Thread: Series revs

:? I would have thought it was the same, as a 8.25R16 is wider than a 7.50R16, not larger (isn't it ?)

can't tell you what I do, no tacho & a holden motor.

Hi Phoenix
Mine is a holden as well,they still rev the same as the gearing is unchanged with a motor change.
8.25 tyres are at least 3 or 4 inches taller than a 7.50,and a good 1 to 2 inches wider.
Andrew

Hi All [img]style_emoticons/<#EMO_DIR#>/smile.gif[/img]
3850 sounds like it could be for a 2.6ltre six, a bit low for a 4cyl they're up around 4k as their SAFE listed max is 4250rpm and they self distruct at between 5100--and 5520rpm (that was done under test conditions in the late Sixties, tha explosion and resultant hemorrhage was spectatualar, all over the test track.) As to the Question, on 8.25 x16 a safe bet would be to assume that the speedo (if accruate in the first place ) would read 10 klm slow IE 90 klms indicated==100klms actual if in miles i would use the same figures, for a more positive calc, measure circumferance of 8.25x16 and that of NEW 7.50x16 then calc the % diff and hence your answer (never could understand how to use a calcuator, weren't invented when I went to school but then I rode a dinosaur to school)
Chers Rocket

Hi Andrew
My holden does somewhere around the 3400 in overdrive at 100 with 15in 31 x 10.5 tyres and 4k in fourth at 100.
My suggestion would find a quiet road with a friend in their car and do some comparisons.

Hi Guys
Thanks for the input.
It turns out the speedo is reading correctly with the 8.25 tyres,checked it today on the trip against the other guys using their GPS.When the needle decided not to flicker it was pretty well right.The oddometer was cheked against the roadside distance markes and was also correct.
Thanks
Andrew