[andrew]

hi guys when my sierra is up for tyres
i was thinking of putting bigger tyres on the stock rims or changing to different wheels
my question is... how big is too big and starts effecting gearing and such or becomes no advantage.
reason for wanting bigger tyres is a bit of a lift and better grip

[Gwagensteve]

215/75/R15 (28") goes on stock rims and gearing effects are minimal. Beyond that you need gears really.

[andrew]

The current size is 235 75 15 thats on there now.
Whats the factory size ?

[Gwagensteve]

So your gearing is already less than ideal. Those tyres should also be on 6-7" rims, not the stock 5.5" rims.

Stock is 205 70 15 from memory.

[whincup]

steves right about the stock size. i ran 215's and they were pretty good on stock gears, never tried 235's (which are about 29"), but dont go bigger until you've sorted gearing. i cooked my clutch in just a few trips on 31's on stock gears, and heaps of people on this forum have similar stories.