Speedo's out, what profile tyres to use?

[fudge]

Hi, I have 73 240k coupe. Finding out what gbox it has was out of gold 78Skyline from simmons. Not sure if it's standard box or a close ratio. The speedo is out by 30kph. Currently running r14 195by 56. Does the gearbox make difference in speedo or should I research what either 240K or 78Skyline had for standard profile. Thankyou for any responses.

[stezza]

hey mate, just my 2 bobs worth... would've thought that if youve changed the gear box then youve changed the spped sender unit. this means track down the original profile of the skylne tyres and you should be o.k. Im guessing this is true but u should also make sure the diff is the same and that the speedo accepts this... somebody will put u in the right direction

Cheers,

Charlie.

[ricecutter]

On the end (gearbox) there is a coloured (usually) plastic drive wheel, these come in a variety of sizes try changing these over and check against a mate with an accurate speedo. This is a bit more practical although may take a bit of mucking around. Good luck.

[Datsunreal]

Hi fudge

your early model 240k should have a higher (3.5:1) diff ratio than the C210 and later model 240ks (3.9:1). this could contribute to your speedo error if you have the original diff. these early diffs usually have 4 stud flange outputs. changing the speedo cog thing maybe out of your old gearbox should cure it. i had this problem once and the cog fixed it.

the speedo senders are colour coded, ill try to find out wots wot for you.

[Datsunreal]

standard 240k has a BLACK 17 tooth sender with 14 inch wheels and a 3.9 diff

my green 240k has a WHITE 19tooth = reads 15% under (115 is 100)
but i have 15 inch wheels so its pretty spot on

i also have a RED 20 tooth = reads more than 20% under (120 is 100)
good if you have a really low diff.

maybe the gold car had a low ratio diff and has a red or lower sender to compensate. putting in a black 17 tooth should cure your problem.

colour codes for 5 speed speedo senders. from the old datsun competition parts list

16t yellow 20t red
17t black 21t purple
18t blue 22t orange
19t white 23t green