Outer Limits 4x4 Board

heh heh heh-that's probably more technical detail than i needed
i was wondering about the difference in odometer readings tho- my 31s must be close to 31, as my speedo is only about 6 kms out. But to do 100km / hr with my 31s i am doing pretty close to 2500 revs.
this thread explains how my fuel economy can be 10km / L !
i guess it also answers the other economy question- generally speaking there isn't going to be a big change, so no worries there. now to find the BFGs at a decent price.........

thanks fellas

okay-got my 33s fitted yesterday-
anyway- i'm sure my revs have dropped when sitting on 100km/hr from nearly 2500 to 2250. I thought this was impossible, as the speedo is connected to the gearbox, and the gearbox to engine and therefore tacho (when in gear) so for any specified engine revs, it would tell you you're doing the same speed no matter how big the tyres-am i missing something or just imagining things? it's impossible for the revs to drop yeah?

i.e if i had 2 inch wheels on it and was in fifth gear at 2500 revs, the speedo should read 100km/hr, even tho i would be doing about 2km/hr yeah? what the hell?

BTW-got BFG 33x10.5R15 and so far i love em-no road noise and they ride much softer than 31s

No Noise
what tread pattern? A/T or M/T
and how much ? if ya don't mind tellin
I have 33x12.5 M/T and the only reason they aren't on the car all the time is the road noise
Scott

ok- i was imagining things- i think i was comparing tacho readings at 110, not 100.

anyway- the tread pattern is AT-there is a bit of road noise, but only with the window down and clutch in rolling up to an intersection or something-i.e when you're actually driving the engine / gearbox drowns it out.

i would only go for muddies if i was actually driving mud a lot. if you are, the ATs are useless.

they were $1400 for a set of 5, fitted and balanced.

i have done some preliminary calculations and as far as i can tell, using ACTUAL distances and speeds etc, i have gone from 9.5km/L to 8.5km/L. so i lost 1km/L, and consequently have had my range reduced by about 130km. bugger. oh well

Did you do calculations with your previous tyres using actual distances? If not the old calculations are wrong...............

no, but i used the speed i got from a gps when i was driving with 31s-when the speedo was 100, i remember the GPS was about 95, therefore 10km/L (what the odometer said i was getting) would convert to 9.5km/L (using GPS speed) with 31s. i will use a GPS speed to calculate a new economy with the 33s, and that should be conclusive.

okay it's confirmed-used GPS yesterday-when the speedo said 100, the GPS said 101.5- pretty friggin close. so i can confidently say that changing from 31x10.5 to 33x10.5 cost me 1km/L in economy.