norm007
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| posted on 23/8/11 at 08:32 AM |
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Trying to achieve 3.8-1 diff ratio
Hi.
As the title suggests, I am try to achieve a 3.8ish-1 ratio.
I have a 3.92 diff in my car at the moment and I am considering going back to my 3.64.
But I am now thinking about changing from 50 profile tyres to 55 profile instead to try and get somewhere in between the two ratios.
I would be grateful if somebody could enlighten me as to wether I am thinking straight or barking up the wrong tree??????
Cheers in advance
Something about this, so very wrong.....I have to laugh out loud, I wish I didn`t like this!!!!!!!!!!!!!!
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mcerd1
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| posted on 23/8/11 at 09:00 AM |
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what size are your tyres at the moment ?
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norm007
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| posted on 23/8/11 at 09:03 AM |
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quote:
Originally posted by mcerd1
what size are your tyres at the moment ?
195/50x15
Something about this, so very wrong.....I have to laugh out loud, I wish I didn`t like this!!!!!!!!!!!!!!
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mcerd1
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| posted on 23/8/11 at 09:22 AM |
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3.64 diff would be ~ 7% higher geared than a 3.92
3.8 would give +3%
195/55 R15 gives about a 3% increase compared to the 195/50's so about the same as a 3.8 diff
(based on a 1870mm circumference for the 195/55 and 1809mm for the 195/50 - you can get a better calc than that if you get the revs/mile figures for
the specific tyres your look at)
(205/50 R15 would give +1.7% and 205/55 R15 would give +5%)
[Edited on 23/8/2011 by mcerd1]
[Edited on 23/8/2011 by mcerd1]
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norm007
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| posted on 23/8/11 at 09:27 AM |
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3.64 diff would be ~ 7% higher geared than a 3.92
3.8 would give +3%
195/55 R15 gives about a 3% increase compared to the 195/50's so about the same as a 3.8 diff
(205/50 R15 would give +1.7% and 205/55 R15 would give +5%)
Thank you very much for the info.
How did you work out the equation, or is there software out there to do it???
Something about this, so very wrong.....I have to laugh out loud, I wish I didn`t like this!!!!!!!!!!!!!!
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mcerd1
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| posted on 23/8/11 at 09:40 AM |
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just a ratio of the old diff (or tyre) by the new one or vice versa (depending on which why round your looking at it)
so 3.92 / 3.8 = 1.0316 or 103.16% of the 3.92 (aka +3.16% on top of the 3.92)
with the tyres I did it from calculated circumferences, but revs pre mile would be better (most manufactures quote these on there websites)
or there are a few free gear cal programs out there if thats easier - personaly I like this one:
http://locost7.info/gearcalc.php
[Edited on 23/8/2011 by mcerd1]
[Edited on 24/8/2011 by mcerd1]
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norm007
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| posted on 24/8/11 at 09:10 AM |
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Thank you again for your help.
I have downloaded the calculator program for future reference
Something about this, so very wrong.....I have to laugh out loud, I wish I didn`t like this!!!!!!!!!!!!!!
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Mopple
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| posted on 26/8/11 at 06:10 AM |
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Another possibility would be 3.77 ratio Sierra diff.
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mcerd1
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| posted on 26/8/11 at 07:15 AM |
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quote:
Originally posted by Mopple
Another possibility would be 3.77 ratio Sierra diff.
isn't that the 6.5" diff ?
they are as rare as hen's teeth over here
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