muzchap
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| posted on 15/7/07 at 09:01 PM |
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Calculation Experts needed :) - My head hurts
Hi guys,
Knowing what a clever bunch you are (angling for the flattery tactic here!  )
I have the following calculation I need to solve.
problem:
I have an engine/gearbox with a pre-calibrated speedo sender unit - the host car runs on 16" rims and has a 4.10 final drive diff
I however am running on 15" wheels with a 3.62 diff.
How far out will my speedo be at this point?
I am planning eventually to upgrade the diff - found a place that will sell me a new final drive gear for a 7" Sierra LSD - but a reconditioned
unit with Quaife internals and this gear is £1000!!! EEEK! So thats for next year, or maybe the year after.
So what I'm basically saying - is - if I upgrade to 16" rims (advice here as well please on handling effects) -
how far out will the speedo be after upgrading
I'm looking to move to 16" as I think I'll need 225 rears to transmit the power, with 205 fronts. I think the limit on 15"s is
205? (Am I correct in this assumption)
Cheers,
Murray
[Edited on 15/7/07 by muzchap]
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If you believe you're not crazy, whilst everybody is telling you, you are - then they are definitely wrong!
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Mark Allanson
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| posted on 15/7/07 at 09:14 PM |
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play around with this
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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lotustwincam
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| posted on 15/7/07 at 09:19 PM |
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Wheel size is irrelevant. It's tyre size that is important.
E.g. a 225, 40 X16 tyre is roughly the same circumference as a 205, 50 X 15 tyre.
You might find THIS LINK at least partly useful in your calculation.
Drew
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muzchap
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| posted on 15/7/07 at 09:23 PM |
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Hi Chris,
Cheers for that - using the standard S2k box.
I could have got the S2k diff - but didn't fancy messing around with driveshafts etc etc - I may do one day - when the budget/time allows
Thanks for the advice about the tyres - that'll save some pennies- I might go 205's on the rear then just to give it a little bit more
- I don't think I'm as good a driver as you on those vids of yours!
Murray
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If you believe you're not crazy, whilst everybody is telling you, you are - then they are definitely wrong!
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muzchap
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| posted on 15/7/07 at 09:25 PM |
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Thanks Drew - I'll take a look.
I don't mind the speedo being out - just wondering about the magnitude.
I suppose I can drive around with the TomTom and double check - obviously my key trigger points are:
20mph
30mph
40mph
50mph
60mph
70mph
That should keep me away from the Poleizi! 
Cheers,
Murray
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If you believe you're not crazy, whilst everybody is telling you, you are - then they are definitely wrong!
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