Thread: 325 or 525??
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Old 8th March 2011, 21:36
Mike Mike is offline
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Glen

The 3 series E36 ratios are different, as is the final drive:
1 = 4.23
2 = 2.52
3 = 1.66
4 = 1.22
5 = 1.00
Final drive =3.15 using 185 x 65 x 15 tyres.

This is probably more to do with the difference between the M20 engine and the M50, (I think the M20 reaches peak power at higher revs than the M50),
I have calculated that with a 3.38 Sierra diff, and 205/65/16 tyres I can achieve almost identical gearing as on the donor 3 series BMW.
Chris Cunliffe initially used a 3.62 diff with his M50, but found 1st gear was useless (too short, and set off in second), so changed to a 3.38: he is using 205/55/16 tyres.
Simon chose 215/55/17 rim/tyre combination, which have an increased rolling radius and compliment his 3.92 diff.
By carefully matching the engine characteristics, gearbox, final diff ratio and the rim/tyre size you can achieve the type of car/performance you want .

Mike
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