Inaccuracy of clocks

[Paul]

Rite im fed up with listening to shit off me mates, they think that speedo clocks are accurate up to the limit ie like 110 absoloute top end having no more barely got there out of a 1.2 8v punto. a 1.2 nova no real mods doing 110 at agian abs. top end no more possible barely getting there.

Would someone please comment on how bloody unacurate these things really are!

110 on the clocks would be realistically around 95mph ish at a push.

130 of a nova clocks would be wot round 110 tops realistically.

My mate reckons 10% out, but im convinced clocks aint dis acurate over 70.

They cud be like up to 20mph out at the top end.

Please would someone verify this, and even with new cars clocks are still unbeleivably more unaccurate.

And wot speed do the clocks start to loose accuracy.

Please reply coz im gonna print this off so they can all shut up bout 95% of smaller engined new cars, ie below 1.4 doing 100mph.

THAT is bollox, aint it?

Maybe summit like 60% or so?

[peester]

most of what you say is right. i don't know all the ins-and-outs with speedos (thats the car speed measuring type not the gay ass swimming brief type; i know even less about them.) the faster they're going the more inaccurate it can get. but don't get too mad about it. i don't think youre mates are going to want to hear they're findings and claims where wrong. one day you'll forget; hit 130mph in your 1.3/1.4 SR and want to tell the world about it.

[Stuart]

Will you please STOP using text messege writing here, its very annoying and takes twice as long to read.


WRT your post

i did a gps test of my speedo,

speedo claimed i was doing 70 acctual 63
80 75
90 84
100 93

Make your own call from that, as all speedos will be different (but never under read)

[Ste_Nova]

between 1% to 10% over... when checked on a rr 100 in my 16v was really 96

[Philsutton]

well i went over line at santa pod with 95 on the clock, but only 80 was recorded so me thinks the 135+ i got out of it is more like 115

[Aragorn]

there are other ways to tell tho

the rev limiter in 5th on a standard GTE gearbox for instance is 135mph

u can work out the revs and get a decent idea of your speed

if u want a listing for your box let me know and ill dig out mine/camb's spreadsheet

[mikeoxford]

:? yes and no aragorn.

velos said my rev counter was out on the rolling road - in fact i saw it! about 500 RPM out at the top end! was accurate to 10 RPM at the bottom though!

[BigRuss]

Speedo's on production cars are calibrated up to 70mph +or- manufacturers tolerances.

I have actually seen a car of mine on a rolling road which was doing exactly 100mph, My speedo was showing 118!!
However at 70mph the speedo was the same as the rollers. I reckon most cars showing 115-120 mph are actually doing around about 100mph.

[Stuart]

I made the spread sheet in the first place :) its quite inaccurate lol

althouh i am working slowly on a new one

[red_devil]

i aint got a clue what my car tops out at but with the 18"s it seems to have alot higher tops speed.. its a 1.4SR running a mildish cam etc.... wot u reckon it should top out at coz its accurate at 70 coz my dads Octavia clock is very accurate and we did the old follow my leads dial check on the road near me....

Wot would u say mines doin if it say 125 on the clocks @ 4750 rpm???

[Puntobabe]

Mine is wrong, but thats prob cause i need a new speedo cable, hehe. Will get it done eventually. :roll:

[jkhilton]

lol, my old MR2 Turbo's speedo only went upto 110, but the needle went much further!! I had it stuck pointing almost straight back down again on the M1 in the middle of the night after hitting the rev limiter in 5th. I dont know what the speed was, but it was probably the fastest I have ever driven. :)