Is the tire shop guy BS'ing me or what?
 

And when I asked the guy working at the counter how much two new front tires are, he then said I needed to get all 4 new ones for my type of jeep or else my differential will mess up. He claims it happened to another Jeep owner, but I think he is full of BS. Then again Jeeps are weird enough as it is.

So do I really need to get 4 new tires or can I just rotate the back tires to the front and put the new ones on the back?

Thanks

If you have full time awd then the size of the tires must be very close.

If the tire sizes are mismatched then they will always be spinning at different speeds ruining your drive line.

If the tires are the same size as the rear, how would changing them affect anything at all? Or am I not getting something?



Ah, see now that does make sense!

It really depends on how worn the tires are.

I usually run the Jeep in 2WD mode 98% of the time. But my two front tires are getting worn down enough to warrant a change soon. Within several weeks I would say. but the back tires still have some good tread on them.

At least the shop dude wasn't lying to me about this.

If you have full time 4wd it does matter (np249), 1/2 worn tread rears vs new fronts is enough difference to ruin a viscous coupler even the same size. If you have part time you will not notice the difference as long as 4x4 is used offroad, which is the intended use anyway.

I have the NP242 btw

If you have a 242 and keep it in 2wd you should be fine just changing 2 of the tires. If it was the 249 AWD tcase you need to get all 4.

Tire sizes are not regulated, a 235-75r15 in one brand will vary from another brand, sometimes there is quite a bit of difference between the two.

I second that, going from Michelins to Coopers, BIG difference. (coopers were noticeably taller, and only swapped the Michelins which were 80% tread because they were 9 years old)

Get the same make/model and don't worry about it. The wear isn't going to matter. This isn't an intelligent system like a newer AWD system.

I had a 95 ZJ v8 with the 249 full time case and simply put buying new tires for one axle with a different tread pattern will...NOT...cause you any grief . i had ran p225's miss matched with p235's and it was fine...Chrysler from the factory even put a space saver spare in that jeep , which did have issues over 35mph , but never killed the t-case . I sold that Jeep in 2005 with 35 ssr's on it and the origional 249 t-case in it still working at almost 300,000 miles ...I would not go as dramatic in size /tread difference as that 22 inch space saver , but simply the difference in Diameter between new tires or brands and tread difference will not be noticed in that Jeep .

Tire sizes are measured at the carcass not the tread, this is why there is a tread depth measurement, overall tire diameter and revs per mile for each tire. However just because a 215/75r15 is one size don't assume that all tires of that measurement are exactly the same. The second number is a percentage of the first. These go in 5% increments. A 75% could be anywhere from 72-77%. Just because it didn't cross 72.5 doest stop them from putting a bigger number on it. Ford says it is a 5.0L but measured it is actually a 4942cc which should be a 4.9L.

To answer the question though no you do not need 4 tires unless there is not enough tread on the rears and you think they are still good because you can see the pattern still. If they are truly good at around 5/32 you can buy 2 they are trying to make money. Just keep those two tires on the same axle