot safer in a given situation than a novice.  The rep sitting a
    foot off your bumper in the fast lane may be safer than Granny in the
    same situation, but then Granny wouldn't be there in the first place,
    and if she was, she'd back off sharpish, unlike the rep, who'll still
    be there when you've passed Manchester.....  And around town, the rep
    will be brisk and arrogant because he's a "professional driver",
    whereas Granny will still be driving cautiously...
    
    Is it safer to mix it with the artics by sitting at 40 in the inside
    lane than it is to keep up with the traffic at twice that in the fast
    lane?  Really slow drivers have been prosecuted for causing an
    obstruction in the past.
    
    The "safe" speed isn't necessarily the slowest speed.
    
    A cautious driver isn't necessarily a skillful driver.  And vice versa.
    
    Richard
    

I've just bought a copy of "Diesel Car" (cos I'm thinking of getting a
diesel!) and as part of their road tests they measure the actual road
speed when the speedo reads 70. The actual speeds range from 63 to 69,
with the majority around the 63-65 mark.

Chris.

    Is that the issue that tests the Pug 405 turbo estate?
    
    Laurie.

    Back to the subject of dodgy speedos, I have come to the belated
    conclusion that my Ford speedo is actually a bit shy of reporting my
    true rate of progress.
    When I first picked up the car we noticed a disparity between its
    reading and that of the Astra hire car that Diane was driving, but
    having read this topic, I put it down to the Astra being a bit
    optimistic.
    Anyway, as time progressed, I got used to cruising along in the fast
    lane at 80mph, passing everything in sight :-)
    
    On Sunday we went to fetch my bike back from Gloucestershire, and
    following Diane on the M27, she was doing 90-100mph all the way, which
    I thought was a bit odd because she doesn't like to go over 80 normally
    in case she gets booked...
    
    Turns out that when she was doing an indicated 75, my bike was
    recording 93. Now whereas I wouldn't particularly expect a Ford or
    vauxhall speedo to be accurate, somehow I would tend to trust Honda San
    to get it right.
    
    Off to the shops for a new cable (and hope that is all it is).
    
    R

    re .43
    
    I think it is unlikely to be the cable. Cable faults usually cause either
    complete failure of the speedo or a needle that is unstable and wobbles
    around (because the cable is not rotating smoothly).
    
    If the odometer records distance correctly then the problem is inside
    the speedo itself. If the odometer records distance wrongly then it is
    probably wrongly geared. This could be because of the wrong gears for
    the speedo drive (usually in the gearbox), the wrong final drive gear
    ratio or the wrong size wheels or tyres.
    
    Andrew

    I'll endorse .44 Sounds about right to me.
    
    Laurie.

    Up to a point, I have once had a speedo record too slow, on another
    car, and the garage found that the cable end was worn, but still had
    sufficient friction to keep turning, just not quite quick enough. 
    
    But as you say, you might expect to see some instability in the
    indication..
    
    I shall check the trip meter out and see how accurate that is.
    
    I would think though that if the speedo has a fault, it is unlikely to
    be incorrect gearing, unless of course a previous owner has swapped the
    speedo from a different car...
    
    And the wheels/tyres are standard.
    
    Maybe this is the excuse to get a shiny new speedo with 0 miles on the
    clock ? On the other hand I only have to wait another nine and a half
    thousand and I will have a grubby old speedo with 0 miles on the clock,
    for free...
    
    R.         

    re .46
    
    OK, I'll concede that you could have a slipping joint between the cable
    and the speedo. I seem to remember that the end of the cable is
    commonly a square section of some metal, which fits into a socket on
    the back of the speedo. This could get rounded corners, allowing it to
    slip (probably more so at higher speed. Is the speedo more accurate at
    low speed ?). Of course it could be that the socket is worn so a new
    cable would also slip !
    
    Andrew

    The other thing to remember is that a speedo that under-reads by any
    amount is illegal.  There's no x% leeway on the slow side.
    
    Richard