I am a Certified GM Mechanic and Technical Trainer and a Certified AM General Tech and Offroad instructor. All of the following tips are from my many years of mechanical experience and a whole lot of trial and error on my own personal vehicles! Some stuff worked and lots of stuff was just a plain waste of time and money and plain SUCKED!
My focus will be on H2s but most of the info can directly transfer to H3s and some of it can be useful for H1s. I will try and mention specific upgrades that I know work and work well per model.
Hopefully I will be able to help most of you get your Hummers to be far more economical than they are presently. Some stuff is free and simple but most stuff will cost you money. Most stuff anyone competent with a wrench will be able to do in their own driveway but some stuff will need a shop to help out! I will try and post pics whenever possible and I will try and be as specific as possible with the results of my testing. If something works better. I will tell you why. If something sucked, I will tell you why. I will also try and give you a rough pricing for most things.
So for the first post, let's start with the basics that anyone can do.
<b>Tire Pressure</b> is far more critical than most people realize. The recommended pressure on the door sticker is a decent starting point but is useless if you are no longer running the exact factory rubber and if you have added any type of gear to your rig. Inside or Out. There is no way to tell you set your tires at this pressure and it will be perfect, Every Hummer is different, every tire and wheel package is different. Now there are formulas to help you calculate what your pressure should be but there is a FAR more effective and precise way to do it since after all, every tire carcass will flex a tad different from another. So our stock H2 tires are 315/75R17 and had a load capacity of 3195lbs @ 50psi and our recommended pressure was 37psi. I currently run Michelin XML 325/85R16 tires which have a load capacity of 5070lbs @70psi and I run them at 30psi front and 25psi rear.
I determined this pressure by doing the following things;
1. Load your Hummer the way it will ride 80% of the time. Make sure your fuel tank is 50% or greater and if you mostly have a passenger make sure they are with you. This will make sure that you are basing your pressure on the load the tire needs to support the majority of the time.
2. Head to your favorite mall parking lot and be sure to bring a portable air compressor and a digital tire pressure gauge. Once you are there, find the straightest section you can drive at least 500ft without having to turn. Once you have located this spot, take some tire crayon or chalk and mark several lines across the tread of each tire. Make sure to extend to the sidewall so you can easily find your marks.
3. Next drive ahead 500ft in a straight line with light throttle and braking. Then back up and do it again...hopefully you can back up in a straight line as well! Once you have done this at least twice, stop and look at your tread.
4. If your tire pressure is perfectly set on all tires the chalk will be worn off completely from tread edge to tread edge...not likely on your first try but hey it could happen!
5. If the chalk is worn on the edges but not in the center, your tire is under inflated and you need to add air and retest. Add air in no more than 5psi increments. Low tire pressure is great offroad to help the tire to conform to obstacles but greatly increases your rolling resistance on asphalt and will accelerate your tire wear.
6. If the chalk is worn in the center but not on the edges, your tire is overinflated and you need to deflate and retest. Remove air in no more than 5psi increments. Too much tire pressure is just as bad as not enough since the tire can no longer conform to the road surface. This will cause irregular wear which will greatly increase your rolling resistance and affect your fuel economy!
7. Keep adjusting your pressures until you get as much of the chalk worn off the tires as possible. Remember to hone your pressure by working your +/- by going 5, 4,3,2 then 1psi increments. This procedure may take about 1 hour but well worth it.
8. Note you should be checking your pressures at least once a month. And btw, don't waste time and money on Nitrogen gas in your tires. Unless you live in the dessert and the arctic at the same time meaning you see a 120F temp swing everyday...you will never notice even a slight difference. Remember the Air we breath is already 78% Nitrogen anyways!
9. Note, your pressures may be different front side to side and front to back. This could happen since each of our trucks are set up different!
Now, some of you are probably saying, this is stupid, but remember we have to start with the basics and work our way up. If overlook the basics it will affect the bigger steps to come!
Tire Pressure can provide up to a 10% increase in mileage.
Stage 1 complete!
Thanks,
Kev
