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road spped with diff. tyres
Posted: Mon Nov 01, 2004 4:57 pm
by eliteforce32
whats the equation or if some one tell how to know my road speed..... 33 tyres, 86 model SC lux, standard 5spd box and diffs? can some one help
cheers
simon
Posted: Mon Nov 01, 2004 6:23 pm
by -Scott-
Real speed = Indicated speed x new tyre diameter / original equipment tyre diameter.
This is still a very rubbery figure because:
Your speedo is 18 years old and may not read correctly even with the original size tyres.
Your 33" tyres may not be exactly 33" tall.
The OE tyres were probably exactly the nominal size.
But, it's probably close enough.
Cheers,
Scott[/list]
Posted: Mon Nov 01, 2004 6:36 pm
by +dj_hansen+
I did this when i ran 33"s for a little while...
Factory tyres are around 30"..... so thats a 10% increase in rolling diametre.
Knock 10% off your speedo reading.
Its not all that accurate... but works

Posted: Mon Nov 01, 2004 7:02 pm
by Utemad
Check your speed with a GPS and figure out the percentage your speedo is out by. Then drive that percentage slower.
Posted: Mon Nov 01, 2004 7:22 pm
by spazbot
should be out by about 10% on the lux so if ya clock says 60 your prolly doing 54 or so
Posted: Mon Nov 01, 2004 7:28 pm
by De-lux
do what utemad did with the GPS idea, but get a bit of white-out and put a dot on your speedo next to 100, 60 etc, just the main speeds that you need to be careful of. simple, yet effective
Posted: Mon Nov 01, 2004 8:59 pm
by DamTriton
spazbot wrote:should be out by about 10% on the lux so if ya clock says 60 your prolly doing 54 or so
Udder ways around...........
10% larger tyres = 10% more speed at same revs = indicated speed
+ 10%.
60 indicated = 66 actual.
Posted: Mon Nov 01, 2004 10:22 pm
by MY45
GaryInOz wrote:spazbot wrote:should be out by about 10% on the lux so if ya clock says 60 your prolly doing 54 or so
Udder ways around...........
10% larger tyres = 10% more speed at same revs = indicated speed
+ 10%.
60 indicated = 66 actual.
Gary is right
Posted: Tue Nov 02, 2004 7:28 am
by eliteforce32
thanks guys! great help