porkflap

New Member

• May 30, 2006

• #1

Hi, is it possible to re-calibrate the speedo on a 300tdi as mine shows 10mph less than you are actually doing! (checked with a gps device)

Chris

 

F

FrogFart

New Member

• May 30, 2006

• #2

Check your GPS device....

 

porkflap

New Member

• May 30, 2006

• #3

Yer i have tried that, and that seems to be ok in most things, also it seems a bit slow in the discovery!, is they andthing else that could affect it, the wheels and tyre's are just standard!

Chris

 

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Felix

New Member

• May 30, 2006

• #4

Hi there

Its quite normal for the speedo to be optomistic usualy by a max of 10%. This is a good thing as it keeps you under the spped limit when you are hovering close or just over. I have only seen Mercs run right on the money. 10 MPH does seem a lot though might be time to look for a new instrument pack or borrow one to see if its a problem with the head or the speed sender (not sure where that is yet) somewhere on the gearbox.

Felix

 

porkflap

New Member

• May 30, 2006

• #5

Thanks, i think that sounds the best think to do scower the internet for a instrument pack and have the gearbox bit out and inspect it!

 

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slob

Well-Known Member

• May 30, 2006

• #6

i doubt that a faulty speed would cause the problem you describe. if any thing you would get an erratic reading, but from what you say its seems to be a steady reading just the wrong speed.
i don't know what diffs are available for your axles, or even if there is a difference in ratios between different engines, be it engine size or fuel type, if you say tyres are correct then i would suspect 'wrong' ratio diffs have been fitted at some time in an effort to get better mileage.


(usual disclaimer applies... this could all be bollocks)

 

porkflap

New Member

• May 30, 2006

• #7

mmm never thourght of that its something to think about though!

 

James

Active Member

• May 30, 2006

• #8

If the GPS is slow to read and more acurate, and the tyres are not brand new then there will be a difference of nearley 10mph at say 70mph.

Is the speed difference constantly 10mph under at even 20mph?

 

porkflap

New Member

• May 31, 2006

• #9

that's what's odd its out by excactly 10mph at any speed so when it says 30mph its 20mph right up to saying 80mph but traveling at 70mph

 

James

Active Member

• May 31, 2006

• #10

Take the pannel to bits and reemark on with a pen the acorrect speed. It is only a needle wafting infront of a piece of cardboard with numbers on it anyway!