What's the largest size tire I can fit in my Xterra?

I get this one all the time from people.

Who has the largest tires under their truck?

It must be either Gothamists 32x11.5 SSR's, or was it Swampwrecker? who put 33 TSL's (not sure who it was).

Will 20 inch rims fit on my Exterra? Dat b pimp'n! :D

I'll add in that you can't fit anything bigger than 31x10.50's before you start rubbing on the Xterra-specific ARB bullbar, which is a bit of a pain to trim (at least compared the stock plastic parts.) There is a lot of rubbing w/ the 32" SSRs, so it's not really something I'd recommend people do unless they know what they're getting into.

Swampwrecker does have the 33x10.50 TSL Radials, and he actually has less rubbing than I do. Those tires seem nice and offer more diff clearance than any other tire people have managed to squeeze under an unlifted X, however they are very narrow for a 10.50" wide tire (7.9" according to Interco.)

Is having a narrow tire a bad thing? I was always told there is two ways of getting through mud, wide tires to "float" over or tall tires to dig to the hard dirt. Oh and is that 7.9" just the road contact patch? I really want to stick 33" on my X :P

I would also like to see the rim specs in the faq.

Ben

Originally posted by Antitree_hugger
Is having a narrow tire a bad thing? I was always told there is two ways of getting through mud, wide tires to "float" over or tall tires to dig to the hard dirt. Oh and is that 7.9" just the road contact patch? I really want to stick 33" on my X :P

Ben

Sometimes yes, sometimes no. Skinny tires are better in snow, sometimes better in mud. The 7.9" is the actual width of the tires, they are very skinny. But they will probably still be my next tire cause I like 'em a lot.

The skinny vs fat tire debate has raged for decades...about when
they started to use use inner tubes instead of a solid rubber strip
around those wooden wagon wheels...

The concensus is:

That a skinny tire has better contact
pressure (Same weight suppoorted, on a smaller contact patch)

That a skinny tire will sink down...and IF there is anything within
an axle depth to bite...it can bite it and grip.

That a fat tire has worse contact pressure (Same weight, distributed over
a larger foot print/contact patch)

A fat tire provides flotation, preventing you from sinking down.
(Good if there is nothing within range to bite down there anyway...)


So - There is no one right tire ratio for every scenario....

Skinnies work better when contact patch pressure wins,

Fatties work better when contact patch size wins


The tricky part is to calculate the contact pressure you need for adequate traction,
once you hit the point of diminishing return...and that is VERY situation specific.

Some tire treads need more pressure than others for the pattern to bite/grab or self clean.
The heavier the rig, generally the fatter the tire can be w/o loosing too much contact pressure..
I find personally that rocks are more navigatable around 20 psi than 10 psi...it gives
more diff clearance, and provides enough pressure to let the tread blocks squeeze
the rock edges for better bite...Mud on the other hand seems to work better as low as you can go w/o
blowing the beads...the RPM needed to clean out the lugs spins the tire out to full diameter anyway,
the exception being some kinds of mud where you need a stiffer bladed lug to get a grip...To clamber up a hill with loose gravel/leaves, etc....the contact pressure seems more important than the size of the patch, so the skinny tire will win...

I'm guessing, w/o Xterra specific empirical evidence, that an 11.5" or so section width/~285 mm sized tire is about right, too much more and the turning radius will be enlarged, tire tuck looks to be at the limit, and the contact pressure will be nearing the point of diminishing return (IE: Hill climbs soon generating wheel spin, etc...)

The stock tires on mine are 29 x 10/16's (Grabbers) = 255/65/16...and it looks like around an inch or so clearance before the torch/dremel (whatever) gets fired up...so a 285/70/16 would be optimal..involving the lose of the mounting point for the mud flaps, and the same distance towards the front, maybe a little adjustment under the rear wells too, like the gas filler area under there...etc... I think. (Theoretically...that size may not be on the shelves anywhere...but in a 15"....around a 32 x 11.5, assuming the common undersizing of the nominal 32" diameter.

You just need to know the limiting factors involved with YOUR terrain.


Does this help at all?

- Lance

Originally posted by Antitree_hugger
Is having a narrow tire a bad thing? I was always told there is two ways of getting through mud, wide tires to "float" over or tall tires to dig to the hard dirt. Oh and is that 7.9" just the road contact patch? I really want to stick 33" on my X :P

I would also like to see the rim specs in the faq.

Ben
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i went to a mud show one time in the midwest. the guy who had an old dodge powerwagon with 7.00x16.5 was whippin' everyones ass. the guy with the deluxe ford or chevy with giant meats and big lift couldn't get anywhere. he would just float on top and spin and get squirrely.

mud and snow ---> thin contact patch

sand and trails ---> wide contact patch

you can have a wide tire with narrow tread, so look at the specs carefully... :p