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Differential queries


kevin
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Hi Iain

I thought you were giving me the finger, which I thought a bit unexpected from one Iain to another Ian!

Jut to add a couple of pieces of info to my previous post:-

My box is Papworth build 3 rail with a 25% J Type O/D. (so same as the original  D Type option)

Wheels are 13" shod with 175/70 rubber, so should be the same as standard in all respects, which the speedo reading confirms.

PS My moderns over-read by about 7% which I think is normal...... I just find it annoying!.

Ian

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back in the 90s i managed our factory tachograph calibration centre  , mech and electronic speedos were calibrated to a read fast tolerance of   10% + 4  mph   so at 60 it could read 70 and be in tolerance if i remember  rightly i would guess construction and use  has changed as electronic accuracy can be more accurate ive not read them for years 

Pete

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1 hour ago, Ian Foster said:

Hi Iain

I thought you were giving me the finger, which I thought a bit unexpected from one Iain to another Ian!

Jut to add a couple of pieces of info to my previous post:-

My box is Papworth build 3 rail with a 25% J Type O/D. (so same as the original  D Type option)

Wheels are 13" shod with 175/70 rubber, so should be the same as standard in all respects, which the speedo reading confirms.

PS My moderns over-read by about 7% which I think is normal...... I just find it annoying!.

Ian

Hi,

 Still will not let me edit so I guess the finger is to me.
 

My tyres are the same diameter as standard. Possible mines a 2500 box. I have OD on 2nd up which is very handy. I wished I had it on 1st as well or neutral would be better.

Cheers,

Iain.

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3 hours ago, Pete Lewis said:

back in the 90s i managed our factory tachograph calibration centre  , mech and electronic speedos were calibrated to a read fast tolerance of   10% + 4  mph   so at 60 it could read 70 and be in tolerance if i remember  rightly i would guess construction and use  has changed as electronic accuracy can be more accurate ive not read them for years 

Pete

C&U for our cars is +/- 10%

Current standard is +20%

I think oust manufacturers aim for a few % over to ensure no chance of misreading speedo

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from a makes point many used the tolerance to kid you the economy was better in reality their miles were shorter so mpg showed as better ...fiddle 

eg the father in laws cortina   clocked 220 miles to torquay and dads hunter clocked   198   they only lived 3 miles apart 

pete

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A few years back I was on a query at the top of the country and recorded the miles, as straight a run as I could make it - 85 miles each way, which avoided the motorway and followed some quite narrow and hilly, but more direct, roads.

When I tried to claim for mileage I was told that Green Flag - by whose wisdom all routes are calculated - made it 69 miles.

I've tried it since for a laugh, in different vehicles, and always end up about 15 miles short of my destination. I hope Green Flag never come to my rescue, it'll be a long way to push the car to meet them... however: don't modern speedos all read slightly optimistic ie a slightly higher speed than the car is actually doing?

.

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