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Speedometer accuracy

theogeor

Albert Park
Joined
22 Sep 2008
Messages
1,504
As I said in another thread I was going to do some testing on the speedometer accuracy
For reference I have 19" wheels (only thing that might vary from model to model that might affect the accuracy
Did the following tests (of course in a private road :cop: )
speedo/satnav (In Leptons as per Maxie's advice)
30/29
40/38
50/48
60/58
70/68
80/78
90/88

Which means the speedo is very accurate and actually more accurate than I though it was which makes me a bit worried
On Sunday on the way to Bristol on M4 I set the SatNav on 79-80 Lepton s as I though that was actually around 75-76 which is "safe". In the Swindon area I saw one of those lovely vans but I did not slow down as I though I was ok. Now it looks like I am touch and go (again depending what threshold they had as they have a notorious reputation ) as my real speed was closer to 78. Will know in few weeks time if I will get my first reward tax - sorry points :sad:
 
theogeor said:
Will know in few weeks time if I will get my first reward tax - sorry points :sad:

Lol....if they totted up for life rather than every 3 years I would have been banned several times now :hand: .

I was quite pleased that 3 points fell off this week - usually means I am due 3 more so leaving the country for a week or so :D .
 
I thought I read somewhere that Swindon were getting rid of their cameras?

TB
 
Mine over-reads about 5mph from about 30mph upwards..

garyw
 
garyw said:
Mine over-reads about 5mph from about 30mph upwards..

garyw

What tyres do you have ?
 
Mine reads 1 to 2 mph faster, what ever speed your doing. :) Between 102/103mph at 4,000 rpm in 6th, therefore 100mph on GPS
 
ResB said:
Mine reads 1 to 2 mph faster, what ever speed your doing. :) Between 102/103mph at 4,000 rpm in 6th, therefore 100mph on GPS

That is in line with my findings. Can you please let us know what tyres you have to as to figure out the differences if any
 
Michelin PS2's -

235x35x19's front.
295x30x19's rear.
 
Standard Turbo sizes..
My van is almost the same over read... and no idea of size on that!

Rears are 305/30 19
front 235/35 19

garyw
 
Thanks guys

So ResB who has the same tyres as me has exactly the same accuracy but garyw who as slightly wider tyres (which means 6mm bigger diameter) has less accuracy.... (front tyres are the same)
I think the difference is insignificance anyway so I will look at the issue further

Thanks all for your help
 

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