[cyprus73]

Hi All.

I want to fine out what is the largest size tires I could put on my Sierra with having to
change gearing.

Already have a 2" lift and 1" body lift, but dont want to have to do gearing at this point.

Thks
Chris.

[Gwagensteve]

Some people would say no larger than standard.
215's (28") dont negatively effect gearing too much. Beyond that you need gears.

[alien]

I ran 215/75r15 on my sierra for a few years and for sand it was fine, but trying to do anything slow/controlled, low range was still way too fast and i was always hitting things at speed when i didn't really want to.

IMO - choose your tyre size based on what you need / what you drive and address the gearing at the same time. The gears are a long term investment in the car's drive-ability and enjoyment and while you'll undoubtedly go through multiple sets of tyres the gears will be a constant so long as you don't change tyre size later.

If cost is the issue, get secondhand tyres of the correct size in order to funnel more money into getting the gearing right.

[bumstein]

+1 for gearing first.

However as a cheaper alternative consider getting hold of a 1ltr switched transfer case. That will reduce your gearing around 10%ish? Quick search here should give you the ratios.

Dropping that you should be able to run 235/75R15 (or thereabouts) with close to stock gearing. For a few hunj it may get you by until you A) decide that works great for you, or B) you can figure out and afford the gearing you want.

[cyprus73]

Thks All.

Currently running 255x70x15 about 29inch. Doesn't seem to bad, but haven't taken it off
road yet.

[alien]

96 coily on here ran 30" tyres with no gearing... his clutch was best described as "sacrificial" =)

29's on the road would suck let alone off!

[bumstein]

With the 255/70R15 your looking at 10.48% increase in circumference over standard.

Drivable on the road, although all things being equal 5th gear will be nearly useless and low range not good for anything other than beach work.

1tr case will help with these tyres

What sort of driving do you do?

This gives you some idea