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Ever since the H3 Hummer obsession took hold of me, I have noticed a bunch of people visit the site searching for what’s the biggest tire an H3 Hummer can fit. Also, I’ve noticed searches for whether or not it is possible to put 35-inch tires on an H3 Hummer. Yes, thirty-five-inch tires will fit on an H3 Hummer with absolutely no modifications. Even the factory spare tire mount on the tailgate will fit a 35″ tire just fine. There is however a few things I recommend when mounting a tire that big on the H3. But overall, having 35-inch tires on an H3 Hummer is worth it.

The absolute biggest tire that will fit without any modification to the vehicle is 315/75r16 which is 34.6 inches tall and about 11 inches wide. Even though the tires are only 34.6 inches tall, most off-roader enthusiasts refer to them as 35’s. I wanted a tire that was aggressive but had a relatively small impact on road-noise, gas mileage, and highway-speed handling when compared to the factory tires. This is why I choose General Grabber 315/75r16. To my surprise, I found them to be a bit more aggressive than I had expected when I finally came face to face with the tires. Despite the tires being more aggressive than I expected, these tires have exceeded all of my expectations. Road noise from the tires is well within an acceptable range, gas mileage seems to be right on, and the extra grip these tires have is fun in the turns. Even though the tire size has changed, the speedometer is still for the most part right where it should be. Typically, an H3 Hummer’s speedometer with 35-inch tires will read 9.5% slower with the base model and only 5.5% with Adventure Package equipped Hummer. Don’t forget to factor that difference in when calculating gas-milage that the vehicle drove 5.5% to 9.5% further on that tank of gas.

The Factory tires that an H3 Hummer comes equipped with are a lighter load range than most typical off-road tires and this has some positive effects and negatives effects. Higher load range tires can handle more physical weight than a lower load range tire can and as a result, they weigh more and affect the gas mileage negatively. City driving is where the biggest difference in gas mileage will be noticed. Whereas highway mileage should go nearly unnoticed. How much this affects the gas mileage is entirely up to the driver. These tires can handle a heavy payload without distorting but this also means the tire doesn’t absorb as many vibrations and can cause the Hummer to ride a little bit rougher than when it was stock. Luckily with my tires at 35 PSI, I haven’t been able to tell for certain if the ride is the same or a bit rougher.

On the positive side of things, a higher load range tire works better for off-road. The first thing everyone should do before some serious off-road driving takes place is to air the tires down. How much the tire should be aired down is debatable. I typically choose 12 to 14 PSI. Airing the tire down increases the size of the tire’s footprint by 2-3 times. This increased traction makes the off-road trails easier on the driver and more importantly on the vehicle. The higher load range of the tires also helps hold the bead on the rim at these lower pressures when off-roading. If the bead were to slip it can cause the tire to become unbalanced, or worse let out all the air pressure.

Once the decision to return to civilization is made, typically it’s going to be a bit of a drive to the nearest gas station before the tires can be aired up to 35 PSI. Driving on low tire pressure is less of concern with a tire with a higher load range because of the extra strength that the tire’s sidewall has. Of course, the biggest, and the only reason to ever consider putting a bigger tire is to increase the ground clearance on the vehicle.

Overall, I’m very happy with the purchase of my Red Letter General Grabber tires. The tires have the aggressive design, extra ground clearance, and the off-road performance gains that I wanted. I look forward to seeing how well they perform in the long run.