This question is asked often enough that I figured it was finally time to put together an answer that gives lots of information, but that doesn't have to be re-typed again and again. Because that will save everyone a bunch of time, hopefully!
So, let's start with the basic question that gets asked:
What's the biggest tire I can run on my 1st gen Toyota Tacoma?
There are of course variations to this question - some people wonder "with no lift," or "with a 1-3 inch lift," or "without cutting" or "with wheel XYZ" - but in the end, the question is really the same and I'll do my best to try to answer it here.
Some background on lifts before we get started
There are several kinds of lifts, but only two that really matter for this conversation - suspension lifts, and body lifts. There are pros/cons to each that I won't discuss here; I'll focus only on the relation of the lift to tire fitment.
- With a suspension lift, you are increasing how much weight your springs (coils in the front; leafs in the back) can hold up without compressing. That means that - at rest - your frame sits higher off the ground, giving you more up travel (and therefore lift). A suspension lift also means that the spacing between your frame and body remains the same as stock. This is critically important because it means that when you fully compress (aka "stuff") the coils/leafs, the tire is in the exact same position as it would be if you had no lift at all. Therefore - a suspension lift does not allow you to fit larger tires than stock suspension!
Also note that I include block/spacer lifts done to the suspension components in this class of lifts as well, even though they don't offer the same performance benefits as coilovers or heavier duty leaf springs.
- With a body lift, you aren't relying on your suspension to push the entire truck up. Rather, you put some spacers between the frame and body to increase the spacing between the two. So, your frame (and suspension) may all be at stock height, but your cab could be 3 (or more) inches higher in the air. This is important because it means that there is now inherently more space between the tires and wheel wells (part of the body), so when the suspension is fully compressed, that space still exists, possibly allowing a larger tire to fit without modification of the body.
Of course, you can do both types of lift at the same time as well.
And a bit of background on wheel positioning...
Where the lifts discussed above move the wheel well vertically with respect to the wheel, the other element that affects fitment is how far in/out the wheel is in the wheel well (i.e. the horizontal alignment of the wheel with respect to the wheel well). This horizontal movement is described by the wheel's offset and backspace. These matter primarily when you turn the steering wheel - because as the wheels pivot left and right, the corners of the tires may rub on various parts of the wheel well.
While it's easy to get bogged down in the details of offset and backspace, the simple truth is this - a wheel with more backspace will be "tucked in" to the wheel well, and will therefore be more likely to rub on the frame or suspension components when turning. A wheel with less backspace will be "pushed out" of the wheel well, and will be more likely to rub on the fender. The trick is to find the backspacing that will best fit the tire size you want to install.
Note that wheel spacers essentially decrease backspacing, pushing the wheel further out of the wheel well.
Besides backspacing, the other thing that can affect wheel positioning is the caster of the wheel. I won't get into exactly how caster works, just know that:
- Changing caster moves the wheel forward and backward within the wheel well.
- The more caster you have, the easier it is to keep the truck going straight down the road (vs. wandering).
The reason it matters is that many aftermarket upper control arms (UCAs) increase the caster by approximately +2º, which moves the wheel ½-¾" backwards in the wheel well - making it more likely to rub on the back of the wheel well (and less likely to rub on the front of the frame), especially when turning. Certain UCAs - notably SPC 25460 arms - allow adjustment of this caster - though as noted above, decreasing it to move the wheel forward makes the truck more prone to wandering (vs. going straight down the road).
And finally, background on tire width (and wheel width)
Don't forget that not all "33-inch" tires are the same width. You can easily find width's that range from 10-inches to 12½-inches - and that makes a difference to fittage as well. Essentially, a narrower tire will have a smaller radius as it turns left/right inside the wheel well, and so is more easily fit (usually). A wider tire can display traits of both more backspacing and less backspacing at the same time since the inner wall of the tire is close to the frame, and the outer wall of the tire is further away from the wheel well - as such, it can rub on both the frame and fenders when turning!
So, what size tire can I fit?
Taking into account the vertical and horizontal movement of the wheel well in relation to the tire discussed above, here's what you can expect for a 1st gen Tacoma as far as tire sizes. Note of course that these are approximate tire sizes - 31's are rarely exactly 31 inches in diameter, and 255/85R16's are close to 33's.
- 31's - Stock tire size. No trimming necessary to fit these tires, and no rubbing occurs since this is the stock tire size. Aftermarket UCAs make little difference with clearancing.
- 32's - Very minor trimming may be necessary to the wheel liner and pinch weld, which can be minimized with stock width wheels and tires. Aftermarket wheels with lower backspacing (or that are wider) are the most likely factor in any rubbing. Aftermarket UCAs that increase caster may also start to play a role.
- 33's - Will require cutting/hammering all of the pinch weld for wheels with stock backspacing, as well as reforming/trimming of the plastic wheel liner. Aftermarket wheels with lower backspacing (or that are wider) are likely to require additional hammering of the firewall, and minor reformation of the fender sheet metal near the pinch weld. Aftermarket UCAs that increase caster will definitely play a role. Finally, you may start running into other issues here (e.g. placement of the wiper fluid reservoir).
- 34's - Regardless of wheel (stock or aftermarket) and UCA selection, will require cutting/hammering all of the pinch weld as well as significant bashing/reformation of the firewall to make as much room as possible. Aftermarket wheels with lower backspacing may require tubbing (significant cutting and welding in a new piece) of the firewall and fender sheet metal in order to fit. You will need to relocate any components that sit inside the wheel wells (e.g. wiper fluid reservoir). A ~1-2" body lift can help reduce the amount of rubbing and tubbing required.
- 35's - Regardless of wheel (stock or aftermarket) and UCA selection, will require tubbing of the firewall and trimming of the fender sheet metal (even with a body lift). Consider a small body lift and aftermarket fiberglass fenders if you're going this route.
- 37's or larger - Seriously. Stop it. If you're reading this article to figure out how to put 37's or larger on your Tacoma, you aren't ready yet. Go drive your truck off-road for a few years first, instead.
So what size tire should I run?
Ha! There's on one answer here - everyone has to make their own choice. Even with stock 31's, our trucks perform very well and allow lots of wheeling. I'd recommend taking several trips and gauging your comfort level off-road before moving away from stock-sized tires, especially since they offer the best fuel economy and the rest of the truck is optimized for the stock size.
If you've done that and are convinced that you need larger tires, then 33's seem to be a sweet spot from a pain/performance perspective, since there (usually) aren't significant modifications necessary, and you gain a full inch of ground clearance over 31's. However, fuel economy decreases dramatically - on the order to 10% or more - since most 33" tires are E-rated and significantly heavier than C-rated 31's. And, while 33's increase stress on other components such as the lower ball joints, the increase is significantly less than going to 35 inch tires.
But seriously, what size tires should I run?
33's with as-near stock width (10.5") as possible. They are just about perfect on our trucks.