ok all you maths experts out there. please help if you can

just had 4.11's installed in my ef I6, 4 spead auto.

20" wheels with 225 35 20 tyres.

what revs should i be doing at 100kmh?

cheers

scott

All depends on what it was doing before the diff swap. Also, your 20" tyres are throwing out the speedo by 3km.

I dont know why you dont go onto the highway at 100ks and look at your speedo. If its already installed why do you need to work it out? Have you not had the speedo corrected (its what Im thinking...). Just asking.

This will give you your speed. You can try different rpm numbers to get your revs at 100km....or you could transpose the formula.

Total diameter of tyre in inches = T
Gearbox ratio = G
Diff ratio = D
RPM /1000 = R

---------------------------------------------------

(T*R*3) divided by (G*D)

ANSWER*1.61

Gives you your speed in Km/h

---------------------------------------------------

For example

24inch tyres at 3000 RPM on a 1.0 ratio gear, with a 3.0 ratio diff is

(24*3*3) divided by (1*3)
=72mph
72*1.61
=115.92km/h

There is another thread on here with the same formula but I couldnt find it.

Hope it helps.