Quick question - how do I calculate final drive ratios?
If I have a diff ratio of whatever and a gear box model A343F, and going from 265/60x17 (factory standard) to 285/70x17 Coopers I was curious to know what impact this will have on driveability - would I need to alter diff ratios etc. Anyway, a bit of googling found this site:
http://www.grimmjeeper.com/gears.html
which is pretty damn good I suspect (although I expect Dr Jon will have his own calcs up his sleeve in the Tardis somewhere )
Anyhoo - the above link shows I'll have taller gearing, as to be expected, with road speed going from 60 to 64mph at 2250 rpm. One to watch out for - I'll have to recalibrate the on-board GPS and also watch out for speed cameras a bit more
So - do I need to alter the gearing now, or is it still in in an OK zone?
Cheers
EDIT: Actually it's the A750F gearbox, which does this:
2250 revs goes from 62 to 67 mph
70 mph comes down from 2527rpm to 2361 rpm
Interesting stuff .... maybe better for economy, slightly, but what about rolling resistance etc.?
If I have a diff ratio of whatever and a gear box model A343F, and going from 265/60x17 (factory standard) to 285/70x17 Coopers I was curious to know what impact this will have on driveability - would I need to alter diff ratios etc. Anyway, a bit of googling found this site:
http://www.grimmjeeper.com/gears.html
which is pretty damn good I suspect (although I expect Dr Jon will have his own calcs up his sleeve in the Tardis somewhere )
Anyhoo - the above link shows I'll have taller gearing, as to be expected, with road speed going from 60 to 64mph at 2250 rpm. One to watch out for - I'll have to recalibrate the on-board GPS and also watch out for speed cameras a bit more
So - do I need to alter the gearing now, or is it still in in an OK zone?
Cheers
EDIT: Actually it's the A750F gearbox, which does this:
2250 revs goes from 62 to 67 mph
70 mph comes down from 2527rpm to 2361 rpm
Interesting stuff .... maybe better for economy, slightly, but what about rolling resistance etc.?