Someone tell me a bit about tires.

[OdiN]

Okay so my 2004 X has P265/65R17 tires.

I see you people talking about 31's or 33's and I've never seen tires without the type of measurement above (P265/65R17) - I looked up what each part of that means, and I know there is a size calculated with that info, but are you just talking about diameter?

Yeah yeah, more n00b questions!

[DamnHippie]

There are several tire measurement standards. The one you cite is called P-metric, it's for passenger car tires.

There's also a similar standard called LT-metric; the numbers mean the same thing, but the load ranges are vastly different. If your vehicle came with one type, you can't switch to the other type without changing the inflation pressure. (LT-metric tires are stronger, but require higher pressure to support a given weight than the same-size P-metric would need.)

For offroad tires, another standard (from the trucking industry) is often used, called "flotation size". With this standard you specify the overall diameter, the width, and the wheel size, such as 33 x 12.50 x 15. These will also require an adjustment in air pressure to support the load.

Basically, if you change the type of tire, the pressure number on your door/glove box placard isn't right any more. You need to use charts from the tire maker to see what the right pressure is to support the total weight of your vehicle at highway speeds.

For best offroad performance, a smaller wheel is better; most wheelers use a 15" wheel. That gives you a taller rubber sidewall on the tire, which will allow the tire to flex more and absorb more bumps when you air it down for offroad use. The tradeoff is reduced performance on the pavement (but once you start modifying your vehicle to work better offroad you usually give up the ability to drive it like it was a Ferrari on the streets.)

[OdiN]

Ahhh...well I do have "off-road" tires but they are the P measurement. I hadn't seen the other measurements. I have 17" wheels - standard stuff.

And are you kidding? I can't drive the 04 X like a Ferrari on the streets anyway - I just jump in the Maxima if I want to do that :P

[CurleyMan]

yea metric sizes are used even for diesel pickup truck tires sometimes... I'm so used to referring to tires by the standard size I am often baffled by metric tire sizes. Here is a calculator I find easy to use....

http://redrock4x4.com/tech/tire_calc.php

[OdiN]

Ahhh, cool.

So mine are 30.6x10.4/17

Seems odd. I usually go check out tires at tirerack.com but they don't use those measurements that I found.

[CurleyMan]

well that would be a 31x10.5x17, some tires run a little off from the listed size. A 31 inch tall tire may only measure 30.8 or 30.6 even though it's listed as 31 inches tall. Some tire manufacturers produce tires very true to size while others like Interco are usually off by quite a bit.

[Sully4x4]

I saw one tire but I am really spacing it out. It was a 32x11.5x15 from 4wheelparts that was surprisingly really true to its size.

[DamnHippie]

The wheel size affects the actual size of mounted tires too... a 33x12.50 might be 32 tall on 15x10 wheels, 32.8 on 15x8, and 33.2 on 15x7. Some manufacturers will list what width wheel they recommend, and they usually base their sizes on that (or on the middle of that range if they give a range).

[Sully4x4]

But you don't wanna run 33x12.50's on 15x7's....the tire is just too wide. I think the smaller rim recommended for the 12.50's is the 15x8

[DamnHippie]

Why wouldn't I wanna do that? In fact, I've been really happy with my 33x12.50 on 15x7s.

[soccerbrace]

I am running 8 inches and there is definitely enough room for another half inch on either side for 33" tires

[Scott Allan]

I am running 8 inches and there is definitely enough room for another half inch on either side for 33" tires

With the greatest of difficulty I will resist commenting on your choice of wording - I doubt others will be able to resist :D

[Sully4x4]

Lol Scott.

And Ian, it's just from what I heard. Like I said, I'm not too knowledgable about most of this stuff. But if you are successfully running the 12.50's on 15x7's then I will retract my statement as you have proof countering it.

[DamnHippie]

Yep, it works for me. When I bought new wheels last year I decided to get the 15x7 because I had seen Clay's truck with 33s on 7" wide, and I liked the way that made the tires stand up tall. Anything to get an extra half-inch of ground clearance.

[woody]

I ain't gonna be so nice........James - you livin' in the squared world again cause I think you meant 2.8284271247461900976033774484194~ inches..........:crazy:


For those of you confused by this number, take out your calculator and calculate the square root of 8.......

[soccerbrace]

WTF? All I am saying is that 8" is 1" more than 7"

1"/2=.5" per side.

[woody]

....and all we are saying is 8" is 6" more than 2" and the average is 6".........If we are confusing you, I will do my part and continue.......


I know the tires that I have purchased were tested and recommended for 8" wide rims. I have a set of 16x8 Cragers they are going to call home in the next week.

[itsme1738]

clays old tires and rims are mine now

[Sully4x4]

I really want to get 33's but I don't wanna trim anything. What do you think I should do Ian to get that clearance? I have to upgrade my steering anyways so that's not an issue. Do I have to get the SL or...?

[tbecktold]

Get some 33x10.5s and maybe do a little bit of a tbar crank, you should be golden.

[DamnHippie]

You should probably try test-fitting some tires before modifying anything else. I've got a set of 32x11.50 sitting next to the house, and a set of 33x12.50 on my truck. We can try each of those on yours and see how close they are to rubbing and you can decide what to do from there.

Also, don't give up on trimming too quickly. It's not like you have to crudely take a sawzall to the body and make a mess. We trimmed Nate's truck back a couple inches and when we were done you can't even tell it happened, unless there's another frontier parked next to it and you notice the shape of the fender flare at the bottom is a bit different on Nate's now. (We should get some pictures of that.)

[Sully4x4]

Sounds good...I'd like to try it. And then we can go from there.