what is the most bigger tire can fit on samurai with original axel???

I would presume that you are talking about a samurai with stock suspension? In that case if you just pull the end caps on the front bumper a 215/75 fits perfectly a 235 rubs considerably.

no, with a suspension kit!!!

most...bigger...tire... I dont even have to say it do I ?  In the future try something like:
What is the biggest tire, or what is the largest diameter rubber sphere...., or well you get the picture.
 Oh by the way its all dependent on how big of a "kit" you get. A simple SPOA is probably good for a 30" or 31" tire. Any manufacturer will tell you what tire to run with what kit. Most people I talk to say that sami axles are good up to a 32" tire and maybe 33"s if you go light on the skinny peddle. Of course this is all a matter of preference since some will swear to mud bog with 35" swampers on stock axles with no problems and others will cry about shattered birfs with 235's so.... do whatever you want and learn  what your needs are

most...bigger...tire... I dont even have to say it do I ?  In the future try something like:
What is the biggest tire, or what is the largest diameter rubber sphere...., or well you get the picture.
 Oh by the way its all dependent on how big of a "kit" you get. A simple SPOA is probably good for a 30" or 31" tire. Any manufacturer will tell you what tire to run with what kit. Most people I talk to say that sami axles are good up to a 32" tire and maybe 33"s if you go light on the skinny peddle. Of course this is all a matter of preference since some will swear to mud bog with 35" swampers on stock axles with no problems and others will cry about shattered birfs with 235's so.... do whatever you want and learn  what your needs are

That reminds me - what's the best way to beef up the stock Birfs? I thought there used to be someone that made a ring that would go around them and help add some strength?

~J~

Save your money on the ring thing, it just moves the problem further in! makes for a real bad day of wheeling.

There is also the CV Unlimited Axels, but there have been pictures of people breaking the shafts on those.

If you want to run 35's, you would probably be better off looking at axel swaps.  They are pretty easy on a spring based vehicle.

So - if going bigger than 33's - look for a toyota swap or something? I don't think I'll ever go bigger than 32" and 5" lift and 1.6L, so I should be safe right?

So - if going bigger than 33's - look for a toyota swap or something? I don't think I'll ever go bigger than 32" and 5" lift and 1.6L, so I should be safe right?

It all depends on your driving style. I have friend out here that run 33's and has very little breakage.  Another friend runs 31's and breaks birfields all the time. One guy is rea meticulous in what he does, the other finds that his throttle seems to solve most of his problems (in one way or another).   

Gotcha - I'm supernoob, so I fugre I'll break something 

I haven't broken anything yet on mine, unless you count the twisted front splines.   But I blame half of that on the Ez-Locker not working right. 

I ran 33's on stock axles for a few years and only once did I have any problems (twisted splines, and those were newfields  )

I'm on 36's and Yota axles now.  No reasion to take any chances...lol