Does anybody know what the biggest size tires that can fit the stock axles on a 1985 4runner?

i have looked on google and i couldnt find it...

 

I know that there are a few people that run 37 with no problem and I have heard of people running 40 but it all depends on how hard you run your truck

 

Any size will "fit" the axle. Fitting the truck is always the issue. In other words, if you take the axle out from under the truck then any tire made that will go onto your rim will fit the axle.

Are you really asking, "What's the largest tire that you can put under a Toyota mini truck?" If so, then you will probablly find answers all the way up to 44" and maybe beyond. Of course the modifications to the truck required to run those tires are not trivial or cheap.

Or are you asking, "What's the largest tire that I can run on my truck without worrying too much about destroying the axles?" If that's the question then I would say 40" if you only go to the mall in it and 35" if you take it off road. But that's just my opinion. Even with 35" tires you need a lift, maybe some sheetmetal work, and different gears in your differentials (3rds if you remember your other thread). Again, not cheap by any means.

 

If you also mean what is the largest size tire you can run with out breaking things like Birfields etc, some people can run 35's w/o issue. Some people break parts with 33's depending on how you wheel. I used to grenade R&P's in my '84 because I was hard on it with 35's. My '81 will soon be seeing a set of Longfield's (guaranteed to 39.5" tire) with his hub gears too--$700 investment but I want to be able to wheel with out worrying too much about the front end being a weak link...

I recommend you spend some time reading this Toyota FAQ you will learn a lot