[zedboy]

Hey Guys

I'm currently running 31x10.5s MT Baja MTZ on my 92 sierra. The transfer case has low range 6.5's crawlers, engine is stock standard no mods. Not sure what the ratios have been changed to in the trasfer case but at 100km/h it sits on 3600rpm in 5th.

I'm tossing up whether I should step down to 30x9.5' - would this help me get up those hills slightly easier and possibly get a few more kms per tank?

What are your thoughts guys?

Thanks Matt.

[christover1]

Get out a tape measure before deciding on a tyre to buy
Tyre sizes are rarely the same as stated on the tyre.
My 31's only measure 29 (worn)
Some 30's are taller than my 31's.

Less weight on a skinnier tyre will help fuel economy, and power a little, too.

[Matthew]

What kinda of rpm range do you want to be sitting on at 100km?

If you change to a 30x9.5, your rpm should be around 3777 at 100km, presuming a new 30" tyre has an od of 29.6".