diff ratio/tyre size change

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mudsurfv6
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diff ratio/tyre size change

Postby mudsurfv6 » Sun Sep 14, 2014 7:39 pm

hi guys

does anyone know of a calculation for changing diff ratios when tyre size changes to keep speedo the same.
apparently mine are 3.58, code A02A. 96 3.4 V6 auto surf, 31 inch factory tyres.
what ratio would I need to go to for 35 inch tyres?

cheers
1996 vzn185 surf, TRD supercharger, SAS, 35s, 4" lift, 2 lockers, ute chopped + more happening. Andrew 0272226292.

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Ashohman
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Re: diff ratio/tyre size change

Postby Ashohman » Sun Sep 14, 2014 7:48 pm

Im running 35's on my lux running 4.88's at 100kms do about 2750rpm there are a few calculators on the net that you can stick your ratios and tyre size in and it will tell you what speed and rpm you will be doing.

Its all about trying to match what you have now so you still have the same torque and somewhat economy driven.

In doing this your motor needs to have enough power to turn em also so take that into account.

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drive it ...
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Re: diff ratio/tyre size change

Postby drive it ... » Sun Sep 14, 2014 8:08 pm

From 31's a 35 is just under 13% bigger rolling diameter so to keep factory gearing 13% bigger diff is 4.05 or whatever the closest you get to that.

BlakeNZ
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Re: diff ratio/tyre size change

Postby BlakeNZ » Sun Sep 14, 2014 8:10 pm

4.1 would be the closest.
the basis of the maths is that the 35" tire has a height and circumference 13% bigger than the 31" tire. (35 divided by 31 = 1.129, hence 113% of 31")
so we need to adjust your ratio by 13%. In this case, we need a lower ratio(numerically higher) to compensate for your higher gearing created by the taller tires. So 3.58 ratio times 1.129 is 4.04 ratio(hence my thinking the 4.1 is the closest)

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mudsurfv6
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Re: diff ratio/tyre size change

Postby mudsurfv6 » Sun Sep 14, 2014 8:20 pm

thanks for that
1996 vzn185 surf, TRD supercharger, SAS, 35s, 4" lift, 2 lockers, ute chopped + more happening. Andrew 0272226292.

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