Technical Tips > Brakes, Suspensions, Steering, Wheels & Tyres

TYRE DIAMETER AND SIZE QUESTIONS??? Re speedo calibration

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Cameron 77C3:
Has anybody got published data on what the running diameter on a 245/60/15 tyre is.  I have measured it but I would like to know the published figure.

Second question.  What DIAMETER size wheel did C3's come out with,  15" or 16"?

CAM:grr

nifty:

--- Quote ---Originally posted by Cameron 77C3
Has anybody got published data on what the running diameter on a 245/60/15 tyre is.  I have measured it but I would like to know the published figure.

Second question.  What DIAMETER size wheel did C3's come out with,  15" or 16"?

CAM:grr
--- End quote ---


easy to work out,.you have a 15 inch rim,with a 245/60 tyre.... so side wall of tyre is 60% of width.
now if only i had a calculater to make it easy for me.

c3's i think came with 15's

Cameron 77C3:
So 60% of 245mm = 147mm  and that = 5&3/4"

So I add 15" + 5 3/4" + 5 3/4" = 26&1/2"

So  my tire on rim measure 26&1/2".

Many Thanks.

Chromie or smokem, whats that equation again for the speedo gear teeth number?

I'm at home and the equation is at the factory.  DOOHH!!

Chromie:
Hi Cam;;-)45;-)
All C3's had 15" X 8" rims with the exception of 1968 which had 15" X 7" rims
Tyre size varied through the C3's from 210 X 60 X 15 up to 255 X 60 X 15
and I believe there were some that were 70 series.;-);-);-);-)
So cam why do you want to know
And nifty is correct with his tyre formula;42

Vette Obsessed:

--- Quote ---Originally posted by nifty

--- Quote ---Originally posted by Cameron 77C3
Has anybody got published data on what the running diameter on a 245/60/15 tyre is.  I have measured it but I would like to know the published figure.

Second question.  What DIAMETER size wheel did C3's come out with,  15" or 16"?

CAM:grr
--- End quote ---


easy to work out,.you have a 15 inch rim,with a 245/60 tyre.... so side wall of tyre is 60% of width.
now if only i had a calculater to make it easy for me.

c3's i think came with 15's
--- End quote ---


This isn't the published figure but from memory the maths to arrive at a figure goes like this:
245mm/100 = 2.45
2.45mm x 60 = 147mm

147mm x 2 = 294mm

294mm + wheel diameter = actual total wheel diameter.

I'm sure if I've overlooked something one of you guys will pull me up on it. ;42

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