What's the biggest tire I can fit..

@exploringyahweh

Are you tired of rolling around looking like your truck skipped leg day? Or, have you already put big tires on your truck and now find you've lost the ability to steer without filling your cabin with the sounds of a buzz saw? Well luckily, you've come to the right place! If you'd like to learn about why you would or wouldn't want bigger tires, check out our previous article here:

https://summit-offroad.com/blogs/news/everything-about-tire-sizes

Our favorite emails to answer usually go something along the lines of "What's the biggest tire I can fit on my..."etc., and as much as we'll miss responding to those multiple times a day, we figure its for the better good to write an article about it. Most of the content here will be tailored for Toyota trucks and SUVs, however most of the information will be applicable to most body on frame trucks. 

The Easy Stuff

Let's say you want to fit a 31-33" tire on your tacoma/4runner/gx. This isn't too hard, and doesn't require that many non-reversible modifications. The change that will make the biggest difference is a lift kit. For a 31" tire the only thing you may need is a level kit. This raises the front of the truck by a small amount, factory suspension usually has the front slightly lower than the rear, and this, in addition to correcting that, gives you clearance for a slightly bigger tire. With a 3-4" lift you can fit an even larger tire, although this is where you might run into modifications that require a bit more commitment.

The Harder Stuff

So around the 33" range is where a lift kit needs to be supplemented with some other changes. First of which is probably a bumper cut, and liner trim. If you are not running an aftermarket bumper, the lower part of the front bumper will most likely need to be trimmed. Any factory mudflaps or plastics near the rear of the fender well will need to be trimmed and/or removed as well. Here are some examples of how the front bumper can be aesthetically trimmed for more clearance:

@rithagram, @thrill_overland, @wvytaco

Additionally, behind the fender liner, there is a pinch weld with a seam that protrudes perpendicularly towards the tire. This will need to be hammered flat; usually it is pretty sturdy, so you really have to give it the beans with a sledge hammer. 

And to round things off, is the Body Mount Chop, or BMC for short. This is where the cab is bolted to the frame and, on most trucks, is a common area where big tires don't get along with the body too well. It is performed by cutting off a section of the protruding mount, and a new plate is welded in with a lower profile. You can look to spend anywhere from $450-600 on this job, and it's become popular enough to the point where companies have templates and weld-it-yourself kits. We prefer to take our trucks to a reputable shop that specializes in off-road fabrication.

A BMC with a custom plate performed by @steve.ssahaus

The Even Harder Stuff

So you've gone off the deep end and want to put 35" tires or bigger on your truck. Well if you've gotten to this point, chances are you don't need to read a write-up on how to do it because you're probably already heavily invested into the whole off-roading thing (we hope). However, as this has become more and more popular and desirable, it's still worth covering some of the commercially available modifications out there. The most common of which is a Body Mount Relocation, or BMR for short. This is when the factory body mount is removed entirely, and replaced with a smaller mount designed from the ground up with clearance in mind. 

@drtfabrication relocation kit

Even though the BMR kits are sold commercially, you still need to find a reputable welder/fabricator, as precise measurements and welding will be paramount to both proper body gaps, as well as structural stability. Anything past this point will usually require more custom fabrication and of course money. 

The reason we are hesitant to simply recommend a tire size to those who ask is because much of this can still be somewhat of a subjective "art". Fitment and rubbing can vary from truck to truck, or even from one side of the truck to the other. We've literally had some trucks that rub only when turning left/right vice versa. And although the mods listed above cover most the bases on the topic of getting more clearance, there are a couple more factors that are sometimes overlooked that are important to note.

Caster

Caster, simply put, is the angle at which the wheel hub is reclined away from the shock tower usually indicated in a positive value in degrees. The higher the value, the more clearance you will have from the rear of the fender well. Most trucks will have a limited amount of adjustment from factory, which for the sake of clearance, should be set to the maximum positive value.

Wheel Offset/Width

Wider wheels, or wheels with a lower offset (fitment further out) will result in a bigger scrub radius. This in turn means the wheel itself will swing in a wider arc as it articulates through the steering range. Even with the same height tire, one mounted on a wider wheel will require more clearance at lock. 

Loaded Weight

It's also important to note if a rig is intended to be used as a overlanding/camping truck, clearances should be measured with the truck loaded. Camping/recovery equipment usually weighs a good amount, especially if you intend to have multiple passengers. Alternatively, if the truck is mostly used to crawl over parking blocks at the local mall, this isn't as much of a concern. 


A two finger gap while static is usually a good rule of thumb

Remember that out on the trail, what may have cleared on flat ground, may possibly rub as the suspension cycles through its full range of motion. A little bit of rubbing may be acceptable for some, and not for others. As long as it's not excessive, a bit of rubbing wont hurt anything. If you fall into the camp of someone who wants no rubbing EVER, you may want to preemptively do more of these mods. And on the contrary, if your truck already squeaks, pops, rattles and you got shit flying around the cabin when off-roading, perhaps you won't care as much to spend the extra money. Whatever the case, we hope this guide serves as a rough introduction into what is needed as you go up in tires sizes. Remember to always do some of your own research and figure out what will work best for you. We hope your big tire dreams come true, and happy wheeling!