315/75r16 = 15mm larger

[Slickspawn]

To fuel the eternal 35" 315/75r16 debate I was playing around in Excel to validate my personal thought that the extra size of the 315/75 vs the 295/75 can't be that impactful. Not from an offroad capability standpoint and not from an size advantage standpoint.

Although mentally the 35" club is where many of us strive to be. 15mm is the total radius difference. That is about the width of my thumbnail. My thumbnail!

What is crazy to me is that 295/75 is the recommended MAXIMUM tire size you can run on a stock rig without rubbing.

This is a mathematical calculation of the tire, of course there will be variations mounted on an 8" rim or an 8.5" rim, etc and you may have 1-2.5mm variation in radius once mounted.

I thought this was interesting. I'm not trying to point anything out, this is coming from a place of ignorance - I do not have 35s or 315s on my truck, nor do I have 295s. I am stock height with torsion bar crank at ~21.25" hub to fender in the front, no idea about the back but I still have some visible rake.

I've been tossing the idea about of purchasing some OME 2860 coils for the rear, installing my diff drop, and the real problem: decide to re-gear when Yotamasters installs my front ARB or not.

If I regear I'll most likely try to get a set of 315s for those times when we go on a trail run or a weekend expo.

A little pinch weld hammering, some fender rolling, and if I had my way I would really like to do some sheet metal modification in the wheel wells all around to make this an easy do. I just wish I had some sheet metal skills.

Food for thought for all of you anyway.

I'm not going anywhere with my 100 this weekend, so hopefully some of you will do some bench wheeling with me.

Brett

 

[Sandroad]

I suppose you know about all the sites that do the calculations for you? These sites also provide the width differences, plus the speedo changes.

http://www.discounttire.com/dtcs/infoTireMath.dos#row1

 

[Slickspawn]

Yes, but before the internet we had to do it manually, so I have always remembered it. 2xwidthxaspect/2540+rim

 

[Hayes]

Nothing magical about running a given tire size, in my opinion. But every little bit does add up. We all try to get every last fraction of an inch out of our suspension, and tire size counts for much more than suspension lifts.
A half inch is also a lot when the tire is impacting sheet metal. We also should not ignore the inflated tread width, which is less commonly specified. It's the big burly treads and extra sidewall tread that often contact rim of the fender, and thsee vary widely from tire to tire in a given size.

 

[sleeoffroad]

We probably answer 20+ tire size questions per day and we are close to only recommending stock sizes. There are so many variables associated with tire fitment and giving a 100% definitive answer does not exist unless you have done that exact setup. Even with that when using adjustable upper control arms there is no guaranteed answer since the alignment can be manipulated to provide more tire clearance. And yes sometimes 15mm will make a huge difference.

One of the major things people are forgetting is that lift does not give tire clearance, especially so on an IFS front suspension. Available tire space is mostly driven by wheel well size. What lift gives you is space for the suspension to cycle. Now there are some subtle nuances like when a read axle cross articulates and tilts clearance change. The movement of the front A arms and how they interact with the wheel position when cycling the suspension.

When the tire is too large for the wheel well it will rub. Pretty simple to understand, but when you lift you only changes how ofter the wheel will rub depending on your driving and how often the suspension will be cycled to the point where it is so compressed that the tire will rub.

 

[Bomar]

Also to take into fact is that you can put any 315 next to another and real life the sizes could be way different. Examples... BFG KM2's run narrow. Toyo MT's run wider. All depends on tire molds and tread design.